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Introduction : The incidence of ventilator associated pneumonia due to Stenotrophomonas maltophilia (SM-VAP) is increasing. This pathology is related with an increase in mortality and morbidity in intensive care, in particular due to unsuitable probabilist antibiotherapy and intrinsic resistance of this bacteria. The aim of this study was to identify risk factors for developping a first episod of SM-VAP, in order to adapt probabilist antibiotherapy as early as possible.Materials and methods : This is a retrospective monocentric study, carried out between 2010 and 2018 in a general intensive care unit (ICU) in the University Hospital of Réunion Island, France. All consecutive patients with a first episod of VAP were included. Patients with SM-VAP and patients with VAP due to other germs were comparated.Results : 89 patients developped a SM-VAP among which 43.8% were polymicrobial. Mortality in ICU was 49,4%. Multivariate logistic regression analysis found that risk factors for developping a first episod of SM-VAP were : chronic respiratory failure (OR4.212 ; CI95% : 1.776 – 9.989 ; p=0.001), chronic kidney failure (OR 2.693 ; CI95% : 1.356 – 5.352 ; p=0.005), prior exposure to third generation cephalosporins active on Pseudomonas Aeruginosa (OR 2.862 ; CI95% : 1.505 – 5.442 ; p = 0.001) and female gender (OR 2.646 ; CI95% : 1.458 – 4.808 ; p = 0.001).Conclusion : In our study, chronic respiratory and kidney failure, prior exposure to third generation cephalosporins active on Pseudomonas aeruginosa and female gender were identify as risk factors for developping a first episod of SM-VAP.; Introduction: L’incidence des pneumopathies acquises sous ventilation mécanique (PAVM) à Stenotrophomonas maltophilia (SM) est en augmentation. Cette pathologie est associée à une augmentation de la morbi-mortalité en réanimation notamment du fait d’une antibiothérapie probabiliste inadaptée et des résistances intrinsèques de ce germe. Le but de cette étude était de déterminer les facteurs de risque de survenue d’un premier épisode de PAVM à SM. Méthode: Etude rétrospective monocentrique réalisée de 2010 à 2018 dans une réanimation polyvalente du CHU de La Réunion. Ont été comparés les patients présentant un premier épisode de PAVM documenté à SM à ceux présentant un premier épisode de PAVM à un autre germe. Résultats: Pendant la période 89 patients ont développé une première PAVM à SM dont 43.8% étaient polymicrobiennes. La mortalité en réanimation était de 49.4%. Après analyse multivariée par régression logistique les facteurs de risque de survenue d’une première PAVM à SM étaient : l’insuffisance respiratoire chronique (OR 4.212 ; IC à 95% : 1.776 – 9.989 ; p = 0.001), l’insuffisance rénale chronique (OR 2.693 ; IC à 95% : 1.356 – 5.352 ; p = 0.005), l’exposition préalable aux céphalosporines de troisième génération actives sur Pseudomonas aeruginosa (OR 2.862 ; IC à 95% : 1.505 – 5.442 ; p = 0.001) et le sexe féminin (OR 2.646 ; IC à 95% : 1.458 – 4.808 ; p = 0.001). Conclusion: L’insuffisance respiratoire et rénale chronique, l’exposition préalable aux céphalosporines de troisième génération actives sur Pseudomonas aeruginosa et le sexe féminin ont été identifiés comme facteurs de risque de développer un premier épisode de PAVM à SM.

