Insight into Bacillus cereus Associated with Infant Foods in Beijing

Abstract

This study was undertaken to investigate the prevalence, antimicrobial resistance, and virulence gene profiles of Bacillus cereus in different brands of infant formula in Beijing supermarkets. Eighty-eight Bacillus cereus isolates were recovered in sixty-eight infant formulas of five domestic brands and fourteen imported brands. The prevalence rate in domestic and imported samples were 70.6% and 52.9%, respectively. Lower mean prevalence level was found in domestic samples (1.17 MPN/g) compared with the imported samples (3.52 MPN/g). Twenty-four virulence gene profiles were found, and most strains carried at least one virulence gene. The prevalence of nheA, nheB, nheC, cytK, bceT, and entFM in domestic and imported brand samples was similar. The occurrence of enterotoxin genes hblA, hblC, and hblD in domestic samples were 22.2%, 27.8%, and 22.2%, respectively, which was significantly higher than imported samples. Antimicrobial drugs-susceptibility analysis showed that all isolates were susceptible to gentamincin, amikacin, and ciprofloxacin; 38%, 7%, and 2.3% were resistant to rifampin, tetracycline, and chloramphenicol, respectively; and only one isolate was resistant to trimethoprim-sulfamethoxazole. Moreover, the cell numbers of Bacillus cereus in prepared infant formula increased rapidly at room temperature. Thus, monitoring guidelines are needed for accepted levels of Bacillus cereus in infant formula.