High prevalence of bla among genetically diverse Escherichia coli recovered from retail raw chicken meat portions in Japan.

Global widespread of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae, especially Escherichia coli poses a greater threat in healthcare and community settings of humans. Raw meats from food animals colonized with ESBL producers may be one of important transmission routes for those bacteria in the community. This study investigated the presence of ESBL-producing E. coli in retail raw chicken and pork meats in Japan. ESBL producers were detected from the 59 of 150 (39.3%) chicken samples, but none were from all the 50 pork samples tested. The bla (17; 24.3%) was most frequently identified, followed by bla (16; 22.9%), bla (11; 15.7%), and bla (10; 14.3%) among a total of 70 ESBL-producing E. coli isolates from 59 chicken samples. The isolates with bla were often combined with phylogroup B1 (9/17) mainly composed of ST162 (7/9), and phylogroup F (5/17) with diverse STs. The bla was basically associated with the common elements ISEcp1 and ΔIS903 or IS903 in all 17 isolates. In 6 isolates, comprising 5 phylogroup B1-ST162 and a nontypeable-ST162 isolates, an IS26-truncated ISEcp1 was identified upstream of the bla, and a fosA3 was further located downstream of ΔIS903. Furthermore, some mobile genetic elements mediating bla unique to raw chicken meat portions were identified. The bla gene was preceded by ISEcp1 or ISCR1 in 16 isolates, whereas the presence of Δorf3 downstream of bla was limited only in 6 isolates from Brazilian samples though they exhibited diverse phylogroups and STs. The bla and bla shared classical flanking structures, ISEcp1-bla-orf477, although the length of spacer sequences between ISEcp1 and the start codon of bla was 45 bp and 80 bp for bla and bla, respectively. Among bla-harboring isolates, ST38 was frequently detected (6/11) though their phylogroup distribution varied. In conclusion, besides transmission of bla gene-harboring E. coli lineages which have adaptability to both human and chicken, spread of mobile genetic elements associated with bla genes from E. coli lineages adapted to chicken to those adapted to human is highly suggested. Our results provide important information to gain a better understanding of the transmission risk of bla genes from retail chicken meats to human.