Growth model of a plasmid-bearing virulent strain of Yersinia pseudotuberculosis in raw ground beef.
The growth kinetics of virulence plasmid-bearing Yersinia pseudotuberculosis (YPST) in sterile ground beef were studied at temperatures ranging from 0 to 30°C. In irradiated sterile ground beef, YPST replicated from 0 to 30°C, with corresponding growth rates (GR) ranging from 0.023 to 0.622 log CFU/h at 0-25°C, and the GR was 0.236 log CFU/h at 30°C. The maximum population densities (MPD) ranged from 8.7 to 11.0 log CFU/g. The growth and MPD of YPST were reduced significantly at 30°C. Models for GR and MPD of YPST in raw ground beef (RGB) as a function of storage temperatures were produced and displayed acceptable bias and accuracy. The models were validated with rifampicin-resistant YPST (rif-YPST) in sterile ground beef stored at 4, 10 and 25°C. The observed GR and MPD were within 95% of the predicted values. When compared to non-sterile retail ground beef, the growth of rif-YPST was not inhibited and displayed similar GR at 0, 10 and 25°C and MPDs as sterile ground beef at 10 and 25°C. Moreover, there was no loss of virulence plasmid in YPST during its growth in ground beef indicating that RGB contaminated with virulence plasmid-bearing YPST could cause disease due to refrigeration failure, temperature (10-25°C) abuse, and if the meat was not properly cooked.
Bhaduri
S
S
Microbial Food Safety Research Unit, Eastern Regional Research Center, Agricultural Research Service, United States Department of Agriculture, Wyndmoor, PA, USA. saumya.bhaduri@ars.usda.gov
Phillips
J G
JG
D000818:Animals; D002417:Cattle; D003080:Cold Temperature; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D005506:Food Contamination / Q000032:analysis / Q000517:prevention & control; D006801:Humans; D007700:Kinetics; D008461:Meat Products / Q000382:microbiology*; D008954:Models, Biological; D010957:Plasmids; D011158:Population Growth; D014774:Virulence; D015011:Yersinia pseudotuberculosis / Q000254:growth & development* / Q000472:pathogenicity*; D015012:Yersinia pseudotuberculosis Infections / Q000635:transmission / Q000662:veterinary