Adaptation to vancomycin pressure of multiresistant Staphylococcus capitis NRCS-A involved in neonatal sepsis

Multiple introductions of NRCS-A Staphylococcus capitis to the neonatal intensive care unit drive neonatal bloodstream infections: a case-control and environmental genomic survey

Background. The Staphylococcus capitis NRCS-A strain has emerged as a global cause of late-onset sepsis associated with outbreaks in neonatal intensive care units (NICUs) whose transmission is incompletely understood.Methods. Demographic and clinical data for 45 neonates with S. capitis and 90 with other coagulase-negative staphylococci (CoNS) isolated from sterile sites were reviewed, and clinical significance was determined. S. capitis isolated from 27 neonates at 2 hospitals between 2017 and 2022 underwent long-read (ONT) (n=27) and short-read (Illumina) sequencing (n=18). These sequences were compared with S. capitis sequenced from blood culture isolates from other adult and paediatric patients in the same hospitals (n=6), S. capitis isolated from surface swabs (found in 5/150 samples), rectal swabs (in 2/69 samples) in NICU patients and NICU environmental samples (in 5/114 samples). Reads from all samples were mapped to a hybrid assembly of a local sterile site strain, forming a complete UK NRCS-A reference genome, for outbreak analysis and comparison with 826 other S. capitis from the UK and Germany.Results. S. capitis bacteraemia was associated with increased length of NICU stay at sampling (median day 22 vs day 12 for other CoNS isolated; P=0.05). A phylogeny of sequenced S. capitis revealed a cluster comprised of 25/27 neonatal sterile site isolates and 3/5 superficial, 2/2 rectal and 1/5 environmental isolates. No isolates from other wards belonged to this cluster. Phylogenetic comparison with published sequences confirmed that the cluster was NRCS-A outbreak strain but found a relatively high genomic diversity (mean pairwise distance of 84.9 SNPs) and an estimated NRCS-A S. capitis molecular clock of 5.1 SNPs/genome/year (95% credibility interval 4.3-5.9). The presence of S. capitis in superficial cultures did not correlate with neonatal bacteraemia, but both neonates with rectal NRCS-A S. capitis carriage identified also experienced S. capitis bacteraemia.Conclusions. S. capitis bacteraemia occurred in patients with longer NICU admission than other CoNS. Genomic analysis confirms clinically significant infections with the NRCS-A S. capitis strain, distinct from non-NICU clinical samples. Multiple introductions of S. capitis, rather than prolonged environmental persistence, were seen over 5 years of infections.

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.

Late-Onset Sepsis Evaluation and Empiric Therapy in Extremely Low Gestational Age Newborns

BACKGROUND

Little is known about late-onset sepsis (LOS) evaluations in extremely low gestational age newborns (ELGANs). We describe frequencies of LOS evaluation in ELGANs, infant characteristics, and empiric therapy choices during evaluations.

METHODS

Cohort study of infants 22-28 weeks gestational age (GA) discharged from 243 centers from 2009 to 2018, excluding infants with congenital anomalies, discharged or deceased prior to postnatal day (PND) 2, or admitted after PND 2. A new LOS evaluation was defined as the first blood culture obtained between PND 3 and 90, or one obtained ≥1 day following a negative culture and ≥10 days from prior positive cultures. We determined numbers of evaluations and percentage positive by GA, center, and over time. We described characteristics associated with positive evaluations, infants with LOS, and empiric antimicrobials. We calculated descriptive and comparative statistics using Wilcoxon rank sum, Fisher's exact, or Pearson chi-square tests, as appropriate.

RESULTS

Of 47,187 included infants, 67% had ≥1 LOS evaluation and 21% of evaluated infants had ≥1 LOS (culture positive) episode; 1.6 evaluations occurred per infant and 10% were positive. The percentage of infants evaluated and positive for LOS was higher at earlier GA. LOS was associated with inotrope support (15% vs. 9%; p < .001) and invasive mechanical ventilation (66% vs. 51%; p < .001). Infants with positive cultures were more likely than infants with negative cultures to receive empiric antimicrobials during the LOS evaluation (95% vs. 73%; p < .001).

CONCLUSIONS

Among ELGANs, earlier GA and postnatal age were associated with LOS evaluation and positive cultures. Most infants undergoing evaluation were started on empiric antimicrobials.

