ESBL-Producing Escherichia coli Bacteremia: Association Between Virulence-Factor Burden, Source of Infection, and Clinical Features

Abstract

(1) Background: Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli are important causes of bacteremia, but integrated genotype–virulence–outcome data from low- and middle-income settings are limited; (2) Methods: Observational study of ESBL-producing E. coli (ESBL Ec) bacteremia at Dr. Soetomo General Academic Hospital, Surabaya, Indonesia (2022–2024). ESBL production was confirmed phenotypically and ESBL genes by PCR; eight ExPEC-associated virulence genes (fimH, hlyA, iutA, cvaC, iha, traT, ompT, papC) were detected by multiplex PCR and summed into a virulence-factor (VF) burden, classifying patients into low- and high-VF groups. (3) Results: Of 188 ESBL Ec isolates, 129 with complete clinical data were included. blaCTX-M predominated (88.3%); blaTEM and blaSHV were less frequent. Isolates showed near-universal resistance to first- and third-generation cephalosporins, ampicillin, and ciprofloxacin, with relatively preserved susceptibility to carbapenems, amikacin, tigecycline, and cefoperazone/sulbactam. The most common virulence genes were fimH (81.9%), traT (78.7%), iutA (74.5%), and ompT (59.0%); overall mortality was 70.5%. High-VF isolates were more often from a urinary-tract source (77.6% vs. 59.2%; p = 0.026), whereas skin and soft-tissue and healthcare-associated infections predominated in the low-VF group. In a multivariable analysis, only iha remained independently associated with a urinary-tract source (adjusted odds ratio [aOR] 2.53, 95% CI 1.14–5.65). Independent predictors of mortality were the SOFA score (aOR 1.95 per point, 95% CI 1.48–2.56), male sex, and traT carriage. (4) Conclusions: ESBL Ec bacteremia in this setting is dominated by blaCTX-M producers with extensive multidrug resistance and high mortality. Outcome was driven by illness severity at presentation rather than bacterial genotype. These findings are exploratory and require confirmation in larger multicenter studies with variant-level and genomic characterization.