Journal
JOURNAL OF ANTIMICROBIAL CHEMOTHERAPY
Volume 71, Issue 1, Pages 181-188Publisher
OXFORD UNIV PRESS
DOI: 10.1093/jac/dkv301
Keywords
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Funding
- Cystic Fibrosis Foundation [BERING14GO]
- Cystic Fibrosis Research Inc.
- National Institute of Dental and Craniofacial Research [5T90DE021982]
- National Institute of General Medicine [F31GM109729, RO1AI22931, R01DE 021341]
- National Cancer Institute [P30CA014089]
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Objectives:Chronic endobronchial infections with Pseudomonas aeruginosa contribute to bronchiectasis and progressive loss of lung function in patients with cystic fibrosis. This study aimed to evaluate the therapeutic potential of a novel macrocyclic peptide, rhesus theta-defensin-1 (RTD-1), by characterizing its in vitro antipseudomonal activity and in vivo efficacy in a murine model of chronic Pseudomonas lung infection. Methods: Antibacterial testing of RTD-1 was performed on 41 clinical isolates of P. aeruginosa obtained from cystic fibrosis patients. MIC, MBC, time-kill and post-antibiotic effects were evaluated following CLSI-recommended methodology, but using anion-depleted Mueller-Hinton broth. RTD-1 was nebulized daily for 7 days to cystic fibrosis transmembrane conductance regulator (CFTR) F508del-homozygous mice infected using the agar bead model of chronic P. aeruginosa lung infection. In vivo activity was evaluated by change in lung bacterial burden, airway leucocytes and body weight. Results: RTD-1 exhibited potent in vitro bactericidal activity against mucoid and non-mucoid strains of P. aeruginosa (MIC90=8 mg/L). Cross-resistance was not observed when tested against MDR and colistin-resistant isolates. Time-kill studies indicated very rapid, concentration-dependent bactericidal activity of RTD-1 with >= 3 log(10) cfu/mL reductions at concentrations >= 4xMIC. No post-antibiotic effect was observed. In vivo, nebulized treatment with RTD-1 significantly decreased lung P. aeruginosa burden (mean difference of -1.30 log(10) cfu; P=0.0061), airway leucocytes (mean difference of -0.37 log(10); P=0.0012) and weight loss (mean difference of -12.62% at day 7; P < S0.05) when compared with controls. Conclusions: This study suggests that RTD-1 is a promising potential therapeutic agent for cystic fibrosis airway disease.
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