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

Abstract

IntroductionEscherichia 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 blaOXA-48,blaKPC,blaNDM, and to a less extent blaVIM and blaIMP. 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 methodsA total of 300 E. coli isolates were collected from outpatient and admitted patients in Tehran. The presence of blaOXA-48,blaKPC,blaNDM, blaVIM and blaIMP 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. ResultsThe prevalence of blaOXA-48gene was 1% (three isolates), and blaKPC,blaNDM, blaVIM and blaIMP genes were not detected. All three blaOXA-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 blaOXA-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. ConclusionThis study showed hidden carbapenem resistance due to the presence of the blaOXA-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 blaOXA-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.