Comparative genetic characterization of third-generation cephalosporin-resistant Escherichia coli from chicken meat produced by integrated broiler operations in South Korea

Vertical integration of the broiler industry allows producers to combine different biosecurity and sanitation practices, housing technologies, and feeding regimens to improve food safety. The objectives of this study were to determine the antimicrobial resistance pattern of β-lactamase-producing E. coli and to compare the characteristics of E. coli recovered from 7 different integrated broiler operations in South Korea. Among 200 chicken meat samples, 101 were observed to be positive for E. coli. However, the prevalence varied from 37.5% to 75.0% in chicken meats from different operations, indicating variation in E. coli occurrence among the operations. Among 101 isolated E. coli from chicken meat, 59 were identified third-generation cephalosporin-resistant E. coli and recovered from 7 different operations. A high proportion of the E. coli isolates were resistant to penicillins (89.8%), quinolones (81.4%). Among 59 third-generation cephalosporin-resistant E. coli isolates, 29 showed phenotypic and genotypic characteristics of β-lactamase-producing E. coli. Prevalence of bla gene, blaCTX-M-1, blaCTX-M-14, blaCMY-2, and blaTEM-1, were identified in 2, 4, 8, and 16 E. coli isolates respectively and only one E. coli had both genes, blaTEM-1 and blaCTX-M-1. Pulsed-field gel electrophoresis (PFGE) analysis was performed on 29 β-lactamase-producing E. coli isolates. In PFGE, E. coli included 7 PFGE patterns showing the same operation and an accorded both resistance to β-lactam antibiotics and presence of the bla-gene. Our findings suggest that E. coli with resistance to third-generation cephalosporins can now be found in association with integrated broiler operations, providing the data to support the development of monitoring and preventing program in integrated operations.

Prevalence and Characterization of β-Lactamases Genes and Class 1 Integrons in Multidrug-Resistant Escherichia coli Isolates from Chicken Meat in Korea

Antimicrobial resistance has become a serious public health threat throughout the world, and therapeutic options for several infectious diseases are currently limited by the presence of multidrug-resistant (MDR) bacteria. This study was designed to examine the drug resistance patterns, the prevalence of the β-lactamases, and class 1 integrons in MDR Escherichia coli isolates from chicken meat in Korea. Among 200 chicken meat samples, 101 isolates were observed to be positive for E. coli, of which 57 were identified as MDR E. coli. Among 57 MDR E. coli isolates, the prevalence of bla gene, bla_CTX-M-1, bla_CTX-M-14, and bla_TEM-1, were identified in 2, 4, and 16 E. coli strains, respectively; only 1 E. coli strain had both, bla_TEM-1 and bla_CTX-M-1 genes. Twenty-one of the 57 MDR E. coli isolates also carried class 1 integrons, and 5 different gene cassette arrangements were found in 14 of the 21 class 1 integron-positive isolates. The β-lactamase-producing E. coli and integron-positive E. coli had significantly higher resistance to 16 antimicrobial drugs than the non-β-lactamase-producing E. coli and the integron-negative E. coli (p < 0.05). Our findings suggest that β-lactamase and class 1 integrons are widely distributed in E. coli isolates from chicken meat, and directly contribute to resistance to diverse antimicrobial agents. Therefore, continuous investigation of integron gene cassette arrays will provide useful information regarding antimicrobial resistance mechanisms.

Prevalence and epidemiological relationship of CMY-2 AmpC β-lactamase and CTX-M extended-spectrum β-lactamase-producing Escherichia coli isolates from broiler farms in Japan

To evaluate the prevalence of extended-spectrum cephalosporin (ESC)-resistant Enterobacteriaceae in broiler chickens, 41 rectal samples taken from 4 commercial farms were examined. Desoxycholate hydrogen sulfide lactose agars, supplemented with either 4 μg/ml cefotaxime or 16 μg/ml ceftazidime, were used to screen ESC-resistant bacteria. ESC-resistant bacteria were isolated from all samples. Of the 164 ESC-resistant bacteria (included 4 isolates per a sample), 163 were Escherichia coli, while 1 isolate was identified as Enterobacter cloacae. Extended-spectrum β-lactamase (ESBL) genes and plasmid-mediated AmpC β-lactamase genes in the isolates were determined by PCR and sequencing. One AmpC β-lactamase gene, bla(CMY-2) (66%), and 4 ESBL genes, bla(CTX-M-1) (26%), bla(CTX-M-55) (10%), bla(SHV-5) (4%) and bla(CTX-M-2) (3%), were detected in the E. coli isolates. The epidemiological relationship of the CMY-2 and CTX-M β-lactamase-producing isolates among the farms was analyzed by pulsed-field gel electrophoresis using the XbaI restriction enzyme. Forty-one (Y1-Y41) and 14 (X1-X14) clusters were found in the CMY-2 and CTX-M-carrying E. coli isolates, respectively. Some clusters included isolates derived from more than 1 farm, indicating some cross-contamination of clonal strains and spread of CMY-2 AmpC β-lactamase or CTX-M ESBL among the farms.

Emergence of Salmonella enterica serovar infantis harboring IncI1 plasmid with bla(CTX-M-14) in a broiler farm in Japan

Cefotaxime (CTX)-resistant and -susceptible Salmonella enterica serovar Infantis isolates obtained from broilers raised on a farm in January 2010 in Japan were characterized to establish their resistance determinants. The CTX-resistant isolates produced CTX-M-14 extended-spectrum β-lactamase and harbored 2 distinct plasmid of approximately 140- and 95-kb, whereas the CTX-susceptible isolates harbored one 140-kb plasmid. The 95-kb plasmids were replicon typed as IncI1 carrying the bla(CTX-M-14) gene, while the 140-kb plasmids were IncP and harbored the aphA1, aadA1, tetA, and sul1 genes. Genetic fingerprinting by pulsed-field gel electrophoresis revealed similar macrorestriction profiles amongst CTX-resistant and susceptible isolates, suggesting a clonal relationship. The presence of CTX-resistant S. Infantis on a broiler farm has occurred through the acquisition of IncI1 resistance plasmid.