PHENOTYPIC CHARACTERIZATION, VIRULENCE POTENTIAL, AND GENETIC DIVERSITY OF BACILLUS CEREUS ISOLATED FROM RAW COW’S MILK OF SOME EGYPTIAN DAIRY FARMS

ASFOUR, HANAA A.E.; ABD EL FATTAH, EMAN, M.; AREF, NOHA E.; DARWISH, SAMAH F.

doi:10.21608/avmj.2024.307413.1332

PHENOTYPIC CHARACTERIZATION, VIRULENCE POTENTIAL, AND GENETIC DIVERSITY OF BACILLUS CEREUS ISOLATED FROM RAW COW’S MILK OF SOME EGYPTIAN DAIRY FARMS

Document Type : Research article

Authors

¹ Mastitis and Neonatal Diseases Department, Animal Reproduction Research Institute (ARRI), Agricultural Research Center (ARC), Giza, Egypt

² Biotechnology Research Unit, Animal Reproduction Research Institute (ARRI), Agricultural Research Center (ARC), Giza, Egypt

10.21608/avmj.2024.307413.1332

Abstract

This study aimed to achieve the incidence, phenotypic characterization, virulence potential, and genetic diversity of B. cereus sensu lato group in raw bulk tank milk (BTM) and mastitic milk, with special concern to the B. cereus sensu stricto (s.s.). Milk samples including122 bulk tank milk (BTM) and 67 clinically mastitic cow’s milk were screened for the existence of B. cereus s.l. group. B. cereus s.s. were isolated and PCR-confirmed with a prevalence of 31.7%. Thirty-two isolates displayed typical morphology, while 28 isolates displayed atypical morphology. Among isolates, 93.4, 46.7 and 85% were hemolytic, biofilm, and slime producers, respectively. The most prevalent toxin genes were cyt-k, bceT and nhe genes in percentages of 86.7, 85, and 46.7%, respectively. One isolate harbored ces-gene (1.7%). Also, 53.3% and 50 % of B. cereus s.s. isolates harbored tasA and sipW genes, respectively. Comparing typical and atypical isolates revealed that 100% of typical isolates were hemolytic versus 85.7% of atypical isolates, 53.1% and 78.1% of typical isolates were biofilm and slime producers versus 39.3% and 92.9% of atypical ones. Nine toxin gene profiles were found. Prevalences of toxin and biofilm-related genes in typical isolates were 53.1, 84.4, 93.8, 0, 46.9 and 46.9 % for nhe, cyt K, bceT, ces, tasA, and sipW genes versus 39.3, 89.3, 75, 3.6, 60.7 and 53.57% in atypical isolates. The obtained finding demonstrated the presence of potentially pathogenic B. cereus s.s. in milk. The isolation of atypical forms of B. cereus s.s. which weren’t less virulent than the typical form was confirmed. Therefore, efforts should be made to prevent their misdiagnosis in dairy plants.

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