Yasser Ghalmi

Farid Habelhames

Abdelfetteh Sayah

Ahmed Bahloul

Balkacem Nessark

Hassina Derbal-Habak

Yvan Bonnassieux

Jean-Michel Michel Nunzi

Enhancement of the capacitance properties and the photoelectrochemical performances of P3HT film by incorporation of nickel oxide nanoparticles

Keywords: NiO, P3HT, composite film, photocurrent, supercapacitors

Introduction

In recent years, increased demand for renewable energy resources take a major attention due to the limited availability of fossil fuels. In order to tackle the problem, researches focused on organic photovoltaic (OPV) devices seem to be one of the issues that may be a solution substitute to the classical energy suppliers. In addition to their powerful conversion rate, organic photovoltaic (OPV) devices are easy to manufacture, low-cost, light weight and eco-friendly compared to classic energy supplier's appliances. In the other hand, organic photovoltaic (OPV) devices are proved to be of high capability for large area roll-to-roll manufacturing [START_REF] Machui | P3HT: Non-Fullerene Acceptor based large area, semi-transparent PV modules with power conversion efficiencies of 5%, processed by industrially scalable methods[END_REF][START_REF] Park | Organic solar cells employing magnetron sputtered p-type nickel oxide thin film as the anode buffer layer[END_REF][START_REF] Krebs | Production of large-area polymer solar cells by industrial silk screen printing, lifetime considerations and lamination with polyethyleneterephthalate[END_REF] and energy storage systems such electrochemical batteries and their capacitors (ECs) [START_REF] Ruzmetov | Electrolyte Stability[END_REF][START_REF] Hall | Energy storage in electrochemical capacitors: designing functionalmaterials to improve performance[END_REF][START_REF] Simon | Materials for electrochemical capacitors[END_REF][START_REF] Notten | 3-D Integrated All-Solid-State Rechargeable Batteries[END_REF][START_REF] Sayah | Electrochemical synthesis of polyaniline-exfoliated graphene composite films and their capacitance properties[END_REF]. Subsequently, organic photovoltaic (OPV) devices are playing a major role in both essential commodities and electronic systems.

The best known basic component of organic photovoltaic (OPV) devices is the Poly (3hexylthiophene) (P3HT) still submitted to researches in terms of electrochemical configuration modification by addition or incorporation of other chemicals. So, several researchers worldwide have studied P3HT as an electron donor (p-type semiconductor) in (OPVs) to improve energy conversion efficiency [START_REF] Irwin | p-Type semiconducting nickel oxide as an efficiency-enhancing anode interfacial layer in polymer bulk-heterojunction solar cells[END_REF][START_REF] Chapel | Effect of ZnO nanoparticles on the photochemical and electronic stability of P3HT used in polymer solar cells[END_REF][START_REF] Gonçalves | Reduced graphene oxide enhancing the photoelectrochemical properties of poly(3-hexylthiophene)[END_REF] and recently, in supercapacitors due to their promising capacitive properties. The most advantageous aspect of P3HT is the easiness to dissolve in a wide range of organic solvents, fact that enables its deposition over a large area following different deposition techniques such as spray deposition, spin coating and dip coating [START_REF] Wang | Fabrication of regioregular poly(3hexylthiophene) field-effect transistors by dip-coating[END_REF][START_REF] Villers | Improving the reproducibility of Solar Cells by Controlling the PCBM/ Cathode Interface[END_REF].

The nickel oxide (NiO) is a p-type semiconductor which has a band energy gap at 3.5-4.0 eV range [START_REF] Chan | Improved performance of the single-layer and double-layer organic light emitting diodes by nickel oxide coated indium tin oxide anode[END_REF]. The remarkable aspect of the nickel oxide (NiO) that attracted searchers' attention [START_REF] Chtouki | Spin-coated Tin-doped NiO thin films for third order non linear optical applications[END_REF] is its polyvalent use in many applications i.e. transparent conducting films, anode buffer layer in (OPVs) [START_REF] Nguyen | Effect of the deposition conditions of NiO anode buffer layers inorganic solar cells, on the properties of these cells[END_REF] and electrochemical super-capacitors [START_REF] Nguyen | Effect of the deposition conditions of NiO anode buffer layers inorganic solar cells, on the properties of these cells[END_REF][START_REF] Wu | Electrodeposition of nanoporous nickel oxide film for electrochemical capacitors[END_REF][START_REF] Jamal | Electrical properties of pure NiO and NiO:Au thin films prepared by using pulsed laser deposition[END_REF][START_REF] Bandara | Fabrication of n-pjunction electrodes made of n-type SnO2 and p-type NiO for control of charge recombination in dye sensitized solar cells[END_REF][START_REF] Srinivasan | An Electrochemical Route for Making PorousNickel Oxide Electrochemical Capacitors[END_REF][START_REF] Gupta | In-situ growth of P3HT/graphene composites supercapacitor application[END_REF][START_REF] Lou | Boron doping effects in electrochromic properties of NiO films prepared by sol-gel[END_REF]. To produce NiO films, there are several available technical ways; those deserving mention are sol-gel [START_REF] Chan | Improved performance of the single-layer and double-layer organic light emitting diodes by nickel oxide coated indium tin oxide anode[END_REF], chemical deposition [START_REF] Xia | Electrochromic properties of porous NiO thin films prepared by a chemical bath deposition[END_REF], spray pyrolysis [START_REF] Patil | Preparation and characterization of spray pyrolyzed nickel oxide (NiO) thin films[END_REF], thermal evaporation [START_REF] Chrissanthopoulos | Synthesis and characterization of ZnO/NiO p-n heterojunctions: ZnO nanorods grown on NiO thin film by thermal evaporation[END_REF], sputtering [START_REF] Lu | Properties of nickel oxide thin films deposited by RF reactive magnetron sputtering[END_REF] and electro deposition [START_REF] Sonavane | Efficient electrochromic nickel oxide thin films by electrodeposition[END_REF].

Among the conducting polymers, poly (3-hexylthiophene) (P3HT), polythiophene (PTh) and polyaniline (PANI) with electrons-supplier property are being particularly used in supercapacitors applications. Electrons-supply flow of conducting polymers could be mitigated by the hybridization of the polymer with a high surface-area material that has additional necessary properties to improve the overall capacitive performance of the final composite. The conducting polymers-electrode porous structure and material surface area are determinant for the optimum capacitance, the fact is due to the surface phenomena-associated with supercapacitors [START_REF] Sayah | Electrochemical synthesis of polyaniline-exfoliated graphene composite films and their capacitance properties[END_REF][START_REF] Gupta | In-situ growth of P3HT/graphene composites supercapacitor application[END_REF][START_REF] Wu | The impact of Fe 3+ doping on the flexible polythiophene electrodes for supercapacitors[END_REF].

