title: Increasing prevalence and diversity of ESBL/AmpC-type β-lactamase genes in Escherichia coli isolated from veal calves from 1997 to 2010.
abstract: OBJECTIVE
  Several studies on faecal carriage of extended-spectrum β-lactamase (ESBL)/AmpC-producing Escherichia coli have been performed in cattle, but little is known about faecal carriage in veal calves. This study describes the prevalence and molecular characteristics of ESBL/AmpC genes in E. coli isolated from faecal samples of veal calves from 1997 to 2010.
  
  
  METHODS
  Pooled faecal samples were inoculated using selective enrichment broth and subsequently selective MacConkey agar. All isolates with reduced susceptibility to cefotaxime were screened by PCR and sequencing analysis for the presence of ESBL/AmpC genes.
  
  
  RESULTS
  The prevalence of E. coli with reduced susceptibility to cefotaxime showed a discontinuous increasing trend, ranging from 4% in 1998 and 1999 to 39% in 2010. Promoter mutations of the chromosomal ampC gene were present in all years. In 2000, ESBL genes blaCTX-M-1, blaTEM-52 and blaTEM-20 were first observed. Before 2005 the majority of E. coli with reduced susceptibility to cefotaxime harboured ampC promoter mutations. From 2005 onwards the majority harboured blaCTX-M genes, of which blaCTX-M-1 was the most abundant, followed by blaCTX-M-14 and blaCTX-M-15. The diversity of blaCTX-M genes gradually increased from one variant in 2000 to six variants in 2010. The prevalence of blaTEM-52 was relatively low, but it was detected from 2000 onwards. blaCMY and blaSHV were found sporadically.
  
  
  CONCLUSIONS
  The prevalence and molecular diversity of genes encoding cefotaxime resistance in E. coli isolated from veal calves over a 14 year period showed an increasing trend. From 2005 onwards, blaCTX-M genes were most abundant, especially blaCTX-M-1.
authors: Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, PO Box 80.165, 3508 TD Utrecht, The Netherlands. j.hordijk@uu.nl
authors: Joost
authors: J
authors: Hordijk
authors: Jaap A
authors: JA
authors: Wagenaar
authors: Arjen
authors: A
authors: van de Giessen
authors: Cindy
authors: C
authors: Dierikx
authors: Alieda
authors: A
authors: van Essen-Zandbergen
authors: Kees
authors: K
authors: Veldman
authors: Arie
authors: A
authors: Kant
authors: Dik
authors: D
authors: Mevius
mesh_terms: D000818:Animals; D001431:Bacteriological Techniques; D002353:Carrier State / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D002417:Cattle; D004926:Escherichia coli / Q000201:enzymology* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D005243:Feces / Q000382:microbiology; D014644:Genetic Variation; D016133:Polymerase Chain Reaction; D015995:Prevalence; D017422:Sequence Analysis, DNA; D001618:beta-Lactamases / Q000145:classification / Q000235:genetics*
chemical_list: D001618:beta-Lactamases
keywords: antimicrobial resistance; cattle; faecal carriage; retrospective