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Shiga toxin-producing Escherichia coli (STEC) are major foodborne human pathogens that cause mild to hemorrhagic colitis, which could lead to complications of hemolytic uremic syndrome. Seven serogroups, O26, O45, O103, O111, O121, O145, and O157, account for the majority of the STEC illnesses in the United States. Shiga toxins 1 and 2, encoded by stx1 and stx2, respectively, and intimin, encoded by eae gene, are major virulence factors. Cattle are a major reservoir of STEC, but swine also harbor them in the hindgut and shed STEC in the feces. Our objectives were to use a culture method to isolate and identify major and minor serogroups of STEC in finisher pig feces. Shiga toxin genes were subtyped to assess public health implications of STEC. Fecal samples (n = 598) from finisher pigs, collected from 10 pig flows, were enriched in E. coli broth and tested for stx1, stx2, and eae by a multiplex PCR (mPCR) assay. Samples positive for stx1 or stx2 gene were subjected to culture methods, with or without immunomagnetic separation and plating on selective or nonselective media, for isolation and identification of stx-positive isolates. The culture method yielded a total of 178 isolates belonging to 23 serogroups. The three predominant serogroups were O8, O86, and O121. The 178 STEC strains included 26 strains with stx1a and 152 strains with stx2e subtypes. Strains with stx1a, particularly in association with eae (O26 and O103), have the potential to cause severe human infections. All stx2-positive isolates carried the subtype stx2e, a subtype that causes edema disease in swine, but is rarely involved in human infections. Several strains were also positive for genes that encode for enterotoxins, which are involved in neonatal and postweaning diarrhea in swine. In conclusion, our study showed that healthy finisher pigs harbored and shed several serogroups of E. coli carrying virulence genes involved in neonatal diarrhea, postweaning diarrhea, and edema disease, but prevalence of STEC of public health importance was low. HIGHLIGHTS

Shiga toxin-producing Escherichia coli (STEC) are major foodborne pathogens and seven serogroups, O26, O45, O103, O111, O121, O145, and O157, that account for the majority of the STEC-associated il...

Shiga toxin-producing

Shiga toxin-producing

Research has demonstrated that medium chain fatty acids (MCFA) can serve as reduction strategies for bacterial and viral pathogens in animal feed and ingredients. However, it is unknown how the type or level of MCFA impact bacteria growth. This can be tested through a minimum inhibitory concentration (MIC) benchtop assay, which identifies the lowest concentration of a chemical that prevents visible growth of a bacterium. The objective of this study was to 1) determine the MCFA MIC of C6:0, C8:0, C10:0, and C12:0 for generic Escherichia coli, Enterotoxigenic Escherichia coli, Salmonella Typhimurium, Campylobacter coli, and Clostridium perfringens; 2) determine the MIC of commercial based MCFA products against the same bacteria; and 3) determine the effect of 2 commercial based MCFA products on the quantification of Enterotoxigenic Escherichia coli. For Exp. 1 and 2, MIC were determined by modified microbroth dilution method using a 96 well microtiter plate with a concentration of 105 CFU/mL for each bacterial strain. For Exp. 3, the two products selected for quantification were mixed with a complete swine diet and inoculated with two concentrations (106 or 102 CFU/g of feed) of a NalR strain of Enterotoxigenic Escherichia coli (ETEC) for bacterial enumeration. From Exp. 1, the MIC of MCFA varied among bacteria species. The lowest MIC of the MCFA was 0.43% of a 1:1:1 blend of C6:0, C8:0, and C10:0 for Campylobacter coli, 0.25% C12:0 for Clostridium perfringens, 0.60% 1:1:1 blend for generic Escherichia coli, 0.53% C6:0 for ETEC, and 0.40% C6:0 for Salmonella Typhimurium. In Exp. 2, products containing high concentrations of C6:0 or C8:0 had lower MIC in gram negative bacteria. In Exp. 3, feed containing either of the commercial based MCFA products reduced (linear, P < 0.05) quantifiable ETEC. Overall, the inhibitory efficacy of MCFA varies among bacteria species. This suggests that MCFA mixtures may provide a wider spectrum of bacterial control. As commercial products containing MCFA become available for livestock, it is important to consider the interaction between MCFA chain length and concentration on the potential to effectively mitigate various feed-based bacteria.

