Assessing decontamination practices at a medical microbiology research laboratory

Abstract

To our knowledge, this is the first study to conduct an objective assessment of the routine decontamination practices at a medical microbiology research laboratory (MRL) a year after a biosafety training was provided to all laboratory staff. Between March 28th and June 28th, 2021, unobtrusive observations were carried out to identify-three high-touch surfaces at the MRL during different working hours. Swabbing was used to evaluate the effectiveness of the disinfectant used in the laboratory. All three high-touch surfaces were sampled before and after decontamination with 200 ppm of 5 % sodium hypochlorite (household bleach) to quantify the microbial load and identify the types of organisms residing on the laboratory surfaces. A higher concentration (500 ppm) of 5 % sodium hypochlorite was employed after refresher training was provided to housekeeping staff, and resampling of the three surfaces was carried out during a 4-week follow-up period using the same procedure. The three high-touch surfaces identified were the two sides of the workbench (22 %–24 %) and the front surface of one incubator (14 %). Anthracoid bacilli and Staphylococcus aureus were the most commonly found organisms on laboratory surfaces pre-intervention (100 % and 89 %, respectively) and post-intervention (56 % and 44 %, respectively). Other microorganisms detected included Salmonella spp. (27.7 %), Proteus spp. (5.6 %), Escherichia coli (5.6 %), and Klebsiella spp. (33.3 %). Employing a higher concentration (500 ppm) of sodium hypochlorite significantly (p ≤ 0.000) reduced the total aerobic colony count from an average of 15–250 cfu/cm² to 10–60 cfu/cm². This study demonstrated suboptimal decontamination practices at the MRL and the need to apply a higher concentration (500 ppm) of sodium hypochlorite to reduce the overall microbial load. It also demonstrated the importance of quantitative assessment to monitor decontamination practices and ensure staff compliance. More studies are needed to identify bacterial communities within the laboratory, which will help provide guidance regarding the types, proper concentrations, and appropriateness of the in -use disinfectants. Furthermore, large-scale studies on the acceptable level of residual contamination following any decontamination process are urgently recommended.