Isolation, Identification, Virulence Genes and Drug Susceptibility of Bacillus cereus from Low-Temperature Chicken Sausage

Bacillus cereus in low-temperature chicken sausage and its processing environment samples was counted following the GB 4789.14-2014 National standards for food safety-microbiological examination of food-test for Bacillus cereus. Polymerase chain reaction (PCR) and biochemical tests were combined to identify eight isolates and determine their virulence genes. The drug susceptibility of the isolates was determined using the disc diffusion method. The results showed that the detection rate of B. cereus in five samples of spoiled low-temperature chicken sausage was 100%. Based on the results of biochemical tests, 16S rDNA sequencing, the house-keeping gene gyrB and the Bacillus thuringiensis specific gene cry, all isolates were identified as B. cereus. Each strain carried at least five virulence genes, among which, the detection rate of the non-hemolytic enterotoxin gene was the highest. Five strains of B. cereus carried the nheA, nheB, and nheC genes simultaneously, but did not carry the vomitoxin gene ces. Strain A3 carried all virulence genes except ces, and was the strain that carried the largest number of virulence genes. Among the 22 antibiotics detected, the 8 strains of B. cereus were resistant to 8 antibiotics, including ampicillin, ceftazidime, cefazolin, streptomycin, penicillin, kanamycin, cotrimoxazole and cefuroxime sodium. In conclusion, the level of contamination of B. cereus in low-temperature chicken sausages was high, and the obtained isolates carried a wide range of virulence genes and were highly resistant to drugs, posing a risk of foodborne diseases and a threat to food safety.