Molecular profiling of antimicrobial resistance and integron association of multidrug-resistant clinical isolates of Shigella species from Faisalabad, Pakistan

Bacillary dysentery, common in developing countries, is usually caused by Shigella species. A major problem in shigellosis is the rapid emergence of multidrug-resistant strains. This is the first detailed molecular study on drug resistance of Shigella isolates from the Faisalabad region of Pakistan. Ninety-five Shigella isolates obtained after screening of 2500 stool samples were evaluated for in vitro resistance to commonly used antimicrobial agents; the presence or absence of 20 of the most relevant drug resistance genes; and the prevalence of integrons 1, 2, and 3. Shigella flexneri was found to be the most prevalent and most resistant species. Collectively, high resistance was found towards ampicillin (96.84%), tetracycline (93.68%), streptomycin (77.89%), and chloramphenicol (72.63%). Significant emerging resistance was detected towards the modern frontline drugs ciprofloxacin (12.63%), cefradine (17.89%), ceftriaxone (20.00%), cefoperazone (22.10%), and cefixime (28.42%). Prevalence rates for bla(TEM), bla(CTX-M), gyrA, gyrB, qnrS, aadA1, strAB, tetA, tetB, catA, and catP were 78.94%, 12.63%, 20.00%, 21.05%, 21.05%, 67.36%, 42.10%, 12.63%, 53.68%, 33.68%, and 25.26%, respectively. Class 2 integrons (42.10%) were more common in the local isolates. Simultaneous detection of class 1 and 2 integrons in some isolates and a rapidly emerging resistance to modern frontline drugs are the major findings of this study.