Prevalence and antibiogram of coagulase negative Staphylococci in bioaerosols from different indoors of a university in India.

BACKGROUND: Staphylococci species are the major constituents of infectious bioaerosols, particularly methicillin-resistant Staphylococci (MRS) have serious health impacts. Here, the bacterial burden was quantified, especially prevalence of MRS in bioaerosols collected from indoors of Dr. B.R. Ambedkar Central Library (DBRACL) and Central Laboratory Animal Resources (CLAR) of Jawaharlal Nehru University, New Delhi, India. Air samplings from DBRACL and CLAR were done using the settle plate method and SKC biosampler, respectively. RESULTS: This study showed a maximum 6757 CFU/m2/hr of bacterial load in the DBRACL reading room, while unacceptable bacterial loads (> 1000 CFU/m3 of air) at different sites of CLAR. Further, at both the sampling sites the predominance of coagulase negative Staphylococci (CNS) was observed. A total 22 and 35 Staphylococci isolates were isolated from DBRACL and CLAR bioaerosols, respectively. Majority (16/22) of the Staphylococcal isolates from DBRACL belonged to human-associated Staphylococci where S. haemolyticus (5/22) was the most dominating species. However, in CLAR facility centre, animal-associated Staphylococci (19/35) were dominating, where S. xylosus (12/35) was the most dominating species. Further, antibiotic sensitivity tests revealed 41% MRS and 73% multidrug resistant (MDR) among airborne Staphylococci from DBRACL indoor bioaerosols. Similarly, in CLAR facility, approximately, 66% Staphylococci isolates were methicillin resistant, out of which 2 isolates showed high MIC value ≥ 16 µg/mL. Further, we confirmed the presence of 49% multidrug resistant Staphylococci in the indoor air of CLAR facility. CONCLUSIONS: This study suggested that the exposure of workers and students in CLAR to such a high concentration of drug-resistant Staphylococci should not be undermined, as these bacterial concentrations are the direct representative of inhalable particulate matter (PM2.5) as per collection procedure. Simultaneously, passive sampling from DBRACL assessed the risks due to microbial contamination in particle agglomerates, which may deposit on the crucial surfaces such as wounds/ cuts or on the frequently used items.

Dogs as reservoir of methicillin resistant coagulase negative staphylococci strains - A possible neglected risk.

The antibiotic resistance among coagulase - negative Staphylococcus (CoNS) species towards methicillin is rarely reported in veterinary medicine. Under the aspect/concept of One Health, those strains pose a risk to human health due to the presence in canine pets where the transfer of resistant genetic markers might occur to other staphylococci species. The aim of this study was to investigate the antimicrobial resistance pattern among Coagulase Negative Staphylococci (CoNS) isolated from asymptomatic dogs and those affected by topic infections. Swabs from 254 dogs were first seeded in Mannitol Salt Agar. Species identification was conducted by Matrix Assisted Laser Desorption ionization - time of flight (MALDI-TOF ms) as previously described. The susceptibility test was performed by disk diffusion according to CLSI standards. Detection of mecA gene was performed. CoNS could be recovered from both groups of dogs and an alarming presence of methicillin-resistant coagulase negative staphylococci (MRCoNS) was confirmed, in 10.2% (17/166) of the samples. Eight of those methicillin resistant strains were isolated from asymptomatic dogs whereas nine were present in dogs affected by pyoderma and otitis externa.

A short course of antibiotic treatment is safe after catheter withdrawal in catheter-related bloodstream infections due to coagulase-negative staphylococci.

