Hidden carbapenem resistance in the community- and hospital-associated OXA-48 gene-carrying uropathogenic Escherichia coli

Abstract Introduction Escherichia coli is the primary pathogen in complicated and uncomplicated urinary tract infections (UTIs). Today, the emergence of E. coli strains resistant to carbapenem antibiotics is a significant concern in UTIs treatment. The main carbapenemase enzymes in the E. coli are bla OXA-48, bla KPC, bla NDM, and to a less extent bla VIM and bla IMP. The aim of this study was the molecular screening of carbapenemase genes in Uropathogenic Escherichia coli (UPEC) isolated from the community- and hospital-associated UTIs. Material and methods A total of 300 E. coli isolates were collected from outpatient and admitted patients in Tehran. The presence of bla OXA-48, bla KPC, bla NDM, bla VIM and bla IMP genes was detected by the PCR method. Antibiotic susceptibility test was performed by disk diffusion. Phylogrouping, serogrouping, and virulence typing (ompT, iha, pic, csgA, fyuA, iucD, papGII, kpsMII, cnf-1, hlyA, traT, and fimH) were performed for carbapenemase genes-carrying strains by PCR method. Results The prevalence of bla OXA-48gene was 1% (three isolates), and bla KPC, bla NDM, bla VIM and bla IMP genes were not detected. All three bla OXA-48-carrying strains were susceptible to carbapenems such as imipenem, ertapenem, and meropenem in disk diffusion methods. The degree of resistance to ceftazidime, cefotaxime, amoxicillin, cefazolin, and augmentin was 100%. Two of the three strains were hospital-associated UPEC, and one strain was community-associated UPEC. Phylogroup and serogroup of isolates were B2-O16, B2-unknown, and B1-O25, respectively. All three bla OXA-48-carrying isolates were ESBL-producer and carried the blaCTX-M1 gene. iha, papП, FyuA, fimH, csgA, iucD, and traT virulence genes were detected in 100% of isolates. Conclusion This study showed hidden carbapenem resistance due to the presence of the bla OXA-48 gene in carbapenem-susceptible, and ESBL-producer UPEC strains. Thus, routine susceptibility tests such as disk diffusion and E-test methods is unreliable for the detection of carbapenem non-susceptibility, so a rapid, easy and inexpensive method is still needed for testing carbapenem nonsusceptibility, especially in ESBL-producer isolates. Additionally, our results indicate the bla OXA-48 gene disseminates in the hospital- and community-associated E. coli isolates in Tehran city. Identification of strains with hidden carbapenem resistance would significantly help to restrict and prevent the spread of such strains in the community and hospital settings.