Antimicrobial resistance profile and molecular analysis of virulence among Escherichia coli isolated from pregnant women with asymptomatic bacteriuria in Gorgan, Iran.

Urinary tract infections (UTIs) are common among pregnant women and are frequently caused by uropathogenic Escherichia coli (UPEC). This cross-sectional study investigated the distribution of key virulence genes, antimicrobial resistance patterns, and their relationship with phylogenetic groups in UPEC isolates obtained from pregnant women with asymptomatic bacteriuria in Gorgan, Iran. Out of 913 urine samples collected between 2018 and 2023, 360 non-duplicate UPEC isolates were confirmed using standard biochemical methods. Nineteen virulence genes, including neuC, fimH, papC, sfaS, sfa/focDE, focG, kpsMTII, ecpA, iutA, ibeA, rfc, fyuA, traT, iroN, papGII, hlyA, cnf1, cdtB, and cvaC, were detected by PCR, while phylogenetic grouping was performed through triplex PCR targeting chuA, yjaA, and tspE4.C2. Antimicrobial susceptibility testing showed that imipenem (96.3%) and nitrofurantoin (93.0%). The capsule gene kpsMTII was the most prevalent, and fimH was the most frequent adhesin gene (89.8%). Phylogenetic group B2 exhibited the highest diversity and frequency of virulence genes. Multidrug resistance (MDR) was observed in 51.4% of isolates, and although 58.3% of B2 strains were MDR, the association between phylogeny and MDR was not statistically significant (p > 0.05). Strong biofilm formation correlated significantly with resistance to ciprofloxacin and ampicillin (p < 0.01). This study documents a high prevalence of antimicrobial resistance and ESBL production among UPEC isolates from pregnant women with asymptomatic bacteriuria. The coexistence of multiple virulence traits with MDR and strong biofilm formation suggests potential biological interactions that warrant further investigation.