Whole-genome sequencing reveals widespread presence of Staphylococcus capitis NRCS-A clone in neonatal units across the United Kingdom

OBJECTIVE

Increased incidence of neonatal Staphylococcus capitis bacteraemia in summer 2020, London, raised suspicion of widespread multidrug-resistant clone NRCS-A. We set out to investigate the molecular epidemiology of this clone in neonatal units (NNUs) across the UK.

METHODS

We conducted whole-genome sequencing (WGS) on presumptive S. capitis NRCS-A isolates collected from infants admitted to nationwide NNUs and from environmental sampling in two distinct NNUs in 2021. Previously published S. capitis genomes were added for comparison. Genetic clusters of NRCS-A isolates were defined based on core-genome single-nucleotide polymorphisms.

RESULTS

We analysed WGS data of 838 S. capitis isolates and identified 750 NRCS-A isolates. We discovered a possible UK-specific NRCS-A lineage consisting of 611 isolates collected between 2005 and 2021. We determined 28 genetic clusters of NRCS-A isolates, which covered all geographical regions in the UK, and isolates of 19 genetic clusters were found in ≥2 regions, suggesting inter-regional spread. Within the NRCS-A clone, strong genetic relatedness was identified between contemporary clinical and incubator-associated fomite isolates and between clinical isolates associated with inter-hospital infant transfer.

CONCLUSIONS

This WGS-based study confirms the dispersion of S. capitis NRCS-A clone amongst NNUs across the UK and urges research on improving clinical management of neonatal S. capitis infection.

Genomic Analysis of a Linezolid-Resistant Staphylococcus capitis Causing Bacteremia: Report from a University Hospital in Central Italy

Although coagulase negative staphylococci are rarely associated with complicated diseases, in some cases they cause life-threatening infections. Here we described a clinical case of a bacteremia due to a methicillin- and linezolid-resistant Staphylococcus capitis in a patient previously treated with linezolid. Whole genome sequencing revealed the common mutation G2576T in all rDNA 23S alleles and several acquired resistance genes. Moreover, the isolate was epidemiologically distant from the NRCS-A clade, usually responsible for nosocomial infections in neonatal intensive care units. Our findings further confirm the ability of minor staphylococci to acquire antibiotic resistances and challenge the treatment of these infections.

Staphylococcus capitis: Review of Its Role in Infections and Outbreaks

In June 2021, a national incident team was formed due to an increased detection of Staphylococcus capitis in samples from hospitalised infants. Staphylococcus capitis has been known to cause outbreaks in neonatal units across the globe, but the extent of the UK spread was unclear. A literature review was undertaken to support case identification, clinical management and environmental infection control. A literature search was undertaken on multiple databases from inception to 24 May 2021, using keywords such as “Staphylococcus capitis”, “NRCS-A”, “S. capitis”, “neonate”, “newborn” and “neonatal intensive care unit” (NICU). After screening, 223 articles of relevance were included. Results show incidences of S. capitis outbreaks have frequently been associated with the outbreak clone (NRCS-A) and environmental sources. The NRCS-A harbours a multidrug resistance profile that includes resistance to beta-lactam antibiotics and aminoglycosides, with several papers noting resistance or heteroresistance to vancomycin. The NRCS-A clone also harbours a novel SCCmec-SCCcad/ars/cop composite island and increased vancomycin resistance. The S. capitis NRCS-A clone has been detected for decades, but the reasons for the potentially increased frequency are unclear, as are the most effective interventions to manage outbreaks associated with this clone. This supports the need for improvements in environmental control and decontamination strategies to prevent transmission.

The Role of Coagulase-Negative Staphylococci Biofilms on Late-Onset Sepsis: Current Challenges and Emerging Diagnostics and Therapies

Infections are one of the most significant complications of neonates, especially those born preterm, with sepsis as one of the principal causes of mortality. Coagulase-negative staphylococci (CoNS), a group of staphylococcal species that naturally inhabit healthy human skin and mucosa, are the most common cause of late-onset sepsis, especially in preterms. One of the risk factors for the development of CoNS infections is the presence of implanted biomedical devices, which are frequently used for medications and/or nutrient delivery, as they serve as a scaffold for biofilm formation. The major concerns related to CoNS infections have to do with the increasing resistance to multiple antibiotics observed among this bacterial group and biofilm cells’ increased tolerance to antibiotics. As such, the treatment of CoNS biofilm-associated infections with antibiotics is increasingly challenging and considering that antibiotics remain the primary form of treatment, this issue will likely persist in upcoming years. For that reason, the development of innovative and efficient therapeutic measures is of utmost importance. This narrative review assesses the current challenges and emerging diagnostic tools and therapies for the treatment of CoNS biofilm-associated infections, with a special focus on late-onset sepsis.

