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  • Author or Editor: Ronald W. Griffith x
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Objective—To investigate the effect of an Escherichia coli that produced microcin 24 (Mcc24) on shedding of Salmonella enterica serotype Typhimurium in swine and evaluate evidence of in vivo activation of the Mcc24-mediated, multiple-antibiotic resistance ( mar) operon.

Animals—36 crossbred weaned pigs.

Procedure—24 pigs were allocated to 2 groups (12 pigs/group). Pigs in 1 group received daily oral administration of an Mcc24-producing E coli, whereas the other group received a non–Mcc24-producing E coli. All pigs were challenge exposed with Salmonella Typhimurium χ4232. A third group of 6 pigs received Mcc24-producing E coli and was challenge exposed with an Mcc24-sensitive, marA-deleted strain of SalmonellaTyphimurium 4232. After challenge exposure, fecal samples from all pigs were cultured to detect shedding of Salmonella Typhimurium and Salmonella Typhimurium isolates were screened for resistance to ciprofloxacin. Fecal samples were collected throughout the study, and tissue samples were collected during necropsy.

Results—Differences in shedding of Salmonella Typhimurium were not detected between groups receiving Mcc24-producing or non–Mcc24-producing E coli. No significant differences were found in quantitative analysis between groups receiving Mcc24-producing and non–Mcc24-producing E coli. Evidence of maractivation was not detected.

Conclusions and Clinical Relevance—Microcin-producing E coli did not exert an effect on shedding of Salmonella Typhimurium or maractivation in pigs. It may be difficult or impractical to create the conditions required for Mcc24 to be an effective part of a food safety intervention to reduce shedding of Salmonella Typhimurium. (Am J Vet Res 2004;65:1616–1620)

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in American Journal of Veterinary Research



To evaluate the efficacy of tulathromycin for prevention of abortion in pregnant ewes when administered within 24 hours after experimental inoculation with Campylobacter jejuni.


20 pregnant ewes between 72 and 92 days of gestation.


All ewes were inoculated with a field strain of C jejuni (8.5 × 108 to 10.6 × 108 CFUs, IV). Eighteen hours later, ewes received either tulathromycin (1.1 mL/45 kg [2.4 mg/kg], SC; n = 10) or sterile saline (0.9% NaCl) solution (1.1 mL/45 kg, SC; sham; 10). Ewes were euthanized immediately after observation of vaginal bleeding, abortion, or completion of a 21-day observation period. Necropsy was performed on all ewes, and tissue specimens were obtained for bacterial culture and histologic examination.


1 sham-treated ewe and 1 tulathromycin-treated ewe developed signs of severe endotoxemia and were euthanized within 24 hours after C jejuni inoculation. Seven sham-treated and 2 tulathromycin-treated ewes developed vaginal bleeding or aborted and were euthanized between 4 and 21 days after C jejuni inoculation. The proportion of tulathromycin-treated ewes that developed vaginal bleeding or aborted during the 21 days after C jejuni inoculation (2/9) was significantly less than that for the sham-treated ewes (7/9).


Results suggested that administration of tulathromycin to pregnant ewes following exposure to C jejuni was effective in decreasing the number of C jejuni–induced abortions. Because of concerns regarding the development of macrolide resistance among Campylobacter strains, prophylactic use of tulathromycin in sheep is not recommended.

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in American Journal of Veterinary Research