title: Carriage and fecal counts of cefotaxime M-producing Escherichia coli in pigs: a longitudinal study.
abstract: Current knowledge on extended-spectrum beta-lactamases (ESBLs) in animals is based largely on cross-sectional studies and qualitative data. The aim of this longitudinal study was to elucidate carriage proportions and fecal counts of ESBL-producing Escherichia coli in pigs during the production cycle. At each of three ESBL-positive single-sited farrow-to-finisher pig farms (farms A, B, and C) included in the study, individual fecal samples were taken from 17 to 20 sows 1 week before farrowing and from 2 piglets of each sow's litter four times from birth to slaughter (as piglets, weaners, and finishers). Cefotaxime (CTX)-resistant coliforms in feces were counted on MacConkey agar containing 2 μg/ml CTX and characterized for the presence of ESBL-encoding genes by PCR and sequencing. CTX-M-positive pigs were detected in all age groups at farms A (bla(CTX-M-9) group, compatible with bla(CTX-M-14/17)) and B (bla(CTX-M-1) group, compatible with bla(CTX-M-1/61)), whereas only three weaners were positive at farm C (bla(CTX-M-1) group, compatible with bla(CTX-M-1/61)). A significant decrease in carriage was detected during the production cycle, with on average 50% carriage immediately after birth, 58% just before weaning, 29% during weaning, and 12% during finishing. The observed reduction in numbers of CTX-M-positive pigs was accompanied by a significant reduction in mean fecal counts of CTX-resistant coliforms from ~10(7) CFU/g in piglets to ~10(3) CFU/g in finishers (P < 0.001). These findings provide novel information about the epidemiology of ESBLs at the farm level and have important implications for assessments of risks of meat contamination during slaughter.
authors.affiliation: University of Copenhagen, Faculty of Health and Medical Sciences, Department of Veterinary Disease Biology, Frederiksberg, Denmark. khha@sund.ku.dk
authors.forename: Katrine Hartung
authors.initials: KH
authors.lastname: Hansen
authors.forename: Peter
authors.initials: P
authors.lastname: Damborg
authors.forename: Margit
authors.initials: M
authors.lastname: Andreasen
authors.forename: Søren Saxmose
authors.initials: SS
authors.lastname: Nielsen
authors.forename: Luca
authors.initials: L
authors.lastname: Guardabassi
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D058491:Bacterial Load; D002353:Carrier State / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D002439:Cefotaxime / Q000494:pharmacology*; D003470:Culture Media / Q000737:chemistry; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D005243:Feces / Q000382:microbiology*; D008137:Longitudinal Studies; D016133:Polymerase Chain Reaction; D015995:Prevalence; D017422:Sequence Analysis, DNA; D013552:Swine; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D004269:DNA, Bacterial; D001618:beta-Lactamases; D002439:Cefotaxime