An automated contact model for transmission of dry surface biofilms of <i>Acinetobacter baumannii</i> in healthcare

Dry surface biofilms have been recognised across environmental and equipment surfaces in hospitals and could explain how microbial contamination can survive for an extended period and may play a key role in the transmission of hospital-acquired infections. Despite little being known on how they form and proliferate in clinical settings, DSB models for disinfectant efficacy testing exist. In this study we develop a novel biofilm model to represent formation within hospitals, by emulating patient to surface interactions. The model generates a DSB through the transmission of artificial human sweat (AHS) and clinically relevant pathogens using a synthetic thumb capable of emulating human contact. The DNA, glycoconjugates and protein composition of the model biofilm, along with structural features of the microcolonies was determined using fluorescent stains visualised by epifluorescence microscopy and compared with published clinical data. The model repeatably transferred trace amounts of microorganisms and AHS, every 5 minutes for up to 120 hours onto stainless steel coupons to generate a biofilm model averaging 1.16 x 103 CFU/cm2 falling within the reported range for clinical DSB (4.20 x 102 to 1.60 x 107 bacteria/cm2). Micrographs revealed the heterogeneity of the biofilm across the surface; and reveal protein as the principal component within the matrix, followed by glycoconjugates and DNA. Our in vitro DSB model exhibits many phenotypical characteristics and traits to those reported in situ. The model highlights key features often overlooked and the potential for downstream applications such as antibiofilm claims using more realistic microbial challenges.