Multi-Locus Sequence Typing and Drug Resistance Analysis of Swine Origin Escherichia coli in Shandong of China and Its Potential Risk on Public Health

The extensive use of antibiotics has caused antimicrobial resistance and multidrug resistance in Escherichia coli to gradually develop into a worldwide problem. These resistant E. coli could be transmitted to humans through animal products, thereby creating a problem for bacterial treatment for humans and resulting in a public health issue. This study aims to investigate the molecular typing and drug resistance of swine and human origin E. coli within the same prefecture-level cities of Shandong province and its potential risk on public health. The drug sensitivity results indicated that tetracycline (TE) (97.17%) was the major antibiotic with high drug resistance in 106 pig origin E. coli. There was a significant difference in the drug-resistant genotypes between the two sources, of which the blaTEM positive rate was the highest in the genera of β-lactams (99% in pigs and 100% in humans). Among the 146 E. coli isolates, 98 (91.51% pig origin) and 31(77.5% human origin) isolates were simultaneously resistant to three or more classes of antibiotics, respectively. The MLST results indicate that the 106 pig origin E. coli isolates were divided into 25 STs with ST 1258, ST 361 and ST 10 being the dominant sequence analysis typing strains. There were 19 MLST genotypes in 40 strains of human E. coli from Tai’an, Shandong Province, with ST1193, ST 73, ST 648, ST 131, ST 10 and ST 1668 being the dominant strains. Moreover, cluster analysis showed that CCl0 and CC23 were the common CCs (clonal complexes) from the two sources. Our results provide a theoretical basis for guiding rational use of antibiotics and preventing the spread of drug-resistant bacteria，and provided epidemiological data for risk analysis of foodborne bacteria and antimicrobial resistance in swine farms in Shandong Province.