Researchers at the Institute for Bioengineering of Catalonia (IBEC), a BIST centre, have managed to recreate the coculture conditions and environmental requisites that would allow the simultaneous and stable growth of Pseudomonas aeruginosa and Staphylococcus aureus, two major pathogens commonly found growing together in intricate biofilms in disease-affected lungs or wounds. Eduard Torrents, IBEC Group Leader and one of the authors of the study, published in Scientific Reports, also received a 2019 BIST Ignite Grant this March.
Most chronic infections occur due to the inherent capacity of some bacterial pathogens to grow in biofilms. Biofilm-associated infections, which have become a critical worldwide threat, have historically been treated as single-species events. Nevertheless, some of these infections are known to be composed of multiple combinations of bacteria, involving complex interactions that can influence their fitness and their antibiotic tolerance and can therefore worsen the disease outcome.
Scientists have been addressing this issue for years, but the coexistence between species that occurs in some infections remains difficult to achieve in vitro, as bacterial fitness differences eventually lead to a single organism dominating the mixed culture.
In more recent years, the discovery of the culture conditions able to maintain mixed P. aeruginosa and S. aureus –two major pathogens commonly found growing together in intricate biofilms in disease-affected lungs or wounds– simultaneous growth in vitro has become a scientific hotspot, and several studies can be found addressing the interactions of these microorganisms.
Now researchers at the Institute for Bioengineering of Catalonia (IBEC), a BIST centre, and at the University of Barcelona (UB) studying the coexistence of P. aeruginosa and S. aureus have realized that antibiotic resistance of both species is critically increased during coculture biofilm growth. Moreover, the experts have discovered that S. aureus survival is strictly dependent on oxygen diffusion, which allows for the formation of a mature mixed biofilm with stable populations of P. aeruginosa and S. aureus.
The findings are published in Scientific Reports in an article in which the researchers decipher the optimal coculture conditions and environmental requisites that would allow the simultaneous and stable growth of P. aeruginosa and S. aureus in mixed biofilms over time. The authors specify that the antimicrobial susceptibilities of P. aeruginosa and S. aureus differ depending on whether they are growing in monoculture or coculture in biofilms.
“Our research will help evaluate and choose the best antimicrobial therapy to treat bacterial chronic infections”, explains Eduard Torrents.
In short, the study provides useful insights about the establishment of a P. aeruginosa and S. aureus combined biofilm in vitro, something that would be of help for the study of phenotypes derived from this clinically challenging bacterial cooperation, as well as for optimizing the antimicrobial therapy used to treat these infections.
“We believe that in the near future there will be better tools for choosing a correct treatment for different chronic infections and for helping cystic fibrosis and chronic obstructive pulmonary disease (COPD) patients to identify which is the best antibiotic treatment needed for each patient.” concludes Torrents.
More information can be found on the IBEC website.