Emergence of livestock-associated MRSA isolated from cystic fibrosis patients: Result of a Belgian national survey.

BACKGROUND: This study aims to determine the prevalence and characteristics of Staphylococcus aureus in Belgian cystic fibrosis (CF) patients. METHODS: Non-duplicate respiratory samples from 510 CF-patients (2012-2013) were examined. One isolate per patient was analysed unless different phenotypes were recovered. Isolates were investigated for mecA/mecC, toxins presence, spa-typing, MLST and SCCmec-typing. Potential livestock-associated (LA) isolates were examined for their immune-evasion-cluster (IEC) genes. RESULTS: S. aureus (n = 380), including 41 small-colony variants (SCVs), were isolated from 66.7% patients. The prevalence of methicillin-resistant S. aureus (MRSA) colonization was 4.9%. Two MRSA isolates carried toxic shock syndrome toxin 1 (TSST-1). Most MRSA (65%) belonged to two nosocomial epidemic clones (CC5, CC8) widespread in Belgium. Methicillin susceptible S. aureus (MSSA) showed great genetic diversity. Five of 33 isolates belonging to potential LA-lineages were IEC negative, including three methicillin-resistant isolates, suggesting an animal origin. CONCLUSIONS: The MRSA-prevalence in Belgian CF-patients remained constant (2001-2013), but SCV-prevalence increased. Most MRSA belonged to health-care-associated clones. Three patients carrying LA-MRSA were found, requiring further investigation to determine the risk factors for LA-MRSA acquisition.

Genetic Diversity among Staphylococcus aureus Isolates Showing Oxacillin and/or Cefoxitin Resistance Not Linked to the Presence of mec Genes.

Methicillin-resistant Staphylococcus aureus isolates lacking mec genes (n = 32), collected from Belgian hospitals, were characterized for their ß-lactamase production and the presence of mutations in pbp genes, the pbp4 promoter, and genes involved in penicillin-binding protein 4 overproduction (gdpP and yjbH). Twelve isolates were ß-lactamase hyperproducers (BHPs), while 12 non-BHP isolates might produce an incomplete GdpP protein. Most isolates showed nucleotide missense mutations in pbp genes. A few isolates also showed mutations in the pbp4 promoter.

CC398 Staphylococcus aureus subpopulations in Belgian patients.

Studies based on genome-wide single nucleotide polymorphisms (SNPs) supported the existence of two subpopulations in clonal complex (CC) 398 Staphylococcus aureus: an ancestral human-adapted clade (HC) and an animal-associated clade (AC). In this study, we have investigated the occurrence of genetic markers that allow discrimination of these subpopulations among CC398 isolates collected during 2014 to 2016 from human patients in Belgium. A collection of isolates was investigated by means of spa-typing and 16S-mecA-nuc PCR. CC398 isolates were classified as belonging to the human or the animal clade by using a canonical SNPs PCR and further studied by antimicrobial susceptibility and the presence of toxins, immune evasion cluster (IEC), and resistance genes. A total of 124 (7.8%) human isolates belonged to CC398. They were grouped into HC (n = 58) or AC (n = 66). The genes erm(T), pvl, chp, and scn were predominantly found in HC-CC398, while AC-CC398 isolates carried more frequently than the mecA, erm(C), tet(K), tet(M), and tet(L) genes. Different combinations of gene profiles were observed according to the clade. CC398 isolates from Belgian patients belonged to different subpopulations including typical HC and AC-isolates. Few HC-strains with mecA and AC-isolates harboring IEC were found. CC398 isolates from Belgian patients belonged to different subpopulations including typical HC and AC-isolates, as well as new emerging subpopulations that underline the ability of this lineage to acquire resistance and virulence genes. Further research is needed to evaluate the emergence of these subpopulations in the clinical setting.

Mutations at the Ribosomal S10 Gene in Clinical Strains of Staphylococcus aureus with Reduced Susceptibility to Tigecycline.

Mutations on the tip of the extended loop of the ribosomal S10 protein have been associated to tigecycline (TGC) resistance in passaged mutants of different bacteria species. This study described the first two clinical TGC-resistant Staphylococcus aureus isolates with these mutations. One strain (TGC MIC = 2 mg/liter) had a 12-nucleotide deletion affecting residues 56 to 59 (HKYK) of the S10 protein. The second strain (TGC MIC = 1 mg/liter) had amino acid substitutions (K57M and Y58F) previously described in S. aureus passaged mutants.

