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Evaluation of antiseptics by the modified phenol coefficient method: sensitivity of methicillin-resistant
Abstract:
The relationship between an effective concentration and the duration of exposure to antiseptics was evaluated in strains of Staphylococcus aureus with a known genetic background, which include methicillin-resistant strains, using a modified version of the phenol coefficient method as part of an effort to investigate the antiseptic resistance of S. aureus. Chlorhexidine digluconate killed an antiseptic-sensitive strain within 1.5 min at 22 degrees C at a standard concentration (0.1%), whereas resistant strains still survived after 1.5 min. Povidone-iodine killed the sensitive strain within 1.5 min at a concentration of 0.1%, whereas it took this agent 3.0 and 4.5 min to kill low- and high-level resistant strains, respectively, at a concentration of 0.8%. These results indicate that the modified phenol coefficient method used is suitable for the evaluation of the sensitivity of microorganisms to antiseptics. An antiseptic-resistant chain that was associated with the ebr gene exhibited cross-resistance to povidone-iodine.
Insights
Antiseptic resistance in Staphylococcus aureus varies with exposure time and concentration. Certain resistant strains, linked to the ebr gene, show cross-resistance to povidone-iodine, impacting disinfection efficacy.
Area of Science:
- Microbiology
- Antiseptic Resistance
- Infectious Diseases
Background:
- Staphylococcus aureus is a significant human pathogen, with increasing prevalence of antibiotic and antiseptic resistance.
- Understanding the efficacy of antiseptics against resistant strains is crucial for infection control.
Purpose of the Study:
- To investigate the relationship between antiseptic concentration, exposure duration, and efficacy against various Staphylococcus aureus strains.
- To evaluate antiseptic resistance mechanisms, including cross-resistance, in Staphylococcus aureus.
Main Methods:
- A modified phenol coefficient method was employed to assess antiseptic efficacy.
- Tested antiseptics included chlorhexidine digluconate and povidone-iodine against sensitive and resistant Staphylococcus aureus strains.
- Evaluated varying concentrations and exposure times to determine killing kinetics.
Main Results:
- Chlorhexidine digluconate (0.1%) killed a sensitive strain in 1.5 minutes, but resistant strains survived longer.
- Povidone-iodine (0.1%) killed a sensitive strain in 1.5 minutes; however, low- and high-level resistant strains required 3.0 and 4.5 minutes at 0.8% concentration, respectively.
- An antiseptic-resistant strain associated with the ebr gene demonstrated cross-resistance to povidone-iodine.
Conclusions:
- The modified phenol coefficient method effectively evaluates microbial sensitivity to antiseptics.
- Antiseptic efficacy is dependent on concentration and exposure duration, particularly against resistant strains.
- The ebr gene is implicated in cross-resistance to povidone-iodine in Staphylococcus aureus.