[Antibacterial effects of niridazole. II. Effects on aerobic and anaerobic bacteria].

Niridazole which is chemically related to metronidazole is endowed with much better antibacterial activity. First, several genera of aerobic bacteria, such as Salmonella and Escherichia, are susceptible to niridazole, whereas metronidazole is completely ineffective. There exist, however, some particular strains which are naturally resistant to niridazole. The in vitro activity of niridazole is still increased, if these facultative anaerobic bacteria are tested under anaerobic growth conditions. Second, niridazole has a higher in vitro activity against anaerobic bacteria, such as Bacteroides spp., Clostridium spp., Fusobacterium spp. and Peptococcus sp., than metronidazole. Extremely low MIC values of niridazole were found ranging from 0.0037 to 0.06 microgram/ml. Propionibacterium acnes, which are resistant to the action of metronidazole, are also relatively resistant to niridazole.