title: Isolation and molecular characterization of nalidixic acid-resistant extraintestinal pathogenic Escherichia coli from retail chicken products.
abstract: Fluoroquinolone use in poultry production may select for resistant Escherichia coli that can be transmitted to humans. To define the prevalence and virulence potential of poultry-associated, quinolone-resistant E. coli in the United States, 169 retail chicken products from the Minneapolis-St. Paul area (1999 to 2000) were screened for nalidixic acid (Nal)-resistant E. coli. Sixty-two (37%) products yielded Nal-resistant E. coli. From 55 products that yielded both Nal-resistant and susceptible E. coli, two isolates (one resistant, one susceptible) per sample were further characterized. Twenty-three (21%) of the 110 E. coli isolates (13 resistant, 10 susceptible) satisfied criteria for extraintestinal pathogenic E. coli (ExPEC), i.e., exhibited >or=2 of pap (P fimbriae), sfa/foc (S/F1C fimbriae), afa/dra (Dr binding adhesins), iutA (aerobactin receptor), and kpsMT II (group 2 capsule synthesis). Compared with other isolates, ExPEC isolates more often derived from virulence-associated E. coli phylogenetic groups B2 or D (74% versus 32%; P < 0.001) and exhibited more ExPEC-associated virulence markers (median, 10.0 versus 4.0; P < 0.001). In contrast, the Nal-resistant and -susceptible populations were indistinguishable according to all characteristics analyzed, including pulsed-field gel electrophoresis profiles. These findings indicate that Nal-resistant E. coli is prevalent in retail poultry products and that a substantial minority of such strains represent potential human pathogens. The similarity of the Nal-resistant and -susceptible populations suggests that they derive from the same source population, presumably the avian fecal flora, with Nal resistance emerging by spontaneous mutation as a result of fluoroquinolone exposure.
authors.affiliation: Department of Medicine, University of Minnesota, Minneapolis, Minnesota 55417, USA. johns007@tc.umn.edu
authors.forename: James R
authors.initials: JR
authors.lastname: Johnson
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Murray
authors.forename: Abby
authors.initials: A
authors.lastname: Gajewski
authors.forename: Maureen
authors.initials: M
authors.lastname: Sullivan
authors.forename: Paula
authors.initials: P
authors.lastname: Snippes
authors.forename: Michael A
authors.initials: MA
authors.lastname: Kuskowski
authors.forename: Kirk E
authors.initials: KE
authors.lastname: Smith
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D002645:Chickens; D016000:Cluster Analysis; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*; D005243:Feces / Q000382:microbiology; D007422:Intestines / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009268:Nalidixic Acid / Q000494:pharmacology*; D019081:O Antigens / Q000235:genetics; D010641:Phenotype; D010802:Phylogeny; D011201:Poultry Diseases / Q000188:drug therapy / Q000382:microbiology*; D011202:Poultry Products / Q000382:microbiology; D019105:Random Amplified Polymorphic DNA Technique; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics
chemical_list: D000890:Anti-Infective Agents; D019081:O Antigens; D037521:Virulence Factors; D009268:Nalidixic Acid