Characterization and use of a DNA probe as an epidemiological marker for Pseudomonas aeruginosa

We used DNA restriction fragments, derived from the exotoxin A gene and surrounding sequences, as an epidemiological marker for Pseudomonas aeruginosa. Using these DNA fragments as probes in Southern blot hybridizations and/or total genomic digestions, we were able to distinguish greater than 100 different strains of P. aeruginosa. The stability of the marker in vitro was established by using well-characterized strains, which were stored under different conditions and subjected to chemical mutagenesis. The stability of the marker within a given strain in vivo was established during experimental infection in the chronic rat lung model of pseudomonas pneumonia. P. aeruginosa serially cultured from individual patients with cystic fibrosis were examined by using this marker. Isolates that varied in colonial morphology, serotype, and biotype were identical when analyzed by Southern blot hybridization using the fragment as a probe. Indistinguishable isolates (by serotyping, biotyping, and antibiograms) cultured from two unrelated patients were easily distinguished by using Southern blot analysis.