Assessment of indole and pyocyanin in the relationship of pseudomonas aeruginosa to escherichia coli

This work evaluated the antiadhesive activity of two microbial exometabolites: indole and pyocyanin. The in vitro quantitative microtiter adherence assay was carried out with Pseudomonas aeruginosa exposed to concentrations of 0.5 and 1.0 mM of indole and Escherichia coli exposed to 0.2 mM of pyocyanin. The incubation took place for 48 hours at 30ºC. Afterwards, the violet crystal test was performed and optical density measurements (590 nm) were used to calculate the percentage of adhesion relative to the control tube, in which the cells were cultured in the absence of exometabolites. Indole and pyocyanindisturbed cell adhesion in all isolates. However, E. coli was more sensitive to pyocyanin than P. aeruginosa to indole. The percentage of E. coli adherence registered an average of around 15%. For P. aeruginosa, the percentage of adherence varied from 21 to 54%, with greater activity in the concentration of 1.0 mM of indole. However, adherent cells were detected when the percentage of adherence was close to 20%, suggesting that in an eventual competition between E. coli and P. aeruginosa, the latter appears to be more tolerant to indole than E. coli to pyocyanin.