Scientists Study Disinfection and MRSA Bacterial Load Reduction on Surfaces

In a presentation at the International Conference on Prevention & Infection Control (ICPIC) held in Geneva, Switzerland June 29-July 2, 2011, researchers from Brazil reported on a study in which they sought to compare two disinfectants -- peracetic acid (0.1 percent) and ethyl alcohol (70 percent) -- on surfaces contaminated with methicillin-resistant Staphylococcus aureus (MRSA).

The study by Shimura, et al. was a case control study, developed on a flowchart. Six sterile glasses surfaces (40x30cm) were contaminated with a suspension with 104 cfu/ml MRSA by spreading with a sterile spatula and left to dry for 10 minutes. The efficacy of disinfection products were measured by imprinting rodac plates with Trypticase Soy Agar holding for 1 minute against the surface, before and after the disinfection procedure. The glass surface was divided in three parts and each part was cleaned three times. A sterile microfiber cloth (40x38cm) made from 10 percent polyester, 20 percent polypropylene and 70 percent viscose was folded three times, with a total of 16 sides, but using nine sides only; they were moistened with 50ml of 0.1 percent peracetic acid or 70 percent ethyl alcohol to clean three surfaces each. Sterile gloves were used and imprints from both hands were made on rodac plates, holding for 15 seconds. Plates were incubated at 37°C for 48 hours.

The median of surface contamination before and after disinfection with peracetic acid was 3.55 cfu/ml and 0 cfu/ml, for ethyl alcohol, 4.26 cfu/ml and 0 cfu/ml respectively. Imprints of gloves after both disinfections had no growth (0 cfu/ml). The test showed a bacterial load reduction although a non-significant (p>0.05) result comparing solutions.

The researchers conclude that disinfection with peracetic acid or ethyl alcohol with adequate technique had successful bacterial load reduction which contributes to environment control. They add that peracetic acid has a good cost benefit, however the microfiber cloth was degrading after five times of use.

Reference: CN Shimura, D De Andrade, E Watanabe, and AM Ferreira. MRSA on surfaces: is it possible to control? Presentation at International Conference on Prevention & Infection Control (ICPIC). BMC Proceedings 2011, 5(Suppl 6):P307doi:10.1186/1753-6561-5-S6-P307