TY - JOUR

T1 - Occurrence of weak mutators among avian pathogenic Escherichia coli (APEC) isolates causing salpingitis and peritonitis in broiler breeders

AU - Pires dos Santos, Teresa M S

AU - Bisgaard, Magne

AU - Kyvsgaard, Niels Christian

AU - Christensen, Henrik

N1 - Copyright © 2013 Elsevier B.V. All rights reserved.

PY - 2014

Y1 - 2014

N2 - A collection of 46 avian pathogenic Escherichia coli (APEC) isolates was examined for the presence of mutators by determining the rate of mutation to rifampicin resistance. The collection included 34 E. coli isolates obtained in pure culture from chronic lesions of salpingitis and peritonitis in 34 broiler breeders, of which 12 were associated with the development of secondary septicemia. Twelve additional isolates were obtained from a clonal outbreak (ST95) of E. coli peritonitis syndrome (EPS), the lesions of which changed gradually over time into a subacute/chronic form. The hypothesis of the present study was that mutation rates would be higher for chronic infection isolates than for isolates from acute infections/exacerbations. The distribution of mutation rates followed a pattern similar to that found for other clinical isolates of E. coli, with a modal/median value of 1.47 × 10(-8). Of the 46 isolates, 24% (n=11) were weakly hypermutable (2.00 × 10(-8) ≤ μ<2.00 × 10(-7)), however, no strong mutators were detected (μ ≥ 2.00 × 10(-7)). Chronic salpingitis isolates had the highest proportion (45%, P=0.001) of weak mutators and also, significantly higher mutation rates (P=0.003) compared to isolates that caused septicemia (4%). In addition, mutation rates were significantly lower among ST95 isolates (P<0.0005), and among isolates from the same clonal group as ST95 (P=0.027), when compared to isolates from other groups. Although a clear association with the time phase of infection (as lesions of EPS became more chronic) could not be observed (ρ=0.523, P=0.081), a higher frequency of weak mutators among chronic infection isolates suggests that increased mutation rates play a role in adaptation of APEC to long-term persistence in an infected host environment.

AB - A collection of 46 avian pathogenic Escherichia coli (APEC) isolates was examined for the presence of mutators by determining the rate of mutation to rifampicin resistance. The collection included 34 E. coli isolates obtained in pure culture from chronic lesions of salpingitis and peritonitis in 34 broiler breeders, of which 12 were associated with the development of secondary septicemia. Twelve additional isolates were obtained from a clonal outbreak (ST95) of E. coli peritonitis syndrome (EPS), the lesions of which changed gradually over time into a subacute/chronic form. The hypothesis of the present study was that mutation rates would be higher for chronic infection isolates than for isolates from acute infections/exacerbations. The distribution of mutation rates followed a pattern similar to that found for other clinical isolates of E. coli, with a modal/median value of 1.47 × 10(-8). Of the 46 isolates, 24% (n=11) were weakly hypermutable (2.00 × 10(-8) ≤ μ<2.00 × 10(-7)), however, no strong mutators were detected (μ ≥ 2.00 × 10(-7)). Chronic salpingitis isolates had the highest proportion (45%, P=0.001) of weak mutators and also, significantly higher mutation rates (P=0.003) compared to isolates that caused septicemia (4%). In addition, mutation rates were significantly lower among ST95 isolates (P<0.0005), and among isolates from the same clonal group as ST95 (P=0.027), when compared to isolates from other groups. Although a clear association with the time phase of infection (as lesions of EPS became more chronic) could not be observed (ρ=0.523, P=0.081), a higher frequency of weak mutators among chronic infection isolates suggests that increased mutation rates play a role in adaptation of APEC to long-term persistence in an infected host environment.

KW - Animals

KW - Chickens

KW - Chronic Disease

KW - Drug Resistance, Bacterial

KW - Escherichia coli

KW - Escherichia coli Infections

KW - Female

KW - Mutation

KW - Mutation Rate

KW - Peritonitis

KW - Poultry Diseases

KW - Salpingitis

U2 - 10.1016/j.vetmic.2013.10.008

DO - 10.1016/j.vetmic.2013.10.008

M3 - Journal article

C2 - 24230977

VL - 168

SP - 141

EP - 147

JO - Veterinary Microbiology

JF - Veterinary Microbiology

SN - 0378-1135

IS - 1

ER -