Mycobacterium tuberculosis (Mtb), the bacterium responsible for causing tuberculosis (TB), is a particularly potent pathogen when it comes to antibiotic resistance. Mismanagement of multi-drug resistant strains has resulted in extensively drug resistant TB, which constitutes ~8.5% of multi-drug resistant TB cases. But the drug regimen to treat extensively drug-resistant TB cause substantial side-effects and are very expensive. The U.S. Food and Drug Administration recently approved new drugs to tackle this form of TB which, as pointed out here, could potentially bridge the gap between patients and affordable therapeutics.
Although a welcome development, this move took several years to come to fruition and patients can rarely afford to wait this long. A recent study by a group of Harvard Medical school-associated researchers took a new approach to this problem. They used a fast-screening method on a library about 3000 bioactive molecules to test which ones were effective in fighting Mtb. They eventually narrowed the list down to about 40 candidate molecules. The beauty of the method is that it allows molecules to be tested against multiple variations of Mtb, each with slightly different genetic makeups. The 40 candidate molecules they ended up with are much more likely to be effective in a wide variety of patients, who all likely have slightly different variants of the bacteria than those tested in the lab.
We can, of course, try and churn out new drugs to keep pace with evolution, but the alternate approach of restraint also warrants some consideration. A study published in August found that antibiotic-resistant E. coli grown in antibiotic-free conditions lose their resistance after about 500 generations. Acquiring resistance sometimes comes at the cost of reduced fitness (survival and reproduction) of the pathogen, implying a tug-of-war between these two characteristics.
Such findings come in the wake of calls for heavy restrictions on antibiotic use, which on occasion actually have led to loss of resistance in clinical populations. While completely halting our use of antibiotics is not the most practical course of action, it is definitely one worth thinking about.