Aspergillus fumigatus (Af, filamentous fungus) and Stenotrophomonas maltophilia (Sm, Gram-negative bacillus) can colonize the respiratory tract of cystic fibrosis patients. These pathogens can form biofilms, a mode of growth that confers some advantages, including a lower antimicrobial susceptibility. An in vitro mixed model biofilm developed in our laboratory describes an antagonism effect of Sm on Af using a couple of clinical reference strains. The first part of this thesis allowed the analysis of mixed biofilm formation using Sm strains from diverse origins in order to investigate whether this antagonism is strain-dependent. Only some clinical strains of Sm can induce an antagonism on Af after 24 h of co-culture at 37°C. The second part of this thesis was to evaluate the antimicrobial susceptibility of single and mixed biofilms by colorimetric, culture and qPCR methods. Our results show that direct contact of Sm increases the Af susceptibility to amphotericin B. On the other hand, Af improves the tolerance to levofloxacin and rifampicin of Sm. This tolerance seems to depend on the fungal biomass, which rely on the degree of antagonism generated by the bacterium. Antifungal-antibacterial combinations were efficient against mixed biofilm, highlighting the importance of microbial interactions to treat biofilms. This thesis work provides new data on the interactions and susceptibility of a filamentous fungal-bacterial biofilm, a field of research that remains little studied., Aspergillus fumigatus (Af, champignon filamenteux) et Stenotrophomonas maltophilia (Sm, bacille à Gram négatif) peuvent coloniser le tractus respiratoire des patients atteints de mucoviscidose. Ces pathogènes peuvent former des biofilms, un mode de vie conférant certains avantages, notamment une diminution de la sensibilité aux traitements. Un modèle in vitro de biofilm mixte développé dans notre laboratoire décrit un antagonisme de Sm sur Af avec un couple de souches cliniques de référence. La première partie de cette thèse a permis d'analyser la formation du biofilm mixte avec des souches de Sm de différentes origines afin de rechercher si cet antagonisme est souche-dépendante. Seules certaines souches cliniques de Sm peuvent induire un antagonisme sur Af après 24 h de co-culture à 37°C. La deuxième partie de cette thèse consistait à évaluer la sensibilité aux antimicrobiens des biofilms simples et mixtes par des méthodes colorimétriques, de culture et par qPCR. Nos résultats montrent que le contact direct de Sm augmente la sensibilité à l'amphotéricine B d'Af. En revanche, Af améliore la tolérance à la lévofloxacine et à la rifampicine de Sm. Cette tolérance semble dépendre de la biomasse fongique elle-même dépendante du degré d’antagonisme généré par la bactérie. Nos essais d’association d'antifongique-antibiotique ont été efficaces contre le biofilm mixte, mettant en lumière l'importance des interactions microbiennes dans la lutte contre les biofilms. Ce travail de thèse vient donc enrichir les données de la littérature sur les interactions et la sensibilité d’un biofilm champignon filamenteux-bactérie, un domaine de recherche qui reste peu étudié.

INTRODUCTION : Les pneumopathies nosocomiales causées par la bactérie Stenotrophomonas maltophilia (Sm) sont rares et sont observées principalement dans les services de réanimation. Peu d'études se sont intéressées à ce type de pneumopathie et les différentes modalités de prise en charge restent très débattues. Les objectifs de cette étude consistaient à évaluer les caractéristiques et les incidences des pneumopathies à Sm contractées à l'hôpital, et plus particulièrement l'efficacité de l'antibiothérapie et de la bithérapie dans la survie des patients. MÉTHODE : Cette étude rétrospective d'observation multicentrique régionale comprenait des patients admis dans les services de réanimation de la région Lorraine qui répondaient aux critères cliniques et microbiologiques de pneumonie Sm (étude Retrosteno). Nous avons recueilli des données démographiques, microbiologiques et de pronostic, et nous avons étudié les différents facteurs de risque de mortalité liés à ces pneumonies. Le critère principal était la mortalité à l'hôpital. Des analyses descriptives et des analyses univariées et multivariées ont été effectuées. RÉSULTATS : Parmi les 70 patients inclus, le score médian IGS et le score SOFA étaient respectivement de 53 [intervalle interquartile (IQR) 40-66] et 8[6-11], avec une durée médiane de séjour en soins intensifs de 29 jours [16-52] et une mortalité de 44%. Soixantequatorze pour cent des pneumopathies étaient des pneumopathies acquises sous ventilation mécanique (PAVM) et 54% de ces pneumopathies étaient polymicrobiennes. Seulement 17% des antibiothérapies probabilistes étaient efficaces sur Sm. Dans l'analyse univariée, les facteurs de risque associés à la mortalité étaient l'âge (p

