Antimicrobial Resistance, Mortality Risk Associated With Specific E coli Isolates in Patients With Bloodstream Infections

Although patterns of antimicrobial resistance (AMR) and an increased length of hospitalization were observed in patients with bloodstream infections (BSI) caused by Escherichia coli sequence type 131 (ST131), ST131 isolates were not associated with an increased risk of mortality, according to the Journal of Antimicrobial Chemotherapy.

In this study, researchers prospectively collected E coli isolates from patients with E coli bacteremia between July 2015 and August 2016. The researched performed whole-genome sequencing to determine whether specific E coli genotypes increase the risk for adverse outcomes in BSIs. The primary outcomes were mortality within 7, 30, and 90 days, as well as the length of hospitalization.

Among a total of 551 patients included in the analysis, 43.4% were men, 56.6% were women, and 60% were aged 65 years and older. Multilocus sequence testing identified 114 unique E coli isolates among the patients, including ST131 in 21.2%, ST73 in 14.5%, ST69 in 9.3%, and ST95 in 8.2%. Of 115 isolates belonging to the ST131 lineage, 11.2% and 10.2% were from the ST131-C2 sublineage and other sublineages, respectively.

Results of AMR testing were available for 537 E coli isolates. Of the 537 isolates, 26.6% were resistant to fluoroquinolones, 19.7% were resistant to third-generation cephalosporins, and 15.1% were resistant to gentamicin. Resistance to amoxicillin and amoxicillin/clavulanic acid was observed in 62.8% and 43.9% of E coli isolates, respectively. In addition, with the exception of amoxicillin and carbapenems, AMR was significantly associated with E coli genotype for all antibiotics tested (P <.001). The most significant AMR in all tested antibiotics was observed among ST131-C2 isolates.

In regard to patient characteristics, E coli isolates ST69 and ST95 were observed more frequently in women and ST131 isolates were more likely in men. Of note, no significant associations were found between specific E coli genotype and patient age or ethnicity. However, compared with patients who were white, those who were Black and infected with an E coli isolate with resistance to gentamicin and piperacillin/tazobactam had an increased risk of mortality within 90 days (odds ratio [OR], 3.09; 95% CI, 1.02-9.26).

Overall, 33.7% of patients with E coli bacteremia died within 1 year. Of these patients, 7.0% died within 7 days of infection onset, 11.0% within 30 days, and 15.7% within 90 days. No significant associations were observed between the risk for 7- and 30-day mortality and E coli genotype. After adjustment for patient characteristics and genotype, an increased risk of death within 90 days was observed among patients with E coli isolates that were resistant to gentamicin (OR, 3.32; 95% CI, 1.17-9.72). An unadjusted logistic regression model showed a 6-fold increased risk for extended hospitalization among patients infected with ST131-C2 E coli isolates (OR, 6.46; 95% CI, 2.02-32.64).

This study was limited by its urban setting, thus the results may not be generalizable to other patient populations.

According to the researchers, “there may also be important associations between reason for [hospital] admission, onset of infection, and gender.” However, they noted that “larger samples and more detailed information would allow these more complex associations and possible interactions to be examined.”

Disclosure: Some authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.

Reference

Jauneikaite E, Honeyford K, Blandy O, et al. Bacterial genotypic and patient risk factors for adverse outcomes in Escherichia coli bloodstream infections: a prospective molecular epidemiological study. J Antimicrob Chemother. Published online March 10, 2022. doi:10.1093/jac/dkac071