CoNS is the main cause of catheter-related bloodstream infections (CRBSI). Current guidelines recommend catheter withdrawal followed by antibiotics for at least 5 days. We aimed to assess the efficacy and safety of a shorter course of antibiotherapy in patients with CoNS CRBSI. All proven cases of CoNS CRBSI at our institution (Jan 12/Dec 17) were retrospectively analysed. Comparison of clinical characteristics and outcomes between patients receiving a short (SC ≤ 3 days) versus long antibiotic course (LC > 3 days) was performed. Cox regression models predicting the risk for complications (including propensity score [PS] for treatment assignment as covariate) were designed to adjust baseline differences among both treatment groups. A total of 79 cases were included. Most patients (75.9%) showed clinical response at day 7 after catheter removal. Complications occurred in 3.8% (three cases of septic thrombophlebitis) with no cases of endocarditis. Microbiological relapse (MR) occurred in 13 patients (16.5%). SC and LC were administered to 25 (31.6%) and 54 (68.4%) patients, respectively, with no significant differences in MR-free survival between SC and LC groups (87.8 vs 86.3%; P = 0.6). In PS-adjusted Cox regression analyses, a tunnelled catheter as the source of CRBSI was the only independent risk factor for MR (hazard ratio, 5.71; 95% confidence interval, 1.6-21) whereas the duration of therapy had no apparent impact. Shortening antibiotic therapy to ≤ 3 days is not associated with a poorer outcome or a greater risk of MR in patients with CoNS CRBI with catheter withdrawal.

Coagulase-Negative Staphylococci Pathogenomics.

Coagulase-negative Staphylococci (CoNS) are skin commensal bacteria. Besides their role in maintaining homeostasis, CoNS have emerged as major pathogens in nosocomial settings. Several studies have investigated the molecular basis for this emergence and identified multiple putative virulence factors with regards to Staphylococcus aureus pathogenicity. In the last decade, numerous CoNS whole-genome sequences have been released, leading to the identification of numerous putative virulence factors. Koch's postulates and the molecular rendition of these postulates, established by Stanley Falkow in 1988, do not explain the microbial pathogenicity of CoNS. However, whole-genome sequence data has shed new light on CoNS pathogenicity. In this review, we analyzed the contribution of genomics in defining CoNS virulence, focusing on the most frequent and pathogenic CoNS species: S. epidermidis, S. haemolyticus, S. saprophyticus, S. capitis, and S. lugdunensis.

Comparative effectiveness of linezolid versus vancomycin as definitive antibiotic therapy for heterogeneously resistant vancomycin-intermediate coagulase-negative staphylococcal central-line-associated bloodstream infections in a neonatal intensive care unit.

Objectives: Heterogeneously resistant vancomycin-intermediate coagulase-negative staphylococci (hVICoNS) are emerging pathogens causing central-line-associated bloodstream infections (CLABSIs) in neonatal intensive care unit (NICU) patients. Given the burden of disease associated with CLABSI and the current lack of therapeutic guidelines, we aimed to compare the effectiveness of linezolid versus vancomycin used as the definitive antibiotic therapy for hVICoNS CLABSI. Methods: We performed a retrospective cohort study of infants with hVICoNS CLABSI from a single NICU between 2009 and 2014, treated with either linezolid or vancomycin as definitive antibiotic therapy. CLABSI duration, early and late recurrence and in-hospital mortality were compared using propensity score-adjusted proportional hazards and logistic regression models. Results: Of 89 infants with hVICoNS CLABSI, 33 (37.1%) treated with linezolid were compared with 56 (62.9%) treated with vancomycin. The median duration of CLABSI was 5 (range 1-12) versus 4 days (range 0-14) ( P = 0.11), early recurrences were 3.0% versus 7.1% ( P = 0.42), late recurrences 0% versus 14.3% ( P = 0.02) and mortality 27.3% versus 28.6% ( P = 0.90), when treated with linezolid versus vancomycin, respectively. When adjusting using a continuous propensity score, linezolid had an HR of 0.78 (95% CI 0.48-1.27) for CLABSI duration, an OR of 0.23 (95% CI 0.02-2.56) for early recurrence and an OR of 0.9 (95% CI 0.3-2.67) for mortality, relative to vancomycin. Conclusions: There was no statistically significant difference between linezolid and vancomycin when used as definitive treatment for hVICoNS CLABSI in NICU patients, in terms of CLABSI duration, recurrence or all-cause mortality.

