Assessment of beef carcass contamination with Salmonella and E. coli O 157 in slaughterhouses in Bishoftu, Ethiopia

Background Salmonella and E. coli O157 are common causes of foodborne diseases. Evisceration and de-hiding steps can lead to carcass contamination during slaughter operation. In Ethiopia, information on the association between the presence of these pathogens in the rectal content and/or on the hide of cattle and their presence on the carcass is lacking. Methods The aim of this study was to assess the sources of beef carcass contamination with Salmonella and E. coli O157 during slaughter. Rectal contents and hide- and carcass-swabs (from three sites: foreleg, brisket and hind leg) were collected from 70 beef cattle at two small scale slaughterhouses. Isolates were genotyped by the Pulsed Field Gel Electrophoresis method and tested for resistance against 14 microbial drugs. Results Salmonella was detected at equal proportions (7.1%) in rectal content samples and hide swabs. E. coli O157 was detected in 8.6% of the rectal contents and 4.3% of the hide swabs. The proportion of contaminated carcasses was 8.6% for Salmonella and 7.1% for E. coli O157. Genetic linkage between the Salmonella and E. coli O157 isolates from the rectal contents and/or hides and carcasses were observed only in a few cases (2 and 1 carcasses, respectively) indicating the limited direct transfer of the pathogens from the feces and/or hide to the carcass during slaughter. Most carcasses became positive by cross contamination. All the S. Typhimurium isolates (n = 8) were multidrug resistant being resistant to ampicillin, chloramphenicol, sulfamethoxazole and tetracycline. The two S. Dublin isolates were resistant to colistin. All E. coli O157 isolates were susceptible to the antimicrobials tested. Conclusion The results indicated that cross contamination may be an important source for carcass contamination.

PSI-8 Effect of breed on the abundance and expression of Shiga toxin in Escherichia coli from the recto-anal junction of feedlot beef cattle

Shiga toxin (Stx) is the main virulence factor of Shiga toxin-producing E. coli (STEC), and ruminants including cattle are the main reservoir of STEC. This study aimed to assess whether cattle breed affects the abundance and expression of Stx and to determine whether the expression of host immune genes can serve as markers of STEC colonization. In total, 143 rectal tissue and content samples were collected from feedlot beef steers in 2014 (n = 71) and 2015 (n = 72) composed of three breeds (Angus, Charolais and Kinsella Composite) with differing feed efficiency. The abundance and expression of Stx1 and Stx2 by STEC associated with rectal tissue was quantified by qPCR and reverse-transcription-qPCR, respectively. Four immune genes (MS4A1, CCL21, CD19, and LTB), previously reported to be down-regulated in super-shedder cattle (i.e., > 104 cfu g-1) were selected and their expression was evaluated using qPCR. The abundance of stx1 and stx2 differed (P < 0.001) among breeds in rectal content samples collected in 2014, while no such difference was detected for 2015 samples. Correlation analysis showed that the expression of stx2 was negatively correlated with MS4A1 (R = -0.56, P = 0.05) and positively associated with LTB (R = 0.60, P = 0.05). The random forest model revealed that the expression of selected immune genes could be used as indicators of Stx2 expression and potential STEC colonization with prediction accuracy of MS4A1 >LTB >CCL21 >CD19. Our results indicate that the abundance and expression of Stx could be affected by cattle breed and the year of sampling, suggesting that host genetics and environment influence STEC colonization. The relationship between the expression of host genes associated with immunity and Stx by STEC expression suggests a role of host in STEC colonization, but further validation is needed to confirm the predictiveness of identified markers.

Evaluation of equine rectal inoculum as representative of the microbial activities within the horse hindgut using a fully automated in vitro gas production technique system

The in vitro gas production technique (IVGPT) has been a valuable tool in ruminant nutrition research for decades and has more recently been used in horse nutrition studies to investigate fermentation activities of the equine hindgut though primarily using feces as inoculum. This study was conducted to evaluate the use of equine rectal content in the IVGPT system as a viable inoculum that can be considered representative of the activities throughout the equine hindgut. Additionally, the study was conducted to measure the effects on fermentation kinetics and end-product production using inoculum from horses fed supplemental levels of coated sodium butyrate in an IVGPT system. Eight warmblood horses were fed a diet consisting of haylage (1% DM intake based on ideal body weight [BW]) and a mash concentrate formulated to provide 2.5 g nonstructural carbohydrate (NSC)/kg BW per meal. The diet was intended to create a NSC challenge to the microbial populations of the hindgut. The horses were randomly assigned to treatment or control group and after a 1-wk diet-adaptation period, the treatment group received 0.4 g/kg BW per day of a coated sodium butyrate supplement, while the control group received a placebo (coating only). After a 3-wk treatment period, the animals were sacrificed and digesta from the cecum, left ventral colon, right dorsal colon, and the rectum were collected within 30 min postmortem and used as inocula for the IVGPT trial. Haylage and concentrates fed to the test animals were also used as substrates in vitro. Sodium butyrate supplementation was not significant for gas production parameters or VFA measured suggesting no effect of sodium butyrate supplementation on the extent or kinetics of gas production or microbial end-product production (P ≥ 0.073). Differences in inocula were significant for organic matter corrected cumulative gas production (P = 0.0001), asymptotic gas production of the second phase (A2) (P < 0.0001); and maximal rate of OM degradation of the second phase (Rmax2) (P = 0.002). Inocula had a significant effect on total VFA (P = 0.0002), butyrate (Bu) (P = 0.015), branched chain fatty acids (P < 0.0001), pH (P < 0.0001), and ammonia (NH3) (P = 0.0024). In conclusion, based on observed results from this study, total tract digestibility may be overestimated if using rectal content inoculum to evaluate forage-based feeds in an IVGPT system.

Quantification of Campylobacter in Swine before, during, and after the Slaughter Process

Campylobacter has been implicated as a major cause of foodborne illness worldwide. Pigs can be subclinically infected, and fecal contamination of meat during slaughter is a food safety risk. The objective of this study was to determine the association between the concentration of Campylobacter pre- and periharvest with postharvest contamination in swine. Samples were collected from 100 individually identified swine during the pre-, peri-, and postharvest periods. For each animal, the following phases were sampled: on farm (fecal sample), in lairage (hide swab), post-stunning and exsanguination (rectal contents), prechilling (carcass swab), and final product (rib meat) sample. The proportions of samples that were Campylobacter positive were 90, 95, 76, 100, and 49% for fecal, rectal content, hide, carcass, and rib meat samples, respectively. The mean Campylobacter concentrations for each sample were fecal sample, 1.7 × 106 CFU/g; rectal content, 1.2 × 107 CFU/g; hide swab, 1.4 CFU/cm2; carcass swab, 1.7 × 103 CFU per half carcass; and rib meat, 18 CFU/g. There was a positive correlation between Campylobacter concentrations in fecal samples (R = 0.20, P = 0.065) and concentration of Campylobacter on rib meat, and between rectal content sample concentration (R = 0.20, P = 0.068) and the concentration on rib meat. There was no association between the isolation of Campylobacter on rib meat and the isolation of Campylobacter at any pre- or periharvest stage. This could indicate that the risk of a meat product being contaminated is associated with pigs that shed higher concentrations of Campylobacter before slaughter.