Identification of Shigella species and their antibiotic resistance patterns from dysenteric patients in Baradaran Rezaei hospital of Damghan, Northeast of Iran

Shigella is a major cause of dysentery across the world. Appropriate antibiotic treatment of shigellosis depends on resistance patterns. The present study was conducted to identify Shigella species and their antibiotic resistance patterns among dysenteric patients in Rezaei Hospital of Damghan. Isolation of Shigella species was conducted by specific culture medium and biochemical tests. The Shigella species were determined by specific antiserum with agglutination on slide. Then, susceptibility to different antibiotics, i. e. nalidixic acid, ciprofloxacin, ampicillin, tetracycline, co-trimoxazole and ceftriaxone, was tested. The antibiotic susceptibility tests were carried out using the Kirby-Bauer standard method on Mueller-Hinton agar.In this study, 29 Shigella species were found in 91 stool samples of the patients. Determination of Shigella spp. by specific antiserum showed S. flexneri (group B) in 13 cases, S. dysenteriae (group A) in 10 cases, and S. sonnei (group D) in 6 cases, while no case of S. boydii (group C) was found. The antibiotic resistance tests indicated that resistance to co-trimoxazole, tetracycline, ampicillin, nalidixic acid, ciprofloxacin and ceftriaxone was 75.8%, 65.5%, 55.1%, 6.8%, 3.4% and 0% respectively. According to lower resistance to ciprofloxacin and ceftriaxone, it seems that the fluoroquinolone antibiotic, as the first choice, and the third-generation cephalosporin, as the second choice, were suitable for treatment of shigellosis, but regarding the multidrug-resistance likelihood and antibiotic resistance patterns variation in Shigella strains, it is recommended to perform the organism susceptibility test to the antibiotic before treatment.