PSEUDOMONAS-AERUGINOSA ADHERENCE TO EXTERNAL AUDITORY-CANAL EPITHELIUM

Background: Pseudomonas aeruginosa is an important causative agent for external otitis. The specific bacterium-host reaction has not been in vestigated. It is therefore unknown whether adhesion of the external o titis strain to the external auditory canal epithelium is increased co mpared with strains isolated from other infections. Design: A cohort s tudy was designed to outline adhesion of P aeruginosa to the external auditory canal epithelium, cultured in vitro, of the guinea pig. Facto rs important for pathogenesis were also studied. Patients: Pseudomonas aeruginosa strains from nonhospitalized patients were collected conse cutively at the bacteriological laboratories at Karolinska Hospital, S tockholm, and Huddinge Hospital, Huddinge, Sweden. External otitis str ains were compared with strains from leg ulcers, urinary tract infecti ons, and cystic fibrosis. Methods: Adhesion to the external auditory c anal epithelium cultured in vitro was measured and compared groupwise with the mean profile of pathogenic factors. Results: Adhesion to the epithelium was significantly increased for external otitis strains. Th ese strains also had a significantly increased deoxyribonuclease produ ction and a significantly decreased production of pyocyanin and algina te. Conclusions: The significantly increased ability of P aeruginosa, isolated from external otitis, to adhere to external auditory canal ep ithelium was combined with a significant production of pathogenic fact ors. The P aeruginosa that causes external otitis could therefore be c onsidered a particular phenotype. The enzyme profile for external otit is strains was similar to that of the control groups except for the st rains from cystic fibrosis. Adhesion to guinea pig vs human epithelium must be compared, and the effects of extracellular proteins on adhesi on should be studied to further understand how P aeruginosa adheres to the external auditory canal.