Diversity of Staphylococcal Cassette Chromosome mec Structures in Methicillin-Resistant Staphylococcus epidermidis and Staphylococcus haemolyticus Strains among Outpatients from Four Countries

Abstract

ABSTRACT In staphylococci, methicillin (meticillin) resistance (MR) is mediated by the acquisition of the mecA gene, which is carried on the size and composition variable staphylococcal cassette chromosome mec (SCC mec ). MR has been extensively studied in Staphylococcus aureus , but little is known about MR coagulase-negative staphylococci (MR-CoNS). Here, we describe the diversity of SCC mec structures in MR-CoNS from outpatients living in countries with contrasting environments: Algeria, Mali, Moldova, and Cambodia. Their MR-CoNS nasal carriage rates were 29, 17, 11, and 31%, respectively. Ninety-six MR-CoNS strains, comprising 75 (78%) Staphylococcus epidermidis strains, 19 (20%) Staphylococcus haemolyticus strains, 1 (1%) Staphylococcus hominis strain, and 1 (1%) Staphylococcus cohnii strain, were analyzed. Eighteen different SCC mec types were observed, with 28 identified as type IV (29%), 25 as type V (26%), and 1 as type III (1%). Fifteen strains (44%) were untypeable for their SCC mec . Thirty-four percent of MR-CoNS strains contained multiple ccr copies. Type IV and V SCC mec were preferentially associated with S. epidermidis and S. haemolyticus , respectively. MR-CoNS constitute a widespread and highly diversified MR reservoir in the community.