Epidemiology and characteristics of Escherichia coli sequence type 131 (ST131) from long-term care facility residents colonized intestinally with fluoroquinolone-resistant Escherichia coli

- A prevalence of E. coli ST131 of nearly 80% was found among incident FQREC isolates in long-term care facility residents.
- ST131 and non-ST131 isolates differed significantly in the prevalence of virulence factors.
- ST131 and non-ST131 isolates did not differ in the proportion of isolates that qualified molecularly as ExPEC.
- PFGE pulsotypes for colonizing ST131 isolates were common among previously characterized clinical ST131 isolates.

The objective of this study was to evaluate molecular and epidemiologic factors associated with Escherichia coli sequence type 131 (ST131) among long-term care facility (LTCF) residents who acquired gastrointestinal tract colonization with fluoroquinolone-resistant E. coli (FQREC). Colonizing isolates from 37 residents who newly developed FQREC colonization at three LTCFs from 2006 to 2008 were evaluated. Twenty-nine (78%) of 37 total FQREC colonizing isolates were ST131. Most ST131 isolates had a distinctive combination of gyrA and parC replacement mutations. The ST131 and non-ST131 isolates differed significantly for the prevalence of many individual virulence factors but not for the proportion that qualified molecularly as extraintestinal pathogenic E. coli (ExPEC) or aggregate virulence factor scores. E. coli ST131 was highly prevalent among LTCF residents with FQREC colonization. Future studies should determine the risk factors for infection among ST131-colonized residents, and assess the potential for increased transmissibility of ST131 in the long-term care setting.