High Rate ofqacA- andqacB-Positive Methicillin-Resistant Staphylococcus aureus Isolates from Chlorhexidine-Impregnated Catheter-Related Bloodstream Infections

Abstract

ABSTRACTChlorhexidine has been widely used for infection control. Although the use of chlorhexidine-impregnated catheters has reduced catheter-related infections, chlorhexidine-resistantStaphylococcus aureushas emerged. The correlation between the existence of the chlorhexidine-resistant genesqacAandqacB(qacA/B) in methicillin-resistantStaphylococcus aureus(MRSA) isolates and the effectiveness of chlorhexidine-impregnated catheters in the prevention of MRSA infections is unknown. Sixty methicillin-sensitiveStaphylococcus aureus(MSSA) and 96 MRSA isolates from the blood cultures of different patients were collected, and a case-control study was conducted to determine whether more clinicalS. aureusisolates from chlorhexidine-impregnated catheter-related bloodstream infections (CRBSI) have the biocide-resistant genes (qacA/Borsmr) than those from other infections. The chlorhexidine MIC50s of MSSA and MRSA isolates were 1 μg/ml and 2 μg/ml, respectively. Results of PCR analyses showed that 3.3% (n= 2) of MSSA and 43.8% (n= 42) of MRSA isolates harboredqacA/Band 5% (n= 3) of MSSA and 25% (n= 24) of MRSA isolates containedsmr. With multivariate logistic regression analyses, the significant risk factors for definite CRBSI with chlorhexidine-impregnated catheters were determined to beS. aureusisolates withqacA/Band a chlorhexidine MIC of ≥2 μg/ml (odds ratios [OR], 9.264 and 8.137, respectively, in all 156S. aureusisolates and 6.097 and 4.373, respectively, in the 96 MRSA isolates). Further prospective studies are needed to investigate the transmission of these biocide-resistant genes.