In vitro activity of azithromycin against bacterial enteric pathogens.

The in vitro activity of azithromycin against enteric bacterial pathogens was determined by agar dilution. Azithromycin was highly active against Campylobacter spp. (MIC for 90% of strains tested [MIC90] = 0.125 micrograms/ml) and against enterotoxigenic, enterohemorrhagic, enteroinvasive, and enteropathogenic Escherichia coli (MIC90 = 2 micrograms/ml), Shigella spp. (MIC90 = 1 micrograms/ml), and Salmonella spp. (MIC90 = 4 micrograms/ml), including Salmonella typhi (MIC90 = 1 microgram/ml). On the basis of the in vitro activity of the drug against these organisms, clinical studies of azithromycin in enteric diseases should be considered; the high intracellular concentrations achieved by azithromycin may be particularly relevant for organisms like S. typhi, Campylobacter spp., and Shigella spp. which typically invade cells as part of their infectious process.