Researchers have discovered a new mechanism by which antibiotic-resistant bacteria can protect non-resistant pathogens. What are the implications?
Scientists have described a new strategy that pathogens use to survive our efforts to eliminate them: resistant bacteria can inactivate antibiotics and allow their neighbor pathogens to grow once the active compound has reached low enough levels. The findings from the University of Groningen in the Netherlands in collaboration with the University of California San Diego were recently published in the journal PLOS Biology.
A time-lapse video of one of the experiments shows how resistant bacteria, labeled in green, allow for the growth of a susceptible strain, once they grow enough to reduce the antibiotic levels in the medium. After 17 hours, the non-resistant bacteria end up outnumbering the strain that helped them overcome the antibiotic.
The green-labeled bacteria used in the experiment was an S. aureus strain resistant to chloramphenicol, a broad spectrum antibiotic that acts by binding bacterial ribosomes and inhibiting protein synthesis. The black bacteria, S. pneumoniae, is an opportunistic human pathogen which is frequently treated with this particular antibiotic.
A similar mechanism has been reported before in bacteria that release the antibiotic-degrading enzyme β-lactamase in the medium. However, this is the first case where an antibiotic was deactivated intracellularly, extending this phenomenon to a wider range of drug classes.
This study may explain why physicians sometimes encounter antibiotic-susceptible bacteria in patients that did not respond to antibiotics. It also highlights the necessity of administering antibiotics with caution. Now we know that healthy microbes in our organism can develop resistance mechanisms they could use to protect pathogens in future infections.
Robin Sorg, first author of the paper, told Science Daily that personalized medicine could offer assistance in deciding when to use which antibiotic. By searching for resistance genes in healthy bacteria living in our bodies, physicians could select the most suitable antibiotic for each patient. He also remarked that there is still little known about resistance mechanisms, making research like this essential towards finding an effective way of stopping microbial resistance.
Image from Pakpoom Nunjui/Shutterstock, video from R. A. Sorg et al. (2016), PLOS Biology 14(12): e2000631