According to the Centers for Disease Control and Prevention (CDC), approximately 76 million cases of foodborne illness occur each year in the United States, and approximately 14 million of those cases can be attributed to known pathogens (Mead, Slutsker, & Dietz, 1999). Foodborne diseases are also to blame for approximately 325,000 hospitalizations and 5,000 deaths in the United Sates each year (Mead et al., 1999). More than 100 outbreaks of Escherichia coli O157:H7 have occurred since 1982, and over half (52%) of those outbreaks have been linked to beef (Barham, Barham, Johnson, Allen, Blanton, & Miller, 2002).
Cattle are a known reservoir for E. coli O157:H7, and some studies estimate that approximately 16% of all cattle carry this organism in their rumen and colon (Chapman, Siddons, Cerdan-Malo, & Harkin, 1997). Hides are considered an important source of pathogenic organisms during slaughter because of fecal contamination experienced during holding (Castillo, Dickson, Clayton, Lucia, & Acuff, 1998). Feedyards can be a likely source of E. coli O157:H7 and Salmonella spp. because cattle there are mixed from multiple locations, and cattle are kept in high-density pens (Barham et al., 2002). Levels of Salmonella on the external surfaces or hides of cattle have been determined to be as high as 15% pre-slaughter (Bacon, Sofos, Belk, Hyatt, & Smith, 2002). The transfer, or shedding, of Salmonella spp. to foods from an animal carrying the organism has the potential to cause human illness (Barham et al., 2002).
Bacteria present on hides can contaminate carcass tissue during the hide removal process. Contamination can occur when manure on the hide surface that has not been washed away before slaughter is carried onto the underlying carcass tissue (Delazari, Iaria, Riemann, Cliver, & Jothikumar, 1998). Pre-harvest cattle washing systems have met with limited success. Previous research has shown that carcass washes solubilized pathogenic bacteria present on hide surfaces enabling the migration of pathogens from areas of heavy contamination on the hide to all areas of the hide. This was particularly true along the mid-line, where the initial openings through the hide are made and are most prone to contamination.
Processors have incorporated carcass wash cabinets in their slaughter and processing lines to reduce levels of microbial contamination. However, to strengthen a food safety system, processors should investigate proactive, preventive procedures that can reduce levels of pathogenic bacteria found on hides before those bacteria have a chance of reaching the carcass.
Major beef processors have also investigated post-exsanguination hide washing systems. However, these systems may not reduce the solubilization and migration of pathogenic bacteria on hide surfaces and these systems will be too costly for most small and medium size beef processors. Selective application of antimicrobial compounds to hide opening areas would be economical and particularly beneficial to small and medium scale processing plants.
This research outlines an innovative approach to minimizing pathogen transfer from the hide to carcass tissues during slaughter and/or processing. This method could serve as a safeguard against carcass contamination during the dehiding process and may assist in developing procedures to follow within the hide removal process.
The objectives of this study were to (1) determine the effectiveness of selected antimicrobial agents in reducing pathogenic microorganisms on hides and (2) verify the efficacy of selected antimicrobial agents in a commercial facility.
Three trials were conducted in this study. Trials I and II were conducted to determine the effectiveness of selected antimicrobial agents (distilled water, isopropyl alcohol, 3% hydrogen peroxide, 2% L-lactic acid, 10% Povidone-iodine, and 1% cetylpyridinium chloride (CPC)) on reducing pathogenic microorganisms on shaved and non-shaved hides.
Trial III was conducted to determine the efficacy of antimicrobial agents (2% L-lactic acid, 3% hydrogen peroxide, and 1% CPC) chosen from Trials I and II in reducing pathogenic microorganisms on shaved hides.
Trial I
Twelve fresh beef hides were selected and cut into sections for study. One half were shaved and one half were not shaved. Hide sections were inoculated with a fecal slurry solution and allowed to attach for 20 minutes before being washed off using a handheld, compressed-air sprayer. Microbiological sponge samples were collected from each untreated hide following water wash to determine pre-treatment counts on hide surfaces. Following treatment, hides sections were again sampled for pathogen levels.
Trial II
Nine beef carcasses were selected for sampling at the Rosenthal Meat Science and Technology Center at Texas A&M University. Cattle were exsanguinated, shaved in the brisket area, and inoculated in the brisket area with a nonpathogenic marker bacterium designed to represent possible contamination with fecal material containing enteric pathogens such as Salmonella or E. coli O157:H7.
Immediately following inoculation, gross fecal material was washed off using a handheld, compressed-air sprayer. Following washing, a sponge sample (covering approximately 100 cm2) was taken to determine initial counts. Carcasses then were assigned to receive one of three antimicrobial agents (2% L-lactic acid, 10% Povidone-iodine, and 1% CPC) deemed most effective from Trial I. After application of antimicrobial agents, hides were again sampled to determine post-treatment counts. Following hide removal, a 100 cm2 area of the carcass in the brisket region was sampled for the marker bacteria strain.
Trial III
Eighteen beef carcasses with hides attached were selected from a small commercial processor for use in Trial III. Following exsanguination, approximately 100 cm2 of the hide in the brisket area was sponge-sampled to determine pre-treatment counts on hide surfaces. Following sampling, hides were shaved in approximately a 400 cm2 area in the brisket region of the carcass. Carcasses then were assigned to receive one of three antimicrobial treatments (2% L-lactic acid, 3% hydrogen peroxide, and 1% CPC) deemed effective in Trials I and II. Treatments were applied using sterile sponges. After application of the designated treatment, hides were sampled again to determine post-treatment counts. Following hide removal, 100 cm2 of the carcass surface in the brisket area was sampled to determine carcass counts.
Trial I
Across all treatments, shaving appeared more advantageous than not shaving when applying antimicrobial agents to reduce bacterial counts on the hide surface. After completion of Trial I, shaving together with 1% CPC, 2% L-lactic acid, and hydrogen peroxide were determined to be the three most effective shaving/antimicrobial combinations, and were selected for further evaluation in Trials II and III.
Trial II
Though few differences existed between the three antimicrobial treatments identified in Trial I, all resulted in approximately a 2 log10 CFU/100 cm2 reduction when applied to shaved hide surfaces in the brisket region of the carcass.
Trial III
The average initial hide counts before treatment application were 8.1 log10 CFU/100 cm2 for APC, 4.2 log10 CFU/100 cm2 for coliforms, and 4.5 log10 CFU/100 cm2 for E. coli. For APCs, 1% CPC produced the greatest reduction on the hide with 3.9 log10 CFU/100 cm2 reported. For coliforms and E. coli, there were no statistically significant differences among treatments for hide reductions. Though few differences existed between antimicrobial treatments, all three resulted in approximately a 3 log10CFU/100 cm2 reduction when applied to shaved hide surfaces in the brisket region of the carcass.
Findings from this study showed that bacterial counts on hide surfaces were reduced by shaving and applying an antimicrobial agent directly to the hide opening area in the brisket region. This method targets a specific area on the hide that is very susceptible to fecal contamination and is very critical when opening up the hide for removal. Selective application of these antimicrobials to shaved hide-opening sites can reduce bacterial counts on hide surfaces, and therefore potentially reduce final carcass counts in these areas by decreasing the bacterial load before opening. Further research should be conducted to determine effectiveness along additional areas of the hide surface, and to evaluate the practicality of this process outside of a research setting.