Changes in genetic lineages, resistance, and virulence in clinical methicillin-resistant Staphylococcus aureus in a Spanish hospital

A total of 204 methicillin-resistant Staphylococcus aureus (MRSA) isolates were isolated in a Spanish hospital in two different periods (2001 and 2009). The percentages of MRSA isolates detected in 2001 and 2009 were 29 and 27 %, respectively. Genetic lineages, resistance mechanisms, and virulence traits were determined in these isolates. The most frequent detected lineage in both periods was S. aureus protein A (spa)-type t067, assigned to clonal complex (CC) 5 (CC5-t067), being more prevalent in 2001 (93 %) than in 2009 (71 %). The remaining CCs and spa-types detected were (%2001/%2009): CC5-t002 (0/5), CC8-t008 (1/16), CC8-t024 (0/1), CC8-t190 (0/3), CC8-t2849 (0/2), CC22-t032 (0/2), CC30-t012 (1/0), CC228-t109 (1/0), CC228-t1318 (2/0), and CC247-t051 (2/0). Most of the MRSA were isolated from wounds, representing 39 % in 2001 and 63 % in 2009. The emergence of MRSA CC8 isolates, mainly from wounds, seemed to occur in the second period. Resistance to (%2001/%2009) quinolones (99/87), aminoglycosides (98/88), macrolides (32/30), lincosamides (30/17), and tetracycline (2/1) was found in isolates in both periods. Trimethoprim-sulfamethoxazole resistance was detected only in 2001 (1 %), and chloramphenicol (1 %) and mupirocin resistance (11 %) were detected only in 2009. An association between staphylococcal enterotoxin gene profiles and CCs was detected in most of the cases. The egc-cluster was related to CC5, CC22, CC30, and CC228 and most of the CC8 isolates presented the sed, sej, and ser genes. Four tst-1-positive (CC5 and CC30) isolates were detected in 2001 and two lukS/F-PV-positive isolates were detected in 2009. Therefore, there is still a predominance of CC5-t067 in our region, although an increase of lineage CC8 was observed.