Prevalence and Characterization of Aerobic Spore Forming Bacteria in Raw Milk and Some Cheeses

Abstract

Prevalence of aerobic spore forming bacteria in raw milk, Ras cheese and Domiati cheese was investigated. Total bacterial and total aerobic spore forming counts were enumerated by using tryptone soy agar medium. All isolated aerobic sporeformers were identified on genus and species levels. The minimum, maximum and the means of total aerobic sporeformers counts in raw milk samples were 3.2×103, 2.7×104 and 1.5×104 cfu/ml, respectively. Counts in Ras cheese samples were, 2×102, 3.5×104 and 1.8×104 cfu/g, and in Domiati cheese samples being, 1.2×103, 2.3×104 and 1.2×104 cfu/g, in the same order. A total of 60 B. cereus group of bacterial cultures isolated from market dairy products were identified as B. anthracis 39(65%), B. cereus 6(10%), B. mycoides 13(21.7%) and B. thuringiensis 2(3.3%). Results also show that all tested 60 isolates could be plotted in different patterns from A to G, e.g. B. cereus (A), B. mycoides (B, C and D), B. thuringiensis (E) and B. anthracis (F and G).