Efficacy of the bovine antimicrobial peptide indolicidin combined with piperacillin/tazobactam in experimental rat models of polymicrobial peritonitis.

OBJECTIVE: To investigate the efficacy of piperacillin/tazobactam combined with indolicidin in the prevention of lethality in two rat models of polymicrobial peritonitis. DESIGN: Prospective, randomized, controlled animal study. SETTING: Research laboratory in a university hospital. SUBJECTS: Adult male Wistar rats. INTERVENTIONS: Adult male Wistar rats were given an intraperitoneal injection of 1 mg of Escherichia coli 0111:B4 lipopolysaccharide or had intraabdominal sepsis induced by cecal ligation and puncture. For each model, all animals were randomized to receive isotonic sodium chloride solution intraperitoneally, 1 mg/kg indolicidin, 120 mg/kg piperacillin/tazobactam, and 1 mg/kg indolicidin combined with 120 mg/kg piperacillin/tazobactam. Each group included 20 animals. MEASUREMENTS AND MAIN RESULTS: Main outcome measures were: bacterial growth in blood, peritoneum, spleen, liver, and mesenteric lymph nodes; endotoxin, interleukin-6, and tumor necrosis factor-alpha concentrations in plasma; and lethality. All compounds reduced significantly bacterial growth and lethality compared with saline treatment. Treatment with indolicidin resulted in significant decrease in plasma endotoxin and cytokine levels, whereas piperacillin/tazobactam exerted the opposite effect. The combination between indolicidin and piperacillin/tazobactam proved to be the most effective treatment in reducing all variables measured. CONCLUSION: Indolicidin may have potential therapeutic usefulness alone and when associated with piperacillin/tazobactam in polymicrobial peritonitis.

In vitro activity of the synthetic lipopeptide PAL-Lys-Lys-NH(2) alone and in combination with antifungal agents against clinical isolates of Cryptococcus neoformans.

The in vitro activity of the lipopeptide PAL-Lys-Lys-NH(2) (PAL), alone or combined with either fluconazole (FLU) or amphotericin B (AMB), was investigated against 14 Cryptococcus neoformans isolates. PAL MICs ranged from 1.0 to 4.0 microg/ml. Fungicidal activity was observed. Synergy, defined as a fractional inhibitory concentration (FIC) index of < or =0.5, was observed in 21.4% of PAL/AMB interactions. Antagonism (FIC index>4) was never observed. The broad antifungal activity and the positive interactions with AMB suggest that PAL can represent a promising candidate in infections due to C. neoformans.

Efficacy of colistin/rifampin combination in experimental rat models of sepsis due to a multiresistant Pseudomonas aeruginosa strain.

OBJECTIVE: To investigate the efficacy of rifampin and colistin in three experimental rat models of Pseudomonas aeruginosa sepsis. DESIGN: Prospective, randomized, controlled animal study. SETTING: Research laboratory in a university hospital. SUBJECTS: Adult male Wistar rats. INTERVENTIONS: Adult male Wistar rats were given a) an intraperitoneal injection of 1 mg of P. aeruginosa 10 lipopolysaccharide; b) 2 x 10(10) colony-forming units of P. aeruginosa ATCC 27853; and c) 2 x 10(10) colony-forming units of one clinically multiresistant strain of P. aeruginosa. For each model, all animals were randomized to receive intravenously isotonic sodium chloride solution, 10 mg/kg rifampin, 1 mg/kg colistin, and 10 mg/kg rifampin plus 1 mg/kg colistin. MEASUREMENTS AND MAIN RESULTS: Lethality, bacterial growth in blood and peritoneum, and endotoxin and tumor necrosis factor-alpha concentrations in plasma were measured. Colistin exerted a strong antimicrobial activity and achieved a significant reduction of plasma endotoxin and tumor necrosis factor-alpha concentration compared with control and rifampin-treated groups. Rifampin exhibited no antimicrobial activity with no substantial impact on endotoxin and tumor necrosis factor-alpha plasma concentrations. The combination of colistin and rifampin resulted in a significant reduction in bacterial count compared with colistin monotherapy, whereas no significant difference was found in positive hem cultures and mortality rates between the two groups. CONCLUSIONS: Colistin and rifampin might have a role in the therapy of multiresistant P. aeruginosa infection.

In vitro activities of tachyplesin III against Pseudomonas aeruginosa.

The in vitro activities of tachyplesin III were investigated against 20 multidrug-resistant Pseudomonas aeruginosa clinical isolates. Methods included minimal inhibitory concentrations, minimal bactericidal concentrations, time-kill studies, checkerboard titration method, endotoxin-binding activity and cytotoxicity assay. Overall the organisms were susceptible to the peptide at concentrations of 0.50-4 mg/l. Tachyplesin III completely inhibits the endotoxin procoagulant activity at 22.36 mg/l concentration. Fractional inhibitory concentration indexes demonstrated synergy between the peptide and betalactams or colistin. In conclusion, the intrinsic antibacterial and antiendotoxin activities and the synergistic interactions demonstrated with clinically used antibiotics make tachyplesin III valuable as potential candidate for new therapeutic strategies aimed to treat P. aeruginosa infection.