Effect of Antibiotic Exposure on Staphylococcus epidermidis Responsible for Catheter-Related Bacteremia

Coagulase-negative staphylococci (CoNS) and especially Staphylococcus epidermidis are responsible for health care infections, notably in the presence of foreign material (e.g., venous or central-line catheters). Catheter-related bacteremia (CRB) increases health care costs and mortality. The aim of our study was to evaluate the impact of 15 days of antibiotic exposure (ceftobiprole, daptomycin, linezolid and vancomycin) at sub-inhibitory concentration on the resistance, fitness and genome evolution of 36 clinical strains of S. epidermidis responsible for CRB. Resistance was evaluated by antibiogram, the ability to adapt metabolism by the Biofilm Ring test^® and the in vivo nematode virulence model. The impact of antibiotic exposure was determined by whole-genome sequencing (WGS) and biofilm formation experiments. We observed that S. epidermidis strains presented a wide variety of virulence potential and biofilm formation. After antibiotic exposure, S. epidermidis strains adapted their fitness with an increase in biofilm formation. Antibiotic exposure also affected genes involved in resistance and was responsible for cross-resistance between vancomycin, daptomycin and ceftobiprole. Our data confirmed that antibiotic exposure modified bacterial pathogenicity and the emergence of resistant bacteria.

Heterogeneous vancomycin resistance in Staphylococcus aureus does not predict development of vancomycin resistance upon vancomycin pressure

BACKGROUND

It is unclear whether Staphylococcus aureus with heterogeneous intermediate vancomycin resistance (hVISA) can develop vancomycin resistance faster than vancomycin-susceptible S. aureus (VSSA) strains.

METHODS

We compared the kinetics of vancomycin MIC increase for 15 days of sustained in vitro vancomycin exposure for clinical hVISA (n = 12) and VSSA (n = 24) isolates, as well as for reference strains Mu3 (hVISA) and ATCC 29213 (VSSA). Clinical isolates were categorized as hVISA using the population analysis profile method. MICs were monitored for 15 days and the rate of MIC increase under exposure, for each strain, was evaluated in a linear regression model relative to time.

RESULTS

All isolates acquired vancomycin resistance upon exposure. Vancomycin MICs increased faster for VSSA compared with hVISA isolates (P < 0.01).

CONCLUSIONS

The hVISA phenotype does not correspond to an enhanced adaptation potential to in vitro vancomycin pressure.

Allogenous Selection of Mutational Collateral Resistance: Old Drugs Select for New Resistance Within Antibiotic Families

Allogeneous selection occurs when an antibiotic selects for resistance to more advanced members of the same family. The mechanisms of allogenous selection are (a) collateral expansion, when the antibiotic expands the gene and gene-containing bacterial populations favoring the emergence of other mutations, inactivating the more advanced antibiotics; (b) collateral selection, when the old antibiotic selects its own resistance but also resistance to more modern drugs; (c) collateral hyper-resistance, when resistance to the old antibiotic selects in higher degree for populations resistant to other antibiotics of the family than to itself; and (d) collateral evolution, when the simultaneous or sequential use of antibiotics of the same family selects for new mutational combinations with novel phenotypes in this family, generally with higher activity (higher inactivation of the antibiotic substrates) or broader spectrum (more antibiotics of the family are inactivated). Note that in some cases, collateral selection derives from collateral evolution. In this article, examples of allogenous selection are provided for the major families of antibiotics. Improvements in minimal inhibitory concentrations with the newest drugs do not necessarily exclude “old” antibiotics of the same family of retaining some selective power for resistance to the newest agents. If this were true, the use of older members of the same drug family would facilitate the emergence of mutational resistance to the younger drugs of the family, which is frequently based on previously established resistance traits. The extensive use of old drugs (particularly in low-income countries and in farming) might be significant for the emergence and selection of resistance to the novel members of the family, becoming a growing source of variation and selection of resistance to the whole family. In terms of future research, it could be advisable to focus antimicrobial drug discovery more on the identification of new targets and new (unique) classes of antimicrobial agents, than on the perpetual chemical exploitation of classic existing ones.

