Prevalence and antimicrobial susceptibility of Salmonella and Shigella spp. among children with gastroenteritis in an Iranian referral hospital

Highlights

• Shigella and Salmonella serogroups can be considered as important etiological agents of acute diarrhea in children.

• Among Shigella spp. isolates, S. sonnei, S. flexneri and other Shigella spp. were isolated from 39 (46%) isolates, 36(42%) and 10(12%), respectively.

• High frequency of cefotaxime resistant was seen in S. sonei and S. flexneri (77% and 56%, respectively), whereas more than 90% of Salmonella serogroup B, C and D were susceptible to this antibiotic.

Abstract

Background

Gastroenteritis is one of the leading cause of illnesses through the world, especially in developing countries.Salmonella and Shigella infections are considered as the main public health problems in children. The aim of this study was to detect the prevalence and antimicrobial susceptibility of Salmonella and Shigella spp. among children with gastroenteritis in an Iranian referral hospital.

Methods

During April 2013 to April 2014, all medical records of children with gastroenteritis admitted to a pediatric medical center were evaluated. Positive stool cultures of children were evaluated and frequency of Salmonella and Shigella spp. and their antimicrobial susceptibility were detected.

Results

In this study, 676 patients with the mean age of 24.94 months were enrolled. Eighty-eight (42%) Salmonella spp., 85 (40%) Shigella spp., 33 (16%) E. coli and 5(2%) candida albicans were isolated from 211 positive stool cultures. Among 85 Shigella spp. isolates, S. sonnei, S. flexneri and other Shigella spp. were isolated from 39 (46%) isolates, 36(42%) and 10(12%), respectively. Among 88 isolated Salmonella spp., 36 (41%) isolates were Salmonella Serogroup D, 26 (30%) were Salmonella Serogroup B, 20 (23%) isolates were Salmonella Serogroup C and 6 (7%) were other Salmonella spp. isolates.

Thirty-eight percent of Salmonella serogroup B were resistant to nalidixic acid, while higher frequency of nalidixic acid resistant was found in Salmonella serogroup C and Salmonella serogroup D. The higher frequency of ampicillin resistant was found in Shigella spp. than Salmonella spp. High frequency of cefotaxime resistant was seen in S. sonei and S. flexneri (77% and 56%, respectively), whereas more than 90% of Salmonella serogroup B, C and D were susceptible to this antibiotic.

Conclusion

In conclusion, Shigella and Salmonella serogroups can be considered as important etiological agents of acute diarrhea in children. Since the prevalence of antibiotic resistance is increasing in recent years in Iran, further studies on the prevalence, antimicrobial susceptibility pattern and mechanisms of antibiotic resistance in these species is highly recommended.

Introduction

Acute gastroenteritis is defined as severe infection of the gastrointestinal tract and is characterized by inflammation in the digestive system, which leads to a combination of diarrhea, dehydration, vomiting, nausea, fever and abdominal pain. Diarrhea is determined as having loose or watery stools, three or more times in 24 h [1].Gastroenteritis is one of the leading causes of illnesses in children throughout the world, especially in developing countries, where a measure of 2.5 million deaths occurs each year in children younger than five years old [2].

Viruses, bacteria and parasites are three major causes of childhood gastroenteritis, which viral agents account for 70 to 80%; bacterial pathogens are included in 10–20% and parasites such as Giardia intestinalis and Cryptosporidium are identified in acute infectious gastroenteritis [3].

Some of the most important bacteria involve in gastroenteritis are Escherichia coli O157:H7, Salmonella spp., Shigella spp., Campylobacter spp., Yersinia enterocolitica and Clostridium difficile [4], [5].Salmonella and Shigella infections are main public health problems around the world, particularly in children. These infections are customary in developing countries where living standards are very low, with poor sanitation and lack of clean water supply [6].

Four species of Shigella namely, Shigella dysenteriae, S. flexneri, S. boydii, and S. sonnei are responsible for causing shigellosis in humans. The most prevalent Shigella spp. in developing countries is S. sonnei and S. flexneri. S. flexneri had been recognized as the chief reason of shigellosis in Tehran, capital city of Iran until 2003, while after that it was replaced by S. sonnei [7]. Salmonella infections have also been regarded as an important public health and caused gastroenteritis among children [8], [9].

Antibiotic resistance has become a major concern to control diarrhea in children. Therefore, evaluation of the prevalence and resistance patterns of Shigella and Salmonella spp. in patients with gastroenteritis is necessary [10]. The aim of this study was to detect prevalence and antimicrobial susceptibility of Salmonella and Shigella spp. among children with gastroenteritis in an Iranian referral hospital.