Study on antibiotic resistance and staphylococcal chromosomal cassette mec molecular epidemiology of methicillin resistant coagulase negative staphylococci in children

Abstract

Objective To learn about the antibiotic resistance status of methicillin resistant coagulase negative staphylococcus(MRCNS), and to investigate the distribution and resistant feature of different staphylococcal chromosomal cassette mec(SCCmec) genotypes of children in Anhui, so as to guide clinical medication. Methods Resistance phenotype screening was conducted in coagulase negative staphylococcus, which were isolated from clinical strains in children in Anhui from 2010 to 2014 each year in September.MecA gene was detected by using PCR method in order to collect MRCNS.Minimal inhibitory concentrations(MIC) of 16 antibiotics were determined by adopting agar dilution method.Vacomycin-resistant strains were identified with population analysis and the Brain Heart Infusion vancomycin screen agar dilution method recommended by Clinical and Laboratory Standards Institute in 2013.Van gene and SCCmec types were detected by using PCR method. Results A total of 148 MRCNS strains were detected through the resistance phenotype screening and the detection of mecA gene.There were methicillin resistant staphylococcus epidermidis, methicillin resistant staphylococcus haemolyticus, methicillin resistant staphylococcus hominis, and other kinds of MRCNS, and the proportions of them were 44.59%(66/148 cases), 25.68%(38/148 cases), 19.59%(29/148 cases) and 10.14%(15/148 cases), respectively.The analysis of antibiotic resistance showed the antimicrobial resistant rates of MRCNS to Penicillin, Cefoperazone, Cefotaxime, Ceftriaxone, Imipenem and Meropenem were all 100%, to Erythromycin and Azithromycin, Ciprofloxacin, Clindamycin, Gentamicin, Levofloxacin, Rifampincin, Chloramphenicol, Teicoplanin and Vancomycin were 92.57%, 97.98%, 83.78%, 79.05%, 43.24%, 35.81%, 24.32%, 8.78%, 2.03% and 0.68%, respectively.There was 1 heterogeneous Vancomycin-resistant strain, which was resistant to both Vancomycin and Teicoplanin (with MIC 32.00 mg/L and 64.00 mg/L). No vanA, vanB, vanC1 or vanC2/3 gene was detected from he-terogeneous Vancomycin-resistant strain by PCR.Ⅰ to Ⅴ SCCmec genotypes were detected from 148 MRCNS strains, and the major SCCmec type was SCCmec type Ⅲ, which was followed by hybrid type.Three subtypes of SCCmec type Ⅳ were identified, including Ⅳa, Ⅳc and Ⅳd.There were 148 MRCNS strains that showed different resistant phenotypes to various antibiotics. Conclusions The MRCNS strains of children in Anhui province showed multiple resistance to antibiotics.It should be on alert when heterogeneous Vancomycin-resistant strain appeared.There were several diffe-rent SCCmec types among several kinds of MRCNS, and SCCmec Ⅲ genotype was the major epidemic isolate.There was no significant correlation between the different resistance rates of non-β-lactamase antibiotics and SCCmec genotypes in MRCNS. Key words: Child; Methicillin resistant coagulase negative staphylococci; Antibiotic resistance; Polymerase chain reaction; Staphylococcal cassette chromosome mecFund program: Natural Science Foundation of Anhui Province(1408085QH157)