The in vitro activity of several beta-lactam agents, macrolides, and cotrimoxazole was investigated against 53 Streptococcus pneumoniae isolates recovered from healthy children. The rates of resistance to penicillin or amoxicillin, cefaclor, and cefuroxime were 30%, 51%, and 37%, respectively. No cefotaxime-resistant isolates were found. Rates of resistance to erythromycin, clarithromycin, and cotrimoxazole were 22.6%, 13.2%, and 83%, respectively. Pneumococci with divergent antimicrobial susceptibility profiles (susceptible or moderately resistant vs. resistant isolates) coexisted in 32% samples, with divergencies more often involving beta-lactam agents and/or macrolides. In five of these samples, isolates belonged to different serotypes.

Outer membrane protein (OMP) profiles of 122 Pseudomonas aeruginosa isolates recovered from the blood of bacteremic patients were analyzed to relate alterations in the expression of OMPs with porin activity to resistance to imipenem, ceftazidime, and ciprofloxacin. Imipenem-resistant isolates lacked or expressed reduced amounts of porin OprD. In contrast, alterations of OMP profiles were absent in most ceftazidime-resistant isolates. Six of 12 ciprofloxacin-resistant isolates had normal OMP profiles. The remaining isolates showed alterations in the expression of either OprC, OprF, or OprD. In addition, imipenem- and ceftazidime-resistant isolates displayed a beta-lactamase activity compatible with that of a group 1 chromosomal cephalosporinase.

The in vivo efficacy of trovafloxacin, intraperitoneally administered as alatrofloxacin (CP-116,517), was assessed and compared with that of erythromycin, alone or in combination with rifampicin, in a model of Legionella pneumophila pneumonia in guinea pigs. Trovafloxacin (5 mg/kg administered as alatrofloxacin once daily for 7 days) gave a survival rate of 100% in infected animals. Clearance of bacteria and of bacteria-induced lesions from lungs was achieved by day 6 post-inoculation. The lungs of trovafloxacin-treated animals remained free of bacteria at day 28 post-challenge. Trovafloxacin proved as effective as erythromycin administered intraperitoneally, but was superior to erythromycin alone. or in combination with rifampicin, when given orally.