Continuous infusion of vancomycin improved therapeutic levels in term and preterm infants

BACKGROUND

Growing evidence suggests that continuous infusion of vancomycin (CIV) is superior to intermittent infusion of vancomycin (IIV) in neonates. This quality improvement (QI) project aimed to transition from IIV to CIV with earlier and improved attainment of therapeutic vancomycin levels.

METHODS

The Model for Improvement framework with Plan Do Study Act cycles was used. Prospective data were collected during three phases: IIV, CIV-1 and CIV-2.

INTERVENTIONS

A QI team developed a CIV drug monograph and a multidisciplinary education package.

RESULTS

Using IIV, 36% (9/25) of first vancomycin levels were within target range. CIV achieved therapeutic levels twice as quickly as IIV (p < 0.05) with improved first vancomycin target levels (IIV 36%, 9/25; CIV-1 55%, 16/29; CIV-2 61%, 14/23) and total therapeutic levels (IIV 44%, 37/84; CIV-1 56%, 55/98; CIV-2 69%, 79/114).

CONCLUSIONS

This QI project demonstrated a successful transition from IIV to CIV with reduced time to achieve target vancomycin and an increased proportion of therapeutic levels.

Safety and Efficacy of Daptomycin in Neonates with Coagulase-Negative Staphylococci: Case Series Analysis

There has been an increase in the prevalence of gram-positive bacteremia in neonates in the last two decades. However, as a consequence of better care, there has been an increase in the survival of premature neonates. Coagulase-negative staphylococci (CoNS) is the most prevalent bacteria, responsible for up to 60% of late-onset sepsis (LOS). Daptomycin, a lipopeptide antimicrobial agent, is active against CoNS. This was an observational, retrospective case series study carried out in the Pediatric Hospital of King Saud Medical City, Riyadh, Saudi Arabia. The medical records of 21 neonates, aged 0-28 days, who were treated in Neonatal Intensive Care Unit (NICU) with intravenous daptomycin as monotherapy or combination therapy for at least 4 days for proven gram-positive infection between June 2019 to July 2020, were included. The median gestational and chronological age were 27 weeks and 5 days, respectively. The most frequent diagnosis in neonates was infective endocarditis (42.9%). Of the 21 patients who received daptomycin therapy, 13 (62%) recovered and 8 died. The clinical cure rate was higher in Staphylococcus hominis (100%) and in patients who received 6 mg/kg/dose twice daily (62.5%). The mean of aspartate aminotransferase significantly elevated after starting daptomycin (p = 0.048). However, no muscular or neurological toxicity of daptomycin was documented in any of the cases. Overall, daptomycin was well tolerated, even with long-term treatment.

Virulence Factors in Coagulase-Negative Staphylococci

Coagulase-negative staphylococci (CoNS) have emerged as major pathogens in healthcare-associated facilities, being S. epidermidis, S. haemolyticus and, more recently, S. lugdunensis, the most clinically relevant species. Despite being less virulent than the well-studied pathogen S. aureus, the number of CoNS strains sequenced is constantly increasing and, with that, the number of virulence factors identified in those strains. In this regard, biofilm formation is considered the most important. Besides virulence factors, the presence of several antibiotic-resistance genes identified in CoNS is worrisome and makes treatment very challenging. In this review, we analyzed the different aspects involved in CoNS virulence and their impact on health and food.

First Report on the Characteristics of Methicillin-Resistant Staphylococcus Capitis Isolates and an NRCS-A-clone Related Isolate Obtained from Iranian Children

BACKGROUND

Methicillin-resistant staphylococcus capitis (MRSC) NRCS-A clone (Multi- resistant and vancomycin-non susceptible) has been recently described as an emerging cause of nosocomial bacteremia, especially in neonatal intensive-care units (NICUs).

OBJECTIVE

The objective of this study was to evaluate the antibiotic and antiseptic resistance patterns, biofilm-producing ability and the prevalence of SCCmec and ACME types among MRSC isolates as well as to check the possible presence of NRCS-A clone at Tehran's Children's Medical Center, Iran.

METHODS

A total of 256 coagulase-negative Staphylococcal isolates were collected, of which 10 S. capitis isolates were obtained and tested for susceptibility against 13 antimicrobial and 3 antiseptic agents, as well as biofilm production. The presence of 15 distinct resistance genes, staphylococcal cassette chromosome mec (SCCmec), and arginine catabolic mobile elements (ACMEs) were tracked.

