Antimicrobial susceptibility patterns of STEC strains

The antimicrobial susceptibility patterns of STEC strains were detected after screening the isolates against a panel of 13 antimicrobial agents (Oxoid, UK; Table 1), selected on the basis of their medical importance. One ml of the calibrated bacterial suspension (0.5 McFarland standard units) which include 1.5 × 10⁸ colony forming unites/ ml were inoculated on Mueller-Hinton agar; E. coli ATCC 25922 was utilized as the quality control. The Kirby-Bauer disk diffusion method was utilized to determine antibiotic sensitivity; the results were interpreted according to Clinical Laboratory and Standards Institute criteria [33]. The multiple antimicrobial resistance index (MAR) for each strain was determined by dividing the number of antimicrobials to which the strain was resistant by the total number of antimicrobials used.

Types, groups, and prioritization of antimicrobials classified as critically important in human and veterinary medicine

Prioritization criterion 1 (P1): an antimicrobial used widely among patients with critical infections and in bacterial diseases in health care settings for which this antimicrobial class is the only or one of few alternatives available. Prioritization criterion 2 (P2): an antimicrobial used widely and of the class that may be useful for treating critical infections in health care settings but whose use may favor the generation of resistance. Prioritization criterion 3 (P3): The antimicrobial class typically chosen to control infections in those infected with resistant bacteria or bacteria that harbor resistance genes from non-human origins; NA, no prioritization has been assigned.