Staphylococcus chromogenes, a Coagulase-Negative Staphylococcus Species That Can Clot Plasma.

Staphylococcus chromogenes is one of the main coagulase-negative staphylococci isolated from mastitis of dairy cows. We describe S. chromogenes isolates that can clot plasma. Since the main pathogen causing mastitis is coagulase-positive Staphylococcus aureus, the coagulase-positive phenotype of S. chromogenes described here can easily lead to misidentification.

Implementation of Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry in Routine Clinical Laboratories Improves Identification of Coagulase-Negative Staphylococci and Reveals the Pathogenic Role of Staphylococcus lugdunensis.

The use of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for staphylococcal identification is now considered routine in laboratories compared with the conventional phenotypical methods previously used. We verified its microbiological relevance for identifying the main species of coagulase-negative staphylococci (CoNS) by randomly selecting 50 isolates. From 1 January 2007 to 31 August 2008, 12,479 staphylococci were isolated with phenotypic methods, of which 4,594 were identified as Staphylococcus aureus and 7,885 were coagulase negative staphylococci. Using MALDI-TOF MS from 1 January 2011 to 31 August 2012, 14,913 staphylococci were identified, with 5,066 as S. aureus and 9,847 as CoNS. MALDI-TOF MS allowed the identification of approximately 85% of the CoNS strains, whereas only 14% of the CoNS strains were identified to the species level with phenotypic methods because they were often considered contaminants. Furthermore, the use of MALDI-TOF MS revealed the occurrence of recently characterized Staphylococcus species, such as S. pettenkoferi, S. condimenti, and S. piscifermentans. Microbiological relevance analysis further revealed that some species displayed a high rate of microbiological significance, i.e., 40% of the S. lugdunensis strains included in the analysis were associated with infection risk. This retrospective microbiological study confirms the role of MALDI-TOF MS in clinical settings for the identification of staphylococci with clinical consequences. The species distribution reveals the occurrence of the recently identified species S. pettenkoferi and putative virulent species, including S. lugdunensis.

Molecular characterization of linezolid-resistant CoNS isolates in Japan.

OBJECTIVES: Linezolid has been reported to remain active against 98% of staphylococci with resistance identified in 0.05% of Staphylococcus aureus and 1.4% of CoNS. The objective of this study was to characterize the linezolid-resistance mechanisms in the linezolid-resistant CoNS strains isolated in Japan. METHODS: Staphylococcus capitis strains exhibiting linezolid MICs >8 mg/L isolated from inpatients between 2012 and 2014 were screened for cfr and mutations in 23S rRNA, L3 and L4 by PCR/sequencing. Isolates were also examined for mutations in the rlmN gene. RESULTS: S. capitis had six 23S rRNA alleles. Five S. capitis isolates displayed linezolid MICs of 8, 16 and 32 mg/L. G2576U mutations were detected in three, four or five copies of 23S rRNA in all isolates. In two isolates exhibiting the highest linezolid MIC (32 mg/L) there was a large deletion in a single copy of 23S rRNA. Repeated 10 bp sequences were found in both 16S and 23S rRNAs, suggesting deletion by recombination between the repeats. One isolate had the mutation Ala-142→Thr in the ribosomal protein L3. All linezolid-resistant isolates also demonstrated mutations in the gene encoding RlmN methyltransferase, leading to Thr-62→Met and Gly-148→Ser. CONCLUSIONS: Multiple mechanisms appeared to be responsible for the elevated linezolid resistance in S. capitis isolates: a G2576U mutation in different numbers of copies of 23S rRNA, loss of a single copy of 23S rRNA and a mutation in the ribosomal protein L3, suggesting the accumulation of independent mutational events.

Coagulase-negative staphylococcal bacteremia: risk factors for mortality and impact of initial appropriate antimicrobial therapy on outcome.

