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ABSTRACT Background and Aim: Diarrhea is recognized as one of the main causes of morbidity and mortality in developing countries. Gastrointestinal diseases can lead to death of many children of less than 5 years of age. The aim of this study was to evaluate the drug resistance pattern in Shigella toxin and non-toxin producing strains in children. Material and Methods: In this descriptive analytic study a total of 80 Shigella strains, 60 strains isolated from stool samples of children with diarrhea from Loghman, Emam and Tebi Koodakan Centre Hospitals, and 20 national collection strains isolated and reserved during the last years. The isolates were evaluated for cytotoxin production by using cell culture technique (Hela cell). Our study included 54 strains of S. flexneri, 14 strains of S.sonnei, 10 strains of S. boydii and 2 strains of S. dysenteriae. Data were analyazed by means of chi-square and Fisher's exact test. Results: Of 80 strains 9 (11.25%) showed cytotoxic effect. Chi-square test showed no significant difference between the isolated and national collection strains (P≥0.05).There was no correlation between the cytotoxic activity and clinical symptoms such as abdominal pain, nausea, and frequency of passing stools / day, but other symptoms like fever and presence of blood in the stool had correlation with cytotoxin production. Conclusion: The results of this study showed that there was no significant difference in the antimicrobial resistance pattern between toxin and non-toxin producing Shigella strains isolated from the clinical samples and the standard national collection. Key words: Shigella, Hela cell, Cytotoxin, Antibiotic resistance. Received: Oct 29, 2012 Accepted: Sep 10, 2013 Conflict of interest: None declared

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Background and Aim: Infections of antibiotic-resistant bacteria make their treatment difficult and sometimes impossible. So, scientists are looking for new solutions to fight these bacteria. Phage therapy can replace antibiotic therapy, especially in multidrug-resistant bacteria. Therefore, we aimed to isolate bacteriophage that is effective against common gram-negative bacteria.
Materials and Methods: In this experimental study, 250 ml of hospital and municipal wastewater samples were gathered. The samples were centrifuged at 4000 rpm for 10 minutes, the supernatants were filtered through a 0.22 μm filter. To phage enrichment, 50 ml of filtered water twice the volume of nutrient broth and host bacteria were incubated at 37 C for 24 hours in a shaker incubator. The double-layer agar method was used to see bacteriophage plaque. Transmission electron microscopy was used to investigate the characteristics of the isolated bacteriophage.
Results: Lytic bacteriophage effective to Shigella sonei was found by testing on municipal wastewater. Electron microscopy showed that the bacteriophage belonged to the family Microviridae. However, bacteriophage against other Gram-negative bacteria was not found in the test on hospital wastewater samples.
Conclusion: The found bacteriophage had a specific lytic effect against Shigella sonei, this bacteriophage could be used for the study of phage therapy for Shigella infection with antibiotic resistance.