Antimicrobial resistance, virulence genes, and phylogenetic characteristics of pathogenic Escherichia coli isolated from patients and swine suffering from diarrhea

Background Escherichia (E.) coli causes colibacillosis in swine and humans, and is frequently associated with antimicrobial resistance. In this study we aimed to compare antimicrobial resistance, O-serogroups, virulence genes, and multi-locus sequence type of E. coli between isolates from pigs and patients suffering from diarrhea, and the most prevalent pathogenic E. coli strain from swine isolates in Korea. Methods We tested 64 and 50 E. coli strains from pigs and patients suffering from diarrhea for antimicrobial susceptibility test, virulence genes, O-serogroups, and multi-locus sequence typing. Results We confirmed that isolates from swine showed significantly higher resistance than from those from patients, especially to fluoroquinolone (ciprofloxacin: 37.5 and 10.0%; norfloxacin: 29.7 and 8.0%, respectively). Stx1 (46.0%) was most frequently detected in patients followed by stx2 (38.0%). There was no significant difference in stx2 (swine: 23.4%, patients: 38.0%). In isolates from patients, O157 (12.0%) was the most prevalent O-serogroup, and two isolates (3.1%) from pigs were confirmed to have O157. Additionally, sequence type (ST) 10 (swine: 6 isolates, patients: 2 isolates) and ST 88 (swine: 2 isolates, patients: 1 isolate) were simultaneously detected. Conclusions We found that both isolates from swine and human had the stx2 gene, which could cause severe disease. Moreover, antimicrobial resistance was significantly higher in pigs than in patients. These results suggest that pig could act as a reservoir in human infection and antimicrobial resistance could be transferred to human from pigs.

Automated summary

This study compared antimicrobial resistance, O-serogroups, virulence genes, and multi-locus sequence type of Escherichia (E.) coli between isolates from pigs and patients suffering from diarrhea, as well as the most prevalent pathogenic E. coli strain from swine isolates in Korea. The results showed that isolates from pigs exhibited significantly higher resistance to fluoroquinolone compared to isolates from patients. Stx2 gene was found in both pig and human isolates, which could potentially cause severe disease. The study also suggested that pigs could act as a reservoir for human infection and transfer antimicrobial resistance to humans.