An analysis of more than 14,000 Escherichia coli bloodstream infections in Canada found that antimicrobial resistance (AMR) was associated with increased mortality, but some of that mortality is explained by patient characteristics, researchers reported yesterday in eClinicalMedicine.
The retrospective cohort study of all people hospitalized with E coli bacteremia in Ontario, Canada, from 2017 through 2020 examined the odds of mortality associated with resistant versus susceptible isolates before and after accounting for clinically relevant patient characteristics, including prior healthcare exposure. Researchers assessed resistance to eight individual classes of antibiotic agents and examined a special category of difficult-to-treat-resistance (DTTR), defined as resistance to multiple classes of antibiotics. The primary outcome of interest was 90-day mortality.
Among 14,548 eligible episodes of E. coli bloodstream infection in 13,706 patients (median age 74, 55.7% women), resistance was most common to aminopenicillins (46.8%), followed by first generation cephalosporins (38.8%), fluoroquinolones (26.5%), sulfonamides (24.1%), third generation cephalosporins (13.8%), aminoglycosides (11.7%), beta-lactam/beta-lactamase-inhibitors (9.1%) and carbapenems (0.2%). Only 18 (0.1%) episodes exhibited DTTR. Overall, 2,585 episodes (17.8%) were associated with death within 90 days.
For each antibiotic class, the unadjusted odds of mortality were much higher among resistant isolates, particularly those antibiotics most commonly used for empiric treatment. After accounting for patient characteristics, the adjusted odds ratio (aOR) of mortality were greatly attenuated but remained statistically significant: aminopenicillins (aOR, 1.09; 95% CI, 0.99 to 1.20), first generation cephalosporins (aOR, 1.07; 95% CI, 0.97 to 1.18), third generation cephalosporins (aOR, 1.29; 95% CI, 1.15 to 1.46), beta-lactam/beta-lactamase-inhibitors (aOR, 1.28; 95% CI, 1.13 to 1.45), carbapenems (aOR, 2.06; 95% CI, 0.91 to 4.66), sulfonamides (aOR, 1.06; 95% CI, 0.95 to 1.18), fluoroquinolones (aOR, 1.16; 95% CI, 1.05 to 1.29), aminoglycosides (aOR, 1.27; 95% CI, 1.11 to 1.46), and DTTR (aOR, 2.58; 95% CI, 0.87 to 7.66).
"Surveillance for AMR-associated mortality should incorporate adjustment for patient characteristics and prior healthcare utilization," the authors wrote.