In the work at hand, we have prepareda composite material (P3HT-NiO) consisting of a blend of two donors, one is a polymer(P3HT), and the other is an oxide (NiO) obtained through chronoamperometry method. The NiO is then added to the P3HT in various proportions (1-10%) so that the P3HT-NiO deposit on indium tin oxide films by spin coating method. The capacity and photo electrochemical properties of the different composite material films were respectively studied by galvanostatic charge/discharge technics and photocurrent measurement.

Experimental

Synthesis of NiO powder

The Figure 1 represents the prepared electrochemically of NiO powder by applying a constant cathode potential of 0.91 V vs SCE on Fluorine-doped tin oxide (FTO) coated glass used as working electrode. Then, a graphite rod and SCE counter electrode used as a reference electrode. The electrolyte consisted in an aqueous solution of 0.1M NiSO4.6H2O, 0.1M Na2SO4, 0.1M CH3COONa dissolved in deionizer water. The deposit of NiO was cleaned

Preparation of (P3HT-NiO) thin films

The ITO coated glass substrates used in this study were commercially obtained from the SOLEMS. The ITO's thickness is 100nm, its resistivity is about 25 Ω/sq and its averaged transmittance in the visible is 93%. The substrates of ITO were cleaned through ultrasound wave device in, successively, deionised water, ethanol and acetone for 15 min.

P3HT containing different amounts of NiO (0-10% wt.) prepared previously was dissolved in solution of Chlorobenzene (C6H5Cl), stirred during 24h and deposited on ITO by spin-coating method at 500rpm for 30s. The spin coated films were annealed at 80 °C in air during 10min (figure 2).

Characterizations

The following electrochemical tests were carried out at normal environment temperature inside a single compartment cell using, as usual, the PGZ-301 Voltalab connected to a computer with operating software (voltamaster 4). The latter enables the electrochemical technique selection and establishes the aimed parameters. The measurements at electrochemical scale were operated in a three-electrode cell where indium tin oxide glass substrate (ITO) acted as working electrode, the saturated calomel electrode (SCE) as a reference electrode and the graphite rod as an auxiliary electrode.

The ITO/P3HT and ITO/P3HT-NiO (1, 5 and 10wt %) film-layers were examined through diverse technical methods. For their parts, the X-ray analysis examination was carried out the Rigaku make powder X-ray diffract meter (model RINT 2100) with a CuKα waves (λ = 1.54 Å). The necessary characterization of the films at hand was then conducted under a UV-visible a Shimadzu UV-1800 UV-VIS spectrophotometer following which the spectra were analyzed and stored in an appropriate file. Later on, the atomic force microscopy (AFM) images got through the MFP 3D atomic force microscope (from Asylum research), was in contact way. Furthermore, the issued images were used to quantify the film-layers roughness. The micrographs got from the Scanning electron microscopy were, as expected, from the Neo Scope, JEOL, JCM-5000.

The photo-electrochemical test of prepared films composites was carried out in (LiClO4 0.1M+CH3CN) electrolyte; the photocurrent was obtained after switching the light on and off, with an applied potential of -1.2 to +1V vs SCE. The working electrode was irradiated with white light and the illumination intensity of the lamp was500W, the intensity of the illumination measured using a Luxmeter testo-540 was100Wm -2 .

Results and discussion

The nickel oxide film diffraction graphic (figure 3) witnessed peaks at 2θ=37°, 43°, 62°. The resulted peaks values are likely to be those characterising the cubic NiO that are in harmony with specific standard values i.e. (JCPDS01-073-1519) [START_REF] Wu | Electrodeposition of nanoporous nickel oxide film for electrochemical capacitors[END_REF][START_REF] Sonavane | Efficient electrochromic nickel oxide thin films by electrodeposition[END_REF]. The NiO grains size assessment is figured out through XRD according to Debye-Scherrer's law:

D = 0.9λ/w cos θ (1)
Where D is the grains size, λ is the XRD wavelength, w is the full width half maxima and θ is the peak position. Debye-Scherrer's law enables the NiO grains size that is estimated nearly around 25 nm. Atomic force microscopy (AFM) was used to investigate the surface morphology of the deposited filmsP3HT and P3HT/NiO, as shown in Figure 6. The rates of surface roughness for P3HT blend (0, 1, 5 and 10 wt %) are respectively 4.42nm, 9.32nm, 10.13nm, and 18.27nm.

It was noticed that the surface roughness enhances with the addition of NiO incorporated in P3HT up to 10wt% and no considerable change manifests over the mentioned addition NiO proportion [START_REF] Wu | Incorporation of dike to pyrrolopyrrole dye to improve photovoltaic performance of P3HT: PCBM based bulk heterojunction polymer solar cells[END_REF]. It is recognized that the surface morphology and the device interfaces are of capital role in order to achieve high performance of the P3HT. The high cyclic voltammetry response currents thus got for the ITO/P3HT-NiO 10wt% composite film shows meaningfully a higher specific capacitance than ITO/P3HT, the observed fact is originated thanks to the rough structure of the ITO/P3HT-NiO composite films itself instead of the ITO/P3HT film. The ITO/P3HT-NiO composite films electrodes engage the high electrical conductivity parameter; as prerequisite, the P3HT with large electrochemical active area is much preferred in order to maximize its draw interest from its The figure 11 represents the GCD plots of the whole electrode materials set at current densities of 0.1, 0.2, 0.5, 1 and 2A/g. It has been found as well that the increase in the current density the decrease in the discharge times of the electrode materials set occurs.

The ITO/P3HT-NiO 10wt% composite films reached the highest discharge time value of the materials tested, witnessing so a better specific capacitance. The specific capacitance (SC) of every electrode material was similarly calculated according the charge-discharge profile from to the equation ( 3):

𝑆𝐶 = 𝑖𝑡 𝑚Δ 𝑉 (3)
Where i/m is the current density used, 'ΔV' the potential window, and 't' the discharge time As the issued outputs experimental facts show, the semicircle diameter decreases with the increase of the NiO content in P3HT matrix. This propose a increase in the electric conductivity and a consequent important decrease in the resistance of the composite films that contain NiO, from 4 906 Ω.cm 2 for ITO/P3HT to 784 Ω.cm 2 for ITO/P3HT-NiO 1wt%, 128 Ω.cm 2 for ITO/P3HT-NiO 5wt% and 70.85 Ω.cm 2 for ITO/P3HT-NiO 10wt%, these values are acceptable (Table 1). The outputted results point to a slower electron transfer in P3HT film. Nonetheless, the insertion of NiO grains in P3HT film causes a significant improvement in the interaction of the conductive polymer chains. The figure 14 shows photocurrent density as a function of applied potential range between -1.2 to 1V vs SCE for ITO/P3HT and ITO/P3HT-NiO electrodes with different NiO amount. The photocurrent of polymer (P3HT) and composite films (P3HT-NiO) were negative at all potential range and this of composite films were higher than that for the nonmodified polymer. Moreover, the obtained specific capacity for the composite films (P3HT-NiO) was higher than that of pure polymer, which is due to the beneficial effect of NiO electronic conductivity.

