title: Vertical transmission of a fluoroquinolone-resistant Escherichia coli within an integrated broiler operation.
abstract: The epidemiology of an enrofloxacin-resistant Escherichia coli clone was investigated during two separate outbreaks of colibacillosis in the Danish broiler production. In total five flocks were reported affected by the outbreaks. Recorded first-week mortalities were in the range of 1.7-12.7%. The clone was first isolated from dead broilers and subsequently demonstrated in samples from associated hatchers and the parent flock with its embryonated eggs, suggesting a vertical transmission from the parents. The second outbreak involved two broiler flocks unrelated to the affected flocks from the first outbreak. However, the clone could not be demonstrated in the associated parent flock. Furthermore, samplings from grand-parent flocks were negative for the outbreak clone. The clonality was evaluated by plasmid profiling and pulsed-field gel electrophoresis. None of the recognized virulence factors were demonstrated in the outbreak clone by microarray and PCR assay. The molecular background for the fluoroquinolone-resistance was investigated and point mutations in gyrA and parC leading to amino-acid substitutions in quinolone-resistance determining regions of GyrA and ParC were demonstrated. Vertical transmission of enrofloxacin-resistant E. coli from healthy parents resulting in high first-week mortality in the offspring illustrates the potential of the emergence and spreading of fluoroquinolone-resistant bacteria in animal husbandry, even though the use of fluoroquinolones is restricted.
authors.affiliation: The Royal Veterinary & Agricultural University, Department of Veterinary Pathobiology, Stigbøjlen 4, 1870 Frederiksberg C, Denmark. andp@kvl.dk
authors.forename: Andreas
authors.initials: A
authors.lastname: Petersen
authors.forename: Jens P
authors.initials: JP
authors.lastname: Christensen
authors.forename: Peter
authors.initials: P
authors.lastname: Kuhnert
authors.forename: Magne
authors.initials: M
authors.lastname: Bisgaard
authors.forename: John E
authors.initials: JE
authors.lastname: Olsen
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002645:Chickens; D003718:Denmark / Q000453:epidemiology; D004196:Disease Outbreaks / Q000662:veterinary; D024901:Drug Resistance, Multiple, Bacterial; D000077422:Enrofloxacin; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000472:pathogenicity; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000635:transmission / Q000662:veterinary*; D005260:Female; D024841:Fluoroquinolones / Q000494:pharmacology*; D018445:Infectious Disease Transmission, Vertical / Q000662:veterinary*; D009154:Mutation; D010063:Ovum / Q000382:microbiology; D011201:Poultry Diseases / Q000382:microbiology* / Q000635:transmission; D014774:Virulence
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D000077422:Enrofloxacin