Emerging pathogens in urinary tract infections: virulence and phenotypic characterization of Pseudomonas aeruginosa strains

ABSTRACT Urinary tract infections (UTIs) affect a broad patient population and inflict a substantial financial burden on the U.S. healthcare system. While uropathogenic Escherichia coli (UPEC) causes the majority of cases, other pathogens are emerging. Patient data from our healthcare system in the Gulf Coast region of Alabama revealed that Pseudomonas aeruginosa accounted for 4.0% of UTI cases, roughly double the national average, prompting further investigation into this historically understudied uropathogen. Here, we performed whole-genome sequencing and phenotypic assays on 55 urinary P. aeruginosa isolates to characterize genomic diversity, antibiotic resistance, and virulence-associated phenotypes in the context of UTI. Multilocus sequence typing identified 19 strains with novel sequence types, underscoring the uncharacterized diversity of urinary P. aeruginosa isolates. Serotype O6 was most common and enriched in patients with indwelling catheters, whereas O4 was linked to diabetes mellitus. Antibiotic susceptibility testing (AST) revealed high levofloxacin resistance (29.1%), with 14.5% multidrug-resistant (MDR) and 9.1% extensively drug-resistant (XDR) isolates. Resistance patterns correlated with demographics, including higher meropenem and aztreonam resistance among isolates from African American patients. Phenotypic assays of growth, motility, and biofilm formation revealed negative correlations between antibiotic resistance and virulence. Specific virulence genes correlated with enhanced iron acquisition, hemolysis, and in vivo colonization. Notably, motility and exotoxin profiles were associated with P. aeruginosa ascension in a murine UTI model. Together, these findings provide insight into the diversity, resistance, and virulence characteristics of urinary P. aeruginosa isolates and highlight the need for further study of this emerging uropathogen. IMPORTANCE Pseudomonas aeruginosa is an emerging but understudied pathogen in urinary tract infections (UTIs). Given its resilience, adaptability, and the growing threat of multidrug resistance, P. aeruginosa remains a significant challenge in clinical microbiology and infection control. Using genomic sequencing, phenotypic assays, a murine infection model, and detailed patient metadata, we characterized 55 urinary clinical isolates and identified substantial genomic diversity, including 19 strains with previously undescribed sequence types. We observed associations between antibiotic resistance patterns and patient demographics, as well as a negative relationship between resistance and virulence phenotypes. In addition, variations in traits such as flagellar alleles and exotoxin profiles were associated with differences in urinary tract colonization. These findings highlight the diversity of urinary P. aeruginosa isolates and identify bacterial traits that may contribute to infection in the urinary tract.