JAC Advance Access originally published online on October 8, 2009
Journal of Antimicrobial Chemotherapy 2009 64(6):1241-1250; doi:10.1093/jac/dkp352
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Original research |
Augmented effect of early antibiotic treatment in mice with experimental lung infections due to sequentially adapted mucoid strains of Pseudomonas aeruginosa
1 Department of Clinical Microbiology, Rigshospitalet, DK-2100 Copenhagen, Denmark 2 Department of International Health, Immunology and Microbiology, University of Copenhagen, DK-2200 Copenhagen, Denmark 3 Department of Forensic Medicine, University of Copenhagen, DK-2100 Copenhagen, Denmark 4 Department of Systems Biology, Technical University of Denmark, DK-2800 Lyngby, Denmark
Received 2 April 2009; returned 1 June 2009; revised 8 July 2009; accepted 30 August 2009
* Corresponding author. Department of International Health, Immunology and Microbiology, University of Copenhagen, DK-2200 Copenhagen, Denmark. Tel: +4535327860; Fax: +4535327853; E-mail: mvg{at}sund.ku.dk
Background: Effects of treatment with tobramycin initiated 1 or 24 h post-infection were investigated in a new version of a pulmonary infection model in mice. The model reflects the differentiated behaviour of Pseudomonas aeruginosa mucoid strains isolated from the lungs of one chronically infected cystic fibrosis (CF) patient at different time periods during chronic lung infection.
Methods: BALB/c mice were challenged with alginate-embedded mucoid clinical isolates isolated in 1988, 1997 or 2003. Mice were euthanized on day 1, 2 or 3 post-infection for estimation of quantitative bacteriology, histopathology, and measurement of granulocyte colony-stimulating factor (G-CSF) and macrophage inflammatory protein 2 (MIP-2).
Results: There was a significant reduction of bacteria when comparing treatment initiated 1 h post-infection with treatment initiated after 24 h for isolates 1997 and 2003. Treatment initiated 1 h post-infection also resulted in a reduction of the pulmonary cytokines G-CSF, for all three isolates, and MIP-2, for isolates 1997 and 2003. Histological evaluation showed a shift from the acute-type inflammatory immune response to a chronic-type in mice infected with isolate 2003.
Conclusions: A significant reduction in the number of bacteria was observed when initiating treatment 1 h post-infection compared with initiating treatment after 24 h, although the latest isolate avoided complete clearance. Early antibiotic treatment directed at the mucoid phenotype in mice also reduced the inflammation and, thereby, the lung tissue damage.
Keywords: tobramycin , MIP-2 , G-CSF , cystic fibrosis