Search

In this work, the development of resistance and the recovery of growth after several consecutive cycles of high hydrostatic pressure (HPP) were for the first time evaluated in different strains of Staphylococcus aureus. Three strains of this important and highly resilient to HPP foodborne pathogen were used: a non-enterotoxigenic ATCC 6538 strain, treated with 600 MPa for 30 min at 20 °C, and the toxigenic strains 2153 MA (with enterotoxin A) and 2065 MA (with the enterotoxins A, G and I), treated with 600 MPa for 15 min at 20 °C. After the first treatment, surviving colonies were used to produce new bacterial cultures. This procedure was repeated nine times more for each bacterium or until total inactivation occurred. The inactivation profile of non-enterotoxic strain and the two enterotoxic strains did not change after consecutive cycles, but the toxic strain with three enterotoxins was completely inactivated after the fourth cycle. The three strains did not recover their viability after 14 days. The results indicate that HPP effectively inactivates non-toxigenic and toxigenic strains of S. aureus after a single treatment. The surviving bacteria did not develop resistance after 10 cycles of pressurization and did not recover their viability after 14 days of incubation., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Staphylococcus aureus is responsible for a large spectrum of diseases, including staphylococcal food poisoning (SFP), due to its ability to produce enterotoxins. To prevent the development of SFP, effective food preservation methods are needed. High pressure processing (HPP) uses pressures, between 100 and 600 MPa, to inactivate pathogenic and spoilage microorganisms. In this study, HPP treatments (450 MPa and 600 MPa, both for 15 and 30 min, at 20 °C) were applied in three different strains of S. aureus in the stationary growth phase and reduction effectiveness was assessed. A non-enterotoxic strain ATCC 6538 and two enterotoxic strains 2153 MA (with enterotoxin A) and 2065 MA (with enterotoxin A, G, I) were used. It was verified that the non-enterotoxic strain was the most resistant to HPP, not being completely inactivated within 30 min at 600 MPa. Additionally, it was demonstrated that HPP had no effect on virulence factors (enterotoxins, β-hemolysin, lipase, lecithinase, coagulase, thermonuclease, catalase), and also in mannitol fermentation capacity and methicillin susceptibility. HPP treatments also proved to be less effective in the strain with higher carotenoids content (non-enterotoxic strain). The results of this study show that S. aureus HPP barotolerance might be related not only to the presence of enterotoxins but also to carotenoids level, although these two factors may not be the only mechanisms responsible for the distinct sensitivity/resistance to HPP shown by different strains of S. aureus . [ABSTRACT FROM AUTHOR]