Molecular characteristics and antimicrobial susceptibility to Staphylococcus aureus strains isolated from children with skin and soft tissue infections

Abstract

Objective To investigate the molecular characteristics, virulence genes and antimicrobial susceptibility to Staphylococcus aureus strains isolated from children with skin and soft tissue infections(SSTIs) in Beijing. Methods A total of 52 Staphylococcus aureus isolates were collected from children with SSTIs in Beijing Children′s Hospital, Capital Medical University, and the clinical data were collected and analyzed.Methicillin-resistant Staphylococcus aureus(MRSA) and methicillin-susceptible Staphylococcus aureus(MSSA) were identified by using the cefoxi-tin disc method and the detection of mecA gene.Multilocus sequence typing (MLST) and staphylococcal protein A(spa) typing were analyzed by the PCR method, and the staphylococcal chromosomal cassette mec (SCCmec) type was analyzed for the MRSA isolates.The pvl, eta, etb, tsst-1 and hlg genes were also detected by PCR.The susceptibility strains to 16 antibiotics were evaluated by using the agar dilution method. Results A total of 52 Staphylococcus aureus SSTIs patients, 30 with MRSA infections and 22 with MSSA infections were included in the study.There were 23 patients (44.2%) less than 1 year old.The most frequent infections were the newborn omphalitis (12/52 strains, 23.1%)and abscess(11/52 strains, 21.2%). ST59-MRSA-SCCmecⅣa-t437 was the most predominant clones of MRSA isolates.Among the MSSA isolates(14/30 strains, 46.7%), no significant epidemic clone was found.Ten sequence types (STs) and 14 spa types were identified in MSSA, and the most common types were ST22(6/22 strains, 27.3%)and t309(5/22 strains, 22.7%), respectively.Notably, the multidrug resistant rates of MRSA and MSSA isolates were all >85%.The percentages of the Staphylococcus aureus SSTIs strains resistant to Erythromycin, Penicillin, Chloramphenicol and Clindamycin were 100.0%, 94.2%, 69.2% and 63.5%, respectively.The tested isolates were susceptible to Trimethoprim/Sulfamethoxazole, Mupirocin, Fusidic acid, Tigecycline, Linezolid and Vancomycin.The pvl gene′s positive rate was 40.4%, and no significant difference between MRSA and MSSA was observed (P>0.05). Eta and etb genes were detected in 2 patients with staphylococcal scalded skin syndrome. Conclusions The Staphylococcus aureus SSTIs strains are most frequently isolated from newborn omphalitis and abscess in Beijing.The multidrug resistant rate is relatively high, so the erythromycin and clindamycin should not be preferred in empiric treatment of children with Staphylococcus aureus SSTIs.The prevalence of pvl gene is 40.1%.ST59-MRSA-SCCmecⅣa-t437 is the common clone of MRSA, while the MSSA isolates have a more diverse genetic background. Key words: Staphylococcus aureus; Skin and soft tissue infections; Molecular characteristics; Virulence; Antimicrobial susceptibility; Child