Our results also demonstrate that NiO nanoparticles improved the optical and photoelectrochemical properties of P3HT composite films. The interface between a conjugated polymer and semiconductor should provide an efficient charge separation for the photo generated excitants, which improve the photocurrent of composites.

F

  and scraped with a blade. The issued powder was annealed for 1 hour at 500°C.

Figure1.

  Figure1.Chronoamperograms of synthesis NiO at applying catholic potential of 0.91 V vs.SCE

Figure2.

  Figure2. Spin-coating process of ITO/P3HT and ITO/P3HT-NiO thin films.

Figure3.

  Figure3. XRD spectra of FTO (a) and NiO (b).

Figure4.

  Figure4. XRD spectra of ITO/P3HT(a), ITO/P3HT-NiO 1wt% (b), 5wt% (c) and 10wt%(d).

Figure5.

  Figure5. SEM images of ITO/P3HT(A), ITO/ P3HT-NiO (B).

Figure 6 .Figure 7 .

 67 Figure 6. Atomic force microscopy images of ITO/P3HT(A), ITO/P3HT-NiO 1wt% (B), 5wt% (C) and 10wt% (D).

Figure 8 .

 8 Figure 8. Cyclic voltammograms of ITO/P3HT (A), ITO/P3HT-NiO 1wt% (B),

1 :

 1 NiO present inside enables a high contact interface between the P3HT and the electrolyte. Thus, the specific capacitance is accurately evaluated from the following equation Voltammetric charge obtained by integration of curve in CV. m : weight of deposited materiel on working electrode, we used a balance with accuracy of 0.01 mg v: Scan rate.Accordingly, the specific capacitances of ITO/P3HT and ITO/P3HT-NiO (1, 5 and 10wt %) composite films in led at different scan rates are depicted in Figure9. The ITO/P3HT film manifests a specific capacity next to 14 Fg -1 at 10mV/s, but with the insertion of the NiO nanoparticles, a significant increase in specific capacitance occurred that were previously 16 Fg -1 , 19 Fg -1 and 25 Fg -1 composite films respectively. It is worth mentioned that the raised enhancement bound in the electrochemical response may be in direct consequence with morphology occurred change following the NiO nanoparticles insertion. Otherwise, any increase in the composite material electro active area could normally occur. To summarize the experimental fact, any change in the morphology is wholly responsible for any ulterior change in the electrochemical behavior as proved by the SEM and AFM analysis.

Figure 9 .

 9 Figure 9. Specific capacitances of ITO/P3HT (a), ITO/P3HT-NiO 1wt% (b), 5wt% (c) and 10wt% (d) obtained at different scan rates.

  in seconds. The ITO/P3HT-NiO 10wt% composite film reached the upmost specific capacitance of about 81.4 F/g at a 0.1 A/g current density. Besides, the ITO/P3HT, ITO/P3HT-NiO 1wt% and ITO/P3HT-NiO 5wt% gained 20.8, 26.2, and 38 F/g capacitance values under the same current density applied (0.1 A/g) as shown in Figure11. Accordingly, the increase in current density causes a decrease in the whole all electrode materials set. The issued incidence is obviously explained by the subsequent fact following which barely fewer electrolyte ions are able to be in close contact with the inner space of the electrodes of energy storage at such high current densities. Likewise, the specific capacitance values at different current densities for the whole electrode materials have been assessed from the mathematical relation equation[START_REF] Park | Organic solar cells employing magnetron sputtered p-type nickel oxide thin film as the anode buffer layer[END_REF].

Figure 10 .

 10 Figure 10. Galvanostatic charge-discharge curves of ITO/P3HT (A), ITO/P3HT-NiO1wt% (B), 5wt% (C) and 10wt% (D), at different current density, in 0.1M LiClO4 / CH3CN electrolyte, carried out from 0.3 to 0.8V vs SCE.

Figure 11 .

 11 Figure 11.Specific capacitance of ITO/P3HT (a), ITO/P3HT-NiO 1wt% (b), 5wt% (c) and 10wt% (d), at different current density. The spectra impedance of ITO/P3HT and ITO/P3HT-NiO composite films computed

Figure 12 .

 12 Figure 12. Nyquist plots of ITO/P3HT, ITO/P3HT-NiO 1wt%, ITO/P3HT-NiO 5wt% and ITO/P3HT-NiO 10wt%, in 0.1M LiClO4 / CH3CN electrolyte.

Figure 13 .

 13 Figure 13. Photocurrent response ofITO/P3HT (a), ITO/P3HT-NiO 1wt% (b),5wt% (c) and 10wt% (d), at: -0.2 (A),-0.4 (B),-0.6 (C),-0.8 (D),-1 (E) and -1.2 (F) V vs.SCE in 0.1M LiClO4 / CH3CN electrolyte, observed upon switching the white light on and off, at light intensity of 100mW cm -2 .

Figure14.

  Figure14.Photocurrent-potential curve of ITO/P3HT (a), ITO/P3HT-NiO 1wt% (b), ITO/ P3HT-NiO5wt% (c) and ITO/P3HT-NiO 10wt% (d), in a range of potential -1,2 to 1 V vs.SCE in 0.1M LiClO4 / CH3CN electrolyte.

Table 1 :

 1 Impedance electrical parameter values corresponding to ITO/P3HT, ITO/P3HT-NiO

	1, 5 and 10wt%.

  Determines Scaling Limits for Solid-State 3DLi Ion Batteries. Nano let 12:505-511. https:// doi:10.1021/nl204047z .

	F F F F
	o r o r o r o r o r
	P P P P P
	e e e e e
	e r e r e r e r e r
	R R R R R
	e v e v e v e v e v
	i i i i i
	e e e e e
	w w w w w

Ionics Ionics


Subimal Majee

Maria Fátima Cerqueira

Denis Tondelier

Bernard Geffroy

Yvan Bonnassieuxa

Pedro Alpuim

Jean Eric Bourée

Flexible organic-inorganic hybrid layer encapsulation for organic optoelectronic devices

Keywords: Permeation barrier, Silicon nitride, HW-CVD, PMMA, Organic electronics

In this work we produce and study the flexible organic-inorganic hybrid moisture barrier layers for the protection of air sensitive organic opto-electronic devices. The inorganic amorphous silicon nitride layer (SiN x :H) and the organic PMMA [poly (methyl methacrylate)] layer are deposited alternatingly by using hot wire chemical vapor deposition (HW-CVD) and spin-coating techniques, respectively. The effect of organic-inorganic hybrid interfaces is analyzed for increasing number of interfaces. We produce highly transparent (∼80% in the visible region) hybrid structures. The morphological properties are analysed providing a good basis for understanding the variation of the water vapor transmission rate (WVTR) values. A minimum WVTR of 4.5 × 10 -5 g/m 2 day is reported at the ambient atmospheric conditions for 7 organic/inorganic interfaces. The hybrid barriers show superb mechanical flexibility which confirms their high potential for flexible applications.

