Effects of microcin 24-producing Escherichia coli on shedding and multiple-antimicrobial resistance of Salmonella enterica serotype typhimurium in pigs.
OBJECTIVE
To investigate the effect of an Escherichia that produced microcin 24 (Mcc24) on shedding of of Salmonella enterica serotypeTyphimurium in swine and evaluate evidence of in vivo activation of the Mcc24-mediated, multiple-antibiotic resistance (mar) operon.


METHODS
36 crossbred weaned pigs.


METHODS
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 chi4232. A third group of 6 pigs received Mcc24-producing E coli and was challenge exposed with an Mcc24-sensitive, marA-deleted strain of Salmonella Typhimurium 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 mar activation was not detected.


CONCLUSIONS
Microcin-producing E coli did not exert an effect on shedding of SalmonellaTyphimurium or mar activation 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.
Frana
Timothy S
TS
Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50010, USA.
Carlson
Steven A
SA
Rauser
Daryl C
DC
Jones
Bradley D
BD
Fergen
Brian J
BJ
Griffith
Ronald W
RW
D000818:Animals; D000900:Anti-Bacterial Agents / Q000096:biosynthesis* / Q000494:pharmacology; D001430:Bacteriocins / Q000096:biosynthesis* / Q000235:genetics; D002939:Ciprofloxacin / Q000494:pharmacology; D003001:Cloning, Molecular; D015169:Colony Count, Microbial; D024881:Drug Resistance, Bacterial / Q000502:physiology*; D018432:Drug Resistance, Multiple; D004926:Escherichia coli / Q000502:physiology*; D005243:Feces / Q000382:microbiology; D005260:Female; D008297:Male; D010455:Peptides; D016133:Polymerase Chain Reaction / Q000662:veterinary; D012333:RNA, Messenger / Q000378:metabolism; D012481:Salmonella Infections, Animal / Q000382:microbiology*; D012486:Salmonella typhimurium / Q000187:drug effects / Q000302:isolation & purification*; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology*
D000900:Anti-Bacterial Agents; D001430:Bacteriocins; D010455:Peptides; D012333:RNA, Messenger; C020411:microcin; D002939:Ciprofloxacin