Isolation of Bacillus cytotoxicus from various commercial potato products.

Bacillus (B.) cytotoxicus is a newly described thermotolerant member of the Bacillus cereus group. This potential foodborne pathogen had so far only been isolated from vegetable products, including mashed potatoes. Here we report the detection of B. cytotoxicus in a variety of potato products taken on retail level or from catering establishments (n=151). Identification of isolates as B. cytotoxicus was performed after enrichment at 50°C, followed by differentiation using Fourier transform-infrared spectroscopy and detection of the specific cytK-1 gene by PCR. Thirty-five percent of all samples were positive for B. cytotoxicus. Highest prevalence was found in dehydrated potato products (44/62=71%) such as powder for mashed potatoes and products made thereof. B. cytotoxicus was not detected in products that were evidently made directly from potatoes (n=24) but in one sample of raw potatoes (n=10; 10%). The high prevalence of this thermotolerant pathogen in potato products could pose a risk for consumers, especially if prepared foods are held at improper holding temperatures.