Pseudomonas aeruginosa from canine otitis externa exhibit a quorum sensing deficiency.

Pseudomonas aeruginosa LasB elastase gene (lasB) transcription depends on cell density-dependent quorum-sensing mechanisms of gene activation. Previously, we collected several non-mucoid P. aeruginosa veterinary isolates and showed that the total matrix protease phenotype was similar for isolates regardless of host and site of isolation. In contrast, isolates from chronic canine ear infections (otitis externa) were significantly more likely to exhibit less elastase activity as measured by elastin Congo red than from any other site [Clin. Diag. Lab. Immun. 8 (2001) 632]. In this study, we found that the elastase deficiency phenotype is stable upon passage in broth culture. Transcript amplification analyses indicated that the elastase deficiency appears to be strain-specific, with each isolate exhibiting a unique expression profile relative to strain PAO1. Although a number of strain-specific transcriptional differences were observed, the overall pattern that emerges is a quorum sensing deficiency among canine ear P. aeruginosa isolates.