Evaluation of antibacterial activity in experimental meningo-encephalitis in mice.

Mice infected intracerebrally (ic) or intraperitoneally (ip) with Pseudomonas aeruginosa were treated subcutaneously with graded doses of five antibiotics all of which displayed anti-pseudomonal activity in vitro. The analysis of MIC, ED50 in the ip infection model (ED50-ip) and that in the ic system (ED50-ic) for each agent showed: gentamicin, the most active agent in vitro, was also active in vivo, with an ED50-ic nearly six-fold higher than ED50-ip; ceftazidime, considerably active both in vitro and in vivo, showed comparable values of ED50 in the two systems; ceftriaxone, also active in vitro, showed limited activity in vivo, its two ED50 values being similar; aztreonam, moderately active both in vitro and in vivo, showed comparable activity in the two infection models; carbenicillin, the least active agent in vitro, gave poor results in vivo, with an ED50-ic 2.6-fold higher than ED50-ip.