Antibiotics can be administered orally or parenterally in swine production, which may influence antimicrobial resistance (AMR) development in gut bacteria. A total of 40 barrows and 40 gilts were used to determine the effects of tylosin administration route on growth performance and fecal enterococcal AMR. The antibiotic treatments followed Food and Drug Administration label directions and were as follows: (1) no antibiotic (CON), (2) 110 mg tylosin per kg feed for 21 d (IN-FEED), (3) 8.82 mg tylosin per kg body weight through intramuscular injection twice daily for the first 3 d of each week for 3 weeks (IM), and (4) 66 mg tylosin per liter of drinking water (IN-WATER). Antibiotics were administered during d 0 to 21 and all pigs were then fed the CON diet from d 21 to 35. Fecal samples were collected on d 0, 21, and 35. Antimicrobial susceptibility was determined by microbroth dilution method. No evidence of route × sex interaction (p > 0.55) was observed for growth performance. From d 0 to 21, pigs receiving CON and IN-FEED had greater (p

Research has confirmed that a 2% inclusion rate of a blend of C6:0, C8:0, and C10:0 in swine diets and ingredients can reduce Salmonella enterica serotype Typhimurium. However, it is unclear how the chain length and concentration of medium chain fatty acids (MCFA) impacts bacteriostatic properties. This can be tested through a minimum inhibitory concentration (MIC) benchtop assay, which identifies the lowest concentration of a chemical that prevents visible growth of a bacterium. The objective of this set of experiments was to utilize MIC as a mechanism to screen commercial or developmental feed additives containing MCFA for potential to mitigate Salmonella Typhimurium. First, the MIC of four synthetic MCFA treatments (C6:0, C8:0, C10:0, and 1:1:1 ratio of C:6:C8:C10 blend) was determined for Salmonella Typhimurium. The MIC of each treatment was conducted in a modified microbroth dilution and had three replicates. The MIC of C6:0 and C8:0 (0.4 and 0.5%, respectively) were similar (P > 0.05) to one another, but lower (P 1.0%, respectively). It was therefore hypothesized that products containing high concentrations of C6:0 or C8:0 would have the greatest potential to mitigate Salmonella Typhimurium. Next, the fatty acid profile of 24 feed additive products that were commercially developed or in the development process and containing MCFA was determined via gas chromatography. As a result, four products in the development phase from varying companies plus coconut oil were selected as having a high potential for mitigating Salmonella Typhimurium based on their C6:0 and C8:0 levels. Development products 1, 2, 3, 4, and coconut oil contained 29.5, 43.1, 27.4, 0.98, and 6.82 mg/g of C6:0 and 123.20, 610.3, 248.7, 227.1, and 72.0 mg/g of C8:0, respectively. The MIC of these products vs. Salmonella Typhimurium was then determined. The MIC of Product 1 and Product 2 (0.5% and 1.3%, respectively) were similar (P > 0.05) to one another, but lower (P 5.0%). In summary, current or future feed additives containing high concentrations of C6:0 and C8:0 appear to be more effective at mitigating Salmonella Typhimurium than those containing C10:0. Furthermore, it is hypothesized that free MCFA have greater antibacterial potential than those in triglyceride form.

Medium chain fatty acids (MCFA), have been researched extensively to reduce the likelihood of animal feed being contaminated by biological pathogens, including bacteria and viruses. Medium chain fatty acids have shown to be bactericidal and bacteriostatic by incorporating themselves into the lipid membrane of bacteria, which alters the cell membrane permeability leading to cell death. However, the effectiveness can be dependent upon the MCFA chain length and species of bacteria. Most research completed prior to 2013 focused on the antimicrobial properties of MCFA. However, with the emergence of Porcine Epidemic Diarrhea Virus (PEDV), MCFA began to gain more attention for their potential uses in feed safety and swine nutrition as a potential antiviral additive. Medium chain fatty acids have shown repeated success against PEDV in vivo and in vitro. Notably, 2% MCFA [1:1:1 blend of caproic, caprylic, and capric] was equally successful at mitigating PEDV as commercially-available formaldehyde products in complete swine feed (P>0.05). However, the effectiveness varies within feed matrix, as MCFA was not as effective as formaldehyde at mitigation in spray dried animal plasma and meat and bone meal (P

Research has demonstrated medium chain fatty acids (MCFA) are bactericidal and potential antibiotic alternatives. However, it is unknown how the type or level of MCFA impact bacteria growth. This can be tested through a minimum inhibitory concentration (MIC) benchtop assay, which identifies the lowest concentration of a chemical that prevents visible growth of a bacterium. Our objective was to determine the MIC of pure MCFA (Experiment 1) and products containing MCFA (Experiment 2) against generic E. coli, enterotoxigenic E. coli (ETEC), or Campylobacter coli (campy). Experiment 1 used a 4 × 3 factorial with four types of pure MCFA (C6:0, C8:0, C10:0, or 1:1:1 blend of C6:C8:C10) against the three bacteria and was repeated 3 times. All interactions and main effects were significant (P 0.05) MIC against campy. This demonstrated that MCFA efficacy varies with MCFA type and bacteria. Pure MCFA are expensive and not easily available to producers. Thus, 24 commercially-available and developmental products were analyzed for MCFA concentration, with 5 selected based on their C6:0, C8:0, and C10:0 concentrations. In Experiment 2, these products were used in a 5 × 3 factorial to determine their MIC using the same procedures in Experiment 1. There were 5 MCFA products (4 developmental products + coconut oil) tested against three bacteria (E. coli, ETEC, and campy). Only the main effect of treatment was significant, resulting in products 1 and 2 having a lower (P