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

Abstract

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-SCCmecIV), the Brazilian clone (CC8-ST239-SCCmecIII), and the Chilean/Cordobés clone (CC5-ST5-SCCmecI). 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 mecA genes, respectively. Molecular characterization included spa typing, SCCmec typing, PFGE and MLST.

Results: Analysis of the MRSA strains collected in 1994 revealed that they belonged to a single clone, the CC5-SCCmecIV, whereas among the isolates from 2008-2010, two dominant clones were identified: CC8-SCCmecIVc, which included spa types t008 and t1610 and is closely related to the USA 300 clone, and CC5-SCCmecI (spa type t149), related to the Chilean clone. The ST5-SCCmecIV 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.