It is uncertain whether an initial inappropriate empirical antibiotic treatment of coagulase-negative staphylococci (CoNS) bacteremia adversely affects the outcome. A retrospective cohort study of CoNS bacteremia was performed at the Dongguk University Ilsan Hospital during a 3-year period. During the study period, 109 patients with CoNS bacteremia were enrolled. The median age of the patients was 72 years and most (96%, 105/109) had one or more comorbid diseases. Among the participants, 29% (32/109) received an appropriate empirical antimicrobial therapy. The 30-day mortality was 24% (26/109) and CoNS bacteremia-related mortality was 14% (15/109). There was no difference in the CoNS bacteremia-related mortality between the group with an inappropriate empirical treatment (13%, 10/77) and that with an appropriate treatment (16%, 5/32) (p = 0.46). In the multivariate analysis using the Cox regression analysis method, Pitt bacteremia scores [hazard ratio (HR) 1.48; 95% confidence interval (CI) 1.09-2.01; p = 0.01] and retention of eradicable focus (HR 5.0; 95% CI 1.39-17.9; p = 0.01) were found to be associated with CoNS bacteremia-related mortality. The results suggest that inappropriate empirical therapy might not necessarily be associated with the 30-day mortality or CoNS bacteremia-related mortality. Conversely, Pitt bacteremia scores and retention of eradicable focus were associated with poor outcomes.

Characteristics of neonates with culture-proven bloodstream infection who have low levels of C-reactive protein (≦10 mg/L).

BACKGROUND: Elevated C-reactive protein (CRP) level is widely used in clinical practice as a marker to distinguish between neonates with or without sepsis. However, some neonates with bacteremia have a CRP level within the normal range and they are not well characterized. METHODS: All episodes of neonatal culture-proven bloodstream infections (BSIs) between July 2004 and June 2012 were enrolled. Patients characteristics were compared for three CRP groups (low, ≤ 10 mg/L; intermediate, 11-100 mg/L; and high, > 100 mg/L) using the Chi-square test and one-way ANOVA. The sepsis-attributable mortality rates were compared using logistic regression analyses. RESULTS: Of 986 episodes of neonatal BSI, 247 (25.1 %) had CRP ≤10 mg/L at the onset of clinical sepsis. In the low CRP group, patients had lower gestational age and birth weight, and an earlier occurrence of BSI. Patients with underlying gastrointestinal pathology, renal disorders, cholestasis, and pulmonary hypertension had a non-significant elevated CRP level at the onset of sepsis. In the blood culture of the low CRP group, coagulase-negative staphylococci (CoNS) were relatively more common (55.9 %, p < 0.001) than the other two groups, although one-fourth were infected with gram-negative bacilli (19.0 %), fungi (2.8 %), or polymicrobial pathogens (3.6 %). Of the BSIs with initial low CRP, 29.1 % were treated with inadequate antibiotics, 13.0 % progressed to septic shock, and 5.3 % had infectious complications. The sepsis-attributable mortality rate was lower in the low CRP group (4.9 %) than in the high CRP group (13.6 %). CONCLUSIONS: A considerable proportion of neonatal BSIs had a normal or low initial CRP level (≤10 mg/L), which was more likely to occur in low birth weight or extremely preterm infants, those with earlier onset of sepsis, and those infected with CoNS. Plasma CRP level should not be used to rule out severe culture-proven sepsis or guide the empirical choice of antibiotics.

Detection of methicillin-resistant coagulase-negative staphylococci by the Vitek 2 system.

