Identifying markers of biofilm formation on medical-grade stainless steel as a representative medical device material

Reusable medical devices are reprocessed between uses, including cleaning and, as necessary, disinfection or sterilization. Healthcare-associated infections have been attributed to reusable medical devices and linked to inadequate reprocessing, which can result in residual soil on the device, insufficient disinfection, microbial resistance to used disinfectants and biofilm-related contamination. These factors can lead to microbial proliferation on and biofouling of reusable medical devices, increasing the risk of patient infection. While there are FDA-recognized standards for cleaning validation (including artificial test soils), there is a lack of standards or guidance documents available to advise on determining whether biofilm has been adequately cleaned off reusable devices after reprocessing. Additionally, relatively few studies report reproducible models of biofilm formation on medical devices or device materials; such models are necessary to begin the identification of the microbial biofilm burden present before and after reprocessing. Moreover, appropriate analytes to quantify that biofilm burden, and the endpoints of those analytes after reprocessing, need to be determined. The study described herein utilized a drip flow reactor (DFR) to develop single-species biofilms of two Gram-negative (Pseudomonas aeruginosa and Klebsiella pneumoniae) and two Gram-positive (Staphylococcus aureus and Enterococcus faecalis) bacterial species that are prone to contaminate medical devices as biofilms. Biofilm was extracted at early and late biofilm stages and then tested for several analytes, including protein, ATP, endotoxin, peptidoglycan and total organic carbon. The levels of these analytes were compared to c.f.u. and metabolic activity to qualitatively compare analyte levels with biofilm burden. The results presented demonstrate that the DFR can be used to model biofilm formation of several medically relevant micro-organisms on stainless steel. Furthermore, the analytical data obtained with this study indicate that the analytes used can be a good starting point for informing the selection of endpoints in future studies that evaluate the efficacy of cleaning and disinfection within the context of biofilm reduction.