Abstract
Chlorhexidine is a widely used antiseptic agent; however, its bactericidal effect against bacterial endospores is limited. The genus Bacillus is spore-forming gram-positive bacteria that are ubiquitously found in the environment and cause opportunistic infection and food poisoning. The susceptibility of bacterial endospores to chlorhexidine was previously evaluated in Bacillus subtilis, but the primary target for disinfection with antiseptic agents, including chlorhexidine, should be harmful strains. We aimed to evaluate the susceptibility of harmful cereus group including Bacillus cereus, and to compare that with harmless Bacillus species, containing B. subtilis. We evaluated the susceptibility of the 15 strains of the cereus group to chlorhexidine in comparison with the 5 other strains, named the subtilis group in this study. Our results indicated that chlorhexidine exerted a bacteriostatic effect against Bacillus species at practical concentrations, especially during long-term exposure. The strains of B. cereus group in this study displayed relatively lower susceptibility to the antiseptic than the B. subtilis group according to the minimum inhibitory and bactericidal concentrations. We concluded that there are intrinsic differences in the susceptibility to chlorhexidine between the groups, but the molecular mechanisms are unknown. The minimum inhibitory or bactericidal concentrations of disinfectants other than chlorhexidine may also need to be clarified in the B. cereus and B. subtilis groups.
Highlights
Chlorhexidine is one of the most widely used biguanides for antiseptic purposes, such as skin surface preparation and intravascular catheter maintenance
This study aimed to evaluate the susceptibility of the B. cereus group to Chlorhexidine gluconate (CHG) and compare it between other genus Bacillus species
The minimum inhibitory concentration (MIC) of CHG were higher in the B. cereus group than in the B. subtilis group (Table 1)
Summary
Chlorhexidine is one of the most widely used biguanides for antiseptic purposes, such as skin surface preparation and intravascular catheter maintenance. The antiseptic activity of CHG has been validated in gram-positive and gram-negative bacteria and enveloped viruses, its efficacy against mycobacteria, nonenveloped viruses, fungi, and bacterial endospores is limited [2]. The efficacy of CHG against bacterial endospores was mainly examined using B. subtilis, the representative species of the genus. The bactericidal or inhibitory concentration of chlorhexidine in Bacillus spp. had not been studied extensively, because most antiseptic agents were generally ineffective against bacterial spores. Bacillus consists of spore-forming, facultative anaerobic or aerobic gram-positive bacilli, and Bacillus spp. is ubiquitously isolated from the environment, including the skin surface. Several studies examined the activity of chlorhexidine against B. subtilis, whereas studies on the sensitivity of harmful species in the B. cereus group, which is the main target of disinfection, to CHG have been limited
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