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E. coli ST131 dominates health care–associated infections
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Data from a retrospective cohort indicate that Escherichia coli sequence type 131 was the dominant clonal group responsible for infections in the health care setting and among the elderly.
“Sequence type 131 (ST131) is a dominant, antimicrobial-resistant clonal group associated with health care settings and elderly hosts,” Ritu Banerjee, MD, PhD, assistant professor at the Mayo Clinic in Rochester, Minn., told Infectious Disease News. “Most epidemiologic studies of ST131 have utilized convenience or highly selected samples, so the true prevalence of ST131 and the risk factors for ST131 infection were undefined. We used an unbiased sampling strategy to determine the true prevalence and predictors of ST131.”
Banerjee and colleagues conducted a study that included 299 consecutive, nonduplicate E. coli isolates that were submitted to laboratories in Olmsted County, Minn., in February and March 2011. They identified ST131 using PCR, and the isolates also were evaluated using pulsed field gel electrophoresis.
Most of the isolates were obtained from urine specimens, and 61% of the isolates were from community-acquired infections. ST131 accounted for 27% of the isolates. The prevalence of ST131 increased with age: 5% of isolates from patients aged 11 to 20 years were classified as ST131 vs. 50% of isolates from patients aged 91 to 100 years. ST131 also was more prevalent in health care–associated isolates (49%) compared with community–associated isolates (15%).
On a multivariable analysis, factors predictive of ST131 carriage were older age, long-term care facility residence, urinary tract infection within the previous 30 days and complex infection. Previous antibiotic use, especially fluoroquinolones, macrolides and extended-spectrum cephalosporins, also was a risk factor.
“Antimicrobial stewardship and infection control interventions in health care and long-term care facilities are urgently needed to reduce further emergence and the spread of ST131,” Banerjee said. “Increased awareness among providers of the ST131 pandemic is also needed. We noted that many patients infected with ST131 were prescribed empiric therapy with fluoroquinolones, which are largely ineffective against this clonal group. As a result, many of the patients with ST131 had persistent or recurrent symptoms.”
Banerjee said that the researchers have initiated active surveillance of ST131 and antimicrobial use at a local nursing home to identify areas for preventive interventions, and to see whether a reduction in the use of fluoroquinolones is associated with a decrease in ST131 prevalence.
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Disclosure: The researchers report no relevant financial disclosures.