The accurate performance of the Vitek 2 GP67 card for detecting methicillin-resistant coagulase-negative staphylococci (CoNS) is not known. We prospectively determined the ability of the Vitek 2 GP67 card to accurately detect methicillin-resistant CoNS, with mecA PCR results used as the gold standard for a 4-month period in 2012. Included in the study were 240 consecutively collected nonduplicate CoNS isolates. Cefoxitin susceptibility by disk diffusion testing was determined for all isolates. We found that the three tested systems, Vitek 2 oxacillin and cefoxitin testing and cefoxitin disk susceptibility testing, lacked specificity and, in some cases, sensitivity for detecting methicillin resistance. The Vitek 2 oxacillin and cefoxitin tests had very major error rates of 4% and 8%, respectively, and major error rates of 38% and 26%, respectively. Disk cefoxitin testing gave the best performance, with very major and major error rates of 2% and 24%, respectively. The test performances were species dependent, with the greatest errors found for Staphylococcus saprophyticus. While the 2014 CLSI guidelines recommend reporting isolates that test resistant by the oxacillin MIC or cefoxitin disk test as oxacillin resistant, following such guidelines produces erroneous results, depending on the test method and bacterial species tested. Vitek 2 cefoxitin testing is not an adequate substitute for cefoxitin disk testing. For critical-source isolates, mecA PCR, rather than Vitek 2 or cefoxitin disk testing, is required for optimal antimicrobial therapy.

Impact of antimicrobial stewardship intervention on coagulase-negative Staphylococcus blood cultures in conjunction with rapid diagnostic testing.

Rapid diagnostic testing with matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) decreases the time to organism identification by 24 to 36 h compared to the amount of time required by conventional methods. However, there are limited data evaluating the impact of MALDI-TOF with real-time antimicrobial stewardship team (AST) review and intervention on antimicrobial prescribing and outcomes for patients with bacteremia and blood cultures contaminated with coagulase-negative Staphylococcus (CoNS). A quasiexperimental study was conducted to analyze the impact of rapid diagnostic testing with MALDI-TOF plus AST review and intervention for adult hospitalized patients with blood cultures positive for CoNS. Antibiotic prescribing patterns and clinical outcomes were compared before and after implementation of MALDI-TOF with AST intervention for patients with CoNS bacteremia and CoNS contamination. A total of 324 patients with a positive CoNS blood culture were included; 246 were deemed to have contaminated cultures (117 in the preintervention group and 129 in AST the intervention group), and 78 patients had bacteremia (46 in the preintervention group and 32 in the AST intervention group). No differences in demographics were seen between the groups, and similar rates of contamination occurred between the preintervention and AST intervention groups (64.3% versus 72.6%, P = 0.173). Patients with bacteremia were initiated on optimal therapy sooner in the AST intervention group (58.7 versus 34.4 h, P = 0.030), which was associated with a similarly decreased mortality (21.7% versus 3.1%, P = 0.023). Patients with CoNS-contaminated cultures had similar rates of mortality, lengths of hospitalization, recurrent bloodstream infections, and 30-day hospital readmissions, but the AST intervention group had a decreased duration of unnecessary antibiotic therapy (1.31 versus 3.89 days, P = 0.032) and a decreased number of vancomycin trough assays performed (0.88 versus 1.95, P < 0.001). In patients with CoNS bacteremia, rapid pathogen identification integrated with real-time stewardship interventions improved timely organism identification and initiation of antibiotic therapy. Patients in the AST group with blood cultures contaminated with CoNS had decreased inappropriate antimicrobial prescribing and decreased unnecessary serum vancomycin trough assays.

Genetic environment of the multi-resistance gene cfr in methicillin-resistant coagulase-negative staphylococci from chickens, ducks, and pigs in China.

