Optimized decision algorithm for the microbiological diagnosis of osteoarticular infections in adults using synovial fluid samples: a prospective study in two French hospitals including 423 samples of synovial fluid.

No consensus exists about the techniques to use for microbiological diagnosis of bone and joint infections (BJIs). The objective herein was to define an algorithm to optimize BJI diagnosis in adults using various bacteriological methods on synovial fluid samples. This prospective multi-center study included 423 synovial fluids collected from adult patients with suspected BJIs. Culture (using five solid media, an enrichment broth, and blood culture bottles), universal 16S rRNA PCR followed by Sanger sequencing, and seven specific bacterial PCRs were systematically performed. Combinations of methods were compared to arrive at the optimized algorithm. Among 423 synovial fluids, 242 infections were diagnosed (57.2 %): 213 mono- and 29 poly-microbial for a total of 284 bacteria (staphylococci at 54.6 %, streptococci-enterococci at 16.5 %, Gram-negative bacilli at 15.5 %, anaerobic species at 8.8 %). Comparing culture techniques, blood culture bottles had the highest sensitivity (67.6 % for pediatric and 63.9 % for anaerobic bottles) but are not sufficient alone and require being combined with solid media. The 16S rDNA PCR detected only 52.3 % of the bacteria, whereas specific PCRs had a higher sensitivity (Staphylococcus spp. at 66.2 %, S. aureus at 85.2 %, Streptococcus spp. at 91.2 %). Based on these results, an algorithm was proposed associating three solid media; inoculation into blood culture bottles; and 16S, Staphylococcus spp., and Streptococcus spp. PCRs, which would have detected 90.5 % of bacteria in the present cohort versus 79.2 % using all culture techniques on synovial fluid. This prospective study shows that a combination of culture and molecular methods on synovial fluids allows the optimization of bacterial detection.

Pathogenicity and virulence of Francisella tularensis.

Tularaemia is a zoonotic disease caused by the Gram-negative bacterium, Francisella tularensis. Depending on its entry route into the organism, F. tularensis causes different diseases, ranging from life-threatening pneumonia to less severe ulceroglandular tularaemia. Various strains with different geographical distributions exhibit different levels of virulence. F. tularensis is an intracellular bacterium that replicates primarily in the cytosol of the phagocytes. The main virulence attribute of F. tularensis is the type 6 secretion system (T6SS) and its effectors that promote escape from the phagosome. In addition, F. tularensis has evolved a peculiar envelope that allows it to escape detection by the immune system. In this review, we cover tularaemia, different Francisella strains, and their pathogenicity. We particularly emphasize the intracellular life cycle, associated virulence factors, and metabolic adaptations. Finally, we present how F. tularensis largely escapes immune detection to be one of the most infectious and lethal bacterial pathogens.

Diagnostic performances and therapeutic impact of the Unyvero Implant and Tissue Infection multiplex PCR in periprosthetic joint infections.

Aim: We evaluated the diagnostic performances of Unyvero Implant and Tissue Infection multiplex PCR (mPCR) (Curetis) and the clinical impact of this PCR on therapeutic decisions. Materials & methods: A mPCR was performed on 33 joint fluids in addition to standard culture. A group of experts analyzed a posteriori the impact of the mPCR in the patient management. Results: The rate of concordance with culture was 74% (20/27). The sensitivity of the PCR was 59% and the specificity 90%. Clinicians would have started an appropriate treatment sooner for six patients (from 2 to 22 days earlier). Conclusion: The PCR would improve the management of 22% of the patients. For other patients, mPCR results have to be completed with the culture.

Case Studies and Literature Review of Francisella tularensis-Related Prosthetic Joint Infection.

