First Report of Prevalence of CTX-M-15 Producing Escherichia coli O25b/ST131 from Iran

Background: The emergence of Escherichia coli ST131 as a multidrug-resistant and virulent pathogen represents a major challenge to public health globally. Recently, the O25b/ST131 E. coli producing CTX-M15 with high virulence potential has been reported worldwide but has received little attention in Iran. This study is the first in Iran to specifically determine the spread of the O25b/ST131 clone producing CTX-M15 among E. coli isolates belonging to the B2 phylogenetic group. Methods: ST131 clone in phylogenetic group B2 was detected based on PCR detection of ST131-specific SNPs in mdh and gyrB. O25b/ST131 E. coli clone was confirmed utilizing O25b-ST131 clone allele-specific PCR for the pabB gene. All group B2 E. coli isolates were characterized based on antibiotic susceptibility, ESBL enzymes and virulence traits. Results: Our results demonstrated that 38 out of the 154 B2 group isolates (24.7%) were identified as belonging to the ST131 clone. Furthermore, of these, 28 isolates (73.6%) were detected as O25b/ST131 clone. Antibiotic resistance of ST131 E. coli isolates to ciprofloxacin, gentamicin, cefixime and aztreonam was significantly higher than non-ST131 isolates. Almost all of the O25b/ST131 isolates with the ability for ESBL production were reported as CTX-M15 producing (95.5%). Our results showed that the most prevalent virulence trait in ST131 clone was ompT (94.7%). Conclusion: This study is the first to report the prevalence of the CTX-M15 producing O25b/ST131 E. coli in Iran. Our findings reinforce the surveillance of dissemination of ST131 E. coli clone as a major drug-resistant pathogen and an important new public health threat.

Keywords:

O25b/ST131 E. coli , Extended-spectrum beta-Lactamases , CTX-M15 , B2 phylogenetic group , Antibiotic resistance