Characterisation of Staphylococcus aureus isolates from bloodstream infections, Democratic Republic of the Congo.

Staphylococcus aureus is known worldwide as an invasive pathogen, but information on S. aureus from bloodstream infections in Central Africa remains scarce. A collection of S. aureus blood culture isolates recovered from hospitals in four provinces in the Democratic Republic of the Congo (2009-2013) was assessed. A total of 27/108 isolates were methicillin-resistant S. aureus (MRSA), of which >70% were co-resistant to aminoglycosides, tetracyclines, macrolides and lincosamides. For MRSA and methicillin-susceptible S. aureus (MSSA) isolates, resistance to chloramphenicol and trimethoprim-sulphamethoxazole (TMP-SMX) was <10%. However, 66.7% (72/108) of all isolates harboured the trimethoprim resistance gene dfrG. More than three-quarters (84/108, 77.8%) of isolates belonged to CC5, CC8, CC121 or CC152. Genetic diversity was higher among MSSA (31 spa types) compared to MRSA (four spa types). Most MRSA (23/27, 85.2%) belonged to CC8-spa t1476-SCCmec V and 17/23 (73.9%) MRSA ST8 were oxacillin susceptible but cefoxitin resistant. Among MRSA and MSSA combined, 49.1% (53/108) and 19.4% (21/108) contained the genes encoding for Panton-Valentine leucocidin (lukS-lukF PV, PVL) and toxic shock syndrome toxin-1 (tst, TSST-1), respectively. PVL was mainly detected among MSSA (51/53 isolates harbouring PVL were MSSA, 96.2%) and associated with CC121, CC152, CC1 and CC5. TSST-1 was associated with CC8-spa t1476-SCCmec V. The immune evasion cluster (IEC) genes scn, sak and chp were detected in 81.5% of isolates (88/108, equally represented among MSSA and MRSA). The present study confirms the occurrence of MRSA with high levels of multidrug co-resistance and PVL-positive MSSA among invasive S. aureus isolates in Central Africa.

In vitro activity of ceftaroline against clinical Staphylococcus aureus isolates collected during a national survey conducted in Belgian hospitals.

OBJECTIVES: The aim of this study was to estimate the in vitro activity of ceftaroline against clinical Staphylococcus aureus isolates collected during national surveillance in Belgian acute-care hospitals. Ceftaroline-resistant isolates were further investigated for their resistance mechanisms. METHODS: From October 2013 to March 2014, 155 laboratories of Belgian acute-care hospitals were invited to send to the National Reference Centre-Staphylococcus aureus (Belgium) up to five non-duplicate S. aureus including three MRSA and two MSSA from hospitalized patients. Isolates were analysed by spa typing, SCCmec typing (for MRSA) and PCR for detection of 16S-mecA-nuc and 16S-mecC. MICs of oxacillin, cefoxitin and ceftaroline were determined by the broth microdilution method. The nucleotide sequences of mecA, native pbp and gdpP genes of isolates with reduced susceptibility to ceftaroline were analysed for the presence of mutations responsible for amino acid substitutions. RESULTS: Ninety-nine percent of isolates, including MRSA (n = 284) and MSSA (n = 131), were susceptible to ceftaroline. Only four MRSA isolates showed resistance to ceftaroline (MIC = 2 mg/L). These four isolates belonged to lineages CC5 (n = 1), CC22 (n = 2) and CC8 (n = 1). Two isolates (CC22 and CC8) carried mutations in mecA, as well as in other pbp genes. The remaining isolates carried mutations in native pbp genes or in gdpP. CONCLUSIONS: This is the first Belgian in vitro survey on ceftaroline activity against S. aureus. This antibiotic showed excellent activity against MRSA and MSSA, and only a few MRSA isolates with resistance were found. Reduced susceptibility to ceftaroline seems a complex phenomenon due to the accumulation of mutations in genes involved in ß-lactam tolerance.

Neuroinvasive Infection from O117:K52:H-Escherichia coli following Acute Pyelonephritis.