The present study focussed on the analysis of the genetic environment of the multi-resistance gene cfr detected among 21, mostly methicillin-resistant, coagulase-negative Staphylococcus (CoNS) isolates obtained from chickens, ducks and pigs in China. It included sequencing of the regions up- and downstream of the cfr gene on various plasmid types in 13 isolates, such as pSS-02 and pSS-02-like (n=7), pSS-03-like (n=1), pJP1-like (n=3), pSS-04 (n=1) and pJP2 (n=1). This analysis revealed that insertion sequences (IS21-558, IS256, IS257, or IS1216E) and other resistance genes (aacA-aphD and aadD for aminoglycoside resistance, ble for bleomycin resistance, fosD for fosfomycin resistance, erm(B) and erm(C) for macrolide-lincosamide-streptogramin B resistance, or fexA for phenicol resistance) coexisted on the respective plasmids. In the chromosomal copies of cfr identified in eight S. lentus isolates, the cfr gene was found to be bracketed by insertion sequences, such as IS256 or ISEnfa5. Stability tests confirmed that all chromosomal cfr-containing regions could be looped out via IS-mediated recombination. The observations made in this study extend the rather rudimentary knowledge about the genetic environment of cfr in staphylococci from chickens and ducks and confirmed that insertion sequences play an important role in the dissemination of cfr, not only among different types of plasmids, but also for the integration in the chromosomal DNA.

Coagulase-negative Staphylococci favor conversion of arginine into ornithine despite a widespread genetic potential for nitric oxide synthase activity.

Within ecosystems that are poor in carbohydrates, alternative substrates such as arginine may be of importance to coagulase-negative staphylococci (CNS). However, the versatility of arginine conversion in CNS remains largely uncharted. Therefore, a set of 86 strains belonging to 17 CNS species was screened for arginine deiminase (ADI), arginase, and nitric oxide synthase (NOS) activities, in view of their ecological relevance. In fermented meats, for instance, ADI could improve bacterial competitiveness, whereas NOS may serve as an alternative nitrosomyoglobin generator to nitrate and nitrite curing. About 80% of the strains were able to convert arginine, but considerable inter- and intraspecies heterogeneity regarding the extent and mechanism of conversion was found. Overall, ADI was the most commonly employed pathway, resulting in mixtures of ornithine and small amounts of citrulline. Under aerobic conditions, which are more relevant for skin-associated CNS communities, several strains shifted toward arginase activity, leading to the production of ornithine and urea. The obtained data indeed suggest that arginase occurs relatively more in CNS isolates from a dairy environment, whereas ADI seems to be more abundant in strains from a fermented meat background. With some exceptions, a reasonable match between phenotypic ADI and arginase activity and the presence of the encoding genes (arcA and arg) was found. With respect to the NOS pathway, however, only one strain (Staphylococcus haemolyticus G110) displayed phenotypic NOS-like activity under aerobic conditions, despite a wide prevalence of the NOS-encoding gene (nos) among CNS. Hence, the group of CNS displays a strain- and condition-dependent toolbox of arginine-converting mechanisms with potential implications for competitiveness and functionality.

Characterization of methicillin-resistant coagulase-negative staphylococci in milk from cows with mastitis in Brazil.

Staphylococci are one of the most prevalent microorganisms in bovine mastitis. Staphylococcus spp. are widespread in the environment, and can infect animals and humans as opportunistic pathogens. The objective of this study was to determine the frequency of methicillin-resistance (MR) among coagulase-negative staphylococci (CoNS) previously obtained from milk of mastitic cows in Brazil and to characterize the antimicrobial resistance phenotype/genotype and the SCCmec type of MRCoNS isolates. Identification of MRCoNS was based on both biochemical and molecular methods. Susceptibility testing for eleven antimicrobials was performed by disk-diffusion agar. Antimicrobial resistance genes and SCCmec were investigated by specific PCRs. Twenty-six MRCoNS were detected (20 % of total CoNS), obtained from 24 animals, and were identified as follows: S. epidermidis (7 isolates), S. chromogenes (7), S. warneri (6), S. hyicus (5) and S. simulans (1). All MRCoNS isolates carried mecA while the mecC gene was not detected in any CoNS. The SCCmec IVa was demonstrated in nine MRCoNS, while the remaining 17 isolates harbored non-typeable SCCmec cassettes. In addition to oxacillin and cefoxitin resistance, MRCoNS showed resistance to tetracycline (n = 7), streptomycin (n = 6), tobramycin (n = 6), and gentamicin (n = 4), and harbored the genes tet(K) (n = 7), str (n = 3), ant(4') (n = 6) and aac(6')-aph(2″) (n = 4), respectively. In addition, seven strains showed intermediate resistance to clindamycin and two to streptomycin, of which two harboured the lnu(B) and lsa(E) genes and two the aad(E) gene, respectively. One isolate presented intermediate erythromycin and clindamycin resistance and harbored an erm(C) gene with an uncommon 89-bp deletion rendering a premature stop codon. MRCoNS can be implicated in mastitis of cows and they constitute a reservoir of resistance genes that can be transferred to other pathogenic bacteria.