Tularemia is a zoonotic infection caused by Francisella tularensis. Its most typical manifestations in humans are ulceroglandular and glandular; infections in prosthetic joints are rare. We report 3 cases of F. tularensis subspecies holarctica-related prosthetic joint infection that occurred in France during 2016-2019. We also reviewed relevant literature and found only 5 other cases of Francisella-related prosthetic joint infections worldwide, which we summarized. Among those 8 patients, clinical symptoms appeared 7 days to 19 years after the joint placement and were nonspecific to tularemia. Although positive cultures are typically obtained in only 10% of tularemia cases, strains grew in all 8 of the patients. F. tularensis was initially identified in 2 patients by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry; molecular methods were used for 6 patients. Surgical treatment in conjunction with long-term antimicrobial treatment resulted in favorable outcomes; no relapses were seen after 6 months of follow-up.

Tularemia treatment: experimental and clinical data.

Tularemia is a zoonosis caused by the Gram negative, facultative intracellular bacterium Francisella tularensis. This disease has multiple clinical presentations according to the route of infection, the virulence of the infecting bacterial strain, and the underlying medical condition of infected persons. Systemic infections (e.g., pneumonic and typhoidal form) and complications are rare but may be life threatening. Most people suffer from local infection (e.g., skin ulcer, conjunctivitis, or pharyngitis) with regional lymphadenopathy, which evolve to suppuration in about 30% of patients and a chronic course of infection. Current treatment recommendations have been established to manage acute infections in the context of a biological threat and do not consider the great variability of clinical situations. This review summarizes literature data on antibiotic efficacy against F. tularensis in vitro, in animal models, and in humans. Empirical treatment with beta-lactams, most macrolides, or anti-tuberculosis agents is usually ineffective. The aminoglycosides gentamicin and streptomycin remain the gold standard for severe infections, and the fluoroquinolones and doxycycline for infections of mild severity, although current data indicate the former are usually more effective. However, the antibiotic treatments reported in the literature are highly variable in their composition and duration depending on the clinical manifestations, the age and health status of the patient, the presence of complications, and the evolution of the disease. Many patients received several antibiotics in combination or successively. Whatever the antibiotic treatment administered, variable but high rates of treatment failures and relapses are still observed, especially in patients treated more then 2-3 weeks after disease onset. In these patients, surgical treatment is often necessary for cure, including drainage or removal of suppurative lymph nodes or other infectious foci. It is currently difficult to establish therapeutic recommendations, particularly due to lack of comparative randomized studies. However, we have attempted to summarize current knowledge through proposals for improving tularemia treatment which will have to be discussed by a group of experts. A major factor in improving the prognosis of patients with tularemia is the early administration of appropriate treatment, which requires better medical knowledge and diagnostic strategy of this disease.

Ulceroglandular Infection and Bacteremia Caused by Francisella salimarina in Immunocompromised Patient, France.

Although Francisella tularensis is a well-known, highly virulent bacterium that causes tularemia in humans, other Francisella species have been associated with sporadic human infections. We describe a human cutaneous infection with bacteremia caused by F. salimarina, a Francisella species recently identified from seawater and fishes, in an immunocompromised patient in France.

Reuse of medical face masks in domestic and community settings without sacrificing safety: Ecological and economical lessons from the Covid-19 pandemic.

The need for personal protective equipment increased exponentially in response to the Covid-19 pandemic. To cope with the mask shortage during springtime 2020, a French consortium was created to find ways to reuse medical and respiratory masks in healthcare departments. The consortium addressed the complex context of the balance between cleaning medical masks in a way that maintains their safety and functionality for reuse, with the environmental advantage to manage medical disposable waste despite the current mask designation as single-use by the regulatory frameworks. We report a Workflow that provides a quantitative basis to determine the safety and efficacy of a medical mask that is decontaminated for reuse. The type IIR polypropylene medical masks can be washed up to 10 times, washed 5 times and autoclaved 5 times, or washed then sterilized with radiations or ethylene oxide, without any degradation of their filtration or breathability properties. There is loss of the anti-projection properties. The Workflow rendered the medical masks to comply to the AFNOR S76-001 standard as "type 1 non-sanitory usage masks". This qualification gives a legal status to the Workflow-treated masks and allows recommendation for the reuse of washed medical masks by the general population, with the significant public health advantage of providing better protection than cloth-tissue masks. Additionally, such a legal status provides a basis to perform a clinical trial to test the masks in real conditions, with full compliance with EN 14683 norm, for collective reuse. The rational reuse of medical mask and their end-of-life management is critical, particularly in pandemic periods when decisive turns can be taken. The reuse of masks in the general population, in industries, or in hospitals (but not for surgery) has significant advantages for the management of waste without degrading the safety of individuals wearing reused masks.