Spontaneous or nosocomial Escherichia coli meningitis remains rare in healthy adults but is still carrying a high mortality rate despite adapted antimicrobial treatment for susceptible strains. A 39-year-old woman was admitted to the hospital with severe subarachnoid haemorrhage complicated by acute hydrocephalus. On hospital day 10, she developed Streptococcus anginosus septicaemia and urinary tract infection due to a multisensitive strain of E. coli. This infection was successfully controlled by antimicrobial therapy. As a late complication in the neurosurgical ward (day 39), she developed fever, alteration of consciousness, and shock, leading to the diagnosis of bacterial meningitis. The culture of blood, cerebrospinal fluid, and urine grew positive for a multisensitive E. coli. The strain was identified as O117:K52:H, a serotype that was until now never associated with acute meningitis or brain abscesses. The source appeared to be the urinary tract with the demonstration of acute pyelonephritis. The patient died on day 94 from delayed complications of multiple brain abscesses.

Low occurrence of the new species Staphylococcus argenteus in a Staphylococcus aureus collection of human isolates from Belgium.

Staphylococcus argenteus is a novel Staphylococcus species closely related to Staphylococcus aureus that has been recently described. In this study, we investigated the proportion and the characteristics of S. argenteus recovered from humans in Belgium. S. aureus. human isolates collected in Belgium from 2006 to 2015 (n = 1,903) were retrospectively characterised via the presence of non-pigmented colonies on chocolate agar, spa typing and rpoB sequencing to determine if some of them were in fact S. argenteus. Out of 73 strains non-pigmented on chocolate plates, 3 isolates (0.16 %) showed rpoB sequences, in addition to spa and sequence types (ST2250/t5787, ST2250/t6675, ST3240/t6675), related to S. argenteus. Two of them were methicillin-resistant, harbouring a SCCmec type IV. The three S. argenteus isolates carried genes (sak, scn) of the immune evasion cluster. This first Belgian nationwide analysis showed a low occurrence of S. argenteus. Further studies should be conducted to identify the distribution range and the clinical impact of this new species.

Infection due to travel-related carbapenemase-producing Enterobacteriaceae, a largely underestimated phenomenon in Belgium.

BACKGROUND: Carbapenemase-producing Enterobacteriaceae (CPE) are emerging worldwide, representing a major threat for public health. Early CPE detection is crucial in order to prevent infections and the development of reservoirs/outbreaks in hospitals. In 2008, most of the CPE strains reported in Belgium were imported from patients repatriated from abroad. Actually, this is no longer the case. OBJECTIVES AND METHODS: A surveillance was set up in Belgian hospitals (2012) in order to explore the epidemiology and determinants of CPE, including the link with international travel/hospitalization. The present article describes travel-related CPE reported in Belgium. Different other potential sources for importation of CPE are discussed. RESULTS: Only 12% of all CPE cases reported in Belgium (2012-2013) were travel related (with/without hospitalization). This is undoubtedly an underestimation (missing travel data: 36%), considering the increasing tourism, the immigration from endemic countries, the growing number of foreign patients using scheduled medical care in Belgium, and the medical repatriations from foreign hospitals. The free movement of persons and services (European Union) contributes to an increase in foreign healthcare workers (HCW) in Belgian hospitals. Residents from nursing homes located at the country borders can be another potential source of dissemination of CPE between countries. Moreover, the high population density in Belgium can increase the risk for CPE-dissemination. Urban areas in Belgium may cumulate these potential risk factors for import/dissemination of CPE. CONCLUSIONS: Ideally, travel history data should be obtained from hospital hygiene teams, not from the microbiological laboratory. Patients who received medical care abroad (whatever the country) should be screened for CPE at admission.

Inhibition by EGTA of the formation of a biofilm by clinical strains of Staphylococcus aureus.

The effect of EGTA on the adhesion and on the formation of a biofilm by two reference and eight clinical strains of Staphylococcus aureus was studied. All the clinical strains were isolated from patients from Kinshasa. Spa typing confirmed that these clinical strains were distinct. The Biofilm Ring Test (BFRT®) showed that EGTA (100 µM-10 mM) inhibited the adhesion of the four clinical methicillin-resistant (MRSA) strains and the crystal violet staining method that it inhibited the formation of a biofilm by all the strains. Divalent cations abolished the effect of EGTA on the formation of a biofilm, specially in the clinical MRSA strains. EGTA had no effect on established biofilms. Only concentrations of EGTA higher than 10 mM were toxic to eukaryotic cells. Our results establish the effectiveness and the safety of lock solutions with EGTA to prevent the formation in vitro of biofilms by S. aureus.

