Co-resistance patterns in fluoroquinolone-resistant E. coli recovered from residents of nursing homes

Background: Nursing home residents are commonly colonized with fluoroquinolone-resistant E. coli (FQREC). Clinical isolates of FQREC recovered from hospitalized patients often express high levels of co-resistance to other classes of antibiotics. Few studies have examined if antibiotic co-resistance is common in FQREC isolates recovered from nursing homes (NHs).

Objective: Determine the frequency of antibiotic co-resistance in FQREC recovered from NH facilities.

Methods: Residents of 6 NHs in Wisconsin were screened to determine if they were colonized with FQREC using swabs of stool as well as wounds and urine (if catheterized) that were then plated on ciprofloxacin-containing selective media. Recovered isolates were identified to the species level using phenotypic and biochemical methods. PFGE was used to identify unique strains. Fluoroquinolone-resistance and co-resistance to 13 other antibiotics was confirmed by disk diffusion susceptibility testing using CLSI interpretive guidelines.

Results: 89 FQREC were recovered from 76 of the 441 subjects (17.2%) who underwent screening. 79 of these 89 isolates were unique by PFGE. The susceptibly profile of the unique isolates is shown in the Figure. Resistance to amoxicillin (86%) and trimethoprim/sulfamethoxazole (38%) were the most frequent co-resistance patterns identified. Resistance to 2^nd and 3^rd cephalosporins as well as nitrofurantoin was uncommon (<10%). Only one FQREC isolate appeared to produce an ESBL.

Conclusions: FQREC isolates recovered from NH residents are often co-resistant to oral antibiotics commonly utilized in this setting suggesting that effective therapy of serious infections caused by this pathogen will increasingly require the use of parenteral therapy. Further studies on the role that antimicrobial prescribing patterns and infection control practices play in the selection and transmission of these pathogens are warranted.