Characteristics of Cefotaxime-Resistant Escherichia coli from Wild Birds in The Netherlands

Abstract

ABSTRACTCloacal swabs from carcasses of Dutch wild birds obtained in 2010 and 2011 were selectively cultured on media with cefotaxime to screen for the presence of extended-spectrum β-lactamase (ESBL)/AmpC-producingEscherichia coli. Subsequently, all cefotaxime-resistantE. coliisolates were tested by broth microdilution and microarray. The presence of ESBL/AmpC and coexisting plasmid-mediated quinolone resistance (PMQR) genes was confirmed by PCR and sequencing. To determine the size of plasmids and the location of ESBL and PMQR genes, S1 pulsed-field gel electrophoresis (PFGE) was performed on transformants, followed by Southern blot hybridization. The study included 414 cloacal swabs originating from 55 different bird species. Cefotaxime-resistantE. coliisolates were identified in 65 birds (15.7%) from 21 different species. In all, 65 cefotaxime-resistantE. coliESBL/AmpC genes were detected, mainly comprising variants ofblaCTX-MandblaCMY-2. Furthermore, PMQR genes [aac(6′)-lb-cr,qnrB1, andqnrS1] coincided in seven cefotaxime-resistantE. coliisolates. Overall, replicon typing of the ESBL/AmpC-carrying plasmids demonstrated the predominant presence of IncI1 (n= 31) and variants of IncF (n= 18). Our results indicate a wide dissemination of ESBL and AmpC genes in wild birds from The Netherlands, especially among aquatic-associated species (waterfowl, gulls, and waders). The identified genes and plasmids reflect the genes found predominantly in livestock animals as well as in humans.