Epidemiological investigation of a nosocomial outbreak of multidrug-resistant Corynebacterium striatum at one Belgian university hospital.

During an 8-month period, 24 Corynebacterium striatum isolates recovered from lower respiratory tract specimens of 10 hospitalized patients were characterized. The organisms were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and by 16S rRNA gene sequencing. The cluster of C. striatum exclusively affected patients who had been admitted to an intensive care unit and/or subsequently transferred to one medium-size respiratory care unit. Prolonged duration of hospitalization, advanced stage of chronic obstructive pulmonary disease, recent administration of antibiotics and exposure to an invasive diagnostic procedure were the most commonly found risk factors in these patients. Seven patients were colonized and three infected. All strains displayed a similar broad spectrum resistance to antimicrobial agents, remaining susceptible to vancomycin only. Typing analysis by MALDI-TOF MS and by semi-automated repetitive sequence-based PCR (DiversiLab typing) showed that all outbreak-associated C. striatum isolates clustered together in one single type while they differed markedly from epidemiologically unrelated C. striatum isolates. Pulsed-field gel electrophoresis (PFGE) profiles revealed three distinct PFGE types among the C. striatum isolates associated with the outbreak while all external strains except one belonged to a distinct type. We conclude that C. striatum is an opportunistic nosocomial pathogen in long-term hospitalized patients and can be at the origin of major outbreaks. The routine use of MALDI-TOF MS greatly facilitated the recognition/identification of this organism in clinical samples and this technique could also offer the potential to be used as an easy and rapid epidemiological typing tool for outbreak investigation.

Comparative epidemiology of Staphylococcus epidermidis isolates from patients with catheter-related bacteremia and from healthy volunteers.

Staphylococcus epidermidis is a major cause of catheter-related bloodstream infections (CRBSIs). Recent studies suggested the existence of well-adapted, highly resistant, hospital-associated S. epidermidis clones. The molecular epidemiology of S. epidermidis in Belgian hospitals and the Belgian community has not been explored yet. We compared a set of 33 S. epidermidis isolates causing CRBSI in hospitalized patients with a set of 33 commensal S. epidermidis isolates. The factors analyzed included resistance to antibiotics and genetic diversity as determined by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and SCCmec typing. Additionally, the presence of virulence-associated mobile genetic elements, the ica operon and the arginine catabolic mobile element (ACME), was assessed and compared against clinical data. CRBSI S. epidermidis isolates were significantly resistant to more antibiotics than commensal S. epidermidis isolates. The two populations studied were very diverse and genetically distinct as only 23% of the 37 PFGE types observed were harbored by both CRBSI and commensal isolates. ACME was found in 76% of S. epidermidis strains, regardless of their origin, while the ica operon was significantly more prevalent in CRBSI isolates than in commensal isolates (P < 0.05). Nine patients presented a clinically severe CRBSI, eight cases of which were due to an ica-positive multiresistant isolate belonging to sequence type 2 (ST2) or ST54. S. epidermidis isolates causing CRBSI were more resistant and more often ica positive than commensal S. epidermidis isolates, which were genetically heterogeneous and susceptible to the majority of antibiotics tested. Clinically severe CRBSIs were due to isolates belonging to two closely related MLST types, ST2 and ST54.

Dynamic pattern and genotypic diversity of Staphylococcus aureus nasopharyngeal carriage in healthy pre-school children.

OBJECTIVES: It is common wisdom that persistent carriage of Staphylococcus aureus is more frequent in young children than in adults. The objectives of this study were to assess the S. aureus temporal carriage pattern among a healthy community of pre-school children, with concomitant description of genotype diversity, toxin-encoding genes and antibiotic resistance. METHODS: Among 333 children 3-6 years of age, S. aureus nasopharyngeal carriage was assessed over one school year by culture of three sequential nasopharyngeal aspirates. Identification, methicillin resistance and toxin production profile were determined by PCR. Genotyping was performed by spa sequencing and multilocus sequence typing (MLST). RESULTS: Out of 830 samples collected, 286 (34%) yielded S. aureus from 185 carriers (55%). Based on consecutive genotype analysis, only 40/268 (15%) children could be classified as persistent carriers, and the remaining 118 (44%) showed intermittent carriage. spa typing revealed 82 types clustered into 13 spa clonal complexes (CCs). Fourteen strains isolated from 11 (3%) children were methicillin-resistant S. aureus (MRSA), half of these strains belonged to the commonly hospital-associated spa t008-ST8-SCCmec IV. Methicillin-susceptible S. aureus (MSSA) were genotypically more diverse. Toxic shock syndrome toxin and egc1/2 complexes were highly prevalent (24%). Contrastingly, Panton-Valentine leucocidin (PVL) was carried only by three MSSA strains (0.6% of children). Exfoliative toxins were detected in 10 (3.5%) MSSA strains, of which 5 were related to the impetigo clone CC121. CONCLUSIONS: Although S. aureus nasopharyngeal carriage was high among healthy pre-school children, persistent carriage seems to be less frequent than previously reported. The prevalence of MRSA carriage was 3%, but was not associated with PVL.