Stenotrophomonas maltophilia and Acinetobacter baumannii are both non-fermenting ubiquitous Gram-negative bacilli. The incidence of lower respiratory tract infections related to these microorganisms is increasing, especially in intensive care units. Their capacity to acquire resistance against several antimicrobials is challenging for clinicians and microbiologists. Despite their low virulence, these pathogens are responsible for colonization and infection in patients with comorbidities, immunosuppression, and critically ill patients. S. maltophilia and A. baumannii are mainly identified in nosocomial infections: ventilator-associated pneumonia, bacteremia and surgical wound infection. Infections related to these microorganism are associated with high mortality and morbidity. Trimethoprime-sulfamethoxazole and carbapenem are the first line treatment for infections related to S. maltophilia and A. baumannii respectively. However, the increasing rate of resistance against these agents results in difficulties in treating patients with infections related to these pathogens. New antimicrobial agents and further randomized studies are needed to improve the treatment of these infections. Prevention of spared of these multidrug-resistant bacteria is mandatory, including hand-hygiene, environment cleaning, and limited usage of large spectrum antibiotics.

Stenotrophomonas maltophilia (S.M.) is a Gram-negative bacillus, naturally resistant to cephalosporins and carbapenems, which can colonize different sites and may be responsible for serious infections for which treatment is a real challenge. We report 2 cases of nosocomial S.M. infection in 2 hospitalized newborns in the neonatal intensive care unit. CASE 1: A 3-day-old newborn presented with infection beginning in the respiratory system, treated with ciprofloxacin, and complicated by septicemia, resulting in death. CASE 2: An 11-day-old newborn presented with brain S.M. suppuration: empyema and multiple abscesses were treated successfully with the combination of amikacin and chloramphenicol with good progression in the short and medium terms.Some epidemiological studies report that S.M. is the second Gram-negative bacillus responsible for nosocomial infection after Klebsiella pneumoniae. While the respiratory location of the bacterium is typical, cerebral parenchyma damage is rare in the newborn. The treatment remains very delicate and difficult because of this bacterium's drug multiresistance.These 2 cases of infection caused by S.M. including respiratory tract infection with bacteremia and cerebral suppuration in newborns have broadened the spectrum of diseases caused by this organism and are a reminder of the emergence of this organism and its natural resistance to several antibiotics.

Pseudomonas aeruginosa and Stenotrophomonas maltophilia, two major opportunistic pathogens, could acquire antibiotic resistance in the environment under heavy metal pressure that co-selects both resistances. We first investigated the distribution and abundance of these species in a wide range of soils of different geographical origin (France and Africa) and evaluated the influence of human activities that may expose soils to metallic elements on this distribution. While the presence of P. aeruginosa is rather sporadic and could be linked to exogenous intake, S. maltophilia is present in all studied soils, that suggests its endemicity. Evaluating resistance capacities of strains isolated from these soils also showed differences between the two species. Environmental strains of P. aeruginosa are mostly characterized by a wild type phenotype, whereas those of S. maltophilia present a wide diversity of phenotypes depending on the site, sometimes similar to those of clinical strains. This diversity could be attributed to a deep adaptation to the very different environmental conditions encountered in the original niche but it is difficult to attribute specifically to metals a role in coselection of resistance. The study conducted on the bacterial community present in a contaminated soil has also highlighted a high proportion of bacteria resistant to different antibiotics represented by species qualified as opportunistic pathogens and the presence of the gene blaIMP, enabling resistance to imipenem, used in the hospital to treat infections due to multidrug-resistant clones.; Pseudomonas aeruginosa et Stenotrophomonas maltophilia, pathogènes opportunistes majeurs, pourraient acquérir leur résistance aux antibiotiques dans l’environnement, sous la pression exercée par les métaux lourds par co-sélection de résistance. Nous avons tout d’abord évalué la distribution et l’abondance de ces espèces dans un large panel de sols d’origine géographique différente (France et Afrique) et évalué l’influence d’activités anthropiques susceptibles d’exposer les sols en éléments métalliques sur cette distribution. Alors que la présence de P. aeruginosa est sporadique et plutôt liée à un apport exogène, S. maltophilia est présente dans tous les sols étudiés, suggérant son endémicité. L’évaluation des résistances des souches isolées de ces sols a également montré des différences entre les deux espèces. Les souches environnementales de P. aeruginosa sont pour la plupart caractérisées par un phénotype sauvage alors que celles de S. maltophilia présentent une grande diversité de phénotypes en fonction des sites, parfois similaires à ceux de souches cliniques. Cette diversité peut être attribuée à l’adaptation aux conditions environnementales très différentes rencontrées mais il est difficile d‘attribuer précisément aux métaux un rôle dans la co-sélection de ces résistances. L’étude menée sur la communauté bactérienne d’un sol contaminé a également permis de mettre en évidence une forte proportion de bactéries résistantes à différents antibiotiques représentée par des espèces qualifiées de pathogènes opportunistes ainsi que la présence du gène blaIMP, permettant la résistance à l’imipénème, utilisé en milieu clinique pour le traitement de clones multi-résistants.

