Contamination of Burkholderia gladioli pathovar cocovenenans in Retail Foods and Its Growth and Toxicity Characteristics
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Abstract:
Burkholderia gladioli pathovar cocovenenans (BGC) is a food-borne pathogen with the highest morbidity and mortality found in China. Outbreaks of severe, BGC-caused food-poisoning have been reported every year in Guangdong Province from 2018 to 2020. The prevalence of BGC in commercial wet rice flour products, white tremella, and agaric in Guangzhou and growth and toxin production characteristics of the pathogen under various conditions were determined. One hundred food samples were subjected to qualitative analysis for BGC using the national food safety standard food microbiological examination (GB 4789.29-2020). By measuring the OD600 values and the contents of toxins under different culture conditions, the growth and the toxin-producing abilities of BGC under different incubation temperatures and durations, pH values, and NaCl concentrations were evaluated. Of the 100 food samples, one sample (in agaric) tested positive for BGC. The growth and toxin production of BGC were greatly affected by the culture medium. BGC grew in potato dextrose, but hardly grew in brain heart infusion broth in an alkaline environment (pH value 9.5~10.5) and at NaCl concentrations of 0.02~0.04 g/mL. The toxin production of BGC in potato glucose semisolid agar (231.24 µg/mL) was much higher than that in BHI and LB semisolid agar (38.84 µg/mL). The growth and toxin production temperature and pH value suitable for growth of BGC were 20~37 ℃ and 4~8.5; optimal growth temperature and pH value were 37 ℃ and 6.0; and the optimal toxin production temperature and pH value were 30 ℃ and 7.0, respectively. BGC survived and produced toxins (2.11 µg/mL) at low temperatures (4~15 ℃). The toxin production of BGC was obviously inhibited at high NaCl concentrations. When the NaCl concentration was 0.005 g/mL, the toxin production decreased from 139.80 μg/mL to 52.27 μg/mL; at 0.04 g/mL, no toxins were produced. There is a risk of BGC contamination in agaric in Guangzhou. BGC-caused food-poisoning outbreaks can be reduced by adding NaCl during food processing or storage.
