Submitted to: Journal Of Food Protection
Publication Acceptance Date: August 21, 2003
Publication Date: February 20, 2004
Publisher's URL: foodprotection.org
 

Interpretive Summary: E. coli O157:H7 is a bacteria that can cause life threatening infections, especially in very young, very old, or immunocompromised people. In many cases, infections are caused by eating undercooked contaminated ground beef. E. coli O157:H7 occurs naturally among beef cattle where it is highly prevalent on the hide. During beef processing the bacteria can contaminate the carcass when the hide is removed. This hide-to-carcass transfer can lead to contaminated beef and ground beef products. Therefore, methods to reduce this contamination are under investigation. One such method involves decontaminating hides with an antiseptic commonly found in mouthwash. This antiseptic, cetylpyridinium chloride (CPC), was investigated to determine its suitability for reducing aerobic plate counts (APC) and Enterobacteriaceae counts (EBC), which are measures of two groups of bacteria that are indicators of overall cleanliness. The specific reduction of E. coli O157:H7 present on hides and carcasses was also determined. First, methods were needed that would allow the detection of bacteria when CPC was picked up with the bacteria during sampling. A neutralization procedure was developed that prevented exaggerated antimicrobial effects of CPC from being measured. The concentrations of CPC and the dwell time of its activity were also measured. It was found that 1% CPC was the lowest effective concentration that could be used and that its activity started as soon as 30 seconds after application and lasted for up to four hours. We applied 1% CPC to cattle, transported them to the processing plant, and compared levels of APC, EBC and numbers of E. coli O157:H7 on their hides and carcasses to those of untreated cattle. No reductions were observed, likely due to the cattle being too dirty when CPC was applied. We determined this was the case in a separate experiment by pressure washing hides and then applying CPC, also with pressure. Using this system, APC and EBC on the hides were reduced by 99.99%. These results indicate that under the proper conditions CPC can effectively reduce hide contamination and further study is warranted to determine if this effect will result in reduced hide-to-carcass contamination during processing.

Technical Abstract: The objective of this study was to establish the protocols necessary for the assessment of cetylpyridinium chloride (CPC) efficacy when used as an antimicrobial intervention on beef cattle hides. Experiments using CPC were conducted to determine: 1) the methods of neutralization needed to obtain valid efficacy measurements, 2) the effect of concentration and dwell time after treatment, 3) the effect of CPC on hide and carcass microbial populations when cattle were treated at a feedlot and then transported to a processing facility for harvest, and 4) the effectiveness of spray pressure and two-spray combinations of CPC and water to reduce hide microbial populations. Residual CPC in hide sponge samples prevented bacterial growth. Dey-Engley neutralization media at 7.8% and a centrifugation step were necessary to overcome this problem. All dwell times, ranging from 30 s to 4 h, after 1% CPC application to cattle hides resulted in aerobic plate counts (APC) and Enterobacteriaceae counts (EBC) 1.5-log10 CFU/100 cm**2 lower than controls. CPC at 1% was more effective at reducing APC and EBC (2- and 1 log10 CFU/100 cm**2, respectively) than CPC at 0.5%. Low-pressure application of 1% CPC at the feedlot, transport to processing facility, and harvest within 5 h of application resulted in no effect on Escherichia coli 0157:H7 prevalence on hides or preevisceration carcasses. Two high-pressure CPC washes lowered APC and EBC by 4-log10 CFU/100 cm**2 and two medium-pressure CPC washes were only slightly less effective. These results indicate that under the proper conditions, CPC can be effective for reducing microbial populations on cattle hides. Further study is warranted to determine if this effect will result in reduction of hide-to-carcass contamination during processing.

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