Aerobic bacterial count & prevalence of bacillus cereus group species in air of selected areas of Karachi

Aerobiological quality of selected regions of Karachi was monitored in terms of total aerobic bacterial count and prevalence of B. cereus group species. The selection of sampling locations was made on seeming cleanliness and dirtiness of the locations. Four locations were selected, Malircantt and Airport terminals as clean areas while Cantt Station and S.I.T.E area as dirty areas. Sampling was carried out by Millipore Air tester. Nutrient agar and Mannitol Egg Yolk Polymixin (MYP) agar were used for estimating total bacterial count and B. cereus group species respectively. Quadruplicate samples per month per location were taken from April 2010 to October 2010 (Total 96 samples). No paradox was observed and apparently dirty locations were contaminated with higher bacterial counts (Max count: Cantt 6000 cfu/m³, S.I.T.E. 3600 cfu/m³ count and vice versa (Max count: MalirCantt 2400 cfu/m³, Airport 912 cfu/m³). As for B. cereus group species Mannitol negative and leci-thinase positive colonies on MYP agar were gram and spore stained to ascertain their preliminary identity. Heamolysis patterns, salicin fermentation, motility and parasporal bodies staining were used for species level identification. A total of 32 isolates were studied which were identified as B. cereus (3/32), B. mycoides(11/32) and B. thuringiensis(18/32).