OBJECTIVES: To determine the phylogenetic group and the production of different virulence factors (VFs) of a collection of Escherichia coli strains overproducing their chromosomal AmpC cephalosporinase. METHODS: Fifty-five E. coli strains, isolated over a 12 year period, and previously identified as AmpC overproducers by increased MICs of third-generation cephalosporins without extended-spectrum beta-lactamase production (negative double-disc synergy test), were phylogrouped by multiplex PCR. As a comparison, 100 E. coli clinical isolates, susceptible to all beta-lactams, were also tested by the same method. The ampC promoter sequence was determined for all these isolates. ERIC-2 PCR (where ERIC stands for enterobacterial repetitive intergenic consensus) was used to compare the isolates. Search for virulence-associated genes (papG alleles, sfa/foc, hly and iucC) was performed by multiplex PCR for the 55 AmpC overproducers. RESULTS: Most of the AmpC overproducers (47/55) belonged to phylogenetic group A, correlated with a low prevalence of the main VFs in these strains. The - 32, -42 and - 11 mutations, responsible for AmpC overproduction, were usually associated with DNA polymorphisms at positions - 88, - 82, -18, +1 and + 58 in the ampC promoter. In the control susceptible isolates, these polymorphisms were detected in 13 ampC promoters (9 group B1 and 4 group A). These polymorphisms were never associated with the main phylogenetic group B2, representing 66% of the susceptible isolates. CONCLUSIONS: AmpC overproduction was clearly correlated with non-virulent commensal phylogenetic groups A and B1, and absence of the main E. coli VFs. Susceptible isolates harbouring the same sequence polymorphisms as AmpC overproducers also belonged to commensal phylogenetic groups.
OBJECTIVES: To determine the phylogenetic group and the production of different virulence factors (VFs) of a collection of Escherichia coli strains overproducing their chromosomal AmpC cephalosporinase. METHODS: Fifty-five E. coli strains, isolated over a 12 year period, and previously identified as AmpC overproducers by increased MICs of third-generation cephalosporins without extended-spectrum beta-lactamase production (negative double-disc synergy test), were phylogrouped by multiplex PCR. As a comparison, 100 E. coli clinical isolates, susceptible to all beta-lactams, were also tested by the same method. The ampC promoter sequence was determined for all these isolates. ERIC-2 PCR (where ERIC stands for enterobacterial repetitive intergenic consensus) was used to compare the isolates. Search for virulence-associated genes (papG alleles, sfa/foc, hly and iucC) was performed by multiplex PCR for the 55 AmpC overproducers. RESULTS: Most of the AmpC overproducers (47/55) belonged to phylogenetic group A, correlated with a low prevalence of the main VFs in these strains. The - 32, -42 and - 11 mutations, responsible for AmpC overproduction, were usually associated with DNA polymorphisms at positions - 88, - 82, -18, +1 and + 58 in the ampC promoter. In the control susceptible isolates, these polymorphisms were detected in 13 ampC promoters (9 group B1 and 4 group A). These polymorphisms were never associated with the main phylogenetic group B2, representing 66% of the susceptible isolates. CONCLUSIONS:AmpC overproduction was clearly correlated with non-virulent commensal phylogenetic groups A and B1, and absence of the main E. coli VFs. Susceptible isolates harbouring the same sequence polymorphisms as AmpC overproducers also belonged to commensal phylogenetic groups.
Authors: S Peter-Getzlaff; S Polsfuss; M Poledica; M Hombach; J Giger; E C Böttger; R Zbinden; G V Bloemberg Journal: J Clin Microbiol Date: 2011-06-08 Impact factor: 5.948
Authors: Margaret A Davis; Thomas E Besser; Lisa H Orfe; Katherine N K Baker; Amelia S Lanier; Shira L Broschat; Daniel New; Douglas R Call Journal: Appl Environ Microbiol Date: 2011-03-18 Impact factor: 4.792
Authors: A Boutet-Dubois; A Pantel; M-F Prère; O Bellon; N Brieu-Roche; E Lecaillon; A Le Coustumier; A Davin-Regli; L Villeneuve; N Bouziges; E Gleize; R Lamarca; C Dunyach-Remy; A Sotto; J-P Lavigne Journal: Eur J Clin Microbiol Infect Dis Date: 2013-03-15 Impact factor: 3.267
Authors: L F Mataseje; N Neumann; B Crago; P Baudry; G G Zhanel; M Louie; M R Mulvey Journal: Antimicrob Agents Chemother Date: 2009-04-27 Impact factor: 5.191