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Analysis of different molecular methods for typing methicillin-resistant Staphylococcus aureus isolates belonging to
Maria J Dos Santos Soares1, Lenise A Teixeira1, Maria DO Rosário Nunes1
1*Universidade Federal do Rio de Janeiro, Instituto de Microbiologia Prof. Paulo de Góes, Laboratório de Biologia Molecular de Bactérias, CCS, Bloco I, Cidade Universitária, Rio de Janeiro, RJ 21941-590, †Universidade Federal do Piauí, CCS, Departamento de Parasitologia e Microbiologia, SG16, Teresina, PI 64049-550 and ‡Universidade Federal Fluminense, Departamento de Tecnologia Farmacêutica, Faculdade de Farmácia, Niterói, Rio de Janeiro, RJ 24241-002, Brazil.
Abstract:
The extensive geographic spread of MRSA isolates belonging to the Brazilian epidemic clone (BEC) limited the value of pulsed-field gel electrophoresis (PFGE) in epidemiological studies of outbreaks caused by these strains. Thus, the discriminatory power of eight different molecular methods was evaluated in an attempt to establish a methodology for genotyping BEC isolates involved in intra-hospital outbreaks. BEC isolates from five hospitals in Teresina City, Piaui State were genotyped by conventional electrophoresis or PFGE of Cla I- or Sma I-digested genomic DNA hybridised with specific labelled mecA, Tn554, IS257 and IS256 probes. The combination of PFGE with Cla I/mecA, Cla I/Tn554, Cla I/IS257, Sma I/mecA and Sma I/IS257 probe-fingerprinting techniques provided a very poor discriminatory power for BEC strains. Although Cla I/IS256 fingerprinting discriminated 17 different polymorphisms among the isolates displaying PFGE A1 pattern, this strategy was not reproducible. In contrast, the combination of PFGE and Sma I/IS256 polymorphisms differentiated BEC isolates into nine stable polymorphisms. Thus combination of PFGE and hybridisation with IS256 probe may be recommended as a useful means of typing BEC strains involved in intra-hospital infections.