Diversity of staphylococcal cassette chromosome mec structures in coagulase-negative staphylococci and relationship to drug resistance

1 Departamento de Microbiología, Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey Nuevo Leon 64460, Mexico 2 Departamento de Biología Molecular y Bioingeniería, UAM Reynosa Aztlán, Universidad Autónoma de Tamaulipas, Tamaulipas, Mexico 3 Hospital Universitario Dr José Eleuterio González, Universidad Autónoma de Nuevo León, Monterrey Nuevo Leon 64460, Mexico Correspondence Elvira Garza-González elvira_garza_gzz{at}yahoo.com Received September 5, 2009 Accepted December 9, 2009 The objective of this study was to determine the distribution of staphylococcal cassette chromosome mec (SCC mec ) elements in meticillin-resistant coagulase-negative staphylococci (MR-CoNS) isolated from a tertiary-care hospital in Mexico and to examine the relationship to drug resistance. Fifty selected MR-CoNS isolates collected from catheters ( n =15), blood ( n =15), bone ( n =9), bronchial lavage ( n =2) and urine ( n =2) and one isolate each from an abscess, cerebrospinal fluid, eye, pleural effusion, synovial fluid, tracheal aspirate and wound secretion were examined. Susceptibility testing was performed by the broth microdilution method. SCC mec types were determined by multiplex PCR and PFGE was carried out as described previously for Staphylococcus aureus . Among the MR-CoNS strains studied, the most frequently isolated species were Staphylococcus epidermidis ( n =26) and Staphylococcus haemolyticus ( n =13). Staphylococcus cohnii ( n =5), Staphylococcus hominis ( n =3), Staphylococcus sciuri ( n =1), Staphylococcus pasteuri ( n =1) and the recently described species Staphylococcus pettenkoferi ( n =1) were also identified. The most frequent MR-CoNS genotype identified was SCC mec type IVa in S. epidermidis isolates, which also showed a high diversity in their PFGE patterns. A clone was found that amplified both SCC mec III and V elements in five isolates examined. The single MR S. pettenkoferi isolate harboured SCC mec type IVd and the single MR S. pasteuri isolate harboured SCC mec type I. The carriage of SCC mec type III was associated with resistance or intermediate resistance to meropenem ( P