In-vitro activity of azithromycin compared with other macrolides and oral antibiotics against Salmonella typhi.

The in-vitro activity of azithromycin against 60 clinical isolates of Salmonella typhi was determined by broth microdilution and compared with eight macrolides, including erythromycin, and with other orally administered antimicrobial agents (ampicillin, amoxycillin, cefaclor, trimethoprim/sulphamethoxazole, chloramphenicol, tetracycline, and ciprofloxacin). Azithromycin was more potent (MIC range 4-16 mg/l; MIC90 8 mg/l) than erythromycin (MIC range 32- greater than 128 mg/l; MIC90 greater than 128 mg/l). Of the other macrolides, only rosaramicin showed increased activity against Salm. typhi (MIC range 16-32 mg/l; MIC90 32mg/l) when compared with erythromycin. All 60 Salm. typhi were susceptible to ciprofloxacin (MIC greater than 0.5 mg/l). In 22 isolates, resistance to one or more of the following compounds occurred: ampicillin, amoxycillin, cefaclor, tetracycline, chloramphenicol, trimethoprim/sulphamethoxazole.