Burden of Food-Related Illness Caused by Resistant Salmonella spp. and Shigella spp.: Harbingers of Multistate Outbreaks in 2012 and 2013

Abstract

Background: In many countries, Salmonella and Shigella species are frequently found to cause gastroenteritis outbreaks. Objectives: We describe nationwide data on infections with Salmonella spp. and Shigella spp. in Iran. Materials and methods: During a two-year period (2012 to 2013), rectal-swab samples were analyzed for the presence of bacteria. Sensitivity of the bacterial isolates to antimicrobial agents was tested according to clinical and laboratory standards institute (CLSI) guidelines. Results: Twenty-nine states reported 249 outbreaks of foodborne illnesses. In total, 1055 patients (604 males and 451 females, age range: < 1 and > 60 years) were enrolled in this study, of whom 18 died. Seventy-four culture-confirmed cases of infection with Salmonella spp. were identified, of which 10.8%, 6.8%, 68.9%, and 13.5% corresponded to Salmonella serotype A, B, C, or D respectively. Similarly, Shigella spp. were responsible for 118 cases of the foodborne illnesses; among them, Shigella sonnei (with 105 cases, 89%) was the leading serovar. Ciprofloxacin (100%) was the most effective antibacterial agent against Salmonella spp. followed by amikacin. Nalidixic acid and gentamycin were the least effective antibacterial agents against Salmonella spp. Similarly, Shigella spp. were also highly sensitive to ciprofloxacin (100%), whereas tetracycline and ampicillin were the least effective antibacterial agents against Shigella spp. Conclusions: These are the first recognized and confirmed outbreaks of foodborne illnesses in Iran. Salmonella and Shigella infections represent a considerable disease burden in our country. Therefore, efforts to reduce transmission of these pathogens via food and other routes must be implemented on a national scale. It is noteworthy that the outbreaks of Shigella and Salmonella infections in our country also pose a threat of antibiotic resistance.