Stenotrophomonas maltophilia (Smalto) is a prominent nosocomial pathogen, commonly isolated in the hospital environment. Multiple Smalto nosocomial outbreaks have been linked to contaminated water sources. This study aimed to develop a medium able to ease healthcare environment Smalto isolation.Financed, from March 2007 to June 2008, by a university hospital of Amiens' clinical research program, this study allowed Stenotrophomonas maltophilia selective medium with coloured indicator (SM2i) development. SM2i is constituted of Mueller Hinton agar (MH), maltose, DL-methionine, bromothymol blue. The mixture sterilized is refreshed at 50 degrees C, its pH adjusted to 7.1, and render selective by addition of vancomycin, imipenem and amphotericin B. Then, SM2i agar is sunk into 90 cm diameter Petri dish dated and stored at 4 degrees C for 4 weeks. SM2i is developed using Pasteur Institute culture type collection (CIP) strains of Smalto, Burkholderia cepacia, Pseudomonas aeruginosa (Psa) and a Smalto strain of our hygiene laboratory collection. It was validate on Psa imipenem-resistant and Enterococcus faecium vancomycin-resistant strains, then, tested on cold water first jet and faucet cotton-swabs samples. SM2i tests were made in comparison with the MH agar, MH agar plus four paper disks loaded 10 microg of imipenem and Cetrimed agar. Its sensitivity, specificity, positive (PPV) and negative (NPV) predictive values, accuracy, likehood-ratio (LR) and Youden index have been determined.SM2i agar is better in culturing Smalto test-strains. On SM2i, Smalto colonies are smooth, round, greeny, olive or lime green, have a green olive centre with a peripheral lighter or a dark green centre with an olive green suburb surrounded by a blue halo. SM2i is a selective, specific, predictive, accurate medium to search for Smalto in healthcare environment. In 122 pairs of cold water first jet and taps cotton-swabs samples, Smalto was isolated from 14.8% of water samples, 10.7% of cotton-swabs samples. It was isolated alone in 6.6% of water samples and 2.5% of swab samples. Thus, smalto has biocontaminated 17.2% of cold water taps. Compared to MH agar, SM2i sensitivity, specificity, PPV, NPV, accuracy, LR were 100, 100, 100, 100, 100% and infinity, and 87.5, 100, 100, 98.1, 98.4% and infinity for water and cotton-swabs samples respectively.SM2i is a selective, specific, predictive medium which can allow easily isolating and identifying accurately Smalto in environmental samples. Its evaluation on clinical samples is on going.

