Characterisation of Methicillin-resistant Staphylococcus aureus isolated from blood cultures in South East Asian hospitals

ABSTRACT

Methicillin-resistance Staphylococcus aureus (MRSA) are common in hospitals in many countries, including South East Asia. Nosocomial MRSA is characteristically resistant to multiple antibiotics but can be treated with vancomycin. More recently MRSA have emerged in the community (CMRSA) and these characteristically are not multiply resistant like the hospital strains. MRSA have been found to spread within and between hospitals, thus are referred to as epidermic MRSA (EMRSA). It is therefore important to characterise isolates so that pathogenic and epidemic strains of MRSA can be identified. For this study 309 MRSA isolated from blood cultures between June 1998 and December 1999 were provided by the Sentry Program Centre in Adelaide, South Australia. The isolates were from hospitals in Australia, South Africa, Singapore, China, Hong Kong, Taiwan, the Philippines and Japan. Isolates were characterised by phenotypic and molecular methods. The methods used were extended antibiograms and resistograms, bacteriophage typing, countour-clamped homogeneous electric field (CHEF) electrophoresis, plasmid profiling and analysis of the mec complex. Most of the isolates were resistant to the majority of the antimicrobials tested although all were susceptible to vancomycin. Three isolates from Hong Kong and seven from Royal Perth hospitals had resistance profiles similar to those of CMRSA. The majority of isolates were not susceptible to the International Bacteriophage Set (IBS). There was a predominant CHEF pattern amongst the South African isolates which had 88% similarity with the Australian CHEF pattern 1. However, the isolates were not related in other respects and had different plasmid profiles and mec complexes. The results indicated that the South African isolates are different from those from other hospitals and that Taiwanese and Japanese isolates are generally more diverse than those in the other countries. Hospitals in Australia, Singapore and Hong Kong appear to have many different strains but do not have predominance of a particular strain. This study has provided a basis for additional studies to further characterise isolates from various countries and to understand the epidemiology of MRSA in the hospitals.