Incidence of Staphylococcus aureus and associated risk factors in Nham, a Thai fermented pork product

• Published in: Food microbiology 2009-08, Vol.26 (5), p.547-551
• Main Authors: Chokesajjawatee, Nipa, Pornaem, Sarinya, Zo, Young-Gun, Kamdee, Sanit, Luxananil, Plearnpis, Wanasen, Srianant, Valyasevi, Ruud
• Format: Article
• Language: English
• Subjects: Animals; bacterial contamination; Biological and medical sciences; Colony Count, Microbial; Consumer Product Safety; Enterotoxins; Fermentation; fermented foods; Fermented pork; food contamination; Food Contamination - analysis; Food Contamination - prevention & control; Food Handling - methods; Food industries; Food Microbiology; food pathogens; food storage; Fundamental and applied biological sciences. Psychology; Humans; Hydrogen-Ion Concentration; incidence; mathematical models; Meat and meat product industries; Meat Products - microbiology; Nham; pork; predictive microbiology; Predictive Value of Tests; Risk Factors; Staphylococcal enterotoxins; Staphylococcal Food Poisoning - epidemiology; Staphylococcal Food Poisoning - prevention & control; staphylococcal intoxication; Staphylococcus aureus; Staphylococcus aureus - growth & development; Swine; Thailand; toxigenic strains; traditional foods
• ISSN: 0740-0020; 1095-9998
• DOI: 10.1016/j.fm.2009.02.009

Staphylococcus aureus is one of the most prevalent bacterial pathogens causing food-borne disease worldwide. Staphylococcal food poisoning is caused by ingestion of staphylococcal enterotoxins (SEs) pre-formed in the implicated food. In this study, the incidences of S. aureus and classical SEs (SEA-SEE) contamination in ‘Nham’, a traditional Thai fermented pork product, were determined. Among 155 Nham samples tested, as high as 39.35% of the samples were positive for S. aureus (2–3500 MPN/g), but none were positive for the SEs. The risk factors for S. aureus contamination were highly correlated with the manufacturer and the pH of the product. A predictive model determined the probability of the presence of S. aureus to be ≤0.24 at the pH ≤ 4.6. During the fermentation process, the number of S. aureus slightly increased in the first day and decreased afterward. S. aureus counts continued to decrease when Nham was stored refrigerated. The negative result for enterotoxins and low counts of S. aureus in Nham surveyed in this study, and reduction of the pathogen counts during fermentation and storage suggested that there is very low risk of staphylococcal food poisoning from consuming properly fermented Nham.