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[A study of resistance to antiseptics of methicillin resistant Staphylococcus aureus (MRSA) in gastroenterological
Y Takesue1, T Yokoyama, T Kodama
1First Department of Surgery, Hiroshima University School of Medicine, Japan.
Abstract:
Highly methicillin-resistant Staphylococcus aureus (H-MRSA, MIC greater than 100 micrograms/ml) was prevalent from 1986 in our institution. The failure of povidone-iodine to reduce the prevalence of MRSA led us to choose chlorhexidine-ethanol solution as an antiseptic, and then the isolation frequency of H-MRSA decreased significantly in 1988. When H-MRSA began to increase again recently, we studied the resistance to antiseptics of MRSA in order to investigate the cause of this re-increase. Common antiseptics were tested against 45 strains of H-MRSA and 22 strains of methicillin sensitive S. aureus (MSSA, MIC less than 12.5 micrograms/ml). Dilute preparations (1:100) of povidone-iodine and chlorhexidine-ethanol solution were more effective on H-MRSA than the other antiseptics. Though there was no significant difference between H-MRSA and MSSA in their sensitivity to povidone-iodine, the killing of H-MRSA strains was more delayed than the killing of MSSA strains in chlorhexidine. Even after a 120-second exposure, 13.3% of H-MRSA strains were resistant to chlorhexidine (more than 1000 colonies were recovered). These highly chlorhexidine-resistant strains have been isolated since 1987 when we chose chlorhexidine-ethanol solution as the antiseptic in our institution. Therefore we suspect that the acquirement of resistance to antiseptics by H-MRSA caused the re-increase of this strain.
Insights
Highly methicillin-resistant Staphylococcus aureus (H-MRSA) developed resistance to chlorhexidine, leading to its resurgence. This study investigated antiseptic resistance in H-MRSA strains to understand the increasing prevalence of this pathogen.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Highly methicillin-resistant Staphylococcus aureus (H-MRSA) was prevalent in the institution starting in 1986.
- Initial attempts to reduce MRSA using povidone-iodine failed, leading to the adoption of chlorhexidine-ethanol solution in 1987.
- A subsequent increase in H-MRSA isolation frequency prompted an investigation into antiseptic resistance.
Purpose of the Study:
- To investigate the cause of the recent re-increase in H-MRSA prevalence.
- To determine the susceptibility of H-MRSA and methicillin-sensitive S. aureus (MSSA) to common antiseptics.
- To identify potential links between antiseptic use and the emergence of resistant strains.
Main Methods:
- Tested 45 strains of H-MRSA and 22 strains of MSSA against common antiseptics.
- Evaluated the efficacy of dilute povidone-iodine and chlorhexidine-ethanol solutions.
- Assessed bacterial killing after 120-second exposure to chlorhexidine.
Main Results:
- Dilute povidone-iodine and chlorhexidine-ethanol were most effective against H-MRSA.
- H-MRSA showed delayed killing by chlorhexidine compared to MSSA.
- 13.3% of H-MRSA strains exhibited high-level resistance to chlorhexidine after 120-second exposure.
Conclusions:
- The emergence of chlorhexidine-resistant H-MRSA strains, first isolated in 1987, is suspected to be the cause of the recent increase in H-MRSA prevalence.
- Antiseptic resistance acquisition by H-MRSA poses a significant challenge in healthcare settings.
- Continued monitoring of antiseptic efficacy and bacterial resistance is crucial for infection control.