Chloramphenicol drug failure in typhoid fever

Two hundred positive blood culture typhoid patients admitted to Embaba Fever Hospital, Giza province, were subjected to: 1) Careful history and thorough clinical examination. 2) Complete blood picture. 3) Widal agglutination test. 4) Urine and stool cultures for Salmonellae. 5) To the isolates of the cultures, disk diffusion chloramphenicol susceptibility test, minimum inhibitory concentrations and chloramphenicol acetyl transferase test were performed. The dose of chloramphenicol was restricted to 50 mg per Kg body weight daily, whatever the route used; whether oral, rectal or intravenous. When fever did not drop up to 5 days or the patient presented with typhoid complications or the blood culture revealed resistant Salmonellae, quinolones or third generation, cephalosporins were administered. Measurement of the level of chloramphenicol in the blood was performed for every patient. Fifty (25%) patients were found to be resistant in vitro and in vivo to chloramphenicol. All their Salmonellae isolates were resistant to chloramphenicol, the mean zone size was 10 mm, the mean inhibitory concentration was 64 microgram per ml. and all were positive for chloramphenicol acetyl transferase. There was no significant difference in the serum level of chloramphenicol between susceptible and resistant groups to the drug. Results were interpreted and discussed.