Amoebae can promote the survival of Francisella species in the aquatic environment.

Francisella tularensis, a tier 1 select agent, is the causative bacterium of tularemia, a zoonosis with a large animal reservoir. However, F. tularensis, like many other Francisella species, is assumed to have an aquatic reservoir. The mechanisms of Francisella species persistence in surface water remain poorly characterized. In this study, we deeply investigated the long-term interactions of the tularemia agent F. tularensis subsp. holarctica, F. novicida or F. philomiragia with amoebae of the Acanthamoeba species. In amoeba plate screening tests, all the Francisella species tested resisted the attack by amoebae. In in vitro infection models, intra-amoebic growth of Francisella varied according to the involved bacterial species and strains, but also the amoeba culture medium used. In co-culture models, the amoebae favoured Francisella survival over 16 days, which was likely dependent on direct contact between bacteria and amoebae for F. novicida and on amoeba-excreted compounds for F. novicida and for F. tularensis. In a spring water co-culture model, amoebae again enhanced F. novicida survival and preserved bacterial morphology. Overall, our results demonstrate that amoebae likely promote Francisella survival in aquatic environments, including the tularemia agent F. tularensis. However, bacteria-amoebae interactions are complex and depend on the Francisella species considered.

Assessment of Respiratory Bacterial Coinfections Among Severe Acute Respiratory Syndrome Coronavirus 2-Positive Patients Hospitalized in Intensive Care Units Using Conventional Culture and BioFire, FilmArray Pneumonia Panel Plus Assay.

BACKGROUND: Approximately 15% of patients infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) present with severe forms of the disease and require hospitalization in intensive care units, which has been associated with high mortality rates. The prevalence of bacterial infections in these patients is not well established, and more data are needed to guide empiric antibiotic therapy and improve patient outcomes. METHODS: In this prospective multicenter study, we assessed bacterial coinfections identified in culture from 99 French patients infected by SARS-Cov-2 and hospitalized in intensive care units. We concomitantly evaluated an innovative molecular diagnostic technology technique, the BioFire, FilmArray Pneumonia Panel plus (FA-pneumo) assay, to identify these coinfections at an early stage, and its concordance with conventional culture. RESULTS: We showed that a bacterial coinfection was detected in 15% of patients based on conventional culture. Staphylococcus aureus and Haemophilus influenzae were the most prevalent pathogens. The sensitivity of FA-pneumo compared with culture was 100%. In contrast, the specificity varied between 88.4% and 100% according to the pathogen, and our results highlighted that 60.5% of bacterial targets reported using this assay were not recovered by culture; 76.9% of discordant results corresponded to bacteria belonging to commensal oral flora and/or reported with ≤105 copies/mL bacterial nucleic acids. CONCLUSIONS: Based on its excellent sensitivity, the FA-pneumo assay is useful to rule out bacterial coinfections in the context of severe SARS-CoV-2 infection and avoid the inappropriate prescription of antibiotics. However, positive tests should be interpreted carefully, taking into consideration deoxyribonucleic acid bacterial load and all clinical and biological signs.

Risk factors for Staphylococcus aureus surgical site infections after orthopaedic and trauma surgery in a French university hospital.