Introduction

Organic opto-electronic devices, such as, organic light emitting diodes (OLEDs) and organic photovoltaic devices (OPVs) are emerging rapidly due to their lower production cost, better mechanical flexibility and lower consumption of materials compared to their inorganic counterparts [1,2]. However, their utilization is limited by the degradation of the devices due to environmental moisture and oxygen. The organic active layers and the metal electrode used in those devices react with water vapor and oxygen leading to the failure of the complete device. Therefore, the primary challenge before the wide spread commercialization of those products is the development of efficient moisture barrier layers which can protect the active layer and the electrodes from the moisture and oxygen. There is a wide range of permeation barrier requirements for different devices and applications. For the normal food packaging technologies, the encapsulation barrier requirement is not as stringent as for the electronic devices and a single polymer film is sufficient to provide the required efficient packaging. Generally, devices such as OLEDs that use chemically reactive electrodes have the highest sensitivity to moisture, and degradation is observed at the organic layer/electrode interface [3][4][START_REF] Burrows | Proc. SPIE[END_REF]. The extensively used term in the literature to define the steady state permeation of water vapor is water vapor transmission rate (WVTR). WVTR is defined as the amount of water molecules diffusing through a unit area of the barrier film per unit time under conditions of the test and is expressed in g/m 2 day. The most widely accepted value for required WVTR for an OLED is in the range of 10 -6 to 10 -5 g/m 2 day. This value was originally estimated by calculating the amount of water and oxy-gen needed to degrade the reactive cathode [START_REF] Burrows | Proc. SPIE[END_REF]. Other experimental methods also confirmed this value to be a reasonable estimate [START_REF] Weaver | [END_REF]. The permeation barrier requirements for organic solar cells are determined mainly by the solar cell absorber material that is used. A water vapor transmission rate of 10 -6 g/m 2 day was previously reported to avoid degradation of organic solar cells [7]. However, recent studies have shown that for organic solar cells WVTR in the range of 10 -4 to 10 -3 g/m 2 day is quite sufficient to achieve lifetimes of several thousands of hours in operation [8,9].

The existing methods of encapsulation such as hermetic sealing of devices fabricated on glass substrates using a metal or glass lid are not useful for flexible applications. Thin film encapsulation is an attractive solution because of its flexibility and light weight. Recently, almost defect free single-layers of thin films deposited by atomic layer deposition (ALD) showed excellent barrier properties [10][11][12][13][14][15]. However, the deposition process is slow and the number of materials that can be deposited is limited. On the other hand, the conventional plasma enhanced CVD (PE-CVD) systems used for developing thin film barriers give rise to less dense materials than requested for effective moisture protection [16][17][18][19]. Multilayer of thin films is the widely used solutions to hinder the propagation of defects from one layer to the next layer. The organic/inorganic alternating layer structure showed excellent barrier properties for devices fabricated on flexible polymer substrates. The soft organic layer being sandwiched between two consecutive hard inorganic layers decouples the defects from both hard layers, thus avoiding pinhole channeling and absorbs the stresses induced in the hard inorganic layers due to its inherent robustness and high compliance [START_REF] Nisato | Proc. Soc. Inform. Display Symp. Dig. Tech.Papers[END_REF][START_REF] Chen | [END_REF][22][23][START_REF] Yan | Proc. IEEE[END_REF][START_REF] Akedo | Proc. Soc. Inform. Display Symp[END_REF][START_REF] Lungenschmied | [END_REF][27][28][29]. In this study, we have deposited inorganic amorphous silicon nitride (SiN x :H) thin films using hot wire chemical vapor deposition (HW-CVD) to be used as the inorganic part of the hybrid(organic/inorganic) barriers. This deposition technique is advantageous in terms of higher deposition rate (compared to ALD) and higher density films due to lower hydrogen content (compared to PE-CVD). HW-CVD also allows depositing thin films at low substrate temperature which is a major issue for the compatibility with the flexible polymer substrates. Additionally, low substrate damage (due to absence of ion bombardments) during processing and con-formal step coverage allows one to deposit high quality barrier films [30][31][32][33][34][35][36][37][38]. The quality of the other part of the hybrid barrier structure, i.e. the organic layer is quite important in order to improve the over-all barrier properties. Very recently, several researchers developed high quality organic films with very precise thickness and optical properties. Initiated-CVD (i-CVD) is one of those techniques which could allow one to grow high quality organic layers [28]. Similar to our previous work, we have deposited organic PMMA [poly (methylmethacrylate)] film in between two consecutive inorganic layers using the simple and widely used spincoating technique [29]. We focus on the effect of organic-inorganic interfaces in reducing the diffusion of water molecules. Several characterizations have been performed in order to interpret the interface effect.

Experimental methods

SiN x :H single-layers have been deposited in this study using HW-CVD. The detailed description of the HW-CVD chamber is given in [36][37][38]. A single coil shaped Ta filament was resistively heated up to 2000•C. Silane and ammonia, diluted in hydrogen were used as reactant gases. The gases are pyrolytically decomposed into radical species at the surface of the heated filament, which as a catalyst and provides the precursors for SiN x :H film growth on the PET substrates. The substrate was kept at a distance of 7.5 cm from the filament and was heated to a temperature of 100•C in order to stay below the glass transition temperature of the plastic substrates. The substrate temperature was measured with a thermocouple embedded in the stainless steel substrate-holder, close to the substrate. SiN x :H single-layers were deposited using the optimized deposition conditions (Table 1) reported previously [37]. In order to avoid the radiation damage of the substrate by the hot filament, the single-layer thickness was kept fixed at 50 nm which is also the critical thickness for permeation as found before [38]. The critical thickness is the single-layer thickness above which there is no more barrier improvement. The critical thickness was used as the inorganic single-layer thickness to fabricate the organic/inorganic hybrid structures.

The above mentioned deposition conditions gave rise to trans-parent (transmittance, T > 80% in the visible region) SiN x :H thin films. The refractive index (n) of the film was measured using spectroscopic ellipsometry. The value found for the films refractive index (2.01 at 632.8 nm) is close to those found in stoichiometric films [37]. The compositional and structural characterizations of the deposited films were previously reported [36][37][38].The organic material to be used as the defect-decoupling inter-layer between two inorganic layers should have some intrinsic properties in order to be compatible with the encapsulation pro-cess. The inorganic layers were deposited by HW-CVD in vacuum, and therefore the organic material should be stable during the deposition process. The organic material has low glass transition temperature, which nevertheless should be higher than 100•C which is the nominal substrate temperature during depositions. Furthermore, they should be stable to the radicals generated in the HW-CVD process.

