[Sensitivity of obligate anaerobes to ofloxacin, pefloxacin, enoxacin and norfloxacin].

The in vitro activity of four new quinolones against 355 obligate anaerobes was investigated. MICs were determined using the reference method of Sutter et al. [14]. The four fluorinated quinolones tested differ from nalidixic acid which is inactive on most anaerobes except for some Clostridium perfringens strains. All strains tested were inhibited by 64 and 16 mg/l pefloxacin and ofloxacin respectively. Except for Bacteroides, all strains were inhibited by 64 mg/l norfloxacin or enoxacin. Clostridium strains other than C. perfringens exhibited heterogeneity; C. difficile and C. ramosum had the highest MICs. Bacteroides fragilis proved less susceptible to fluorinated quinolones than the other obligate anaerobes. Ofloxacin showed the greatest activity, with 4 mg/l inhibiting 100% of C. perfringens and 83% of all anaerobes investigated.