BACKGROUND: Surgical site infections (SSI) after orthopaedic surgery are responsible for reduced quality of life, increased length of hospital stay and costs. The most commonly identified organism is Staphylococcus aureus but risk factors for S. aureus SSI are not well-known. The aim of this study was to evaluate the incidence rate trend of S. aureus SSI over the years and risk factors of these infections in a French University Hospital. METHODS: SSI rates were expressed as cumulative incidence rates per year. A case-control study nested within a prospective cohort of patients undergoing orthopaedic or trauma surgery from January 1st, 2012 to April 30th, 2015 was performed. Cases were patients with S. aureus SSI; controls were patients without SSI. Risk factors of S. aureus SSI were identified by univariate and multivariable analysis. RESULTS: Of 7438 interventions, 50 (0.7%) S. aureus SSI were identified, without significant increase by years. A total of 46 S. aureus SSI was matched to 91 controls. Risk factors for S. aureus SSI were smoking (odds-ratio (OR) = 8.4, 95%CI 1.2-59.6) and National Nosocomial Infections Surveillance System score (NNISS) ≥1 (OR = 5.8, 95%CI 1.8-19.1). Having 1 or 2 preoperative antiseptic showers (OR = 0.3, 95%CI 0.1-0.7) was a protective factor. CONCLUSION: The rate of S. aureus SSI is not negligible after orthopaedic and trauma surgery. It seems imperative to strengthen smoking cessation recommendations, and to recall the importance of preoperative antiseptic showers. Systematic screening and decolonization for S. aureus carriage before orthopaedic and trauma surgery could be a means to prevent these infections.

Optimized MALDI TOF Mass Spectrometry Identification of Francisella tularensis Subsp. holarctica.

Francisella tularensis is a tier 1 agent causing the zoonosis tularemia. This highly infectious Gram-negative bacterium is occasionally isolated from human samples (especially blood samples) in routine clinical microbiology laboratories. A rapid and accurate method for identifying this pathogen is needed in order to optimize the infected patient's healthcare management and prevent contamination of the laboratory personnel. MALDI TOF mass spectrometry has become the gold standard for the rapid identification of most human pathogens. However, F. tularensis identification using such technology and commercially available databases is currently considered unreliable. Real-time PCR-based methods for rapid detection and accurate identification of F. tularensis are not available in many laboratories. As a national reference center for tularemia, we developed a MALDI TOF database allowing accurate identification of the species F. tularensis and its differentiation from the closely related neighbor species F. tularensis subsp. novicida and F. philomiragia. The sensitivity and specificity of this database were validated by testing 71 F. tularensis strains and 165 strains from 63 species not belonging to the Francisella genus. We obtained accurate identification at the species level and differentiation of all the tested bacterial strains. In particular, F. tularensis could be accurately differentiated from other small Gram-negative bacilli occasionally isolated from human samples, including species of the HACEK group and Brucella melitensis.

Slowly or Nonresolving Legionnaires' Disease: Case Series and Literature Review.

BACKGROUND: Rarely, Legionnaires' disease (LD) can progress into a slowly or nonresolving form. METHODS: A nationwide retrospective study was conducted by the French National Reference Center for Legionella (2013-2017) including cases of slowly or nonresolving LD defined as persistent clinical symptoms, computed tomography (CT) scan abnormalities, and Legionella detection in lower respiratory tract specimens by culture and/or real-time (RT) polymerase chain reaction (PCR) >30 days after symptom onset. RESULTS: Twelve cases of community-acquired slowly or nonresolving LD were identified among 1686 cases of culture-positive LD. Median (interquartile range [IQR]) age was 63 (29-82) years. Ten (83.3%) patients had ≥1 immunosuppressive factor. Clinically, 9 patients transiently recovered before further deterioration (median [IQR] symptom-free interval, 30 [18-55] days), 3 patients had uniformly persistent symptoms (median [IQR] time, 48 [41.5-54] days). Two patients had >2 recurrences. CT scan imagery found lung abscess in 5 (41.6%) cases. Slowly or nonresolving LD was diagnosed on positive Legionella cultures (n = 10, 83.3%) at 49.5 (IQR, 33.7-79) days. Two cases were documented through positive Legionella RT PCR at 52 and 53 days (cycle threshold detection of 21.5 and 33.7, respectively). No genomic microevolution and no Legionella resistance to antibiotics were detected. The median (IQR) duration of treatment was 46.5 (21-92.5) days. Two empyema cases required thoracic surgery. At a median (IQR) follow-up of 26 (14-41.5) months, LD-attributable mortality was 16.6% (n = 2). CONCLUSIONS: Slowly or nonresolving LD may occur in immunocompromised patients, possibly leading to lung abscess and empyema.

