AI Insight
Researchers investigated interactions between two common opportunistic pathogens, Pseudomonas aeruginosa and Klebsiella pneumoniae, which frequently co-infect the urinary tract and lungs. They found that P. aeruginosa inhibits K. pneumoniae growth through the production of phenazine compounds, specifically pyocyanin and pyorubin, which are both necessary and sufficient to suppress K. pneumoniae. Crucially, this antagonistic interaction is not universal but depends on strain variation in both species and on the environmental redox conditions at the site of infection.
Why it matters
Understanding how co-infecting pathogens interact could improve clinical decision-making in polymicrobial infections, which are associated with worse patient outcomes, and may inform future therapeutic strategies that exploit or disrupt inter-pathogen competition.
by Katlyn Todd, Olivia Schneider, Joshua M. Lawrence, Josefina L. Aronoff, Bartosz Witek, Valerie Velázquez-Colón, Verónica Santana-Ufret, Nicole L. Anderson, Krista Gunter, Moraima Noda, Ryan F. Relich, Lifan Zeng, Dominique H. Limoli, Christopher Whidbey, Jay Vornhagen
Pseudomonas aeruginosa and Klebsiella pneumoniae are gram-negative opportunistic pathogens that frequently colonize the human body and are major causes of infection. These bacteria are often co-isolated in polymicrobial urinary tract and lung infections, the latter of which is associated with increased disease severity and worse clinical outcomes. Despite their overlapping niches and clinical relevance, little is known about how these two pathogens interact and how those interactions influence human health. Given the growing recognition that microbial interactions are key drivers of disease, we investigated how P. aeruginosa and K. pneumoniae influence one another. We discovered an antagonistic interaction in which P. aeruginosa restricts the growth of K. pneumoniae. This inhibition is driven by phenazine production in P. aeruginosa, specifically the secondary metabolites pyocyanin and pyorubin, which are both necessary and sufficient to suppress K. pneumoniae growth. Using a diverse set of clinical isolates, we found that this antagonism is strain-dependent. Both the susceptibility of K. pneumoniae to phenazines and the ability of P. aeruginosa to restrict K. pneumoniae growth varies between strains. Moreover, the necessity of phenazine production is specific to the site of infection. Together, these findings demonstrate that strain background and environmental context are critical determinants of pathogen interactions. These findings reveal that both strain background and environmental redox conditions govern the ecological rules of pathogen interaction, providing a framework for predicting outcomes.