Increasing resistance in multiresistant methicillin-resistant Staphylococcus aureus clones isolated from a Chinese hospital over a 5-year period.

Background: The aim was to study the changes in the antimicrobial resistance of methicillin-resistant Staphylococcus aureus (MRSA) clones over a 5-year period (from 2000 to 2005) at a representative hospital in Beijing, China.
Methods: A total of 100 randomly selected MRSA strains were analyzed using antimicrobial susceptibility testing, pulsed-field gel electrophoresis, spa typing, multilocus sequence typing, SCCmec typing, and PCR for the Panton-Valentine leukocidin virulence factor.
Results: Resistance to rifampin greatly increased from 32% (16/50) to 68% (34/50). High-level mupirocin-resistant isolates were found only in 2005, when four were identified. Intermediate susceptibly to quinupristin-dalfopristin increased from 22% (11/50) to 52% (26/50) between 2000 and 2005. The main antimicrobial resistance profiles changed from TC-GM-CI-EM-CM in 2000 to TC-GM-CI-EM-CM-RI in 2005. The main pulsed-field gel electrophoresis type changed from types C, L, and E in 2000 to types J, F, and N, respectively, in 2005. ST239-MRSA-III was the most predominant clone in 2000 and 2005, whereas ST5-MRSA-II was found only in 2005.
Conclusions: There were increasing levels of antimicrobial resistance and epidemiological changes in the hospital-associated MRSA strains isolated in this facility between 2000 and 2005.