Emergence of sequence type 779 methicillin-resistant Staphylococcus aureus harboring a novel pseudo staphylococcal cassette chromosome mec (SCCmec)-SCC-SCCCRISPR composite element in Irish hospitals.

Methicillin-resistant Staphylococcus aureus (MRSA) has been a major cause of nosocomial infection in Irish hospitals for 4 decades, and replacement of predominant MRSA clones has occurred several times. An MRSA isolate recovered in 2006 as part of a larger study of sporadic MRSA exhibited a rare spa (t878) and multilocus sequence (ST779) type and was nontypeable by PCR- and DNA microarray-based staphylococcal cassette chromosome mec (SCCmec) element typing. Whole-genome sequencing revealed the presence of a novel 51-kb composite island (CI) element with three distinct domains, each flanked by direct repeat and inverted repeat sequences, including (i) a pseudo SCCmec element (16.3 kb) carrying mecA with a novel mec class region, a fusidic acid resistance gene (fusC), and two copper resistance genes (copB and copC) but lacking ccr genes; (ii) an SCC element (17.5 kb) carrying a novel ccrAB4 allele; and (iii) an SCC element (17.4 kb) carrying a novel ccrC allele and a clustered regularly interspaced short palindromic repeat (CRISPR) region. The novel CI was subsequently identified by PCR in an additional 13 t878/ST779 MRSA isolates, six from bloodstream infections, recovered between 2006 and 2011 in 11 hospitals. Analysis of open reading frames (ORFs) carried by the CI showed amino acid sequence similarity of 44 to 100% to ORFs from S. aureus and coagulase-negative staphylococci (CoNS). These findings provide further evidence of genetic transfer between S. aureus and CoNS and show how this contributes to the emergence of novel SCCmec elements and MRSA strains. Ongoing surveillance of this MRSA strain is warranted and will require updating of currently used SCCmec typing methods.

The risk of peritonitis after an exit site infection: a time-matched, case-control study.

BACKGROUND: Exit site infections (ESIs) have been previously associated with the development of peritonitis; however, the evidence to support this association is limited. We conducted a time-matched, case-control study to determine the association between ESIs and subsequent peritonitis. METHODS: The cohort comprised 962 incident adult peritoneal dialysis (PD) patients from January 2000 to December 2009. Patients with an ESI were matched to those with no ESI based on the duration of PD. The subsequent risk of peritonitis was determined using Cox models and conditional logistic regression. RESULTS: During the study period, there were a total of 1002 ESI and 1228 peritonitis episodes among 962 individuals. The time to subsequent peritonitis was shorter in individuals who had at least one ESI [hazard ratio (HR) 1.59; 95% confidence interval (CI) 1.22-2.07, P<0.001]. The risk of peritonitis post-ESI was increased for all Gram-positive infections [adjusted hazard ratio (aHR) 1.75; 95% CI 1.25-2.43], and for the subtypes of coagulase-negative Staphylococcus (CNS) and S. aureus, but not for Gram-negative or culture-negative infections. These findings were similar when examining the odds of subsequent peritonitis within prespecified time intervals of the ESI through conditional logistic regression. CONCLUSIONS: The risk of peritonitis after ESI is increased, particularly with S. aureus and CNS, despite appropriate antibiotic treatment of the ESI.

