Staphylococcus capitis: insights into epidemiology, virulence, and antimicrobial resistance of a clinically relevant bacterial species.

SUMMARYStaphylococcus capitis is divided into two subspecies, S. capitis subsp. ureolyticus (renamed urealyticus in 1992; ATCC 49326) and S. capitis subsp. capitis (ATCC 27840), and fits with the archetype of clinically relevant coagulase-negative staphylococci (CoNS). S. capitis is a commensal bacterium of the skin in humans, which must be considered an opportunistic pathogen of interest particularly as soon as it is identified in a clinically relevant specimen from an immunocompromised patient. Several studies have highlighted the potential determinants underlying S. capitis pathogenicity, resistance profiles, and virulence factors. In addition, mobile genetic element acquisitions and mutations contribute to S. capitis genome adaptation to its environment. Over the past decades, antibiotic resistance has been identified for S. capitis in almost all the families of the currently available antibiotics and is related to the emergence of multidrug-resistant clones of high clinical significance. The present review summarizes the current knowledge concerning the taxonomic position of S. capitis among staphylococci, the involvement of this species in human colonization and diseases, the virulence factors supporting its pathogenicity, and the phenotypic and genomic antimicrobial resistance profiles of this species.

Persistent microbial contamination of incubators despite disinfection.

BACKGROUND: In neonatal intensive care units (NICUs), hygiene and disinfection measures are pivotal to protect neonates from nosocomial infections. This study aimed to evaluate the efficacy of the classical incubators disinfection procedure and to follow-up neonates housed in the incubators for the development of late-onset sepsis (LOS). METHODS: In a tertiary NICU, 20 incubators were monitored for bacterial contamination at three times: before disinfection, after disinfection, and 24 h after turning on and housing a new neonate. Clinical data of neonates housed in these incubators were retrieved from the medical records. RESULTS: All 20 incubators were contaminated at the 3 times of the study, mainly on mattresses and balances. Coagulase-negative Staphylococci, Enterococcus, and Bacillus-resisted disinfection while enterobacteria and Staphylococcus aureus were eradicated. After 24 h, the bacterial colonisation was similar to the one observed before disinfection. The bacteria isolated on incubators were also found on the caregivers' hands. During the study, two preterm neonates developed a LOS involving a bacterial species that has been previously isolated in their incubator. CONCLUSION: Pathogenic contaminants persist on incubators despite disinfection and represent a risk for subsequent infection in preterm neonates. Improvements are needed concerning both the disinfection process and incubator design. IMPACT: Procedures of disinfection that are usually recommended in NICUs do not allow for totally eradicating bacteria from incubators. Preterm neonates are housed in incubators colonised with potentially pathogenic bacteria. The control of nosocomial infections in NICUs requires further researches concerning mechanisms of bacterial persistence and ways to fight against environmental colonisation.

Disinfection of incubators in neonatal intensive care units: impact of steam pulverization on bacterial colonization.

BACKGROUND: In neonatal intensive care units (NICUs), neonates requiring medical care after birth, including very vulnerable preterm infants, are housed in incubators. Previous studies have reported that the standard chemical disinfection measures used to disinfect these incubators are insufficient to eradicate contaminating bacteria, leading to a worrying infectious risk for preterm neonates. This study aimed to evaluate the efficacy of a disinfection method based on steam pulverization to eradicate the persistent bacterial contamination in such incubators. METHODS: In a tertiary NICU, 20 incubators were monitored qualitatively for bacterial contamination at five different sites (the rubber grommet, the left door handles, the temperature adjustment button, the mattress and the scale) using a culture method at three times: before and after steam pulverization then 24 h after turning on and housing a new neonate. Clinical data of neonates housed in each incubator were retrieved from the medical records to identify potential occurrence of late onset sepsis (LOS). RESULTS: Just after steam pulverization, only two incubators were free from bacteria. Before disinfection 87% of all the samples were contaminated compared to 61% after disinfection. After 24 h, the proportion of contaminated samples reached 85%. Mattresses and scales were the most frequently contaminated incubator sites with respectively 90% and 80% positive samples after disinfection compared to 100% and 90% before disinfection. Coagulase-negative staphylococci, Enterococcus, Enterobacteria and Bacillus resisted disinfection and were identified on respectively 90%, 20%, 5% and 45% of incubators just after disinfection. Three preterm neonates developed LOS after being housed in a disinfected incubator but the bacterial species involved have not been identified in their incubator after disinfection. In two cases, the bacterium had been isolated from the mattress 24 h after housing the infected patient. CONCLUSION: Steam pulverization is not sufficient to eradicate bacterial contamination of incubators. These results highlight the urgent need for an effective disinfection method, especially for mattresses that are in constant contact with patients. In parallel, new incubator designs and mattress protections must be developed.

