Resistance and Virulence Factor Determinants of Carbapenem-Resistant Escherichia Coli Clinical Isolates in Three Hospitals in Tehran, Iran

Escherichia coli (E. coli) strains are among predominant agents causing nosocomial and community acquired infections. The majority of strains encode numerous virulence factors including fimbrial adhesions, secretory proteins and toxins, siderophores, and capsule. This study aimed to investigate the prevalence rate of virulence encoding genes and carbapenem resistance-encoding genes among imipenem-resistant E. coli isolates collected from patients hospitalized in Tehran, Iran.
In this cross-sectional study (April 2015-December 2017), 50 non-duplicated carbapenem-resistant E. coli isolates were collected from clinical specimens (stool, urine, blood, and wound) of hospitalized patients in three hospitals in Tehran, Iran. The antibiotic susceptibility profile was determined against 15 antibiotics on Mueller Hinton Agar (MHA) as per CLSI guidelines version 2016. The PCR was used to detect virulence and antibiotic resistance encoding genes.
From a total of 50 carbapenem-resistant E. coli isolates, the highest resistance rate was observed to ceftazidime (100%), tetracycline (88%), amoxicillin (100%), sulfonamide (60%), and the least resistance rate was observed against amikacin (14%), gentamicin (22%), and fosfomycin (0%). The genes mediating resistance were as follows: beta-lactams OXA-48 (8%), IMP (16%), VIM (0%), NDM-1 (0%), fosA3 (0%), quinolones (qnrA 48%), and colistin mcr-1(0%). Furthermore, the prevalence rates of of fimA, hlyA, cnf1, vat, pic, crl, and papH were 88, 36, 28, 10, 12, 54, and 88%, respectively.
In this study, all imipenem-resistant E. coli isolates were susceptible to fosfomycin, and all were fosA3 negative. Among carbapenemase genes, IMP and OXA-48 type enzymes associated with higher MIC levels (8 to 32 µg.mL-1) were detected. In this study, data suggest the role of these carbapenemases in resistance to carbapenems. Furthermore, the presence of multiple drug resistant strains encoding adhesive and secretory virulence factors is a concern for the infections treatment.