Dynamics of staphylococcal enterotoxin production in model experiments simulating the fresh cheese environment

Abstract

The aim of this study was to evaluate the impact of internal factors (pH, NaCl) and external factors (temperature, incubation time) on the ability of Staphylococcus aureus to grow and to produce staphylococcal enterotoxins SEA, SEB, and SEC. The fresh cheese environment was modelled in Brain Heart Infusion Broth media and food matrices (pasteurized milk from retail outlets) by internal and external factors (pH = 4.5 and 5.5, 2% NaCl, and t = 8 °C and 15 °C). The counts of enterotoxigenic strains of S. aureus at baseline, i.e. at the time of inoculation of model samples, corresponded to those encountered in the production of fresh cheeses as a result of post-pasteurization contamination. Enumeration of S. aureus was performed in accordance with EN ISO 6888-1, using agar medium. Staphylococcal enterotoxins were detected by the enzyme-linked fluorescence assay. The pH (4.5) and refrigeration temperature (8 °C) used prevented S. aureus from achieving the critical count of 10 5 cfu·ml -1 specified in Commission Regulation (EC) No. 2073/2005. The highest rates of enterotoxin production were recorded for enterotoxin A. The growth curves of S. aureus derived from model experiments were compared with the growth curve generated by a predictive microbiology program -Pathogen Modelling Program. The results of this study proved the Pathogen Modelling Program to be suitable for use in the Hazard Analysis Critical Control Points system in the process of the fresh cheese production to help manufacturers prevent the growth of S. aureus and enterotoxin production.

The production characteristics of volatile organic compounds and their relation to growth status of Staphylococcus aureus in milk environment

“…The dose of enterotoxins reaches a certain level when the Staph. aureus population in contaminated food exceeds 10 5 cfu/g or cfu/mL, and this toxin level could produce symptoms of staphylococcal intoxication (Necidová et al, 2012). In the present study, we detected 3-methyl-butanoic acid when Staph.…”

Short communication: Pasteurization as a means of inactivating staphylococcal enterotoxins A, B, and C in milk

“…The limit of 10 5 cfu/g or mL is considered a high-risk count of Staph. aureus in food, which enables the production of enterotoxins (European Commission, 2005;Necidova et al, 2012). From the results of our study, it is evident that diverse strains of the same species may produce various amounts of enterotoxins.…”

Assessment of the development of Staphylococcus aureus during the production of soro on a laboratory scale

“…As described on literature reports, the production of staphylococcal enterotoxins occurs in food matrices with populations of S. aureus larger than 10 5 CFU.mL -1 or UFC• g -1 (Necidová et al,2012). Asao et al (2003) verified that staphylococcal enterotoxin type A was only detected in reconstituted powdered milk when the S. aureus population reached levels of 10 5 CFU•mL -1 .…”

“…Despite the flaws in epidemiological data from Brazil, S. aureus was the third pathogen described as the cause of foodborne diseases outbreaks and highly associated with dairy products (Brazil, 2019b;SVS, 2019). Although the microorganism does not cause any disease when ingested in its vegetative form, counts greater than 10 5 CFU•mL -1 in whey can produce heat-resistant enterotoxins that cause food poisoning (Necidová et al, 2012;da Silva Cândido et al, 2020). A systematic efficacy evaluation of the whey powder processing in reducing the S. aureus population has not yet been described in previous studies.…”