Community-acquired methicillin-resistant Staphylococcus aureus clones circulating in Belgium from 2005 to 2009: changing epidemiology.

The present study reports the evolution of the demographic characteristics and the molecular epidemiology of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) in Belgium from 2005 to 2009. Four hundred and ten CA-MRSA isolates were prospectively collected and screened for the presence of Panton-Valentin leucocidin (PVL) and toxic shock syndrome toxin 1 (TSST-1) encoding genes, while clinical information were recorded. PVL- and TSST-1-positive isolates were genotyped by pulsed-field gel electrophoresis (PFGE). Staphylococcal cassette chromosome mec (SCCmec) type, spa type and multilocus sequence type (MLST) were determined on representative isolates. One hundred and fifty-nine (39 %) isolates were PVL-positive. PVL-positive isolates were significantly more frequently isolated from skin or soft tissue than PVL-negative isolates, causing mainly subcutaneous abscesses and furuncles. Patients with PVL-positive CA-MRSA were significantly younger than patients with PVL-negative CA-MRSA. Eighty-seven percent of the PVL-positive isolates belonged to a limited number (n = 7) of PFGE types belonging to sequence types (ST) ST80, ST8, ST30, ST5, ST152, ST338 and a new ST, a single-locus variant of ST1. A temporal evolution of the distribution of these PFGE types was observed, characterised by (1) the dissemination of the ST8-SCCmecIV arcA-positive (USA300) genotype and (2) a genetic diversification. Forty-seven (11 %) strains were TSST-1-positive, of which 65 % clustered into four PFGE types, all belonging to ST5. The epidemiology of CA-MRSA in Belgium is changing, as the rapid diffusion of the USA300 clone seems to occur, together with a clonal diversification.

Sequence-based typing of Legionella pneumophila serogroup 1 clinical isolates from Belgium between 2000 and 2010.

Sequence-based typing (SBT) is a discriminatory method widely used to genotype Legionella pneumophila strains. A total of 86 clinical L. pneumophila serogroup 1 (sg1) isolates, collected between January 2000 and December 2010 in the two Belgian National Reference Centres for Legionella pneumophila, were genotyped using the internationally standardised SBT protocol of the European Working Group for Legionella Infections (EWGLI). The isolates could be classified into 31 different sequence types (ST, index of diversity: 0.879). The obtained STs were submitted to the EWGLI SBT-database for L. pneumophila. In our study, ST47 (27.9%) and ST1 (19.8%) were the most frequently detected STs. The detected profiles were a combination of both frequently isolated and unique STs, and of both worldwide distributed and more local strains. Two STs, ST880 and ST881, were new to the EWGLI database. In conclusion, we characterised L. pneumophila sg1 isolates with the SBT method, and created a Belgian profile database that will be useful for future epidemiological studies.

Previous healthcare exposure is the main antecedent for methicillin-resistant Staphylococcus aureus carriage on hospital admission in Belgium.

