Molecular characterization of Escherichia coli producing extended-spectrum β-lactamase CTX-M-14 and CTX-M-28 in Mexico

The spread of ESBL-producing Escherichia coli has constantly increased in both clinical and community infections. Actually, the main ESBL reported is the CTX-M family, which is widely disseminated between the Enterobacteriaceae family. The epidemiology of the CTX-M family shows the CTX-M-15 variant dominating worldwide, followed by CTX-M-14 and CTX-M-27. The specific ESBL-producing E. coli clones included mainly the sequence types ST131, ST405, and ST648. In this report, we present the molecular characterization of ESBL-producing E. coli clinical isolates from eight hospitals in Mexico. From a collection of 66 isolates, 39 (59%) were identified as bla CTX-M-14 and bla CTX-M-27 belonging to the group CTX-M-9. We identified 25 (38%) isolates, producing bla CTX-M-28 belonging to the group CTX-M-1. bla CTX-M-2 and bla TEM-55 were identified in one isolate, respectively. Fourteen isolates (21%) were positive for bla CTX-M-14 (13%) and bla CTX-M-28 (7.3%) that were selected for further analyses; the antimicrobial susceptibility showed resistance to ampicillin (> 256 µg/mL), cefotaxime (> 256 µg/mL), cefepime (> 64 µg/mL), and ceftazidime (16 µg/mL). The ResFinder analysis showed the presence of the antimicrobial resistance genes aacA4 , aadA5 , aac(3)lla , sul1 , dfrA17 , tet(A) , cmlA1 , and bla TEM-1B . PlasmidFinder analysis identified in all the isolates the replicons IncFIB, which were confirmed by PCR replicon typing. The MLST analysis identified isolates belonging to ST131, ST167, ST405, and ST648. The IS Ecp1B genetic element was found at 250 pb upstream of bla CTX-M-14 and flanked by the IS 903 genetic element at 35 pb downstream. The IS 1380 -like element IS Ec9 family transposase was identified at 250 pb upstream of bla CTX-M-14 and flanked downstream by the IS 5 /IS 1182 at 80 pb. Our study highlights the significant prevalence of CTX-M-14 and CTX-M-28 enzymes as the second-most common ESBL-producing E. coli among isolates in Mexican hospitals. The identification of specific sequence types in different regions provides valuable insights into the correlation between ESBL and E. coli strains. This contribution to understanding their epidemiology and potential transmission routes is crucial for developing effective strategies to mitigate the spread of ESBL-producing E. coli in healthcare settings.