Preliminary evaluation of a new clinical algorithm to interpret blood cultures growing coagulase-negative staphylococci.

Evaluating the clinical significance of blood cultures positive for coagulase-negative staphylococci (CoNS) is of critical importance since these microorganisms represent both the first contaminants of blood cultures and one of the leading causes of bloodstream infection (BSI). This prospective 2-centre study aimed to compare a previously reported algorithm to a clinical algorithm based on our experience. We identified 84 patients with CoNS-positive blood cultures. Twenty-seven (32%) were considered to have BSI according to our study algorithm. Thirty-seven (44%) patients were considered to have CoNS BSI according to the previously reported algorithm. The 2 algorithms isolated patients with similar rates of recurrences and hospital mortality. Our algorithm seemed to result in less diagnoses of CoNS BSI without harmful consequences compared to the previously reported algorithm. The impact on patient outcome and the inappropriate use of antibiotics deserves further investigation.

Rapid microarray-based identification of different mecA alleles in Staphylococci.

To screen isolates and to identify mecA alleles, published mecA sequences were analyzed, and a microarray for the rapid discrimination of mecA alleles was designed. A GenBank analysis yielded 135 full-length gene sequences annotated as mecA. These sequences clustered into 32 different alleles corresponding to 28 unique amino acid sequences and to 15 distinct hybridization patterns on this microarray. A collection of 78 clinical and veterinary isolates of Staphylococcus spp. was characterized using this assay. Nine of the 15 expected patterns, as well as one as-yet-unknown pattern, were identified. These patterns were detected in various epidemic methicillin-resistant Staphylococcus aureus strains, in S. pseudintermedius, and in coagulase-negative species such as S. epidermidis, S. fleurettii, or S. haemolyticus. There was no correlation between the different mecA hybridization patterns and the SCCmec type. Determination of MICs showed that mecA alleles corresponding to only four of these nine patterns were associated with ß-lactam resistance. The mecA alleles that did not confer ß-lactam resistance were largely restricted to coagulase-negative staphylococci of animal origin, such as S. sciuri and S. vitulinus. Because of the diversity of sequences and the different impact on ß-lactam susceptibility, the existence of different mecA alleles needs to be taken into account when designing diagnostic assays for the detection of mecA.

Evolution of nasal carriage of methicillin-resistant coagulase-negative staphylococci in a remote population.

Nasal carriage of methicillin-resistant coagulase-negative staphylococci (MR-CoNS) is highly prevalent in community subjects, but its dynamic has been little investigated. Nasal swabbing was performed in 2006 and 2008 in 154 Amerindians living isolated in French Guiana. MR-CoNS strains were identified and characterized by non-ß-lactam susceptibility testing and staphylococcal cassette chromosome mec element (SCCmec) typing, characterizing the associations of ccr and mec gene complex allotypes, and for MR Staphylococcus epidermidis (MRSE), multilocus variable number of tandem repeats analysis (MLVA) was used. The impact of sociodemographic and medical characteristics on the persistence of MR-CoNS carriage was assessed by bivariate analysis. Prevalence of MR-CoNS carriage was 50.6% in 2006 and 46.8% in 2008. The 274 MR-CoNS isolates, including S. epidermidis (n = 89, 62 MLVA patterns), Staphylococcus haemolyticus (n = 78), and Staphylococcus hominis (n = 72), exhibited 41 distinct ccr and mec gene complex associations. Persistent carriage (in 2006 and 2008), intermittent carriage (either in 2006 or 2008), and noncarriage were documented in 25.3, 47.4, and 27.3% of the participants, respectively. Persistent carriage of a given MRSE isolate was rarely observed (n = 8 isolates). Furthermore, no epidemiological factor, including antibiotic exposure, was associated with persistent carriage. The high diversity of MRSE clones and their ccr and mec gene complex associations contrasted with the high carriage rates in this isolated community, which might reflect the occurrence of SCCmec rearrangement and the generation of new MR-CoNS strains.