Environmental Persistence of Staphylococcus capitis NRCS-A in Neonatal Intensive Care Units: Role of Biofilm Formation, Desiccation, and Disinfectant Tolerance.

The clone Staphylococcus capitis NRCS-A is responsible for late-onset sepsis in neonatal intensive care units (NICUs) worldwide. Over time, this clone has evolved into three subgroups that are increasingly adapted to the NICU environment. This study aimed to decipher the mechanisms involved in NRCS-A persistence in NICUs. Twenty-six S. capitis strains belonging to each of the three NRCS-A clone subgroups and two other non-NRCS-A groups from neonates (alpha clone) or from adult patients ("other strains") were compared based on growth kinetics and ability to form biofilm as well as tolerance to desiccation and to different disinfectants. S. capitis biofilm formation was enhanced in rich medium and decreased under conditions of nutrient stress for all strains. However, under conditions of nutrient stress, NRCS-A strains presented an enhanced ability to adhere and form a thin biofilm containing more viable and culturable bacteria (mean 5.7 log10 CFU) than the strains from alpha clone (mean, 1.1 log10 CFU) and the "other strains" (mean, 4.2 log10 CFU) (P < 0.0001). The biofilm is composed of bacterial aggregates with a matrix mainly composed of polysaccharides. The NRCS-A clone also showed better persistence after a 48-h desiccation. However, disinfectant tolerance was not enhanced in the NRCS-A clone in comparison with that of strains from adult patients. In conclusion, the ability to form biofilm under nutrient stress and to survive desiccation are two major advantages for clone NRCS-A that could explain its ability to persist and settle in the specific environment of NICU settings. IMPORTANCE Neonatal intensive care units (NICUs) host extremely fragile newborns, including preterm neonates. These patients are very susceptible to nosocomial infections, with coagulase-negative staphylococci being the species most frequently involved. In particular, a Staphylococcus capitis clone named NRCS-A has emerged worldwide specifically in NICUs and is responsible for severe nosocomial sepsis in preterm neonates. This clone is specifically adapted to the NICU environment and is able to colonize and maintain on NICU surfaces. The present work explored the mechanisms involved in the persistence of the NRCS-A clone in the NICU environment despite strict hygiene measures. The ability to produce biofilm under nutritional stress and to resist desiccation appear to be the two main advantages of NRCS-A in comparison with other strains. These findings are pivotal to provide clues for subsequent development of targeted methods to combat NRCS-A and to stop its dissemination.

Bacteriophage-based decontamination to control environmental colonization by Staphylococcus capitis in neonatal intensive care units: An in vitro proof-of-concept.

Introduction: In neonatal intensive care units (NICUs), the standard chemical-based disinfection procedures do not allow a complete eradication of pathogens from environmental surfaces. In particular, the clone Staphylococcus capitis NRCS-A, a significant pathogen in neonates, was shown to colonize neonatal incubators. The aim of this study was to evaluate the in vitro effect of a bacteriophage cocktail on NRCS-A eradication. Methods: Three bacteriophages were isolated, genetically characterized and assessed for their host range using a collection of representative clinical strains (n=31) belonging to the clone NRCS-A. The efficacy of a cocktail including these three bacteriophages to eradicate the reference strain S. capitis NRCS-A CR01 was determined in comparison or in combination with the chemical disinfectant Surfanios Premium on either dry inoculum or biofilm-embedded bacteria. The emergence of bacterial resistance against the bacteriophages alone or in cocktail was evaluated by growth kinetics. Results: The three bacteriophages belonged to two families and genera, namely Herelleviridae/Kayvirus for V1SC01 and V1SC04 and Rountreeviridae/Andhravirus for V1SC05. They were active against 17, 25 and 16 of the 31 tested strains respectively. Bacteriophage cocktails decreased the bacterial inoculum of both dry spots and biofilms, with a dose dependent effect. The sequential treatment with bacteriophages then Surfanios Premium did not show enhanced efficacy. No bacterial resistance was observed when using the bacteriophage cocktail. Discussion: This study established a proof-of-concept for the use of bacteriophages to fight against S. capitis NRCS-A. Further investigations are needed using a larger bacterial collection and in real-life conditions before being able to use such technology in NICUs.