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TITLE:  Antimicrobial susceptibility and molecular characterization of avian pathogenic Escherichia coli isolates
AUTHORS:  Zhao S;Maurer JJ;Hubert S;De Villena JF;McDermott PF;Meng J;Ayers S;English L;White DG;
YEAR:  2005
JOURNAL ABBREV:  Vet Microbiol
JOURNAL FULL:  Veterinary microbiology
VOLUME:  107
ISSUE:  40972
END PAGE:  224
KEYWORDS:  Animals;Anti-Bacterial Agents;Base Sequence;chemistry;Chickens;classification;Cluster Analysis;Dna;DNA Gyrase;DNA Topoisomerase IV;DNA,Bacterial;Drug Resistance,Multiple,Bacterial;drug therapy;Escherichia coli;Escherichia coli Infections;Food;genetics;Georgia;metabolism;Microbial Sensitivity Tests;microbiology;Molecular Sequence Data;Mutation;Nalidixic Acid;pathogenicity;pharmacology;Phenotype;Point Mutation;Polymerase Chain Reaction;Poultry Diseases;Research;Ribotyping;Sequence Alignment;Sequence Analysis,DNA;Streptomycin;Sulfamethoxazole;Tetracycline;veterinary;Veterinary Medicine;Virulence;Virulence Factors;
ABSTRACT:  Ninety-five avian pathogenic Escherichia coli (APEC) isolates recovered from diagnosed cases of avian colibacillosis from North Georgia between 1996 and 2000 were serotyped and examined for typical virulence-factors, susceptibility to antimicrobials of human and veterinary significance, and genetic relatedness. Twenty different serotypes were identified, with O78 being the most common (12%). The majority of the avian E. coli isolates (60%), however, were non-typeable with standard O antisera. Eighty-four percent of isolates were PCR positive for the temperature-sensitive hemagglutinin (tsh) gene and 86% positive for the increased serum survival (iss) gene. Multiple antimicrobial-resistant phenotypes (> or =3 antimicrobials) were observed in 92% of E. coli isolates, with the majority of isolates displaying resistance to sulfamethoxazole (93%), tetracycline (87%), streptomycin (86%), gentamicin (69%), and nalidixic acid (59%). Fifty-six E. coli isolates displaying resistance to nalidixic acid were co-resistant to difloxacin (57%), enrofloxacin (16%), gatifloxacin (2%), and levofloxacin (2%). DNA sequencing revealed point mutations in gyrA (Ser83-Leu, Asp87-Tyr, Asp87-Gly, Asp87-Ala), gyrB (Glu466-Asp, Asp426-Thr), and parC (Ser80-Ile, Ser80-Arg). No mutations were observed in parE. Twelve of the quinolone-resistant E. coli isolates were tolerant to cyclohexane, a marker for upregulation of the acrAB multi-drug resistance efflux pump. Quinolone-resistant isolates were further genetically characterized via ribotyping. Twenty-two distinct ribogroups were identified, with 61% of isolates clustering into four major ribogroups, indicating that quinolone resistance has emerged among multiple avian pathogenic E. coli serogroups and chromosomal backgrounds
AFFILIATIONS:  Office of Research, Center for Veterinary Medicine, U.S. Food and Drug Administration, 8401 Muirkirk Road, Laurel, MD 20708, USA