Prevalence and Antibiotic Susceptibility Patterns of Salmonella and Shigella Species Isolated from Pediatric Diarrhea in Tehran

Salmonella and Shigella infections are important public health concerns among children. The emergence of antibiotic resistance amongst Salmonella and particularly Shigella isolates has posed serious problems in antimicrobial treatment worldwide. Data on local antibiotic resistance patterns are essential to design suitable antibiotic treatment guidelines.

The aim of the present study was to determine the prevalence and drug susceptibility patterns of Shigella and Salmonella species in addition to the detection of extended-spectrum β-lactamase producing isolates among diarrhea samples of pediatric patients.

A total of 5300 diarrheic samples from children were examined for the presence of Salmonella and Shigella species. Biochemical and microbial tests, as well as specific polyvalent antisera, were used for the identification of the bacterial species. Antibiotic susceptibility tests and extended-spectrum β-lactamase detection were conducted by disc diffusion and combination disc methods, respectively.

A total of 371 (7%) and 472 (8.9%) samples were positive for Salmonella and Shigella species, respectively. The most prevalent Salmonella isolate was serogroup D (n: 176, 47.5%). Of the Shigella isolates, 60.8% were found as Shigella sonnei and 39.2% as Shigella flexneri. The highest level of antibiotic resistance was noted among Shigella flexneri isolates. Overall, 35.7% of the Shigella flexneri isolates and 31% of the Shigella sonnei isolates produced extended-spectrum β-lactamases.

This study provided information on the prevalence and antimicrobial susceptibility patterns of Salmonella and Shigella isolates in Iran. It also indicated a high-level resistance among Shigella isolates to co-trimoxazole and ampicillin and among Salmonella isolates to nalidixic acid