RESULTS

Seven out of 10 S. capitis isolates were MRSC (MIC90 van=8μg/mL) and resistant to trimethoprim/sulfamethoxazole, produced biofilm, (3 as strong biofilm producers) and carried ACME types I and II. Despite the identification of mec and ccr complexes in some isolates, all the SCCmec cassettes were untypeable (UT).

CONCLUSION

According to the studied features, only one isolate belonged to the NRSC-A clone. The results indicate that MRSC with high antibiotic resistance and unknown SCCmec might become a serious problem in the future for the treatment of patients, particularly children.

Hyperosmotic Infusion and Oxidized Surfaces Are Essential for Biofilm Formation of Staphylococcus capitis From the Neonatal Intensive Care Unit

Staphylococcus capitis is an opportunistic pathogen often implicated in bloodstream infections in the neonatal intensive care unit (NICU). This is assisted by its ability to form biofilms on indwelling central venous catheters (CVC), which are highly resistant to antibiotics and the immune system. We sought to understand the fundamentals of biofilm formation by S. capitis in the NICU, using seventeen clinical isolates including the endemic NRCS-A clone and assessing nine commercial and two modified polystyrene surfaces. S. capitis clinical isolates from the NICU initiated biofilm formation only in response to hyperosmotic conditions, followed by a developmental progression driven by icaADBC expression to establish mature biofilms, with polysaccharide being their major extracellular polymer substance (EPS) matrix component. Physicochemical features of the biomaterial surface, and in particular the level of the element oxygen present on the surface, significantly influenced biofilm development of S. capitis. A lack of highly oxidized carbon species on the surface prevented the immobilization of S. capitis EPS and the formation of mature biofilms. This information provides guidance in regard to the preparation of hyperosmolar total parenteral nutrition and the engineering of CVC surfaces that can minimize the risk of catheter-related bloodstream infections caused by S. capitis in the NICU.

Niche specialization and spread of Staphylococcus capitis involved in neonatal sepsis

The multidrug-resistant Staphylococcus capitis NRCS-A clone is responsible for sepsis in preterm infants in neonatal intensive care units (NICUs) worldwide. Here, to retrace the spread of this clone and to identify drivers of its specific success, we investigated a representative collection of 250 S. capitis isolates from adults and newborns. Bayesian analyses confirmed the spread of the NRCS-A clone and enabled us to date its emergence in the late 1960s and its expansion during the 1980s, coinciding with the establishment of NICUs and the increasing use of vancomycin in these units, respectively. This dynamic was accompanied by the acquisition of mutations in antimicrobial resistance- and bacteriocin-encoding genes. Furthermore, combined statistical tools and a genome-wide association study convergently point to vancomycin resistance as a major driver of NRCS-A success. We also identified another S. capitis subclade (alpha clade) that emerged independently, showing parallel evolution towards NICU specialization and non-susceptibility to vancomycin, indicating convergent evolution in NICU-associated pathogens. These findings illustrate how the broad use of antibiotics can repeatedly lead initially commensal drug-susceptible bacteria to evolve into multidrug-resistant clones that are able to successfully spread worldwide and become pathogenic for highly vulnerable patients.

Clinical impact of vancomycin heteroresistance in staphylococcal strains involved in neonatal sepsis: Discussion of a case report

Heteroresistance to vancomycin (HRV) represents a decreased susceptibility to vancomycin and is frequently observed in multidrug-resistant coagulase-negative staphylococci. The clinical significance of such heteroresistance is controversial, but several failures of vancomycin therapy have been related to HRV, especially in the neonatal population. Here we report the case of a preterm neonate, born at 26 weeks of gestation, who developed sepsis due to a multidrug-resistant HRV Staphylococcuscapitis isolate. Bacteremia persisted despite adequate vancomycin serum concentration and catheter removal. The patient finally recovered after replacing vancomycin by linezolid. Through this case report, we would like to alert clinicians of the potential clinical impact of HRV and to discuss the lack of therapeutic alternatives in neonates.

