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Approximately one-third of the human population is asymptomatically colonized by Staphylococcus aureus. However, much of the global diversity within the carriage populations remains uncharacterized, and it is unclear to what degree the variation is geographically partitioned. We isolated 300 carriage isolates from 1,531 adults contemporaneously in four countries: France, Algeria, Moldova, and Cambodia. All strains were characterized by multilocus sequence typing. Six clonal complexes (CCs) were present in all four samples (CC30, -45, -121, -15, -5, and -8). Analyses based on the genotype frequencies revealed the French and Algerian samples to be most similar and the Cambodian sample to be most distinct. While this pattern is consistent with likely rates of human migration and geographic distance, stochastic clonal expansion also contributes to regional differences. Phylogenetic analysis revealed a highly divergent and uncharacterized genotype (ST1223) within Cambodia. This lineage is related to CC75, which has previously been observed only in remote aboriginal populations in northern Australia.

Staphylococcus aureus is an important human pathogen, but it appears more commonly in asymptomatic colonization of the nasopharynx than in cases of invasive disease. Evidence concerning the global population structure of S. aureus is limited by the overrepresentation in the multilocus sequence testing database of disease isolates recovered from Western Europe, the Americas, Australia, and Japan. We address this by presenting data from the S. aureus carriage population in Mali, the first detailed characterization of asymptomatic carriage from an African population. These data confirm the pandemic spread of many of the common S. aureus clones in the carriage population. We also note the high frequency (approximately 24%) of a single divergent genotype, sequence type 152 (ST152), which has not previously been recovered from nasal carriage isolates but corresponds to a sporadic Panton-Valentine leukocidin (PVL)-positive, community-acquired methicillin-resistant S. aureus clone noted mostly in Central Europe. We show that 100% of the ST152 isolates recovered from nasal carriage samples in Mali are PVL positive and discuss implications relating to the emergence and spread of this virulent genotype.

Our objective was to assess the incidence of and risk factors for methicillin-resistant Staphylococcus aureus (MRSA) acquisition among patients in acute care wards. For 5 months, patients were screened for MRSA colonization at admission and at discharge. At admission, 6.6% of patients had cultures positive for MRSA, and 3.1% of patients who had tested negative for MRSA on admission had cultures positive for MRSA at discharge. Only the presence of chronic skin breaks at admission was independently associated with MRSA acquisition.

Pig farming is a risk factor for increased nasal Staphylococcus aureus colonization. Using sequence typing and phylogenetic comparisons, we showed that overcolonization of farmers was caused by a few bacterial strains that were not present in nonfarmers but often caused swine infections. This finding suggests a high rate of strain exchange between pigs and farmers.

Background: Despite contact isolation precautions for patients with methicillin-resistant Staphylococcus aureus (MRSA), MRSA infections are increasing in many countries., Objective: To evaluate the role of a potential unrecognized reservoir of MRSA carried by patients in acute care wards, we determined the prevalence of MRSA at hospital admission, with special emphasis on screening-specimen yields., Setting: A 1100-bed teaching hospital in Paris, France., Methods: Nasal screening cultures were performed at admission to a tertiary-care teaching hospital for patients older than 75 years., Results: MRSA was isolated from 63 (7.9%) of 797 patients. On the multivariate analysis, variables significantly associated with MRSA carriage were presence of chronic skin lesions (adjusted odds ratio [AOR], 5.10; 95% confidence interval [CI95], 2.52-10.33); transfer from a nursing home, rehabilitation unit, or long-term-care unit (AOR, 4.52; CI95, 2.23-9.18); and poor chronic health status (AOR, 1.80; CI95, 1.02-3.18). Without admission screening, 84.1% of MRSA carriers would have been missed at hospital admission and 76.2% during their hospital stay. Furthermore, 81.1% of days at risk for MRSA dissemination would have been spent without contact isolation precautions had admission screening not been performed., Conclusions: MRSA carriage at hospital admission is far more prevalent than MRSA-positive clinical specimens. This may contribute to failure of contact isolation programs. Screening cultures at admission help to identify the reservoir of unknown MRSA patients.

Infection by methicillin-resistant Staphylococcus aureus (MRSA) presents a serious problem, as these organisms are resistant to a wide range of antibiotics. Moreover, MRSA with reduced susceptibility to glycopeptides (GISA) have emerged in recent years. In our hospital we were faced with an outbreak of GISA between January and March 2000, involving six patients who were free of MRSA when the GISA isolate emerged, and five of whom had not been given glycopeptides. The initial GISA isolate from the six patients was compared with six 'historical' multiple-resistant MRSA isolates (1996-1999), which had not been found to be GISA by the routinely used method. Antibiotic susceptibility was studied through the disc diffusion method, and MICs of glycopeptides were determined by Etest, agar and broth dilution techniques. Molecular strain typing was done by PFGE and multilocus sequence typing (MLST). All 12 isolates that belonged to the gentamicin-resistant group of MRSA were susceptible to vancomycin, but showed reduced susceptibility to teicoplanin through at least one MIC method. PFGE typing yielded five different but closely related profiles, and eight of the 12 clinical isolates were classified into a single PFGE type. MLST yielded an identical allelic profile for all 12 isolates, corresponding to the profile (3-3-1-12-4-4-16) of the 'Iberian' clone HPV107 of MRSA. MLST allowed us to confirm the presence of the 'Iberian' MRSA clone HPV107 with the same allelic profile in our hospital for several years. We can now note that strains of this clone have acquired reduced susceptibility to teicoplanin.