Specific PCR and Quantitative Real-Time PCR in Ocular Samples from Acute and Delayed-Onset Postoperative Endophthalmitis.

PURPOSE: Rapid identification of virulent pathogens is essential to strengthen the therapeutic strategy of acute endophthalmitis. OBJECTIVES: This study sought to compare the contribution of a combination of polymerase chain reaction (PCR)-based tests to culture methods, in patients with postoperative endophthalmitis. DESIGN: Prospective multicenter study diagnostic evaluation. METHODS: Setting: university referral centers. PARTICIPANTS: 153 consecutive patients presenting with acute or delayed-onset postoperative endophthalmitis, between 2008 and 2015. There were a total of 284 aqueous humor (AH) and/or vitreous fluid (VF) samples. Outcomes and measurements: microbiological tests of intraocular samples included bacterial culturing of pediatric blood culture bottles; 16SrDNA amplification and sequencing (panbacterial PCR) for detection and identification of all bacterial species; real-time PCR (qPCR) assays targeting the femA or lytA gene for detection of Staphylococcus aureus (S. aureus) or Streptococcus pneumoniae (S. pneumoniae), respectively; and a qPCR assay targeting the tuf gene for detection and quantification of Staphylococcus epidermidis (S. epidermidis). RESULTS: At the time of admission, the rate of detection of microorganisms by PCR-based tests was not significantly different than that by culturing (38% versus 30% in AH samples [n = 69]; 66% versus 63% in VF samples [n = 82], respectively). In contrast, after 1 intravitreal injection (IVI) of antibiotics, the identification rate by PCR-based tests was higher than that in VF by culturing (62% vs 48%, respectively; n = 94; P = 0.05). Bacteria were identified in 70% of patients, with a predominance of Gram-positive bacteria (93%). Specific qPCR tests targeting S. aureus and S. pneumoniae did not provide additional diagnoses but provided earlier results. The S. epidermidis load in vitreous at the time of patients' admission was higher in cases of final visual acuity (VA) of <20/40 (127,118 ± 125,848 DNA copies/mL) in patients with a VA of ≥20/40 (40350,000 ± 46,912 DNA copies/mL; P = 0.09). No significant changes in S. epidermidis load was found after one IVI. CONCLUSIONS: Patients with acute or delayed-onset endophthalmitis should benefit from microbiological identification in vitreous samples by combined analysis using bacterial cultures in pediatric blood culture bottles and panbacterial PCR. The last test was more effective than cultures in vitreous samples collected after an IVI of antibiotics. The qPCR tests targeting S. aureus and S. pneumoniae gave earlier results than culture and panbacterial PCR but did not provide additional diagnoses. As for S. epidermidis infections, determination of bacterial load using the qPCR test targeting the tuf gene could help evaluation of the visual prognosis of patients. Its role in the follow-up of patients after antibiotic treatment needs further investigation.

Unexpected categories at risk of S. aureus nasal carriage among hospital workers.

