In vitro activity of chlorhexidine gluconate against methicillin-resistant and -sensitive staphylococcus aureus strains

A wide variety of antimicrobial cationic agents, such as chlorhexidine gluconate, are commonly used in antiseptic preparations in the prevention of nosocomial infections caused by methicillin-resistant Staphylococcus aureus (MRSA). In this study was investigated the activity of chlorhexidine gluconate against MRSA and methicillin-sensitive Staphylococcus aureus (MSSA). The quantitative suspension test was carried out with 1% and 4% chlorhexidine gluconate and contact time of 30 s, 60 s and 120 s. Since the plasmid-borne gene qacA/B confers resistance to cationic antiseptic agents in S. aureus, activity was also examined with regard to the presence of qacA/B. The results indicate that neither 1% nor 4% chlorhexidine gluconate achieved a log10 reduction factors (RF) >5 against MRSA and MSSA strains at 30 s, 60 s and 120 s. At all concentrations, the RF for MRSA qacA/B negative strains were significantly higher when compared to MRSA qacA/B positive strains at 60 s and 120s