Antagonistic interactions between Pseudomonas aeruginosa isolated from different age groups of cystic fibrosis patients

Abstract

Pseudomonas aeruginosa is an opportunistic human pathogen affecting cystic fibrosis (CF) patients and immunocompromised individuals contributing significantly to morbidity and mortality. Once infected with P. aeruginosa, patients are chronically colonized and unable to clear the infection even with antimicrobial treatment. P. aeruginosa is inherently resistant to many antimicrobials which has encouraged the hunt for novel potential therapeutics. Recently, P. aeruginosa isolates obtained from the same CF patient were shown to interact antagonistically where secreted signals from one isolate decreased protease production by another isolate. This antagonistic interaction also decreased the virulence of the virulent P. aeruginosa isolate. The purpose of this study was to determine if P. aeruginosa isolates from a variety of patients in three different age groups (under 13, between 13 and 18, and above 18) would respond to the antagonistic signals. Two antagonistic signal producing P. aeruginosa isolates (14672 and 14651) were co-cultured with P. aeruginosa isolates obtained from various patients. After P. aeruginosa cultures are grown and mixed they are spotted onto skim milk plates to test for the levels of protease production. Protease production is measured by a zone of clearing around the bacterial culture. The mixed cultures are then compared to individual strains also spotted on the skim milk plates. This method was used to test P. aeruginosa isolates from all age groups and isolates from all groups did respond to the antagonistic signals. These results suggest that P. aeruginosa from a wide range of patients responds to the antagonistic signal, indicating this signal may have potential as a future therapeutic agent for CF patients.