Microbiological studies of cockroaches from three localities in Gaborone, Botswana

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 mediawere 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 thosefrom 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 householdsprevents cockroaches from foraging in the kitchen and toilet

Short-term response of three soil types in Botswana to sewage sludge application

Changes in the moisture content (MC), volatile solid content (VS), water retention capacity (WRC), bulk density (Db), porosity, pH, electrical conductivity (EC), organic matter content (OM), and cation exchange capacity (CEC) of 2 luvisols, a vertisol and an arenosol from Botswana brought about by sludge addition were investigated. Each soil type was mixed separately with a 36 months and 3 months old sludge at volume per volume percent ratios of 5:95, 10:90, 20:80, and 40:60 sludge:soil. Ninety days after sludge addition, there was an increase in the porosity, WRC, VS, CEC OM and EC of the soils and a decrease in the pH and Db. Changes were more evident in soils amended with the 3 months old sludge than in soils amended with the 36 months old sludge. Sludge application rate and soil type affected the changes observed in the pH, EC, VS Db and WRC of the different soils types. Application of sludge to these soils significantly improved their physical condition after 90 days.Keywords: Soil physico-chemistry; sludge application rate; sludge ag