Characterization of in Isolates from Animals, Retail Meat, and Human Patients in Guangzhou, China.

The purpose of this study was to investigate the prevalence and genetic elements of among isolates from animals, retail meat, and humans (patients with infection or colonization) in Guangzhou, China. A total of 1,354 isolates were screened for by PCR. Fifty -positive isolates were further characterized by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), S1-PFGE, genetic environment analysis, plasmid replicon typing, and plasmid sequencing. was detected in 172 (33.79%), 60 (17.34%), and 90 (18.07%) isolates from animal, food, and human, respectively. High clonal diversity was observed among -positive isolates. In 21 -containing transformants, was flanked by two IS elements in the same orientation, formed a composite transposon Tn in 19 transformants, and was located on plasmids (33.3~500 kb) belonging to IncN1-F33:A-:B- ( = 3), IncHI2/ST3 ( = 3), F-:A18:B- ( = 2), F-:A-:B54 ( = 2), or others. Additionally, was co-located with multiple resistance genes on the same plasmid, such as ' and/or , which were identified in two F-:A18:B- plasmids from pigs, and , , and , which were detected in two N1-F33:A-:B- plasmids from patients. The two IncHI2/ST3 -bearing plasmids, pHNLDF400 and pHNYJC8, which were isolated from human patient and chicken meat, respectively, contained a typical IncHI2-type backbone, and were similar to each other with 2-bp difference, and also showed 99% identity to the Typhimurium -carrying plasmids pHXY0908 (chicken) and pHK0653 (human patient). Horizontal transfer mediated by mobile elements may be the primary mechanism underlying spread in isolates obtained from various sources in Guangzhou, China. The transmission of identical -carrying IncHI2 plasmids between food products and humans might pose a serious threat to public health.