This study aimed to estimate the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) carriage upon hospital admission and to study the molecular epidemiology of MRSA in order to assess the proportion of Panton-Valentine leukocidin (PVL)-positive community-associated (CA) and livestock-associated (LA) MRSA strains. Epidemiological data on MRSA carriage upon hospital admission (2006-2009) were collected in a compulsory, continuous, national MRSA surveillance in Belgian acute-care hospitals. Additionally, 328 MRSA strains in 2005 and 314 strains in 2008 were collected in a separate, multicenter microbiological survey. Spa-typing, SCCmec-typing and MLST were performed; toxin genes were detected by PCR. The overall prevalence of MRSA carriage upon hospital admission was 8.9 cases/1,000 admissions between 2006 and 2009. Of MRSA carriers, 37.5% had a known MRSA history, 39.4% had stayed in a care facility, 12.2% reported no contact with healthcare. Over 90% of MRSA belonged to five healthcare-associated clones. Of these, MRSA spa-CC038-ST45-IV was in decline, mainly in favor of spa-CC008-ST8-IV. MRSA spa-CC002-ST5-IV, spa-CC002-ST5-II and spa-CC032-ST22-IV remained relatively stable. The proportion of PVL-positive CA-MRSA and LA-MRSA ST398 was below 2% of all MRSA. The extra-hospital MRSA reservoir in Belgium mainly consists of persons with previous healthcare exposure. PVL-positive CA-MRSA and LA-MRSA strains remained infrequent among hospitalized patients.

Pseudo-outbreak of extremely drug-resistant pseudomonas aeruginosa urinary tract infections due to contamination of an automated urine analyzer.

By the end of May 2010, an increase in the number of urine specimens that were culture positive for extremely drug-resistant (XDR) Pseudomonas aeruginosa was observed in our 800-bed university hospital. This led to an infection control alert. No epidemiological link between the patients and no increase in the frequency of XDR P. aeruginosa in non-urine samples were observed. Therefore, a pseudo-outbreak due to analytical contamination in the laboratory was rapidly suspected. A prospective and retrospective search of cases was initiated, and the sampling of the automated urine analyzers used in the laboratory was performed. Antibiotypes were determined by disc diffusion, and genotypes were determined by pulsed-field gel electrophoresis (PFGE). From February to July 2010, 17 patients admitted to 12 different departments and 6 outpatients were included. The mixing device of the cytometric analyzer used for the numeration of urinary particles (Sysmex UF1000i) proved to be heavily contaminated. Isolates recovered from 12 patients belonged to the same antibiotype and PFGE type as the isolate recovered from the analyzer. Extensive disinfection with a broad-spectrum disinfectant and the replacement of the entire tubing was necessary to achieve the complete negativity of culture samples taken from the analyzer. A pseudo-outbreak caused by an XDR P. aeruginosa clone was proven to be due to the contamination of the cytometric analyzer for urinary sediment. Users of such analyzers should be aware that contamination can occur and should always perform culture either before the processing of the urine sample on the analyzer or on a distinct sample tube.

Heterogeneity of disease and clones of community-onset methicillin-resistant Staphylococcus aureus in children attending a paediatric hospital in Belgium.

The increase in the number of methicillin-resistant Staphylococcus aureus (MRSA) infections in children has prompted paediatricians to broaden th empirical treatment of common community-onset (CO) infections in children in several countries. Most European countries have reported low rates of CO-MRSA infection, but limited data on paediatric CO-MRSA infections are available. A prospective study was conducted from January 2002 to December 2004 in Brussels. CO-MRSA was defined as MRSA first detected by culture within 48 h of admission or in outpatients. Clinical and epidemiological data were recorded. CO-MRSA strains were genotyped by pulsed-field gel electrophoresis and multilocus sequence typing. Staphylococcal chromosomal cassette mec, toxin (Panton-Valentin leukocidin (PVL), toxic shock syndrome toxin 1, and Eta/b), enterotoxin and antibiotic resistance genes were detected by PCR. The antibiotic resistance phenotype was determined by disk diffusion. S. aureus was isolated in 1681 children. Among these, 107 harboured MRSA. Fifty-one children were colonized or infected by CO-MRSA, 20% of whom had no healthcare exposure. Twelve infants <3 months old and five cystic fibrosis patients were colonized. None of the 22 infected patients (59% with acute otitis media and 36% with skin and soft tissue infections (SSTIs)) required hospitalization. Two-thirds of them failed to respond to empirical antibiotic therapy. The 37 characterized CO-MRSA strains were genetically diverse. Most of them had healthcare-associated genotypes. Only six strains were PVL-positive, all of which were ciprofloxacin-susceptible and more common in children with SSTIs (p 0.001). CO-MRSA remains uncommon in our paediatric population. So far, there is no need to modify the empirical treatment of common S. aureus infections. Monitoring of MRSA rates in S. aureus CO infections remains mandatory, and further investigation is warranted to establish the source of colonization in young infants.