OBJECTIVES: Thirty percent of the general population are Staphylococcus aureus nasal carriers. It has been shown that this increases with repeated contact with patients, but it is not known whether all categories of healthcare workers are at equal risk of carriage. We aimed to explore S. aureus nasal carriage among healthcare professionals. METHODS: Prospective study conducted in two French university hospitals in 2014 and 2016. Volunteers were screened for S. aureus nasal carriage. Profession and hygiene habits were collected. Based on the results of this initial study, a second study focused on semi-skilled workers and biomedical equipment technicians (BETs) only; participants were given education on the basic rules of hygiene, then re-screened three months later. RESULTS: In the initial study, 38.8% of the 436 participants were detected as nasal carriers. There was a significant difference in nasal carriage according to professional category (p < 0.0001); the lowest was found among administrative agents (17.3%), followed by healthcare providers (37.4%), laboratory technicians (37.6%). The greatest proportion was found among semi-skilled workers and BETs (52.9%). Spa-typing ruled out the hypothesis of a single clone dissemination among colleagues. After the three-month hygiene awareness campaign, all re-screened individuals remained positive, and with their respective initial strain. CONCLUSIONS: To the best of our knowledge we report here for the first time that semi-skilled workers and BETs are specifically more at risk of S. aureus nasal colonisation. This striking finding urges hospital hygiene departments to evaluate this specific professional category and implement strategies to improve hygiene awareness.

Tularemia as a waterborne disease: a review.

Francisella tularensis is a Gram-negative, intracellular bacterium causing the zoonosis tularemia. This highly infectious microorganism is considered a potential biological threat agent. Humans are usually infected through direct contact with the animal reservoir and tick bites. However, tularemia cases also occur after contact with a contaminated hydro-telluric environment. Water-borne tularemia outbreaks and sporadic cases have occurred worldwide in the last decades, with specific clinical and epidemiological traits. These infections represent a major public health and military challenge. Human contaminations have occurred through consumption or use of F. tularensis-contaminated water, and various aquatic activities such as swimming, canyoning and fishing. In addition, in Sweden and Finland, mosquitoes are primary vectors of tularemia due to infection of mosquito larvae in contaminated aquatic environments. The mechanisms of F. tularensis survival in water may include the formation of biofilms, interactions with free-living amoebae, and the transition to a 'viable but nonculturable' state, but the relative contribution of these possible mechanisms remains unknown. Many new aquatic species of Francisella have been characterized in recent years. F. tularensis likely shares with these species an ability of long-term survival in the aquatic environment, which has to be considered in terms of tularemia surveillance and control.

Francisella tularensis: FupA mutation contributes to fluoroquinolone resistance by increasing vesicle secretion and biofilm formation.

Francisella tularensis is the causative agent in tularemia for which the high prevalence of treatment failure and relapse is a major concern. Directed-evolution experiments revealed that acquisition of fluoroquinolone (FQ) resistance was linked to factors in addition to mutations in DNA gyrase. Here, using F. tularensis live vaccine strain (LVS) as a model, we demonstrated that FupA/B (Fer-Utilization Protein) expression is linked to FQ susceptibility, and that the virulent strain F. tularensis subsp. tularensis SCHU S4 deleted for the homologous FupA protein exhibited even higher FQ resistance. In addition to an increased FQ minimal inhibitory concentration, LVSΔfupA/B displayed tolerance toward bactericidal compounds including ciprofloxacin and gentamicin. Interestingly, the FupA/B deletion was found to promote increased secretion of outer membrane vesicles (OMVs). Mass spectrometry-based quantitative proteomic characterization of vesicles from LVS and LVS∆fupA/B identified 801 proteins, including a subset of 23 proteins exhibiting differential abundance between both strains which may therefore contribute to the reduced antibiotic susceptibility of the FupA/B-deleted strain. We also demonstrated that OMVs are key structural elements of LVSΔfupA/B biofilms providing protection against FQ. These results provide a new basis for understanding and tackling antibiotic resistance and/or persistence of Francisella and other pathogenic members of the Thiotrichales class.

High prevalence of spa type t571 among methicillin-susceptible Staphylococcus aureus from bacteremic patients in a French University Hospital.

