Biochemical characterization and antimicrobial susceptibility of bacillus cereus isolates from some retailed foods in Ogun state, Nigeria

Abstract

Food borne disease caused by Bacillus cereus has been a major health issue because of its ability to cause two syndromes: diarrhoeal and emetic which sometimes lead to death. Six hundred (600) samples of some retailed foods: cooked rice, jollof rice, fried rice, meat pie, smoked fish: African chad, Titus, blue whiting, fried meat, smoked hide, carrot, runner beans, cabbage and raw green pea were collected from the eight main markets in Ogun State. Serial dilutions of the samples were carried out and cultured on Mannitol Egg Yolk Polymyxin Agar (MYP) using the spread plate technique. B. cereus was confirmed with standard biochemical methods. Antibiotic susceptibility was performed by the Kirby-Bauer disc diffusion method with nine antibiotics. The mean microbial load in the retailed food was in the range of 1.00 x 104-8.92 x 104cfu/g. All the isolates were gram positive rods, catalase and citrate positive. Most of the isolates were motile (97.7%). Two hundred and twenty one (221) isolates were confirmed as B. cereus with biochemical tests. They were 100% sensitive to gentamicin and 100% resistant to penicillin and ampicillin which are β-lactam antibiotics. All the isolates showed resistance to more than two antibiotics. This study has clearly revealed the presence of B. cereus in some retailed foods sold in Ogun State, Nigeria in which all the isolates were resistant to β-lactam antibiotics. Therefore, extreme caution should be taken when handling foods to avoid contamination by B. cereus and prevent any future food-borne outbreak by B. cereus.