A few weeks ago, we had a blog post about the issues we’re facing due to our overuse of specific antibiotics, namely Cephalosporins. The overuse of these and similar antibiotic compounds has resulted in selecting for a whole new breed of multi-drug resistant bacteria, which is a serious threat to our collective well-being. So now that we have this problem, what do we do about it? For many researchers, the answer continues to be the discovery and classification of novel antibiotic compounds. Just this month there have been two papers published that describe two new antibiotics that are showing effectiveness against major health issues caused by drug resistant organisms, mainly tuberculosis and methicillin-resistant Staphylococcus aureus (MRSA) infections.
The tuberculosis drug, code named Q203, was found in a survey of over one hundred thousand different chemical compounds that a team of researchers were testing for potential effectiveness. The researchers isolated around 100 potential compounds, where Q203 stood out for its ability to kill drug resistant strains. With a few chemical tweaks, the researchers were able to test the drug on mice, and found that it was tolerated at high doses, and more effective than the current tuberculosis drug isoniazid. Q203 is part of a larger group of chemical compounds called imidazopyridine amides, or IPA’s and there have been other studies done on similar IPA’s, but none have shown the same effectiveness on drug resistant TB. The researchers found that Q203 works by targeting the cytochrome b1 complex in the bacteria, and inhibits the energy transduction system in the cells, inhibiting their growth. Other researchers working on similar compounds hope that the knowledge they gain from Q203 will lead to a whole new class of IPA antibiotic agents that are easy and inexpensive to manufacture. You can find the paper in its entirety here at Nature Medicine.
While the tuberculosis drug Q203 was found by surveying thousands of different previously classified chemical compounds, the antibiotic effective against MRSA was found through a different method entirely. Researchers at the Scripps Institution of Oceanography, La Jolla recently published a paper in the journal Angewandte Chemie, describing a new antibiotic they found being produced by Streptomyces sp. they had isolated from ocean sediment off the coast of Santa Barbara, CA. They named the drug Anthracimycin, for its ability to inhibit Bacillus anthracis, which causes anthrax, and MRSA. Anthracimycin is different from the antibiotics produced by other strains of Streptomyces, and has the potential to work on a wide variety of additional pathogens. The full paper can be found here.
Unfortunately though, finding novel antibiotics like the two just described are extremely rare, and involve a lot of research effort. It can take many years just to isolate the specific compound, and it still has to go through a number of rigorous studies to determine its effectiveness and any potential side effects it may have. This process can take many years, and sometimes the smallest issue with one of the preliminary studies can prevent a drug from getting FDA approval. Also some scientists argue that developing and using new antibiotics will just perpetuate the microbial arms race, and we’ll be in the same situation again in a matter of years. While we will still need to figure out this issue for the long term, for the short term at least we have a few new promising candidates that may help humanity battle off serious infection. At least for a little while.
Kevin Pethe, Pablo Bifani, Jichan Jang, Sunhee Kang, et al. 2013. Discovery of Q203, a potent clinical candidate for the treatment of tuberculosis. Nature Medicine; doi:10.1038/nm.3262
Kyoung Hwa Jang et al. 2013. Anthracimycin, a Potent Anthrax Antibiotic from a Marine-Derived Actinomycete. Angewandte Chemie, vol. 52, pages 7822–7824; doi: 10.1002/anie.201302749
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