Whole-genome characterisation of Escherichia coli isolates from older women with urinary tract infection and asymptomatic bacteriuria.

OBJECTIVES

Diagnosing urinary tract infections (UTIs) in older women is challenging due to the high prevalence of asymptomatic bacteriuria (ASB). This study aimed to investigate whether pathogen-related factors differ between older women with UTI and those with ASB, and to gain further insight into the persistence of Escherichia coli in ASB.

METHODS

In this exploratory study, E. coli isolates from 46 participants were analysed. The study included community-dwelling and long-term care facility women aged ≥ 65 years diagnosed with either UTI (defined as ≥ 2 new-onset lower urinary tract symptoms, pyuria, and bacteriuria) or ASB (E. coli ≥ 104 CFU/mL in two consecutive urine samples). Whole-genome sequencing (WGS) was performed to identify previously described putative uropathogenicity factors (PUFs), antimicrobial resistance genes, multilocus sequence typing (MLST) sequence types (STs), and Clermont phylogroups.

RESULTS

We analysed 31 isolates from UTI patients and 32 sequential isolates from 15 ASB patients. All ASB patients carried genetically similar E. coli strains in two consecutive samples taken 2-4 weeks apart. The isolates represented a diverse range of STs, with ST69, ST73, and ST141 being the most prevalent. Although no significant difference in the overall number of PUFs between UTI and ASB groups was observed, distinct patterns emerged. UTI-associated isolates more frequently harbored cnf1 and sfaH, whereas iha, iucC and sat were more common in ASB isolates.

CONCLUSIONS

Our findings suggest potential individual differences in the presence of PUFs between UTI and ASB isolates. Further functional studies are warranted to explore the role of these factors in bladder colonization and UTI pathogenesis. Additionally, their interactions with host-specific factors should be examined to better understand bacterial persistence and disease development in older women.