Microbiological studies of cockroaches from three localities in Gaborone, Botswana

Abstract

Cockroaches have become the most common pests in a majority of households in Gaborone, the capital city of Botswana Their presence has always raised safety concerns, especially as carriers of food-borne pathogens and food-spoilage organisms. To address the safety issues, bacteriological investigations were carried out on cockroaches trapped from the kitchens and toilets of three localities in Gaborone, households in Botswana. The bacterial, total spore forming, Bacillus cereus, coliforms and E. coli counts from the surfaces of cockroaches were estimated using bacteriological media. Aerobic and facultatively anaerobic bacteria from the fecal pellets were isolated and characterized. Specialized media
were used for culturing pathogens. 67 %, 22.2 % and 28.6 % of the cockroaches trapped in the kitchen from Central/Broadhurst, Old Naledi and Tlokweng, respectively, had aerobic plate counts of > 106 CFU/cockroach. The cockroaches trapped from the toilets had higher counts than kitchens. Sporeformers were present in most samples though in lower numbers. However, Bacillus cereus was only found in some of the cockroaches at much lower numbers. As much as 70– 98.3% of the cockroaches had coliforms; but, E. coli was only found in 5–6.5% of the cockroaches at > 103 CFU/cockroach. 70 species of bacteria representing 37 genera were isolated from the surface and fecal pellets. Even though the majority of the bacteria that were isolated from the surfaces were Gram negative those
from the pellets were mostly Gram positive. The most common and abundant species belonged to Pseudomonas and Serratia, with members of the Enterobacteriaceae following. In the pellets, species of Bacillus were predominant, but, there were some members of Enterobacteriaceae. Pathogens like Salmonella, Shigella and B. cereus were isolated. Opportunistic pathogens like species of Pseudomonas, Klebsiella and Vibrio and food spoilage bacteria such as species of Enterobacter, Citrobacter, Escherichia, Erwinia, and Pseudomonas were also found. Proper care in disposal of food remnants and overall cleanliness at the households
prevents cockroaches from foraging in the kitchen and toilet.