Introduction: Sternal wound infection (SWI) after cardiac surgery is a severe complication. Among preventive measures, pre-operative decolonization of nasal carriage of Staphylococcus aureus has recently been shown to be beneficial. This quasi-experimental study assessed the effect of decolonization on the incidence of S. aureus-associated SWI based on 19 years of prospective surveillance.Methods: Segmented negative binomial regression was used to analyse the change over time in the incidence of S. aureus mediastinitis requiring re-operation after cardiac surgery in a French university hospital between 1996 and 2014. Universal nasal decolonization with mupirocin was introduced in December 2001. The association between pre-operative nasal carriage and SWI due to S. aureus was analysed between 2006 and 2012.Results: Among 17,261 patients who underwent a cardiac surgical procedure, 565 developed SWI (3.3%), which was caused by S. aureus in 181 cases (1%). The incidence of mediastinitis caused by S. aureus decreased significantly over the study period (1.43% in 1996-2001 vs 0.61% and 0.64% in 2002-2005 and 2006-2014, respectively; P<0.001). In segmented analysis, there was a significant break in 2002, corresponding to the introduction of decolonization. Despite this intervention, pre-operative nasal carriage remained a significant risk factor for S. aureus mediastinitis (adjusted odds ratio 2.2; 95% confidence interval 1.2-4.2), as were obesity, critical pre-operative status, coronary artery bypass grafting (CABG), and combined surgery with valve replacement and CABG.Conclusion: Universal nasal decolonization before cardiac surgery was effective in decreasing the incidence of mediastinitis caused by S. aureus. Nasal carriage of S. aureus remained a risk factor for S. aureus-associated SWI. [ABSTRACT FROM AUTHOR]

Clin Microbiol Infect 2010; 16: 1435–1441 We performed an 11-year retrospective analysis of consecutive nonduplicate methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates in two neighbouring hospitals in the Paris area. MRSA isolates were classified according to resistance (R) to fluoroquinolones (Fq), kanamycin (K), tobramycin (T) and gentamicin (G). The yearly number of MRSA isolates (3446 in total) decreased, from approximately 350 in 1997–2002 to 212 in 2007. Four patterns (P) were found: P1 (KTGFq R, n = 776), P2 [KTFq R; G susceptible (S), n = 1630], P3 (Fq R; KTG S, n = 397) and P4 (Fq S; any KTG susceptibility, n = 201). P1 predominated in 1997 (183 isolates) then dropped sharply (nine in 2007); P2 and P4 remained stable over time; and P3 increased from 13 isolates in 1997 to 72 in 2007. Patterns were significantly and positively associated with several variables, independently of the year of collection: P1, age < 80 years, male gender, intensive care unit stay, and hospital onset; P3, age > 80 years and stay in intermediate or long-term care wards; and P4, age < 40 years, stay in an obstetric ward, and imported cases. Molecular typing of 79 isolates in 2005 and 2007 using multilocus sequence typing, spa type, and SCC mec showed that P1, P2 and P3 isolates were mainly clonal, whereas P4 isolates were more diverse. P1 comprised mainly ST247-I isolates, P2 mainly ST8-IVc, and P3 mainly ST8-IVc and ST5-VI. In conclusion, the epidemiology of MRSA in Paris is changing rapidly at the local level, with phenotypically defined clones being substituted by others, with associations existing between changes in specific patient populations or circumstances. [ABSTRACT FROM AUTHOR]

Purpose Surveillance of preventable healthcare associated infections and feedback of the results to clinicians is central in the efforts to improve performance. We assessed Staphylococcus aureus healthcare associated bloodstream infection (HA-BSI) as an indicator of healthcare quality. Patients and method Between 2002 and 2012, we carried out a ten-year prospective bedside surveillance of S. aureus healthcare associated bacteraemia in a 940-bed university hospital using standard definitions. Results Overall, 2784 HA-BSI were identified during the study period, among which 573 (18%) were due to S. aureus . Among these 573 S. aureus bacteraemias, 189 originated from intravascular catheters (32.8%) of which 84% (158/189) in patients outside intensive care units. The proportion of catheter related HA-BSI due to S. aureus was 56% (61/109) in PVC-related HA-BSI and 34% (103/301) in CVC-related HA-BSI. A sharp decrease of PVC-related HA-BSI from 20 to 7 per year was obtained during the same period. Conclusion In our experience, S. aureus HA-BSI is a simple and useful indicator of catheter associated infections, and therefore of healthcare quality, especially in units not covered by other type of surveillance. [ABSTRACT FROM AUTHOR]