High prevalence of B2-ST131 clonal group among extended-spectrum β-lactamase-producing Escherichia coli isolated from bloodstream infections in Quito, Ecuador.

Objectives: The purpose of this study was to describe the clonal relationships and phylogroups of extended-spectrum β-lactamase-producing Escherichia coli (ESBL-Ec) isolated from patients with bacteraemia in three hospitals in Quito, Ecuador.
Methods: Between June 2013 and September 2014, a total of 4354 blood cultures were performed in three hospitals located in different areas of Quito. A BACTEC ^TM system was used for blood culture, and the VITEK®2 system was used for species identification and in vitro antimicrobial susceptibility testing. The ESBL genotype, presence of the bla _CTX-M , bla _TEM and bla _SHV genes, and the phylogenetic group of E. coli isolates was determined by PCR. Clonal groups were established by multilocus sequence typing (MLST).
Results: Of 929 blood cultures positive for Gram-negative bacilli, 181 (19.5%) were positive for E. coli, representing the most frequent bacteraemia isolates in each hospital. Of the 181 E. coli isolates, 57 (31.5%) were ESBL-Ec. The main sources of ESBL-Ec bacteraemia were urinary tract infection (40; 70.2%), biliary tract infection (10; 17.5%) and other infections (7; 12.3%). The majority of ESBL-Ec isolates (39; 68.4%) from the three hospitals belonged to the virulent phylogenetic group B2, of which 36/39 (92.3%) were ST131 and 33/36 (91.7%) carried the bla _CTX-M-15 gene.
Conclusion: These results provide knowledge of the phylogenetic relationships of E. coli from bacteraemia in Ecuadorian patients. ST131 has emerged in ESBL-Ec, representing an important public-health problem because this multiresistant clone is considered to be a vehicle for the propagation of antimicrobial resistance genes and is a highly virulent, well-adapted human pathogen.
(Copyright © 2019 International Society for Antimicrobial Chemotherapy. Published by Elsevier Ltd. All rights reserved.)