Pseudomonas aeruginosa (Psa) and Stenotrophomonas maltophilia (Smalto) are major opportunistic waterborne pathogens causing hospital-acquired infections. This study aimed to assess the biocontamination level of cold water used in Amiens' university hospital wards, from March to June 2008.We cultivated 122 pairs of cold water first jet and taps cotton-swabs on Cetrimide agar for Psa, on Stenotrophomonas maltophilia selective medium with coloured indicator (SM2i) for Smalto, on Mueller Hinton agar used as isolation medium reference for both, 48h at 30 degrees C. Data analysed with Epi-Info 6.04dFr were compared with chi(2) test, significant at p.05.Psa and Smalto were isolated in 26.2 and 14.8% of water samples and in 21.3 and 10.7% of swab samples respectively. They were associated in 11.5% of water samples and 5% of swab samples. Psa was alone in 13.1% of water samples and 7.4% of swab samples whereas Smalto was found in 6.6% of water and 2.5% of swabs. Psa and Smalto were isolated from 14.8% of water samples and 8.2% of swab samples of the same tap. Finally, respectively 35.2 and 17.2% of the cold water taps were biocontaminated by Psa and Smalto. In fact, microbiologic water taps contamination risk was two-fold higher for Psa than for Smalto, p.001, without variation between wards.Sm2i and Cetrimide are suited and efficient medium respectively for Smalto and Psa isolation. Cold-water samples are sufficient for waterborne pathogens biocontamination risk appraisal. Our results urged healthcare workers on efficient water fittings microbiologic risk control to prevent healthcare associated waterborne infections, notably due to Psa and Smalto.

To study the beta-lactamases content of Stenotrophomonas maltophilia strains and to evaluate the virulence potential of these strains with the in vivo Caenorhabditis elegans model.From 1st January 2006 to 31st December 2006, a monitoring programme to study multidrug resistant Gram-negative bacteria including extended-spectrum beta-lactamases (ESBL)-producing S. maltophilia was conducted at Nîmes University Hospital and Perpignan Hospital. The ESBL production was confirmed by the double-disk synergy test using ceftazidime, cefotaxime and cefepime disks associated with clavulanic acid disk. The strains were characterized phenotypically (beta-lactamase[s] identification) and genotypically (pulsed-field gel electrophoresis, plasmid analysis) and evaluated for their virulence with the in vivo nematode C. elegans model (establishment of survival curves [LT50]).Twelve ESBL-producing S. maltophilia strains were isolated in eight patients (median age: 65 years+/-19) mainly during skin infections (41.7%). The ESBL content revealed the presence of four CTX-M-15-producing strains at the same patient. The analysis by ECP confirmed that the four strains were identical. The plasmid analysis demonstrated that the plasmid carrying CTX-M-15 in the worldwide clonal Escherichia coli O25-ST131 strain and S. maltophilia were different. The C. elegans model confirmed that S. maltophilia strains presented a low virulence potential (LT50=4.5days+/-0.5 according to the strains and nematode death in 10days+/-1) whatever their resistance.For the first time in France, a CTX-M-15-producing S. maltophilia strain has been identified. The in vivo model confirmed that these bacteria have a low potential virulence. However, these strains were isolated from "immunocompromised" and multihospital patients demonstrating the necessary monitoring of these patients. The CTX-M after diffusing in hospitals and community in E. coli strains seem to spread in other Gram-negative bacteria.

Since nonfermenting, Gram negative bacilli recovered from patients with cystic fibrosis could be misidentified with phenotypic procedures, we used partial 16S ribosomal RNA gene (16S gene) sequencing to identify these "Pseudomonas-like" isolates. 473 isolates were recovered from 66 patients in 2003. Sequencing was used to identify 29 (from 24 patients) of the 473 isolates, showing unclear results with routine tests. PCR with specific primers was carried out to amplify a 995 bp fragment, which was then sequenced. The sequences were analyzed with GenBank database for species assignment. Phenotypic and genotypic results were concordant for 20/29 isolates (10 Pseudomonas aeruginosa, 5 Burkholderia cepacia, 3 Stenotrophomonas maltophilia, 2 Achromobacter xylosoxidans). However, 3 of the 5 B. cepacia isolates were then identified as Burkholderia multivorans with a PCR-RFLP procedure. Phenotypic misidentification was observed for 9/29 isolates: 4 A. xylosoxidans, 1 P. aeruginosa, 1 Bordetella petrii, 1 Bordetella bronchiseptica, 1 Ralstonia respiraculi and 1 Ralstonia mannitolilytica. Partial 16S gene sequencing improved the identification of "Pseudomonas-like" isolates from cystic fibrosis patients, but the accuracy to distinguish between genomovars of the B. cepacia complex was inadequate.

