Q-285. Surveillance of Susceptibility Profile to Antiseptics in ITU Isolates of Staphylococcus aureus, including MRSA

K. E. Cheeseman1, J-Y. Maillard1, G. J. Williams1, S. P. Denyer1, I. K. Hosein2;
1Cardiff Univ., Cardiff, UNITED KINGDOM, 2Univ. Hosp. of Wales, Cardiff, UNITED KINGDOM.

Background: The most common mode of microbial transmission in the healthcare environment is the hands of healthcare workers. Therefore hand hygiene is considered the most important measure for preventing their transmission and reducing hospital-acquired infection. This study tested the efficacy of alcohol hand rubs (AHR) used in intensive therapy units (ITU). Methods: Fifty nine isolates of Staphylococcus aureus (32 MRSA, 27 MSSA) were obtained from blood cultures from bacteraemia patients in two local hospitals. The efficacy of three AHRs used at the two hospitals was determined using a standard carrier test. An inoculum of S. aureus with organic load was placed on the surface of stainless steel disks and dried before AHRs were applied for a range of contact times. Surviving cells were enumerated using the Bioscreen Microbial Growth analyser. Experiments were also performed on a standard strain using both plate count and Bioscreen methods of enumeration. Observations of hand sanitizing practices were made in the ITUs of both hospitals. Results: ITU staff took on average 11-15 seconds to rub AHR into their hands. Carrier testing of the standard strain revealed Soft Care and Guest Medical AHRs had a biocidal effect (≥4 log10 reduction) within 30 s, whereas Cutan AHR had a biocidal effect after 5 min. Variability in log10 reduction was observed among the hospital isolates, particularly with Guest Medical AHR. The log10 reduction was significantly lower for the plate count method than the Bioscreen method for Guest Medical AHR, indicating cells were damaged but able to recover. Bioscreen growth curves were shown to underestimate survival of bacteria with the other AHRs because the short incubation period did not allow for recovery of damaged but viable cells, therefore only growth of healthy cells was observed. Conclusion: AHRs do not necessarily show high activity against clinical S. aureus isolated from ITUs. Although not as representative as a hand rub protocol, the use of a carrier test safely tested the activity of AHRs against pathogenic bacteria. Comparison of plate count and Bioscreen methods allow a better understanding of the antimicrobial action of AHRs.