Longitudinal analysis of chlorhexidine susceptibilities of nosocomial methicillin-resistant Staphylococcus aureus isolates at a teaching hospital in Taiwan.
BACKGROUND
Chlorhexidine has been widely used for hand hygiene to prevent transmission of nosocomial pathogens, including methicillin-resistant Staphylococcus aureus (MRSA). However, data on longitudinal surveillance of the susceptibility of MRSA isolates to chlorhexidine are limited.


METHODS
A total of 240 nosocomial MRSA isolates obtained in 1990, 1995, 2000 and 2005 at National Taiwan University Hospital (NTUH), a hospital where chlorhexidine gluconate was used for hand hygiene for more than 20 years, were included in the study. Chlorhexidine susceptibility, molecular typing using multilocus sequence typing and distribution of the qacA/B gene of these MRSA isolates were studied.


RESULTS
The proportion of tested MRSA with a high MIC of chlorhexidine (>or=4 mg/L) was 1.7% in 1990, 50% in 1995, 40% in 2000 and 46.7% in 2005. Among these 83 isolates with high chlorhexidine MICs, 55.4% carried the qacA/B gene. MRSA isolates carrying the qacA/B gene were first detected in 1995 and belonged to a single clone at that time. However, the qacA/B gene was detected in MRSA isolates belonging to seven different clones in 2005.


CONCLUSIONS
The proportion of tested MRSA isolates with high chlorhexidine MICs at NTUH increased from 1990 to 1995 and remained steady thereafter. The presence of the qacA/B gene may contribute to the spread of specific MRSA clones.
Wang
Jann-Tay
JT
Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
Sheng
Wang-Huei
WH
Wang
Jiun-Ling
JL
Chen
Duckling
D
Chen
Mei-Ling
ML
Chen
Yee-Chun
YC
Chang
Shan-Chwen
SC
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D015373:Bacterial Typing Techniques; D002710:Chlorhexidine / Q000494:pharmacology*; D003428:Cross Infection / Q000382:microbiology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004202:Disinfectants / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D005838:Genotype; D006784:Hospitals, Teaching; D006801:Humans; D008137:Longitudinal Studies; D026901:Membrane Transport Proteins / Q000235:genetics; D008826:Microbial Sensitivity Tests; D017422:Sequence Analysis, DNA; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D013624:Taiwan
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004202:Disinfectants; D026901:Membrane Transport Proteins; C099272:QacB protein, Staphylococcus aureus; C068498:qacA protein, Staphylococcus aureus; D002710:Chlorhexidine