The organic layer should also have smoothing effect in order to enhance the growth of the next inorganic layer with better structural quality. Additionally, the organic material should have lower Young's modulus (Y) in order to be compliant and flexible [39]. In the present study, PMMA (Y ≈ 3 GPa) was used as an organic material, because it is widely used and inexpensive compared to other organic polymers. The glass transition temperature (T g ) of 106•C allows it to be stable during the inorganic film deposition. However, the impact of radicals produced inside hotwire CVD chamber on PMMA material has not been investigated in this study.

The organic polymer layer was deposited by spin-coating pro-cess after each SiN x :H single-layer deposition by HW-CVD. After the SiN x :H film deposition the sample was transferred to the spin-coater system. The commercially available PMMA was dissolved in chloroform (5 wt.%) and the solution was spin-coated on the already grown SiNx:H film at 4000 rpm for 50 s. The thickness of the polymer layer was kept fixed at 300 nm and the thickness was measured using Dektak 150 profilometer. The polymer layer was annealed at 100•C when it was transferred again inside the HW-CVD chamber for the next SiN x :H film deposition. These steps were repeated in order to increase the number of organic/inorganic interfaces. Four different structures have been developed with increasing number of interfaces from 1 to 7 where the interface between the organic PET substrate and the first inorganic SiN x :H film has been also counted. The hybrid structures are shown in Fig. 1. The surface roughness of the produced hybrid structures was measured using tapping mode atomic force microscopy (AFM) technique. Five different measurements on different positions of the samples have been performed in order to achieve the error value approximation and analyzed using the instrument software. The optical transparency of the hybrid layers was assessed using a Perkin Elmer Spectrophotometer with Integrating Sphere, taking into account the accuracy of the measurement (±1%).

The diffusion barrier properties of the above mentioned hybrid samples have been assessed through electrical calcium degradation test implemented inside the glove box system. The detailed description and schematic diagram of the test setup were reported previously [37,38]. The Ca thin film (100 nm) and the four Al electrodes (150 nm) were deposited via a thermal evaporator inside the glove box filled with N 2 on the side opposite to the barrier coated PET substrate. Very low deposition rate of 0.2 nm/s at a pressure <10 -6 mbar was chosen to obtain smooth layers, for both Ca and Al depositions. The whole system was covered with a glass lid using epoxy resin. The water permeation through the epoxy edge-seal is confirmed to be negligible by performing the same test using a glass plate as a reference substrate [37]. Water molecules after diffusing through the whole thickness of the barrier coated substrate reach the Ca sensor and react to form Ca(OH) 2 decreasing the conductance of the sensor. The evolution of conductance in time was measured using a four point probe system at the ambient atmosphere. The lag-time of permeation was assessed from the stable region at the beginning of the evolution which is defined as the minimum time taken by the water molecules to diffuse through the whole thickness of the barrier coated substrate to reach the sensor. The WVTR values have been evaluated through the slope of the fitting curve to the conductance curve using the relation:

where N is the molar equivalent of the degradation reaction which is assumed as N = 2 from the chemical reaction of Ca with water [Ca + 2H 2 O → Ca(OH)2+ H 2 ], M is the molar mass of the reactive elements,  Ca is the density of calcium (1.55 g/cm 3 ),  Ca is the calcium resistivity (9 × 10 -8  m), l and are the effective length and width of Ca layer respectively and G is the conductance. From the geometry of our setup, the value of Area (Ca)/Area (window) is taken to be unity. It should be noted that sensitivity of the test set-up (10 -6 g/m 2 day) was evaluated using a glass substrate and the reproducibility of the set-up was assessed using 20 bare PET substrates which give rise to a WVTR of 0.17 ± 0.05 g/m 2 day [37].

The actual purpose of the permeation barrier layers is to protect the sensitive devices deposited on plastic substrates for flexible applications. The brittle inorganic materials used as a permeation barrier film for hybrid layer structures have pinholes or defects which arise due to the processing conditions. However, the failure mechanics of the layers depends extensively on their mechanical properties and adhesion to the underlying layer or to the substrate. The mechanical flexibility of the barrier-coated substrates was characterized by bending the structure for several time cycles to a fixed radius of curvature (r). For the bending test, a home-made four-point bending bridge was used and the sample was bent for several load/unload cycles using an automated motor system. The bending of the sample gives rise to tensile strain inside the films, which in turn forms cracks by the formation and/or propagation of interfacial delamination cracks between two consecutive layers [40]. Ca degradation test was performed on deformed samples after release from the bridge, i.e. under no applied strain, in order to verify the possible damage inflicted by the bending on the permeation barrier properties. The mechanical flexibility of the hybrid structure was investigated by bending the hybrid structures with a radius of curvature of 5 mm for different number of cycles of bending.

Results and discussion

Morphological properties

The surface morphology of the as deposited and annealed PMMA films was analyzed by depositing the films on clean corning glass substrates. PMMA becomes smoother when annealed near its glass transition temperature (T g ) of 106•C [41]. The average surface roughness of the PMMA layer (R avg .= 1.6 nm) decreases ∼80% when it is annealed (R avg .= 0.3 nm) [29]. The change in the morphology at the annealing temperature of around 100•C is possibly due to intensified thermal diffusions of molecules at the surface of the polymer layer at higher temperatures. The external energy (heat) leads to the minimization of surface energy at the surface of the film which in turn minimizes the effective surface area. Minimization of effective surface area is equivalent to the reduction of surface roughness. Morphological modification of the PMMA layer helps in hindering the propagation of any structural defects and produces the subsequent inorganic layer with high quality. Fig. 2 shows the three dimensional surface topographies of the hybrid structures and the variation of average surface roughness values of those structures with increasing number of organic/inorganic interfaces is shown in Fig. 3. The average rough-ness of the bare PET substrate after exposure to the hot filament for the same time (400 s) as it takes for one single-layer (50 nm) deposition, but without film growth, is around 55 nm. The roughness of PET increases strongly from 1.4 nm to 55 nm when the PET foil is exposed to the heated Ta filament, probably due to the fact that the glass transition of PET at around 80•C is somewhat overcome (100•C) inducing a warping of the foil. This explains the high initial roughness of the SiN x :H single-layer film (1 inter-face) deposited on PET substrates. The roughness decreases sharply when the first PMMA layer is inserted between two consecutive SiN x :H single-layers (3 interfaces) which decreases monotonically with increasing number of organic/inorganic interfaces reaching down to a minimum surface roughness of 7.2 ± 1.5 nm for 7 interfaces. This result shows the planarization effect of PMMA layer which in turn reduces the roughness of the whole structure. It was reported previously that the permeation of the water molecules through the barriers depends largely on the roughness of the layers [38,42,43] and it is desired to obtain flat surfaces in order to ease the stacking of successive layers. From this initial result of average roughness reduction, it is expected that the permeation of water molecules will be reduced similarly when the number of organic/inorganic interfaces will be increased. Figure 3 -Variation of average surface roughness with number of organic/inorganic interfaces.

