Transfer of dry surface biofilm in healthcare environment : the role of healthcare worker's hands as vehicles

Background: Dry surface biofilms (DSB) persist for extended period in hospital, may play significant role in healthcare-associated infections transmission. This study aims to determine if DSB can be transferred from hospital surfaces to healthcare worker’s hands. Method: 12-day Staphylococcus aureus DSB was grown on polycarbonate and glass coupons in CDC bioreactor. 1.8x106 and 8.8x105 bacteria grew on polycarbonate and glass coupons respectively. Transmission was tested by lifting the coupon with forefinger and thumb of ungloved hands to a height of 30 cm then touching horse blood agar (HBA) plates 19 sequential times. Transferred bacterial number was determined by colony forming units. The effect of DSB wetting, on biofilm transfer was tested with 5 seconds 5% neutral detergent treatment. Results: Between 5.5 and 6.6% of the DSB bacteria were transferred to hands with one touch and approximately 20% were then transferred to HBA with one touch giving an overall transfer rate of 1.26% and 1.04% for polycarbonate and glass coupons respectively. Detergent treatment had little effect on bacterial removal from coupons but for biofilm grown on polycarbonate, significantly increased transferal to HBA (P<0.001) to 5.2%. Large numbers of bacteria were transferred by bare hands to multiple fomites. 1/3rd of polycarbonate coupons transferred >1000 colonies during first five sequential touches. Sufficient bacteria to cause infection were transmitted up to 19 times following one touch of the DSB. Conclusion: DSB bacteria are transferred by hands from one fomite to multiple fomites suggesting that DSB may serve as a persistent environmental source of pathogens.