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

Abstract

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.

Keywords: Escherichia coli; Long-term care; ST131.

Figure 1. Pulsed field gel electrophoresis patterns of 28 fluoroquinolone-resistant ST131 fecal Escherichia coli isolates from long-term care facility residents

Data columns to the right of the PFGE profiles are the strain number, pulsotype, H30Rx subclone status, and long-term care facility of origin (1, 2, or 3). Pulsotypes were assigned by comparison to an existing large private PFGE profile reference library (33). All isolates represented the H30 subclone within ST131.