Gram-Negative Bacteria Associated with Laboratory Workbenches in Microbiology Department, University of Benin

Abstract

More often than not, uncertainties in microbiological diagnosis could
arise from the contamination of cultures in the laboratory.
Contaminants in the lab could stern from the personnel, air currents,
dusts, mites or other environmental components. This study was
carried out to evaluate Gram-negative bacteria associated with
laboratory workbenches in Microbiology Department, University of
Benin, Benin City. Ten (10) workbenches were mapped out and
evaluated for bacterial contamination before and after disaffection
with 1% sodium hypochlorite solution (v/v). The bacterial isolates
were enumerated and identified using standard culture-based
techniques. Phenotypic virulence was evaluated for the bacterial
isolates and Kirby–Bauer disc diffusion method was used for
antibiotic susceptibility testing. The result revealed that disinfected or
cleansed workbench surfaces had lower bacterial load compared to
uncleansed surfaces. The disinfection could reduce bacterial
contamination in the range of 55% - 92% if workbench surfaces are
disinfected prior to analysis. The isolated bacteria identified in this
study were Escherichia coli, Enterobacter aerogenes, Pseudomonas
aeruginosa, Proteus mirabilis and Salmonella enterica. E. coli
(28.00%) was the most common contaminants in laboratory work
benches while E. aerogenes (16.00%) had the least occurrence. S.
enterica and E. aerogenes were recovered from laboratory
workbenches even after disinfection with 1% hypochlorite solution.
The bacterial isolates were found to harbour certain enzymes and
factors, which contributes to virulence and by extension the public
health significance of the isolates. The multiple antibiotic resistance
index of the isolates, were above the permissible limit of 0.2 and thus
were of public health importance. This study revealed that disinfection
or cleaning of laboratory benches can reduce bacteria contamination
from 55% to 92% using 1% sodium hypochlorite solution (v/v).