Evaluation of the prevalence rate and antibiotic resistance pattern of Bacillus cereus in infant formula and foods containing formula

The present study was conducted with the aim of evaluating the antibiotic resistance pattern of Bacillus cereus in ice cream, cake, cheese, and infant formula. For this purpose, 600 samples were prepared from food sales centers in Tehran and transferred to the quality control laboratory of the Faculty of Veterinary Medicine of Tehran University of Medical Sciences and cultured on the special culture medium of Bacillus cereus, MYP, which contained polymyxin B supplement and egg yolk. Then, from the pink colonies, gram staining and catalase test were performed and the sensitivity of the isolated bacteria to ampicillin, penicillin, vancomycin, cefazolin, methicillin, cefixime, sulfamethoxazole, trimethoprim, chloramphenicol, cefepime and tetracycline was evaluated based on the disc diffusion method. According to the results, no contamination with B. cereus was observed in any of the cake, cheese and ice cream samples. However, out of 150 infant formula samples, 30 samples were infected with B. cereus (18 samples < 10 CFU/g, 7 samples had 10-102 CFU/g, and 5 samples>102 CFU/g). B. cereus isolated from infant formula has the highest sensitivity to vancomycin (67.76%), tetracycline (70%), and chloramphenicol (33.63%) antibiotics and had the highest level of resistance to penicillin (100%), cefixime antibiotics (100%) and ampicillin (67.96%). The general results indicated a significant prevalence of B. cereus in the tested milk, which due to the growing trend of using milk powder and more importance to the quality and health evaluation of milk powders for consumption, contamination investigation and preventive approaches should be given more attention.