Microbial assessment and prevalence of foodborne pathogens in natural cheeses in Japan

The production and consumption of domestic natural cheese in Japan is increasing year by year. More than ninety percent of domestic natural cheese is produced in Hokkaido region of Japan, while information on its quality and safety related to foodborne pathogens is limited. To assess the microbiological safety of domestic natural cheese, a total of 126 natural cheese samples produced in Hokkaido were collected from December, 2012, to July, 2013. In addition to standard plate count (SPC) and coliform counts, the prevalence study of three pathogens (Listeria monocytogenes, pathogenic Escherichia coli, and Salmonella spp.) was performed on each sample. Real-time PCR and matrix-assisted laser desorption-ionization time-of-flight mass spectrometer methods were employed for identification of presumptive pathogens. Coliform was detected in 25 samples (19.8%) with a minimum of 25 cfu/g and a maximum of more than 3.0 × 10(6) cfu/g. Salmonella spp. and L. monocytogenes were not isolated from any of the samples. Only one sample (0.80%) showed positive PCR amplification for ipaH gene suggesting possible contamination of enteroinvasive E. coli or Shigella in this product. Overall results indicate that natural cheeses produced in Hokkaido region were satisfactory microbiological quality according to existing international standards.