Extended spectrum beta-lactamase-producing Klebsiella pneumoniae outbreak reveals incubators as pathogen reservoir in neonatal care center

In the context of a 3-month extended-spectrum beta-lactamase-producing Klebsiella pneumonia (ESBL-KP) outbreak in a neonatal care center (NCC), hygiene practices and hospital environment were investigated. ESBL-KP strains isolated from patients and environment were compared by molecular typing. The density of incidence of multi-drug-resistant bacteria (MDRB) was calculated from January 2014 to September 2016. The 3-month ESBL-KP outbreak involved 19 patients. Clinical strains from the 19 patients displayed the same molecular profile between them, and with a strain isolated from an incubator after cleaning. Furthermore, 52.4% of incubator mattresses were positive for diverse pathogens. Hygiene practices were acceptable except for external practitioners and parents. In addition to classical infection control (IC) measures, the replacement of mattresses and the improvement of incubators disinfection stopped the outbreak. The protocol of disinfection was revised and microbiological control was implemented. A significant decrease of MDRB incidence was concomitant (p value = 0.03219) but 3 months later, MDRB incidence increased again.Conclusion: This investigation highlighted incubators and mattresses as critical materials associated to infectious risk in NCC. NCC and IC teams should implement efficient protocol for incubators disinfection and monitoring. What is Known: • Environment in neonatal intensive care units is often suspected as reservoir for Enterobacteriaceae outbreaks but is scarcely investigated. • Incubators and mattresses offer wet and warm conditions suitable for pathogens multiplication, but microbiological survey is not performed routinely for assessing bacterial contamination. What is New: • Incubators and mattresses serve as reservoir for pathogens and relay in outbreak. • An infection control protocol associating efficient disinfection and microbiology analysis is proposed.

Staphylococcus capitis and NRCS-A clone: the story of an unrecognized pathogen in neonatal intensive care units

BACKGROUND

In neonatal intensive care units (NICUs), nosocomial late-onset sepsis (LOS), mostly due to coagulase negative staphylococci, constitute a major cause of death or impairment. Staphylococcus capitis, usually considered as a poorly virulent species, has been reported as a cause of LOS.

OBJECTIVES

To review data regarding S. capitis neonatal LOS and the features of isolates involved.

SOURCES

PubMed was searched up to August 2018 to retrieve studies on the topic; the keywords used were 'S. capitis', 'neonate', 'neonatal ICU', 'bloodstream infection' and 'late onset sepsis'.

CONTENT

Published data highlight the worldwide endemicity of a single S. capitis clone, named NRCS-A, specifically involved in LOS. NRCS-A harbours a multidrug resistance profile (including resistance to the usual first-line antibiotics used in NICUs). It is also able to adapt under vancomycin selective pressure that could confer an advantage for its implantation and dissemination in NICUs where this selective pressure is high. Moreover, a severe morbidity has been observed in NRCS-A-related LOS. The NICU environment, and especially incubators, constitute reservoirs of NRCS-A from which it could diffuse inside the setting. Finally, the virulome and resistome of S. capitis NRCS-A contain many genes potentially implicated in its specific epidemiology and pathophysiology, including the gene nsr that may be involved in its fitness and implantation in neonatal gut flora.

IMPLICATIONS

S. capitis must be considered as a true pathogen in neonates. The decreased susceptibility to vancomycin may be involved in failure of vancomycin therapy. Further studies are needed to better manage its diffusion inside each NICU but also worldwide.

Evolution of Daptomycin Resistance in Coagulase-Negative Staphylococci Involves Mutations of the Essential Two-Component Regulator WalKR

Coagulase-negative staphylococci (CoNS) represent one of the major causes of health care- and medical device-associated infections. Emerging antimicrobial resistance has complicated the treatment of systemic infections caused by CoNS. Here, we describe the prevalence of antimicrobial resistance in clinical CoNS strains from a tertiary care hospital over a 4-year period, and we observed a significant increase in resistance to daptomycin. Notably, Staphylococcus capitis accounted for the majority of these daptomycin-resistant (DAP-R) CoNS. To further investigate the mechanisms of daptomycin resistance in CoNS, daptomycin-susceptible clinical strains of S. capitis and Staphylococcus epidermidis underwent in vitro daptomycin exposure to generate DAP-R CoNS mutants. Unlike that seen with Staphylococcus aureus, alteration of cell surface charge was not observed in the DAP-R CoNS strains, but biofilm formation was compromised. Whole-genome sequencing analysis of the DAP-R CoNS strains identified single nucleotide polymorphisms (SNPs) in walKR, the essential two-component regulatory system controlling cell wall biogenesis. PCR and sequencing of walK and walR from 17 DAP-R CoNS clinical isolates identified seven nonsynonymous mutations. The results were confirmed by the recreation of the walK SNP in S. epidermidis, which resulted in reduced susceptibility to daptomycin and vancomycin. This study highlights the significance of CoNS in evolving daptomycin resistance and showed that walKR is shared among the staphylococcal species and is involved in antibiotic resistance development. Notably, we did not observe mutations in genes responsible for phospholipid biosynthesis or an altered cell surface charge, suggesting that reduced daptomycin susceptibility in CoNS may emerge in a fashion distinct from that in S. aureus.

