Objective: The objective of this study was to evaluate, using an in vivo handwash methodology, the effectiveness of three hand hygiene products containing different active ingredients versus MRSA. An additional objective of the study was to assess whether in vitro Time-Kill data are adequate predictors of in vivo product efficacy.
Methods: The test products were commercially available hand hygiene products: an alcohol-based hand sanitizer (ABHS) with 62% ethanol, an antibacterial handwash with 0.3% triclosan (TCS), and an antibacterial handwash with 4% chlorhexidine gluconate (CHG). MRSA (ATCC#33591) was the test organism. In vitro Time-Kill experiments were carried out according to ASTM E 2315 guide using a 15-second contact time. A modification of ASTM E 1174-06 was used to evaluate test product efficacy on the hands of human volunteers. Twelve volunteers evaluated each test product (1.5 ml volume) in a cross-over design. Statistical comparison of log10 reductions (LR) was performed using the Fisher’s LSD Test (p<0.05).
Results: The ABHS achieved complete reduction (≥6.297 LR) of MRSA when tested with in vitro Time-Kill. The TCS and CHG handwashes produced a 3.11 LR and a 1.22 LR, respectively. By the in vivo method, the ABHS, the TCS handwash, and the CHG handwash produced LR ± standard deviations of 2.05 ±0.54, 1.93±0.35 and 1.53±0.27, respectively. The ABHS and TCS handwash were statistically equivalent, and both were significantly more effective than the CHG handwash.
Conclusions: ·In vitro time kill data were predictive of relative in vivo efficacy, but did not correlate with in vivo LRs; therefore, caution should be exercised when interpreting efficacy data for hand hygiene products.
·When tested using realistic product volumes, the ABHS and the TCS handwash were effective against MRSA, reducing levels on human hands by approximately 99%.
·The CHG handwash was less effective against MRSA, suggesting that CHG may not be an appropriate hand hygiene option for MRSA, particularly after a single use.