Staphylococcus aureus bacteremia is one of the most frequent severe bacterial infections worldwide, with an associated mortality of about 20-40% in developed countries. In 2013, we noted an increase in this infection in the teaching hospital in Grenoble, France, compared to 2012. The mean incidence of S. aureus bacteremia was 0.28 per 1,000 patient-days in 2012 and 0.35 per 1,000 patient-days in 2013. This trend was confirmed in 2014 (0.35 per 1,000 patient-days). In the present work we aimed to study the population of patients presenting with S. aureus bacteremia in 2013 and to genotype the corresponding S. aureus strains in order to identify a successful and/or virulent genotype to design a specific infection control program. One hundred ninety-one S. aureus isolates (including 9 methicillin-resistant) out of 199 corresponding cases of bacteremia were characterized with the spa typing method. Among 108 spa types, t571, t002, t008 and t084 were the most prevalent. Although not widely prevalent, t571 was the most frequently identified clone (8.4% of all isolates). Spa type t571 has been described in previous studies as belonging to the clonal complex CC398, which is consistent with the recent emergence of methicillin-susceptible S. aureus CC398 reported in blood cultures in Europe.

Changing patterns of human migrations shaped the global population structure of Mycobacterium tuberculosis in France.

Mycobacterium tuberculosis (Mtb) exhibits a structured phylogeographic distribution worldwide linked with human migrations. We sought to infer how the interactions between distinct human populations shape the global population structure of Mtb on a regional scale. We applied the recently described timescaled haplotypic density (THD) technique on 638 minisatellite-based Mtb genotypes from French tuberculosis patients. THD with a long-term (200 y) timescale indicated that Mtb population in France had been mostly influenced by interactions with Eastern and Southern Europe and, to a lesser extent, Northern and Middle Africa, consistent with historical migrations favored by geographic proximity or commercial exchanges with former French colonies. Restricting the timescale to 20 y, THD identified a sustained influence of Northern Africa, but not Europe where tuberculosis incidence decreased sharply. Evolving interactions between human populations, thus, measurably influence the local population structure of Mtb. Relevant information on such interactions can be inferred using THD from Mtb genotypes.

Genetic and Phenotypic Traits of Staphylococcus Epidermidis Strains Causing Postcataract Endophthalmitis Compared to Commensal Conjunctival Flora.

PURPOSE: The aim of this study was to compare the virulence and antibiotic resistance traits of Staphylococcus epidermidis strains causing acute postcataract endophthalmitis to those isolated from the conjunctiva of uninfected control patients. DESIGN: Case-control study. METHODS: We isolated an S epidermidis strain from each of the 22 endophthalmitis patients, and from 43 of the 72 controls. Species identification was confirmed using both Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry and tuf gene amplification and sequencing. Antibiotic susceptibilities were evaluated using the AST-P631 card and the Vitek II automated system. The S epidermidis strains were tested for the presence of 7 virulence genes (icaA, icaB, icaC, icaD, atlE, aap, and capA), the insertion sequence IS256, and the mecA gene. RESULTS: The S epidermidis strains from the endophthalmitis patients displayed higher prevalence rates for aap, atlE, and mecA gene carriage compared to those of the control group (77% vs 42%, P = .007; 100% vs 79%, P = .02; and 54% vs 11%, P < .001, respectively). They also harbored the combination of the mecA and icaA genes more frequently compared to the control group (13% vs 2%, P = .01). They were significantly more resistant than control strains to methicillin, fluoroquinolones, and the aminoglycosides. CONCLUSIONS: A higher capacity of adhesion to the intraocular lens and formation of biofilms as well as greater resistance to antibiotics were found in S epidermidis strains causing postcataract endophthalmitis. The usefulness of such virulence and antibiotic resistance markers warrants further evaluation for prevention, treatment, and prognostic evaluation of S epidermidis endophthalmitis.