Antimicrobial-resistance pattern of Shigella species in children: a six-year study in an Iranian referral Hospital.

BACKGROUND

Shigella species are a frequent cause of shigellosis and shigellosis is considered as one of the most common causes of diarrhea in children. This disease is endemic in many developing countries such as Iran. This study was carried out to determine the prevalence and pattern of antimicrobial resistance of Shigella species among pediatric patients with acute diarrhea in Children Medical Center (CMC) Hospital, with a diagnosis of acute diarrhea to CMC Hospital from March 2011 through March 2016. Isolation and identification techniques, as well as the susceptibility tests are described in detail.

RESULTS

Of the 46,795 stool specimens that were sent to the microbiology laboratory of the CMC Hospital for culture and susceptibility testing, 573 (1.2%) were positive for Shigella species. The most common species of Shigella were S. sonnei (n= 335, 58.4%) and S. flexneri (n=229, 40%), followed by S. boydii (n=8, 1.4%) and S. dysenteriae (n=1, 0.2%). S. flexneri was most sensitive to gentamicin (n=17/19, 89%) and amikacin (n=15/18, 83%), while high frequency of resistance to trimethoprim- sulfamethoxazole (n=204/224, 91%) and ampicillin (n=216/228, 95%) was seen. S. boydii was most sensitive to ampicillin (n=5 out of 7, 71%) and cefotaxime (n=6/7, 86%) and the high frequency of resistance was seen against trimethoprim-sulfamethoxazole (n=5/7, 71%). For S. sonnei, the highest sensitivity was reported against amikacin and gentamicin (87% and 80%, respectively), while the highest resistance to trimethoprim- sulfamethoxazole (n=325/331, 98%) and ciprofloxacin (n= 66 out of 76, 87%) was reported. Ciprofloxacin was examined on 115 out of 573 isolates and 84 isolates were resistant (73%). Multidrug-resistance (MDR), (i.e. resistance to three or more classes of antimicrobial agents) was classified into 11 distinct patterns.

CONCLUSIONS

In this study, S. sonnei was the predominant Shigella species. High frequency of resistance to common antimicrobials such as trimethoprim-sulfamethoxazole and ampicillin limits the empirical therapy for the management of shigellosis in Iran. On the other hand, it should be noted that third-generation cephalosporins can be convenient replacing drugs.