In-vitro susceptibility of hospital-acquired, community-acquired, and laboratory MRSA strains to topical antiseptics

Background: Methicillin-resistant Staphylococcus aureus (MRSA) strains are increasingly problematic hospital-acquired (HA) and community-acquired (CA) pathogens. Hand hygiene is widely recognized as a key component of prevention and control for MRSA, although the efficacy of topical antiseptics has primarily been established based on performance against laboratory MRSA strains. However, the correlation between laboratory and pathogenic clinical strains has not been determined.

Methods: A time-kill procedure with a 15 second exposure was used to assess the susceptibility of Staphylococcus aureus strains to topical antiseptics. A laboratory methicillin-suseptible S. aureus (ATCC 6538), a laboratory MRSA (ATCC 33591), clinical HA-MRSA (USA200, USA 500), and clinical CA-MRSA (USA300, USA400, USA1000, USA1100) were used to challenge 14 antiseptics with different active ingredients (ethanol, triclosan, chloroxylenol, or chlorhexidine gluconate).

Results:

• Products with >62% ethanol achieved a >6 log reduction against all strains

• Products with non-ethanol actives generally had inferior efficacy to ethanol with log reductions ranging from <1 log to >5 log

• Strain susceptibility to topical non-ethanol antiseptics is variable; USA1100 was the most resistant

• Laboratory S. aureus MRSA has intermediate resistance against topical antiseptics and appears to be predictive of clinical strain susceptibility

Conclusions:

• As demonstrated by the results of this study, CDC recommendations for alcohol-based instant hand sanitizer use to control and prevent MRSA are supported

• Hand hygiene products containing non-alcohol active ingredients have variable efficacy

• Efficacy data for non-alcohol hand hygiene products should be evaluated prior to use in areas at risk for HA-MRSA and CA-MRSA transmission