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 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, bla and bla 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 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.