Resistome and Virulome of Multi-Drug Resistant E. coli ST131 Isolated from Residents of Long-Term Care Facilities in the Northern Italian Region

Long-term care facilities (LTCFs) are important reservoirs of antimicrobial-resistant (AMR) bacteria which colonize patients transferred from the hospital, or they may emerge in the facility as a result of mutation or gene transfer. In the present study, we characterized, from a molecular point of view, 43 E. coli strains collected from residents of LTCFs in Northern Italy. The most common lineage found was ST131, followed by sporadic presence of ST12, ST69, ST48, ST95, ST410 and ST1193. All strains were incubators of several virulence factors, with iss, sat, iha and senB being found in 84%, 72%, 63% and 51% of E. coli, respectively. Thirty of the ST131 analyzed were of the O25b:H4 serotype and H30 subclone. The ST131 isolates were found to be mainly associated with IncF plasmids, CTX-M-1, CTX-M-3, CTX-M-15, CTX-M-27 and gyrA/parC/parE mutations. Metallo-beta-lactamases were not found in ST131, whereas KPC-3 carbapenemase was found only in two ST131 and one ST1193. In conclusion, we confirmed the spread of extended-spectrum beta-lactamase genes in E. coli ST131 isolated from colonized residents living inside LTCFs. The ST131 represents an incubator of fluoroquinolones, aminoglycosides and other antibiotic resistance genes in addition to different virulence factors.

Automated summary

In this study, E. coli strains collected from LTCF residents in Northern Italy were characterized. The most common lineage found was ST131, followed by sporadic presence of other lineages. All strains were carriers of multiple virulence factors. The ST131 isolates were mainly associated with different plasmids and mutations. ST131 serves as a reservoir for the spread of extended-spectrum beta-lactamase genes in LTCF residents and also incubates fluoroquinolone, aminoglycoside, and other antibiotic resistance genes.