Optical properties

High optical transparency of the encapsulation barrier film is required for the application to the organic opto-electronic devices. Fig. 4 shows the reflectance (R) and the transmittance (T) measurements of the alternating layer structures. The transmittance curves indicate that all the alternating layer structures are highly transparent (∼80%) in the range between 350 and 800 nm. The transmittance is slightly reduced (∼5 percentual points) when the number of interfaces is increased from 3 to 7. It can also be seen from Fig. 4 that reflectance and transmittance of this hybrid layer structures together add to almost 100%, meaning that no absorption takes place inside the layers in the visible region and the barrier structures can be perfectly used as window layers for organic opto-electronic devices. Slight absorption below 350 nm wavelength is due to the plastic substrate itself [37].

Barrier properties

The evolutions of normalized conductance of the Ca sensors deposited on such hybridbarrier coated PET substrates are shown in Fig. 5(a). The lag-time and WVTR values are assessed from the evolution of the conductance and are shown in Fig. 5(b). The results show a clear trend of barrier improvement with an increasing number of interfaces, the most dramatic change occurring for an increase from one to three interfaces. The single-layer of SiN x :H (50 nm) shows no significant reduction of permeation rate. The WVTR value for 50 nm SiN x :H single-layer is ∼10-2g/m 2 day which is only one order of magnitude lower than the bare PET substrate(0.17 g/m2day). This value is far beyond the desired permeation rate. When the PMMA layer is inserted between two consecutive SiN x :H single-layers, the organic layer hinders the native nucleation centres that already existed at the top of the first SiN x :H layer from propagating into the next layer. When a second SiN x :H layer is grown on top of the PMMA layer, there is a low probability of alignment of pinholes with the first SiN x :H layer. Thus the organic interlayer decouples the defects between two successive inorganic layers and makes the diffusion path of water molecules more complex and tortuous. This complex diffusion path makes the total diffusion path of the water molecules longer to reach the calcium sensor which is at the opposite side of the barrier coated PET substrate. This in turn increases the total time of diffusion and the lag-time is increased. The lag-time increases monotonically with increasing number of organic/inorganic interfaces, at least up to 7 interfaces which was the maximum number of inter-faces tested here, and thus with the increase in the total barrier thickness. A maximum lag-time of 155 h is achieved for the 7 inter-faces structure. The WVTR value decreases similarly with variation of average surface roughness (Fig. 3) when the number of interfaces is increased from 1 to 7. As mentioned above, there is a significant drop of WVTR value when the first PMMA layer is inserted between two 50 nm SiN x :H single-layers (3 hard/soft interfaces), reaching down to 9.2 × 10 -5 g/m 2 day, confirming the defect-decoupling effect of the smooth PMMA layer. After that WVTR values decreases monotonically with increasing number of interfaces reaching a minimum value of 4.5 × 10 -5 g/m 2 day for 7 interfaces.

Mechanical properties

Fig. 6 shows the Ca degradation test results after different number of bending cycles performed on the SiN x :H double-layer without any PMMA layer and SiN x :H doublelayer separated by one PMMA layer (3 interface structure). The barrier properties of the SiN x :H double-layer without any PMMA layer degrade consider-ably when the number of bending cycles is increased, possibly due to the formation of channel cracks by the deformation. The SiN x :H double-layer separated by one PMMA layer shows almost no significant degradation of the barrier properties even after 500 bending cycles. This is probably due to the fact that during deformation, the more compliant under-layer (PMMA) absorbs the stress induced by the bending thus releasing the stress from the inorganic layers and decreases the probability of any crack formation. The observations show that these hybrid structures can keep its moisture barrier properties even if it is bent many times and that the structure can therefore be used for flexible barrier applications.

Conclusion

In conclusion, we demonstrated excellent permeation barrier properties of organic/inorganic hybrid barrier layers produced by combining HW-CVD technique, for growing inorganic SiN x :H layer, and simple spin-coating procedure for the organic PMMA polymer layer. The organic layer to improve the quality, we have focussed our attention to realize the effect of organic-inorganic interfaces. The effect of interface is quite critical in order to hinder the nucleation centres of defects at the surface of the inorganic films and thus prevent the alignment of pinholes in the consecutive SiN x :H layers. Increasing the number of organic/inorganic interfaces, we have obtained an overwhelming reduction of the WVTR value down to4.5 × 10 -5 g/m 2 day and an increase of the lag-time up to 155 hat the ambient atmospheric conditions. This low value of WVTR should be sufficient for extending the shelf-lifetimes of organic devices by protecting them from the moisture and oxygen. The variation of the WVTR values showed a high degree of correlation with the variation of the average surface roughness values and thus qualified the planarization effect of the polymer layer. The hybrid barriers showed excellent transparency (∼80%) in the visible region and therefore proved the effectiveness in the utilization for flexible organic opto-electronic devices. The barrier structure also showed superb flexibility even after 500 bending cycles which allows for flexible barrier applications. Further development of the barrier structures can be obtained by improving the structural quality of the organic interlayers.

Figure 1 -

 1 Figure 1-Schematic diagrams of organic/inorganic hybrid structures (not to scale) deposited on PET substrates (175m): (a) 1 interface, (b) 3 interfaces, (c) 5 interfaces and (d) 7 interfaces.

Figure 2 -

 2 Figure 2 -Three dimensional AFM images of the surfaces of the hybrid structures with increasing number of organic/inorganic interfaces: (a) 1 interface, (b) 3 interfaces, (c) 5 interfaces and (d) 7 interfaces.

Figure 4 -

 4 Figure 4-Reflection and transmission spectra of hybrid structures deposited on PET substrates.

Figure 5 -

 5 Figure 5 -(a) Evolution of normalized conductance of the Ca sensor with time for different hybrid structures deposited on PET with increasing number of interfaces. (b) Variation of the corresponding lag-time and WVTR with number of interfaces (lines are mere guides to the eye).

Figure 6 -

 6 Figure 6 -Variation of lag-time and WVTR with number of bending cycles.

Table 1 -

 1 Optimized deposition conditions for SiN x :H films by HW-CVD system.

Acknowledgments

The authors would like to thank Dr. J.C. Vanel for help in electrical characterizations used in this study. The first author (S.M) acknowledges the financial support from Direction des Relations Extérieures, Ecole Polytechnique during his thesis.


