Search PubMed⌕ Search

Biomedical subjects

F T Coleman

Publications and source records attributed to F T Coleman.

3 recordsLinked to original sources
PubMed2001

Transgenic cystic fibrosis mice exhibit reduced early clearance of Pseudomonas aeruginosa from the respiratory tract.

The cystic fibrosis (CF) transmembrane conductance regulator (CFTR) has been proposed to be an epithelial cell receptor for Pseudomonas aeruginosa involved in bacterial internalization and clearance from the lung. We evaluated the role of CFTR in clearing P. aeruginosa from the respiratory tract using transgenic CF mice that carried either the DeltaF508 Cftr allele or an allele with a Cftr stop codon (S489X). Intranasal application achieved P. aeruginosa lung infection in inbred C57BL/6 DeltaF508 Cftr mice, whereas DeltaF508 Cftr and S489X Cftr outbred mice required tracheal application of the inoculum to establish lung infection. CF mice showed significantly less ingestion of LPS-smooth P. aeruginosa by lung cells and significantly greater bacterial lung burdens 4.5 h postinfection than C57BL/6 wild-type mice. Microscopy of infected mouse and rhesus monkey tracheas clearly demonstrated ingestion of P. aeruginosa by epithelial cells in wild-type animals, mostly around injured areas of the epithelium. Desquamating cells loaded with P. aeruginosa could also be seen in these tissues. No difference was found between CF and wild-type mice challenged with an LPS-rough mucoid isolate of P. aeruginosa lacking the CFTR ligand. Thus, transgenic CF mice exhibit decreased clearance of P. aeruginosa and increased bacterial burdens in the lung, substantiating a key role for CFTR-mediated bacterial ingestion in lung clearance of P. aeruginosa.

Animals↗
PubMed2000

Acquisition of expression of the Pseudomonas aeruginosa ExoU cytotoxin leads to increased bacterial virulence in a murine model of acute pneumonia and systemic spread.

Pseudomonas aeruginosa is the nosocomial bacterial pathogen most commonly isolated from the respiratory tract. Animal models of this infection are extremely valuable for studies of virulence and immunity. We thus evaluated the utility of a simple model of acute pneumonia for analyzing P. aeruginosa virulence by characterizing the course of bacterial infection in BALB/c mice following application of bacteria to the nares of anesthetized animals. Bacterial aspiration into the lungs was rapid, and 67 to 100% of the inoculum could be recovered within minutes from the lungs, with 0.1 to 1% of the inoculum found intracellularly shortly after infection. At later time points up to 10% of the bacteria were intracellular, as revealed by gentamicin exclusion assays on single-cell suspensions of infected lungs. Expression of exoenzyme U (ExoU) by P. aeruginosa is associated with a cytotoxic effect on epithelial cells in vitro and virulence in animal models. Insertional mutations in the exoU gene confer a noncytotoxic phenotype on mutant strains and decrease virulence for animals. We used the model of acute pneumonia to determine whether introduction of the exoU gene into noncytotoxic strains of P. aeruginosa lacking this gene affected virulence. Seven phenotypically noncytotoxic P. aeruginosa strains were transformed with pUCP19exoUspcU which carries the exoU gene and its associated chaperone. Three of these strains became cytotoxic to cultured epithelial cells in vitro. These strains all secreted ExoU, as confirmed by detection of the ExoU protein with specific antisera. The 50% lethal dose of exoU-expressing strains was significantly lower for all three P. aeruginosa isolates carrying plasmid pUCP19exoUspcU than for the isogenic exoU-negative strains. mRNA specific for ExoU was readily detected in the lungs of animals infected with the transformed P. aeruginosa strains. Introduction of the exoU gene confers a cytotoxic phenotype on some, but not all, otherwise-noncytotoxic P. aeruginosa strains and, for recombinant strains that could express ExoU, there was markedly increased virulence in a murine model of acute pneumonia and systemic spread.

Animals↗