Efficacy and pharmacodynamics of gemifloxacin versus levofloxacin in guinea pig pneumococcal pneumonia induced by strains with decreased ciprofloxacin susceptibility

Quinolone in vivo bactericidal activity was investigated in a guinea pig pneumonia model using three Streptococcus pneumoniae strains with decreasing susceptibility to ciprofloxacin. Treatment regimens resulted in values of AUC(0-24 h) and C(30 min) similar to those of standard oral regimens in human serum. Efficacy was defined as a significant difference in number of viable bacteria in the lungs compared with the control. Ciprofloxacin, levofloxacin and gemifloxacin were effective against the levofloxacin-susceptible strain. Only gemifloxacin achieved a >/=99.9% reduction versus control against the levofloxacin intermediate-resistant strain. Gemifloxacin achieved a 99.69% reduction and was the only quinolone significantly different from the control (P<0.05) against the levofloxacin-resistant strain. Gemifloxacin offers in vivo activity against ciprofloxacin- to levofloxacin-resistant pneumococci.

Effect of dexamethasone and pentoxifylline in combination with amoxicillin in the treatment of penicillin-insensitive pneumococcal pneumonia in guinea pigs

A fatal guinea pig model of pneumococcal pneumonia was developed in order to evaluate the efficacy of amoxicillin combined with either pentoxifylline or dexamethasone. Parameters assessed were survival time and lung changes (alterations, bacterial colony counts, inducible nitric oxide synthase [iNOS] and cyclooxygenase-2 [COX-2] protein expression). Animals receiving pentoxifylline (50 mg/kg) showed higher survival rates than controls (p < 0.05). Animals which received amoxicillin (50 mg/kg), alone or combined, showed significantly higher survival rates than controls (p < 0.05). Animals dying in spite of receiving amoxicillin alone or combined had lung colony counts significantly lower than those that did not receive the antibiotic (p < 0.001), but their lungs showed identical changes. The correlation between COX-2 protein expression and mortality was rather high (r = 0.75). The addition of either dexamethasone or pentoxifylline to amoxicillin improved neither survival rates nor lung pathology when compared with the antibiotic alone.