Julie Bodin

Maria-Pilar Gallego-Hernanz

Plouzeau Chloé

Anthony Jayle

Lauranne Michaud

Julie Broutin

Christophe Cremniter

Maxime Burucoa

Pichon

Chloé Plouzeau Jayle

Anthony Michaud

Broutin

Julie Cremniter

Christophe Burucoa

Maxime Pichon
email: maxime.pichon@chu-poitiers.fr

Bacteremia due to Lachnoanaerobaculum umeaense in a patient with acute myeloid leukemia during chemotherapy: A case report, and a review of the literature

Keywords: Lachnoaerobaculum umeaense, bacteremia, 16S rRNA gene sequencing, phylogenetic analysis, 21 acute myeloid leukemia

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

The present case describes a bacteremia caused by Lachnoanaerobaculum umeaense in an 85-year-old man 24 with acute myeloid leukemia undergoing chemotherapy and discusses the characteristics of this infection 25 and drug susceptibility. This case was supported by phylogenetic analyses to examine the pathogenicity 26 determination of these Lachnoanaerobaculum sp. 27

Clinical relevance of genus Lachnoanaerobaculum 28

Lachnoanaerobaculum species are known to be obligate anaerobes, Gram-positive, filamentous, spore-29 forming rod-shaped bacilli. The genus Lachnoanaerobaculum, which was registered as a new genus in 2012, 30 belongs to the family Lachnospiraceae and is composed of Lachnoanaerobaculum umeaense, 31

Lachnoanaerobaculum oral, Lachnoanaerobaculum sabbureum, and Lachnoanaerobaculum gingivalis [START_REF] Hedberg | 176 Lachnoanaerobaculum gen. nov., a new genus in the Lachnospiraceae: characterization of 177 Lachnoanaerobaculum umeaense gen. nov., sp. nov., isolated from the human small intestine, and (Prevot 1966) Holdeman and Moore 1970 as Lachnoanaerobaculum saburreum comb[END_REF]. These 32 species were first isolated from the small intestine biopsy of a young girl with celiac disease in 2007, saliva 33 from a healthy young man in 1998, dental plaque from a healthy young man, and human subgingival 34 plaque from a gingivitis lesion in 2019 [START_REF] Okada | First reported case of 182 Lachnoanaerobaculum gingivalis bacteremia in an acute myeloid leukemia patient with oral mucositis 183 during high dose chemotherapy[END_REF]. 35

The genus Lachnoanaerobaculum is present in the human mouth and intestine. With regard to the intestinal 36 microbiota, decrease in the abundance of Lachnoanaerobaculum may be associated with more severe 37 functional constipation [START_REF] Zhang | Fecal Microbiota Transplantation Modulates the Gut Flora 185 Favoring Patients With Functional Constipation[END_REF]. According to the literature, it constitutes a small proportion of the oral 38 microbiome, with total relative abundance of less than 5% [START_REF] Mok | The oral microbiome 188 community variations associated with normal, potentially malignant disorders and malignant lesions of 189 the oral cavity[END_REF]. These bacteria are known to be more 39 numerous in the saliva of smokers and in the intestines of lean people [START_REF] Andoh | Comparison of the gut 191 microbial community between obese and lean peoples using 16S gene sequencing in a Japanese 192 population[END_REF]. In addition, anaerobic 40 bloodstream infections are increasingly recognized as an important sequela of high-dose chemotherapy 41 [START_REF] Lark | Risk factors for 194 anaerobic bloodstream infections in bone marrow transplant recipients[END_REF]. 42

To date, there are few reports in the literature of human infections caused by these microorganisms. In 43 2021, the first case of L. gingivalis bacteremia was reported in a patient with acute myeloid leukemia who 44 presented with oral mucositis during high-dose chemotherapy. The bacterium, identified by 16S rRNA 45 gene analysis, showed sensitivity to a number of drug classes and intermediate sensitivity to moxifloxacin 46 [START_REF] Okada | First reported case of 182 Lachnoanaerobaculum gingivalis bacteremia in an acute myeloid leukemia patient with oral mucositis 183 during high dose chemotherapy[END_REF]. The first case of bacteremia caused by L. oral, identified by MALDI-TOF, was described in a patient 47 with acute lymphocytic leukemia undergoing chemotherapy. The Antibiotic Susceptibility Testing (AST) 48 profile showed sensitivity to anti-microbial therapies (including beta-lactam, clindamycin, and 49 metronidazole). However, it also showed high minimum inhibitory concentration (MIC) values for 50 fluoroquinolones, suggesting possible development of resistance to fluoroquinolones [START_REF] Ida | First description of 197 Lachnoanaerobaculum orale as a possible cause of human bacteremia[END_REF]. 51

Description of the case 52

An 85-year-old man with a history of acute myeloid leukemia was admitted to the emergency room of the 53 Poitiers University Hospital, complaining of gingival pain, loss of appetite and weight [START_REF] Padmakumar | A concise review on the molecular genetics of acute myeloid leukemia[END_REF].

anemia and aplasia for which anti-infective prophylaxis with cotrimoxazole, valaciclovir and 56 posaconazole was initiated. 57 On arrival, he was febrile at 38.7°C and hemodynamically stable with normal vitals (respiratory rate < 58 25/min, blood pressure 111/56 mmHg, GCS 15, oxygen saturation 97%, heart rate 86bpm). Clinical 59 examination was normal, without palpated adenopathy except for the revelation of an intraoral infection. 60

The latter of fungal appearance with a white indurated lesion and ulcerations on the left inner cheek 61 revealed, after biopsy for histologic examination, that the tissue contained numerous actinomycosis grains 62 and was necrotic, without visible structures that were suspect for malignancy. At the time of admission, 63 blood tests showed cytopenia: aplasia (leukocyte count: 1.2 G/l, neutrophil count: 0.02 G/l), anemia 64 (hemoglobin: 7.6 g/dl) without thrombocytopenia (platelet count: 183 G/l), in a context of inflammation 65 (CRP: 72 mg/l). Anaerobic blood cultures became positive after approximately 36 hours of incubation 66 using the BacT/Alert 3D system (bioMerieux, Marcy-l'étoile, France). 67 Direct examination of the blood culture smear showed fine Gram-negative discolored rods (Figure 1 Genetic identification by sequencing of the V1-V3 region of the 16S rDNA was performed (as previously 76 described in [START_REF] Bouguerra | First Bacteremia 203 Due to Corynebacterium gottingense in an Immunocompromised Child: A Case Report, 16S rDNA-Based 204 Phylogenetic Analyses and Review of the Literature[END_REF]) and identified Lachnoanaerobaculum sp. after analysis using NCBI reference sequences 77 (BLASTn) and BIBI-IV [START_REF] Broutin | First description of 207 bacteremia caused by Oscillibacter valericigenes in a patient hospitalized for leg amputation[END_REF]. Finally, a retrospective phylogenetic analysis was performed using Seaview 78 V4 [START_REF] Flandrois | leBIBIQBPP: a set of databases and a webtool for automatic 210 phylogenetic analysis of prokaryotic sequences[END_REF][START_REF] Gouy | SeaView version 4: A multiplatform graphical user interface for 213 sequence alignment and phylogenetic tree building[END_REF][START_REF] Minh | IQ-216 TREE 2: New Models and Efficient Methods for Phylogenetic Inference in the Genomic Era[END_REF][START_REF] Hu | Sequence Similarity Searching[END_REF][START_REF] Cabrol | Phylogeny of Catabacter 221 hongkongensis Strains Responsible for Bacteremia Is Not Associated with Clinical Outcomes or 222 Therapeutic Efficacy[END_REF]. 79

