Comparative Study of CTX-M-15 Producing Escherichia coli ST131 Clone Isolated from Urinary Tract Infections and Acute Diarrhoea

Background and Purpose: The alarming increase in the prevalence of CTX-M-15 extended-spectrum beta-lactamase (ESBL) producing E. coli has been significantly linked to the clonal expansion of emerging sequence type (ST131). This study aimed to screen for the O16/O25-ST131 clones among different phylogenetic types of E. coli strains isolated from urinary and diarrhoeal samples. Methods: A total of 205 E. coli strains isolated from patients with UTI and acute diarrhoea were investigated by phenotypic and genotypic methods for ESBL identification. Molecular methods were used for identification of O25/O16-ST131 clone and phylogenetic typing of E. coli isolates. Results: O25-ST131 clone was detected in 89/105 (84.8%) and 47/100 (47%) of urinary and intestinal E. coli isolates, respectively, with a significant difference (P-value<0.001). There was a significant high rate of occurrence of ESBLs, MDR, and antibiotic resistance to most antibiotic classes among O25-ST131 than non-O25-ST131 isolates. CTX-M-15 gene was detected in 64/71 (90%) of ESBLs producing intestinal isolates and 54/79 (68.4%) of urinary ESBLs producing isolates. The O25-ST131 clone was reported among all phylogenetic groups. The O16-ST131 clone serotype was not detected in the study isolates. Conclusion: High prevalence of the O25-ST131 clone was reported among extraintestinal and intestinal E. coli isolates. First detection of the O25-ST131 clone among phylogenetic groups other than group B2 draws attention of the ability of this clone to transfer among commensal groups. An increasing in the prevalence of CTX-M-15 among E. coli strains especially of intestinal origin is alarming as the intestine is the main reservoir for ExPEC strains causing UTI.