Postantibiotic effects and bactericidal activities of clarithromycin-14-hydroxy-clarithromycin, versus those of amoxicillin-clavulanate, against anaerobes.

The bactericidal activities and postantibiotic effects (PAE) of clarithromycin-14-hydroxy-clarithromycin and amoxicillin-clavulanate against Bacteroides fragilis and Peptostreptococcus anaerobius were determined. A concentration of twice the MIC resulted in bactericidal activity against four of four and three of four organisms at 24 h with clarithromycin-14-hydroxy-clarithromycin and amoxicillin-clavulanate, respectively. The PAE of clarithromycin-14-hydroxy-clarithromycin was 1.44 to 3.20 h, compared to the less than 1 h of amoxicillin-clavulanate. Clarithromycin-14-hydroxy-clarithromycin possesses good activity against susceptible anaerobes.