Chloramphenicol- and Ampicillin-Resistant Typhoid Fever

To the Editor.— The report of chloramphenicol-resistant Salmonella typhi in Saigon (231:162, 1975) emphasized the poor clinical response of patients infected with chloramphenicol-resistant strains of S typhi to chloramphenicol alone. Chloramphenicol-resistant typhoid fever has also been noted in Bangkok, Thailand, with evidence of in vitro and in vivo resistance to chloramphenicol. 1-3 During 1974, thirty-two percent (22 of 67) of the S typhi strains from Children's Hospital, Bangkok, were resistant to chloramphenicol. Fortyone percent (9 of 22) of these chloramphenicol-resistant strains were resistant to ampicillin also (minimal inhibitory concentrations > 128μg/ ml). Ampicillin has been ineffective therapy in patients with S typhi isolates resistant to ampicillin and chloramphenicol. One such patient receiving 150 to 200 mg/kg/day of ampicillin intravenously remained febrile, in a toxic condition, and had positive blood cultures after seven days of therapy. Recovery occurred following therapy with trimethoprimsulfamethoxazole. All of the S typhi isolates have been sensitive