Genomic Analysis of Multiresistant Staphylococcus capitis Associated with Neonatal Sepsis

Coagulase-negative staphylococci (CoNS), such as Staphylococcus capitis, are major causes of bloodstream infections in neonatal intensive care units (NICUs). Recently, a distinct clone of S. capitis (designated S. capitis NRCS-A) has emerged as an important pathogen in NICUs internationally.

Coagulase-negative staphylococci (CoNS), such as Staphylococcus capitis, are major causes of bloodstream infections in neonatal intensive care units (NICUs). Recently, a distinct clone of S. capitis (designated S. capitis NRCS-A) has emerged as an important pathogen in NICUs internationally. Here, 122 S. capitis isolates from New Zealand (NZ) underwent whole-genome sequencing (WGS), and these data were supplemented with publicly available S. capitis sequence reads. Phylogenetic and comparative genomic analyses were performed, as were phenotypic assessments of antimicrobial resistance, biofilm formation, and plasmid segregational stability on representative isolates. A distinct lineage of S. capitis was identified in NZ associated with neonates and the NICU environment. Isolates from this lineage produced increased levels of biofilm, displayed higher levels of tolerance to chlorhexidine, and were multidrug resistant. Although similar to globally circulating NICU-associated S. capitis strains at a core-genome level, NZ NICU S. capitis isolates carried a novel stably maintained multidrug-resistant plasmid that was not present in non-NICU isolates. Neonatal blood culture isolates were indistinguishable from environmental S. capitis isolates found on fomites, such as stethoscopes and neonatal incubators, but were generally distinct from those isolates carried by NICU staff. This work implicates the NICU environment as a potential reservoir for neonatal sepsis caused by S. capitis and highlights the capacity of genomics-based tracking and surveillance to inform future hospital infection control practices aimed at containing the spread of this important neonatal pathogen.

Vancomycin treatment is a risk factor for vancomycin-nonsusceptible Staphylococcus capitis sepsis in preterm neonates

OBJECTIVES

Multidrug-resistant, vancomycin-nonsusceptible Staphylococcus capitis is an emerging cause worldwide of late-onset sepsis (LOS) in preterm neonates. The pathophysiology and risk factors for S. capitis-related LOS are poorly understood, but we hypothesized that S. capitis LOS follows translocation from the gut microbiota rather than catheter invasion. The objective of this study was to investigate the risk factors of S. capitis LOS and gut colonization.

METHODS

We conducted a prospective single-centre cohort study of patients hospitalized in a tertiary-care unit (Lyon, France) from June 2011 to January 2012. S. capitis gut colonization was determined weekly from stool cultures. The determinants of gut colonization and LOS were established by multivariate Cox proportional hazards models.

RESULTS

Eighty-three (36.2%) of 229 patients had S. capitis-positive stool culture, and 28 (12.2%) developed S. capitis LOS during hospitalization. Independent risk factors for S. capitis LOS included prior administration of vancomycin independent of a previous LOS episode (hazard ratio 6.44, 95% confidence interval 2.15-19.3, p 0.001) and low birth weight (hazard ratio 0.72 per 100 g increase, 95% confidence interval 0.55-0.95, p 0.02). The prior administration of vancomycin was also an independent risk factor for S. capitis colonization (hazard ratio 3.45, 95% confidence interval 2.07-5.76, p <0.001), particularly in the first week of life and in noncolonized neonates.

CONCLUSIONS

Neonates treated with vancomycin are at a higher risk of LOS caused by vancomycin-nonsusceptible S. capitis. The use of vancomycin in neonates must urgently be optimized to limit the selection of vancomycin-nonsusceptible strains, for which alternative antibiotics are lacking.