Decontamination of beef subprimal cuts intended for blade tenderization or moisture enhancement.

The prevalence of Escherichia coli O157:H7 on beef subprimal cuts intended for mechanical tenderization was evaluated. This evaluation was followed by the assessment of five antimicrobial interventions at minimizing the risk of transferring E. coli O157:H7 to the interior of inoculated subprimal cuts during blade tenderization (BT) or moisture enhancement (ME). Prevalence of E. coli O157:H7 on 1,014 uninoculated beef subprimals collected from six packing facilities was 0.2%. Outside round pieces inoculated with E. coli O157:H7 at 10(4) CFU/100 cm2 were treated with (i) no intervention, (ii) surface trimming, (iii) hot water (82 degrees C), (iv) warm 2.5% lactic acid (55 degrees C), (v) warm 5.0% lactic acid (55 degrees C), or (vi) 2% activated lactoferrin followed by warm 5.0% lactic acid (55 degrees C) and then submitted to BT or ME. Prevalence (n=196) of internalized (BT and ME) E. coli O157:H7 was 99%. Enumeration of E. coli 0157:H7 (n=192) revealed mean surface reductions of 0.93 to 1.10 log CFU/100 cm2 for all antimicrobial interventions. E. coli O157:H7 was detected on 3 of the 76 internal BT samples and 73 of the 76 internal ME samples. Internal ME samples with no intervention had significantly higher mean E. coli O157:H7 populations than did those internal samples treated with an intervention, but there were no significant differences in E. coli O157:H7 populations among internal BT samples. Results of this study demonstrate that the incidence of E. coli O157:H7 on the surface of beef subprimal cuts is low and that interventions applied before mechanical tenderization can effectively reduce the transfer of low concentrations of E. coli O157:H7 to the interior of beef subprimal cuts.

Fecal prevalence of Escherichia coli O157, Salmonella, Listeria, and Bacteriophage Infecting E. coli O157:H7 in feedlot cattle in the Southern Plains region of the United States.

Escherichia coli O157:H7, Salmonella, and Listeria are foodborne pathogens of critical importance that often colonize cattle. E. coli O157:H7 can be specifically killed by lytic bacteriophage, and lytic bacteriophage treatment has been suggested as a pre-harvest intervention strategy to reduce foodborne pathogens in cattle. To date, no systematic approach to determine the incidence of E. coli O157:H7-infecting lytic bacteriophage has been published. Therefore, the current study was designed to determine (1) the incidence of E. coli O157, Salmonella spp., and Listeria and (2) the incidence of E. coli O157:H7-infecting bacteriophage in the feces of feedlot steers in commercial feedlots in the United States. Fecal samples (n=60) were collected from four feedlots in two Southern Great Plains states (total (n=240 fecal samples). Salmonella and E. coli O157:H7 were found in 3.8% and 11.7% of the fecal samples, respectively. Bacteriophage targeting E. coli O157:H7 were found in all four feedlots, in 15% of the individual fecal samples, and in 55% of the cattle pens. Our results indicate that such bacteriophage are widespread in feedlot cattle, suggesting that further research into the ecological role of bacteriophage in the gastrointestinal tract is needed.

Role of curli fimbriae in mediating the cells of enterohaemorrhagic Escherichia coli to attach to abiotic surfaces.

AIMS: The objectives of this study were to evaluate the role of curli in assisting the cells of enterohaemorrhagic Escherichia coli (EHEC) in attaching to abiotic surfaces and to determine the influence of cell-surface contact time on the efficiency of the attachment. METHODS AND RESULTS: Three pairs of EHEC cultures, each with a curli-expressing and a noncurli-expressing variant (O111:H- 7-57C+ and O157:H7 5-9C-, O157:H7 5-11C+ and 5-11C-, as well as O103:H2 7-52C+ and 7-52C-), were allowed to interact with polystyrene, glass, stainless steel and rubber surfaces at 28 degrees C for 24 h (short-term attachment) or 7 days (long-term attachment). The quantities of the cells that attached to the surfaces were measured daily in the long-term attachment study, and in 4 h intervals in the short-term attachment study. Quantification of the cells that attached to the surfaces was accomplished with a crystal violet binding assay. The results of the long-term attachment study indicated that 7-57C+ attached to the polystyrene and glass surfaces more efficiently (P < 0.05) than did 5-9C-. The curli-expressing variant of 5-11 possessed a better ability to adhere to the polystyrene and glass surfaces than did its noncurli-expressing counterpart (P < 0.05). The differences in attachment between 7-52C+ and 7-52C- on polystyrene and stainless steel surfaces were statistically significant (P < 0.05). However, the attachment of the pair on the glass surfaces was statistically insignificant (P > 0.05). In addition, the two members of all three EHEC pairs attached equally well to rubber surfaces (P > 0.05). In the short-term attachment study, only the pair of 7-52 attached differently on glass and stainless steel surfaces (P < 0.05). CONCLUSIONS: These results suggest that curli could be an important cell surface component to mediate the attachment of some EHEC cells to certain abiotic surfaces. Cell-surface contact time could have a significant influence on EHEC attachment to abiotic surfaces. SIGNIFICANCE AND IMPACT OF THE STUDY: The study signifies a possible role of curli in assisting the cells of EHEC in attaching to food-contact surfaces. It underlines the importance of cleaning and sanitizing food-contact surfaces regularly and thoroughly, and of identifying chemical agents that can effectively remove the attached EHEC cells from these surfaces.