Contamination and drug resistance characteristics of Bacillus cereus isolated from raw vegetable from May to September 2021 in a district in Beijing

Abstract

ObjectiveTo analyze the contamination and drug resistance characteristics of Bacillus cereus isolated from raw vegetable.MethodsOne hundred and twenty raw vegetable samples were collected in this study in Beijing City， Shuiyi District from May to September in 2021. Plate counting， bacterial culture， real-time PCR for the ces vomiting toxin gene and the 16S rDNA gene of B. cereus were performed. Drug resistance to 14 antibiotics in B. cereus strains were determined.ResultsThe positive ratios of B. cereus in raw vegetable samples was 84.17% （101/120）. Significant differences were observed in the positive ratio of B. cereus between rhizome and leaf vegetables （χ2=14.181， P=0.000 correction）， in the positive ratio of B. cereus （χ2=11.050， P=0.004） in supermarkets， agricultural markets， and farmland， and also in the positive ratio of ces on enriched samples （P=0.001 Fisher）. Average Ct values of 16S rDNA and ces by real-time PCR in 12 ces+ enriched samples were 19.96 and 31.80， respectively； however， ces+ B. cereus was not isolated. The drug resistance ratios of B. cereus isolates to AMP， PEN， and SXT were 100%， 99.01%， and 61.39%， respectively. Five patterns of drug resistance distribution were observed and the dominant pattern was AMP+PEN+SXT （59.41%）； the multidrug resistance ratio （resistant to three or more classes of antibiotics） was 0.99% （1/101）.ConclusionB. cereus and the ces gene were widely distributed in local raw vegetable samples with a low level of multiple drug resistance in the isolates. ces+ B. cereus was present in low proportions in the B. cereus flora in s single sample of raw vegetable.

Keywords

• bacillus cereus
• raw vegetable
• vomiting toxin
• drug resistance
• foodborne pathogenic
• shunyi district