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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Food Safety and Enteric Pathogens Research » Research » Publications at this Location » Publication #160067
Title: EFFECTS OF MICROCIN 24-PRODUCING ESCHERICHIA COLI ON SHEDDING AND MULTIPLE-ANTIMICROBIAL RESISTANCE OF SALMONELLA ENTERICA SEROTYPE TYPHIMURIUM IN PIGS

Author
item FRANA, T - IOWA STATE UNIVERSITY
item CARLSON, STEVEN
item RAUSER, D - IOWA STATE UNIVERSITY
item JONES, B - UNIVERSITY OF IOWA
item FERGEN, B - CENTER FOR VET BIOLOGICS
item GRIFFITH, R - IOWA STATE UNIVERSITY

Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2004
Publication Date: 12/20/2004
Citation: Frana, T.S., Carlson, S.A., Rauser, D., Jones, B.D., Fergen, B.J., Griffith, R.W. 2004. Effects of microcin 24-producing Escherichia coli on shedding and multiple-antimicrobial resistance of Salmonella enterica serotype Typhimurium in pigs. American Journal of Veterinary Research. 65(12):1616-1620.

Interpretive Summary: Microcin 24 (Mcc24) is an antibacterial peptide that kills Salmonella although small doses of Mcc24 can make Salmonella resistant to multiple antibiotics. We set out to investigate the effect of daily, oral inoculations of an Escherichia coli producing Mcc24 on Salmonella shedding in swine and to look for evidence of Mcc24-mediated multiple antibiotic resistance in vivo. Two groups of crossbred, 17-day-old, weaned pigs (12 pigs/group) were orally dosed on a daily basis with either a Mcc24-producing E. coli or a non-Mcc24-producing E. coli and then challenged with Salmonella. After Salmonella challenge each pig was monitored for shedding by fecal culture and Salmonella isolates were then screened for resistance to antibiotics. Fecal and tissue samples were collected until 20 days post-challenge. No difference in Salmonella shedding was found between groups receiving Mcc24-producing or non-Mcc24-producing E. coli. No significant differences were found in quantitative analysis between groups receiving Mcc24-producing E. coli and non-Mcc24-producing E. coli. No evidence of antibiotic resistance in Salmonella was seen in any group. Under the conditions of this experiment, Mcc24-producing E. coli did not exert an effect on Salmonella shedding or multiple antibiotic resistance in pigs. If Mcc24 is to be considered as part of a competitive exclusion intervention to reduce Salmonella the conditions need to be carefully considered. Bacterial host, method of delivery, and Salmonella ecology are important factors. These studies will essentially allow scientists to rule out Mcc24 as an anti-Salmonella agent.

Technical Abstract: We set out to investigate the effect of daily, oral inoculations of an Escherichia coli-producing microcin 24 (Mcc24) on Salmonella enterica serotype Typhimurium (ST) shedding in swine and to look for evidence of Mcc24-mediated mar (multiple antibiotic resistance) activation in vivo. Two groups of crossbred, 17-day-old, weaned pigs (12 pigs/group) were orally dosed on a daily basis with either a Mcc24-producing E. coli or a non-Mcc24-producing E. coli and then challenged with ST *4232 (ST4232). After ST challenge each pig was monitored for ST shedding by fecal culture and ST isolates were then screened for resistance to ciprofloxacin. Fecal and tissue samples were collected until 20 days post-challenge. No difference in ST shedding was found between groups receiving Mcc24-producing or non-Mcc24-producing E. coli. No significant differences were found in quantitative analysis between groups receiving Mcc24-producing E. coli and non-Mcc24-producing E. coli. No evidence of mar activation in of ST was seen in any group. Under the conditions of this experiment, Mcc24-producing E. coli did not exert an effect on ST shedding or mar activation in pigs. If Mcc24 is to be considered as part of a competitive exclusion intervention to reduce ST the conditions need to be carefully considered. Bacterial host, method of delivery, and ST ecology are important factors.