Changing prevalence and antibiotic susceptibility patterns of different shigella species in Tehran, Iran

摘要

During the 3 years of study period (April 2002 to April 2005) 220 strains of shigella isolated from fecal samples of patients having acute diarrhea. Shigella sonnei with 157 (78.5%) isolates had the highest frequency of isolation. Resistance to Ampicillin and Trimethoprime/sulphamethoxazole was observed in 88.5% and 98% isolates respectively. 11.5% of isolates were resistant to nalidixic acid and 5.5% to ceftriaxone. Resistance to Chloramphenicol and Ciprofloxacin was 2.5% and 1% respectively. Introduction Shigelosis is an acute gastroenteritis caused by Shigella specis, including Shigella dysenteriae, Shigella flexneri,Shigella boydii and Shigella sonnei. It is one of the most common causes of morbidity and mortality in children with diarrhea in developing countries. Worldwide, approximately 165 million cases of shigellosis occurs and 1,100,000 death are caused by the disease per year, which two-third of the patients are children under 5 years of age .Epidemic usually occur in area with crowding and poor sanitary conditions ,where transmission from person to person common, or when food or water are contaminated by organism (1,2). Emergence of multiple drug resistance to cost effective antibiotics against shigella is a matter of concern for the health authorities in developing countries.(3) Outbreak of shigellosis have been reported from different parts of world. Two studies from Bangladesh showed an increasing frequency of shigella strains with multiple resistance to ampicillin, Trmethoprime –sulfamethoxazole (TMP-SMZ) and nalidixic acid .outbreaks of shigellosis caused by strains that were resistant to ampicillin and TMP-SMZ ,or both drugs have been reported in other countries in Asia ,Africa central America and Europe. . However, reports regarding various serogroups of shigella. In our country there are only a few documented studies regarding the prevalence and susceptibility pattern of shigeloosis. The present study was therefore undertaken-(i) to study the incidence and serogroup prevalence of shigella isolated from cases of dysentery during threes year period (ii) to determine drug resistance pattern and (iii) to compare the results of present study with that of previous years regard that serogroup and antimicrobial sensitivity of shigella spp isolated. Material and Methods All patients admitted to the Milad hospital in Tehran during 3 years from 2003 to 2005 with history of diarrhea of less than 7 days duration were included in this study. A total 4351 patients were admitted. Individual case records of these patients were scrutinized. A special Performa was designed to collect information regarding epidemiological variables such as age, sex, date of admission;other information such as the result of faecal cultures were also included. Incomplete records were excluded. for enteric pathogens. Samples of faeces were collected in sterile wide mouth containers and rectal swabs were transported in Cary- Blair transport medium and were processed within 2 hours of collection. The samples were examined microscopically for pus cells, RBCs, leukocyte , cysts and ova of parasites. The samples were inoculated directly on the MacConky agar, Xylose-lysine desoxycholate (XLD), Hekton Enteric agar (HE) and, Salmonella Shigella agar (SS). Enrichment was done on selient F broth and incubated for 6 hours. After the 6 hours subculture was done on SS agar. All plates incubated at 35°C for overnight. All specimens were also processed for other enteropathogens by using standard laboratory procedures. For isolation of Yersinia entercolitica samples, were inoculated on Cefsulodin –irgasin Novobiocin agar ( CIN agar) and incubated at 20-25°C for 24 hours. For isolation of Campylobacter jejuni we used Campy- Blood Agar plate (Campy-BAP) medium and after inoculation of samples plates incubated at microaerophilic condition in 42°C for 48 hours. Finally, sorbitol Mackonky agar was used for isolation of Enteroheamprrhagic E.coli . All isolated enteric