The battle against antimicrobial resistant microorganisms continues and one newly identified factor that is affecting the efficacy of antimicrobials is the variety of different bacteria present within a given niche.
The data has been gathered in relation to lung disease. The findings may explain why some patients, such as those with cystic fibrosis who contract a pathogen and require antimicrobials, have hard to treat infections. This could lead to a new focus where microbial interactions need to be considered when considering the type of antimicrobial to use when attempting to treat certain infections.
With the research, microbiologists studied polymicrobial cultures comprised of important cystic fibrosis associated pathogens against species-specific antimicrobial agents. The agents selected were: colistin (targets the bacterium Pseudomonas aeruginosa), fusidic acid (which targets Staphylococcus aureus), and fluconazole (targets the yeast Candida albicans).
By polymicrobial, this refers to diseases where the clinical and pathologic manifestations are induced by the presence of multiple microorganisms.
The scientists found that growth in a polymicrobial environment serves to protect the target microorganism (by several orders of magnitude) from the effect of the antimicrobial agent. This decreased antimicrobial efficacy was found to have both non-heritable (physiological) and heritable (genetic) components.
With lung disease patients who contract infections, the findings indicate that the polymicrobial nature of the cystic fibrosis airways will have a significant impact on the individual patient’s clinical response to a given antimicrobial therapy.
For example, the antibiotic colistin (polymyxin E) which usually can destroy colonies of P. aeruginosa, was unable to destroy the mixture of the three microorganisms. Colistin is an antibiotic medication used as a last-resort treatment for multidrug-resistant Gram-negative infections including pneumonia.
According to lead researcher Martin Welch, Professor of Microbial Physiology and Metabolism at the University of Cambridge: “All three species-specific antibiotics were less effective against their target when three pathogens were present together.”
It is hoped a new model system can be devised to allow for the effectiveness of potential new antibiotics to be tested against a mixture of microbe species. The results appear inThe ISME Journal. The research paper is titled “Decreased efficacy of antimicrobial agents in a polymicrobial environment.”