Even before species identification, the drug susceptibility of the isolate was determined using the disk 80 diffusion method according to the CA-SFM recommendations [START_REF]CASFM / EUCAST[END_REF]. It revealed multi-sensitivity to all the 81 antimicrobials tested (co-amoxiclav, piperacillin-tazobactam, imipenem, clindamycin, rifampicin, 82 linezolid, and metronidazole). The MIC values obtained using the Etest (bioMerieux), thereafter were as 83 follows: amoxicillin <0.016mg/l (breakpoint 0.5 mg/l) ciprofloxacin >256mg/l (breakpoint 0.5 mg/l), 84 objectifying the fluoroquinolone resistance described in the literature [START_REF] Ida | First description of 197 Lachnoanaerobaculum orale as a possible cause of human bacteremia[END_REF]. Based on these results, treatment 85 with co-amoxiclav 3 grams and ciprofloxacin 1 gram (to cover possible non-identified pathogen) per day excellent clinical tolerance (apyrexia) and improved biological parameters, including a decrease in C-88 reactive protein, improved leukocyte counts and normalization of ionogram, hepatic, and coagulation 89 assays, the patient was discharged from the hospital. Even though the treatment resulted in apyrexia a 90 few days later, a second episode of infection occurred a week later, without microbial exploration. Indeed, 91 given his poor leukemic prognosis and therapeutic escape, it was collectively decided to stop the 92 treatments (including antibiotics and symptomatic therapy). He died a few weeks later in a context of 93 radiologically suspected invasive pulmonary aspergillosis. 94

The obtained sequence of the bacterial strain (deposited on GenBank under accession number: OR186325) 95 was compared to the sequences published in the literature at the time of writing (June 2023) (Figure 2

.). 96

Evolutionary analyses were performed on 606 informative positions in the final data set in MEGA11 [START_REF] Tamura | MEGA11: Molecular Evolutionary Genetics Analysis Version 11[END_REF]. 97 Sequences were represented according to the origin of the strains. Thirteen sequences isolated from 98 strains of human origin and considered non-pathogenic are shown here. Other sequences from strains 99 isolated of human origin and considered pathogenic (n=11) and from strains isolated of environmental 100 origin (n= 11) are also represented. The trees of these partial 16S rDNA gene sequences were not sufficient 101 to classify these strains according to clinical outcome or bacterial strain origin (p > 0.05). Finally, the 102 present strain revealed significant proximity with non-pathogenic strains of human origin such as L. 103 umeanse [START_REF] Saitou | The neighbor-joining method: a new method for reconstructing phylogenetic 228 trees[END_REF]. 104 sequences from isolated strain of human origin and considered as pathogenic. In green are represented 106 sequences from isolated strain of human origin and considered as non-pathogenic. In blue are represented 107 sequences from isolated strain of environmental origin. The percentage of replicate trees in which the 108 associated taxa clustered together in the bootstrap test (1000 replicates) are shown next to the branches. 109

The evolutionary history was inferred using the Neighbor-Joining method. All ambiguous positions were 110 removed for each pair of sequences (pairwise removal option). The bootstrap consensus tree deduced 111 from 1000 replicates is considered to represent the evolutionary history of the analyzed taxa. The 112 percentage of replicate trees in which the associated taxa clustered in the bootstrap test is indicated next to 113 the branches (only bootstrap values ≥ 70 have been shown).

The genus Lachnoanaerobaculum is a rod-shaped, obligate anaerobic, spore-forming, Gram-positive bacillus 116 that is easily discolored and may appear Gram-negative. For this reason, the initial diagnosis was false, 117 finding a Gram-negative bacterium on direct examination after Gram staining. In addition, the present 118 bacillus has morphological characteristics and culture conditions like those described in previous reports. 119

Quinolone resistance is a growing concern in many bacterial species, including Lachnoanaerobaculum sp., 120 as in the present case. This Gram-positive anaerobic bacterium has recently shown the ability to develop 121 resistance mechanisms against quinolones, which are commonly used antibiotics for bacterial infections. 122

Studies have revealed the emergence of mutations targeting topoisomerase enzymes, the primary targets 123 of quinolones, thereby altering their affinity for the antibiotics. These findings underscore the importance 124 of monitoring and of understanding resistance mechanisms in this bacterial species, the objective being to 125 ensure the ongoing effectiveness of quinolones as therapeutic agents. 126

As mentioned previously and summarized in Table 1., only two reports of bacteremia due to 127 Lachnoanaerobaculum.sp have been described in the literature involving L. gingivalis and L. oral and they 128 occurred in patients with the same condition as this patient [START_REF] Ledger | Historical review of the treatment of bacterial vaginosis[END_REF]20]. Both had been diagnosed with acute 129 myeloid or lymphoid leukemia and were undergoing chemotherapy. However, the patient in the present 130 case was a non-smoker, whereas the patients in the previous reports were smokers. Several studies have 131 suggested that smoking affects the oral microbiome, which may increase the risk of Lachnoanaerobaculum 132 sp. entering the bloodstream from the oral cavity [START_REF] Andoh | Comparison of the gut 191 microbial community between obese and lean peoples using 16S gene sequencing in a Japanese 192 population[END_REF]. This indicates that factors such as smoking history 133 may play a role in the susceptibility to Lachnoanaerobaculum infections in chemotherapy patients. Further 134 research is needed to explore the potential impact of smoking and other host-related factors on the 135 development of Lachnoanaerobaculum infections in this population and its potential association with fungal 136 infection. 137

Table 1. Comparison between the different strains of Lachnoanaerobaculum spp. 138

It should be noted that in this case, contrary to Sanger sequencing of the bacterial 16S rDNA, and due to a 139 lack of library database, MALDI-TOF did not identify the bacterium . Sanger sequencing of 16S rDNA for 140 identification purposes is a valuable approach in characterizing bacterial infections in cases where other 141 methods, such as MALDI-TOF mass spectrometry, have failed to provide accurate identification. Sanger 142 sequencing of 16S rDNA gene offers high resolution and sensitivity, thereby enabling the detection and 143 characterization of bacteria that are not identifiable through other techniques. By employing this 144 approach, clinicians can obtain precise information about the infectious agent, which is essential for 145 guiding appropriate treatment choices. Studies such as Janda and Abbott (2007) have demonstrated the

Figure 1 .

 1 Figure 1. A/Direct microscopic examination of Lachnoanaerobaculum umeaense after Gram staining 73 (x1000 magnification). B/Colonies of Lachnoanaerobaculum umeaense isolated on blood agar. The 74 colonies from subcultures could be considered eroded edge and were not hemolytic. 75

Figure 3 .

 3 Figure 3. Phylogenetic analysis of Lachnoanaerobaculum sp. sequences. In red are represented 105

A/ B/ B.fibrisolvens ATCC19171 (U41172)