Electrochemical monitoring of the impact of polymicrobial infections on Pseudomonas aeruginosa and growth dependent medium

The opportunistic human pathogen Pseudomonas aeruginosa (Pa) causes several infections acquired in a healthcare setting. During initial stages of infection, Pa produces redox-active phenazine metabolites, including pyocyanin (PYO), 5-methylphenazine-1-carboxylic acid (5-MCA), and 1-hydroxyphenazine (OHPHZ), which have toxic effects on surrounding host cells and/or other microbes. Rapid and sensitive detection of these metabolites provides important evidence about the onset of Pa infections. Herein, we investigate differences in Pa phenazine production and dynamics in polymicrobial communities. Specifically, Pa was co-cultured with two pathogens of clinical relevance, Staphylococcus aureus (Sa) and Escherichia coli (Ec), which typically populate infection sites with Pa. Phenazine production rates and biosynthesis dynamics were electrochemically monitored during a 48-h period using recently developed transparent carbon ultramicroelectrode arrays (T-CUAs). Moreover, the effect on phenazine production rates and dynamics was explored in two growth media, lysogeny broth (LB) and tryptic soy broth (TSB). The concentrations of PYO and highly reactive 5-MCA were determined in different polymicrobial culture samples in both media. The results demonstrate that other bacterial pathogens noticeably influence Pa phenazine production and dynamics. In particular, Sa caused a decrease in phenazine production in TSB. However, the presence of Ec in polymicrobial samples drastically inhibited phenazine production rates in both LB and TSB. Conclusively, the media type significantly influences phenazine product distribution, especially in polymicrobial co-cultures, signifying the need for analytical standardization of simulation media in the study of polymicrobial communities.