Non-fermentative Gram negative rods are opportunistic pathogens responsible for nosocomial infections. Using phenotypic markers (serotypes for Pseudomonas aeruginosa and antibiotic susceptibility) allows a preliminary screening of epidemiologically-related strains. However, genotypic markers are necessary to better characterize nosocomial strains for the investigation of outbreaks or cross-transmissions in the hospital setting. Infections due to P. aeruginosa, Burkholderia. cepacia or Stenotrophomonas. maltophilia are usually hospital-acquired and responsible for a high mortality rate as illustrated by the lethality of nosocomial pneumonia due to P. aeruginosa. The severity of these infections is due to the virulence factors of the bacteria and to their occurrence in debilitated patients in whom invasives devices are used. The hospital environment can act as a reservoir with a rate of exogeneous transmission of these bacteria as high as 50% in some studies. To better prevent nosocomial infections related to Gram negative non fermentative rods, the control of the aqueous hospital environment, the strict application of hand disinfection and the investigation of potential cross-transmission in the hospital setting are needed.

Stenotrophomonas maltophilia is a Gram negative, opportunistic bacteria. We describe a case of community-acquired superficial pyoderma due to this bacteria in a immunocompetent host.A 59-year-old man presented with an ulceration of the sole for two months. Several topical and systemic treatments had failed to cure the lesion, including oral ofloxacin for ten days. Microbiological study of the lesion showed numerous Gram negative bacilli with growth of S. maltophilia. This bacterium initially responded to ofloxacin, but became resistant after the oral use of this antibiotic. Finally, a topical treatment with polymyxin/tetracycline ointment resulted in complete healing within two weeks.S. maltophilia may be responsible for superficial pyoderma and serious opportunistic infections in immunocompetent persons. Topical antimicrobial therapy is efficient when oral quinolone therapy has failed to cure the lesion.

Platelet concentrates contaminated with bacteria are a main source of transfusion-associated sepsis. Several studies have reported a very wide incidence (0-10%) of contamination. The aim of this study is to assess the prevalence of bacterial contamination of standard platelet units at the regional blood transfusion center in Casablanca.During 15.5 months, 3,458 platelet concentrates (PCs) were analysed. The plasma from the bag and the tube was homogenised. One-fifth of the tube contents were inoculated every day for five days in two tubes containing 2.5 mL of Tryptic soy broth. One tube was incubated at room temperature and the other at 37 degrees C for 24 hours. The bacteria were identified by standard procedures.Twenty-five (0.72%) of 3,458 platelet bags were contaminated. Twenty-two bacteria (88%) were found in the platelet bags stored three days or more, of which 14 (56%) were Staphylococci coagulase negative, two Staphylococcus aureus, one alpha-haemolytic Streptococcus, four bacillus cereus, one Enterobacter cloacae, one Escherichia Coli and two Xanthomonas maltophilia.The incidence reported in this series is higher than that reported by most authors.

The authors report the first case of early postoperative endocarditis after mitral valvuloplasty due to Stenotrophomonas Maltophilia, a Gram negative organism, in a 37 year old man with no special risk factors. Pyrexia and mitral valve vegetations were the main features, and, in the absence of complications or of embolism, the patient was treated initially with triple antibiotherapy (ceftazidime, amikacine, ciprofloxacine). Relapse two weeks after withdrawal of treatment due to two variants of Stenotrophomas Maltophilia, one of which was resistant to ciprofloxacine, and the presence of a large vegetation, required repeat mitral valvuloplasty and a change in antibiotic therapy (ticarcilline with clavulanic acid, trimethoprim sulphamethoxazole, colistine). This time, the outcome was good. The little known Stenotrophomonas Maltophilia infectious endocarditis is a serious complication and, in the absence of standardised management, the authors suggest that, in view of the multi-resistant character of the organism and in the light of this case, surgery should be considered in association with prolonged antibiotic therapy.