[Changes over time in the distribution of dominant clonal complexes of methicillin-resistant Staphylococcus aureus in Medellín, Colombia].

INTRODUCTION

Part of the success of methicillin-resistant Staphylococcus aureus (MRSA) as a pathogen responds to the rapid spread of pandemic lineages with diverse virulence and antimicrobial susceptibility profiles. In Colombia, several healthcare-associated MRSA (HA-MRSA) clones have been found, including the pediatric clone (CC5-ST5-SCC mec IV), the Brazilian clone (CC8-ST239-SCC mec III), and the Chilean/Cordobés clone (CC5-ST5-SCC mec I). Moreover, the community-associated MRSA (CA-MRSA) clone USA300 has been reported as causing hospital-acquired infections.

OBJECTIVE

To describe the changes over time in the distribution of MRSA clones from a university hospital in Medellín collected at two time points a decade apart.

MATERIALS AND METHODS

A total of 398 MRSA strains were analyzed. Of these, 67 strains were collected in 1994, while the remaining 331 strains were collected between 2008 and 2010. Species identification and methicillin resistance were confirmed by detection of nuc and mec A genes, respectively. Molecular characterization included spa typing, SCC mec typing, PFGE and MLST.

RESULTS

Analysis of the MRSA strains collected in 1994 revealed that they belonged to a single clone, the CC5-SCC mec IV, whereas among the isolates from 2008-2010, two dominant clones were identified: CC8-SCC mec IVc, which included spa types t008 and t1610 and is closely related to the USA 300 clone, and CC5-SCC mec I ( spa type t149), related to the Chilean clone. The ST5-SCC mec IV clone from 1994 was not detected.

CONCLUSIONS

This study identifies temporal dynamics in MRSA clone diversity, and highlights the importance of local surveillance and dissemination of results, especially in countries like Colombia where MRSA is prevalent and knowledge regarding its epidemiology is still insufficient.