Background & Objective: The emergence of multi-drug resistant salmonella strains h ave made t h e treatment of typhoid fever difficult all over the world. It is even more complicated w h en t h e hi g h cost of newly marketed antibiotics, their side effects and arising bacterial resistance to them are considered. Knowledge of antibiotic sensitivity and resistance of salmonella can make prevention of side-effects and emergence of resistance as well as the treatment measures more effective in this region.

  Methods : This descriptive study was performed in a 6-year period between 1992-97 on 397 patients who were culture positive (blood and stool) in terms of typhoid. The drug resistance was determined based on the anti-biogram of salmonella separated from blood and stool culture of the patients.

  Results: The total number of patients was 397 (237 males, 160 females). All of the subjects were above 12 years old. The resistance of strains of salmonella separated from the blood and stool culture to an antibiotic was 76.9 and 79.6 percent respectively. Resistance to ampicillin, amoxicillin, co-trimoxazole and chloramphenicol was highest among others. There were 60 strains with multi-drug resistance 34 of which (8.57% of all patients) were separated from blood culture and 26 (6.55% of all patients) from stool-culture. The amount of microorganisms multi-drug resistance separated from blood and stool was 6.55% and 8.57% respectively (15.12% in total).

  Conclusions : Using antibiotics without the knowledge of bacterial resistance and sensitivity can complicate the issue.

Background & objectives: Shigella spp. are gram negative bacteria that can cause shigellosis in human. It is important in young children as well as elderly and immunocompromised people. Threatening complications can occur in severe cases with multidrug resistance species. It has been observed that Shigella spp. have become resistant to antibiotics like other bacteria. Investigation of resistance to azithromycin, tetracycline and pattern of resistance are the objectives of this study.

Methods: Fifty isolates of Shigella spp. which have been collected from three hospitals in Tehran were studied. Isolates identified and confirmed as Shigella spp. by biochemical, serological and molecular methods (ipaH, wbgz, rfc genes). Antimicrobial susceptibility test was performed for ampicillin, azithromycin, ciprofloxacin, doxycycline, levofloxacin, minocycline, nalidixic acid, norfloxacin, streptomycin, trimethoprim-sulfamethoxazole and tetracycline by disc agar diffusion method. Minimal inhibition concentrations were performed for azithromycin and tetracycline.

Results: From a total of 50 Shigella spp. isolates, 16% of them were Shigella flexneri and 84% Shigella sonnei. The majority of isolates were multidrug resistant. The most resistance was seen to doxycycline, streptomycin, trimethoprim-sulfamethoxazole and tetracycline. Resistance to azithromycin was 6%  and all of the isolates were susceptible to norfloxacin and levofloxacin. Nine patterns of resistance were revealed to these isolates.

Conclusion: High resistance to tetracycline was observed and resistance to azithromycin as an alternative treatment choice was also considerable.