Abstract
Bacillus cereus widely distributed in the environment and can survive all types of heat treatment so, The present study was undertaken to assess the presence of Bacillus cereus in 60 milk samples (boiled milk, pasteurized milk and ultra-heat milk “UHT”) (20 each) were collected randomly from different dairy shops and supermarkets in Kafr El-Sheikh governorate. The results revealed that the incidence of B. cereus was 50%, 15% and 15% from boiled milk, pasteurized milk and ultra-heat milk(UHT), respectively. Susceptibility of B. cereus isolates to 14 antimicrobial agents showed that B. cereus isolates were high sensitive to Ciprofloxacin (Cp) 87.5%, Gentamicin 81.2%, Enrofloxacin (En) 62.5, Norfloxacin (NoR) 50%, Erythromycin (E) 43.8%, followed by Cephalothin (CN) 25%, Ampicillin (Am) 31.2%, Chloramphenicol (C), 18.8%, Cefixime (CF) 12.5%, Streptomycin (S 12.5%. Finally Oxytetracycline (T) 6.3%, while the isolates showed the highest resistance against Neomycin(N) 100%, followed by Kanamycin (K) 93.7% and finally Sulphamethoxazol (SXT) 81.2%. Detection of virulence genes of 16 isolates of B. cereus by multiplex PCR indicates that only 4 isolates (25%) were positive for hbl C gene, 2 isolates (12.5%) for cyt K gene and 10 isolates (62.5%) were positive for both hbl C and cyt K genes. Our data showed that the occurrence of the gene sequences that code for enterotoxins production increases the virulence and the public health hazard of these bacteria.

Key words: Bacillus cereus ,heat-treated milk and virulence factors