High Prevalence of Escherichia coli-Producing CTX-M-15 Extended-Spectrum Beta-Lactamases in Poultry and Human Clinical Isolates in Romania

Use of antibiotics in food animals may contribute to development and spread of resistant organisms, particularly so in some countries. The aim of this study was two-fold; first, to establish the prevalence of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in chicken production in a region within Romania. Second, to study the relatedness of ESBL-producing E. coli isolates recovered from broilers, abattoir workers where the chickens were slaughtered and from the human clinical specimens from two regional hospitals. The results indicated a very high (69%) rate of carriage of ESBL and AmpC-producing E. coli in chickens with 36% CTX-M producers. Sequencing showed that chickens in Romania have the highest worldwide prevalence (53%) of bla(CTX-M-15) reported in poultry E. coli isolates. The majority (53%) of the extended-spectrum cephalosporin-resistant E. coli carried plasmid-mediated bla(ampC) genes, mostly bla(CMY-2) type, one of the highest prevalences reported in Europe. The predominant CTX-M type found in the human clinical E. coli isolates was bla(CTX-M-15) and most isolates coharbored bla(OXA-1), bla(TEM), and aac(6)-ib-cr. The majority (60%) of the human clinical isolates belonged to the pandemic virulent clone B2-ST131. The clonal relationship between broiler and the human CTX-M-producing E. coli isolates was assessed by macrorestriction pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST), which indicated strain diversity with no common STs found between human and poultry isolates. Moreover, IncI1 was the most prevalent replicon found in broiler ESBL-producing E. coli isolates and also in transconjugants, indicating that plasmids and not clonal spread may play a role in the transfer of bla(CTX-M) genes. This study identifies a high prevalence of ESBL-producing E. coli from broiler chickens in Romania with a high occurrence incidence of bla(CTX-M-15), which reflects the main ESBL type found in human E. coli infections in this country.