Contamination of Laboratory Bench-tops, Incubators and the Effects of a Spray-Disinfectant - A Quarterly Ammonium Compound

Abstract

We surveyed the prevalence of contaminants associated with bench-tops and incubators during a routine working day in our clinical microbiology laboratories in Benin City. A total of 93 swabs, 50 from bench-tops and 43 from inside incubators were randomly collected. One ml of sterile phosphate buffered saline was added into the swab and incubated aerobically at 37oC for 48 hours. Isolated organisms were characterized biochemically. Spray disinfectant, was applied on the bench top and cultured accordingly. Swabs were collected from the incubators every day for 10 consecutive days. Results indicate, that both bench-tops and incubators are contaminated with organisms of clinical importance. Thirty-six (72%) of the swabs yielded growth, with Bacillus subtilis (24%) being the predominant organism, followed by coagulase negative Staphylococcus (CNS) (12%), Staphylococcus aureus (10%), Proteus spp. and Escherichia coli (8%) each, Pseudomonas aeruginosa (4%), moulds (2%) and Candida albicans (2%). Eighteen (41%) swabs from incubators yielded growth, with B. subtilis (13.8%) dominating, followed by Proteus spp. (9.3%), Staphylococcus aureus (6.9%), CNS (4.5%) and moulds (2.2%). Three hours after the spray disinfection, only 5 (10%) of the bench-top swabs yielded growth of B. subtilis, while the swabs from incubators, even after 10 days yielded no growth. This study recommends that spray disinfectant, mostly quaternary ammonium compounds, free of aldehydes can minimize contamination of bench-tops and microbiology incubators during routine working hours.

Keywords: Laboratory, contaminants, incubators, bench-tops, spray-disinfectants.

Journal of Medical Laboratory Science Vol. 13 (2) 2004: pp. 33-37