Relative efficacy and critical interval of antimicrobial agents in experimental infections involving bacteroides fragilis
J. G. Bartlett, M. Dezfulian and K. Joiner
Activity of seven antimicrobial agents was examined using a mouse model of
a subcutaneous infection that involved Bacteroides fragilis. Untreated mice
had encapsulated abscesses with approximately 10(10) bacteria.
Pharmacokinetic studies showed that all drugs tested penetrated into
abscesses to provide mean peak levels that were 17% to 53% of mean peak
serum levels. In vivo efficacy v 15 strains was measured by the reduction
in counts of viable organisms when treatment was initiated one hour after
challenge. This showed that the most active agents, in order of activity,
were metronidazole hydrochloride, clindamycin phosphate, moxalactam
disodium, and cefoxitin sodium. A delay in treatment of eight to 120 hours
after challenge showed a noticeable reduction in activity, except with
metronidazole. It is presumed that bacteria within an abscess are in a
stationary growth phase, and this has an important influence on in vivo
efficacy.
