Molecular types and related clinical features of methicillin-resistant Staphylococcus aureus in Jingzhou area

Abstract

Objective To investigate the molecular types and related clinical features of methicillin-resistant Staphylococcus aureus (MRSA) in Jingzhou area, Hubei Province. Methods A total of 80 MRSA strains confirmed by mecA gene were isolated from inpatients in Jingzhou Central Hospital of Hubei province during January and December 2014. Vitek 2 Compact was used for antibiotic susceptibility test. Staphylococcus protein A (SPA) types and Staphylococcal cassette chromosome mec (SCCmec) genotypes were detected by multiplex polymerase chain reaction (PCR) and gene sequencing. Panton-valentine leucocidin (pvl) gene of the strains was detected by PCR. Chi-square test and Wilcoxon test were used for data analysis. Results There were 16 spa types in 80 MRSA isolates, in which t030 and t437 were the most prevalent ones accounting for 50.0% (40 strains) and 28.8% (23 strains) of the total strains, respectively. There were 77 strains of SCCmec type Ⅰ-Ⅴ, in which SCCmecⅢ and SCCmecⅣ were the most prevalent ones accounting for 45.0% (36 strains) and 35.0% (28 strains), respectively. t030 was the main spa type in isolates of SCCmecⅢ (33/36, 91.7%), while t437 was the main spa type in isolates of SCCmecⅣ (20/28, 71.4%). Patients infected with t030/SCCmecⅢ MRSAs were with higher ages than those infected with t437/SCCmecⅣ MRSAs (T=446.500 and 607.500, P<0.01). Patients infected with t030/SCCmecⅢ MRSAs were mainly from surgical wards and intensive care unit (ICU), while those infected with t437/SCCmecⅣ MRSAs were mainly from pediatrics wards, and there were significant differences in ward distribution between two groups (χ2=33.724 and 29.768, P <0.01). Seventy percent and above strains of t030/SCCmec type Ⅲ were resistant to rifampin, erythromycin, clindamycin, tetracycline, levofloxacin, moxifloxacin, ciprofloxacin and gentamicin. Strains of t437/ SCCmec type Ⅳ were resistant to erythromycin, clindamycin and tetracycline, but were sensitive to most non-β-lactam antimicrobial drugs (with resistance rates <20%). Virulence gene pvl was found in 11 strains (13.8%), in which 7 were strains of t437-SCCmec type Ⅳ. Conclusions MRSAs in Jinzhou are of various genotypes, in which t030-SCCmecⅢ and t437-SCCmecⅣ are the most prevalent ones. Strains of t030-SCCmec type Ⅲ are usually multiple-drug resistant, mainly seen in elderly patients in surgical wards and ICU. Strains of t437-SCCmecⅣ are sensitive to most non-β-lactam antimicrobial drugs, and its infection is mainly seen in children and young people. Key words: Methicillin-resistant Staphylococcus aureus; Molecular typing; Staphylococcal protein A; Staphylococcal chromosome cassette mec; Leukocidins