High prevalence of multidrug-resistance and toxin-encoding genes in staphylococcus aureus isolated from children attending the emergency department of a university hospital in southern Brazil

Staphylococcus aureus can be found as a member of human microbiota, but it is also a successful pathogen capable of causing a wide variety of infections. Herein, the prevalence of colonization by S. aureus in children attended in a university hospital was investigated. Furthermore, phenotypic and genotypic characteristics of the bacterial isolates were analyzed. S. aureus isolates were characterized according to their antimicrobial susceptibility, presence of mecA and three virulence-encoding genes. SCCmec typing and genetic relatedness of methicillin-resistant S. aureus (MRSA) were analyzed. Of 197 children, 31.0% were colonized by S. aureus. Among the isolates, 40.0% were classified as MRSA. Three isolates were susceptible to cefoxitin and harbored the mecA gene. The mecA-harboring isolates displayed the SCCmec types I (14.3%), II (9.5%), IV (47.6%), V (4.8%) and 23.8% of the isolates were non-typeable. All S. aureus isolates were susceptible to vancomycin and rifampicin and high rates of resistance were observed for penicillin (93.4%), erythromycin (63.9%) and clindamycin (42.6%). Thirty-two isolates were classified as multidrug-resistant. Most isolates (90.2%) harbored at least one virulence-encoding gene and the prevalence was icaA, 85.2%; lukS-PV/lukF-PV, 44.2%; and tst, 24.6%. rep-PCR analysis identified high genetic diversity among most MRSAs. Most MRSA SCCmec IV belonged to two of the major clonal complexes, CC5 and CC30. A high prevalence of tst and lukS-PV/lukR-PV genes in multi-drug resistant S. aureus colonizing children was detected, highlighting the importance of continuous monitoring of S. aureus colonization as a measure to control staphylococcal infections in this population.