History and Objectives: Due to high prevalence of typhoid fever and its antibiotic treatment which may lead to the release of high levels of endotoxins and subsequent side effects, determination of the level of antibiotic induced endotoxin release is essential. With this in mind, the present study is carried out at Pasteur Institute of Iran in 1995.

Materials and Methods: A descriptive study was conducted to determine the MIC and MBC on antibiotics such as ampicillin, chloramphenicol and co-trimoxazole, used for the treatment of typhoid fever. Cell culture and their maintenance, preparation of antibiotic solutions, determination of MIC and MBC on each bacteria and determination of endotoxin release were carried out using standard methods by triple measurements (pg/ml). Analytical variance was used as a statistical method.

Results: MIC and MBC for ampicillin was lower compared to other antibiotics (MIC=MBC=1.25 ?g/ml). Level of endotoxin release from ampicillin, chloramphenicol and co-trimoxazole was 113±8, 87±2.5 and 134±11.6 pg/ml respectively (P<0.05).

Conclusion: Chloramphenicol produces less endotoxin compared to other antibiotic tested. Similar in vivo experiments are suggested