Molecular characterization of local human extraintestinal Escherichia coli isolates

Abstract

Extraintestinal pathogenic E.coli are major pathogens responsible for causing urinary tract infections. These are associated with multiple drug resistance (MDR) and high virulence. A triplex PCR was employed to segregate each isolate into different phylogenetic groups. Among fifty nine uropathogenic E.coli isolates majority belonged to phylogenetic group B2 (50%) where as 19% each belonged to groups A and B1, and 12% to group D. Phylogenetic group D isolates were found to be less frequent but harbored multiple drug resistance and virulence related genes to a greater extent. Drug resistance was evaluated by disc diffusion method and relevant drug resistance gene detection. It was found that most effective drugs were gentamicin and amikacin among aminoglycosides; aztreonam, ceftriaxone, cefoperazone and cefixime among β lactams, and ciprofloxacin among quinolones. Streptomycin, trimethoprim-sulfamethoxazole, tetracycline and nalidixic acid were relatively ineffective. Chloramphenicol was found to be very effective for urinary tract infections. Highly prevalent drug resistance gene was mutated gyrA (83%) followed by tem (46%), bltTEM (41%), tetB (34%), catP (31%), and tem β lactamase (15%); blaSHV and tetA were not detected. Among virulence related genes most prevalent was hlyA (37%) followed by sfaDE (27%), papC (24%), cnf1 (20%), eae A (19%) and afaBC3 (14%). Some of isolates were highly hemolytic to human erythrocytes and some were highly cytotoxic to Vero cells. Highly hemolytic isolates mainly belonged to group D, where as highly verotoxic isolates belonged to group B2 followed by group D. It was also noted that in cnf1 negative isolates cytotoxicity was related to papC, sfaDE, afaBC3, eae A and hlyA genes.