by Soham Jha

With the emergence of the COVID-19 virus and its multiple mutations, many of us have questions about how these pathogens manage to adapt and counter vaccines and cures created to kill them. In the lines that follow, I will explain how they manage to do this, and discuss the different processes through which resistance is built up by these pathogens.

Drug resistance or chemical resistance is a consequence of evolution. It occurs as a result of the environmental pressure imposed on any living organism. Every organism has a different pace of resistance development – this is why the organisms that mutate faster are considered extremely dangerous.

The only way to completely destroy any pathogen is to stop it from reproducing or multiplying. If it is able to multiply or reproduce, the pathogen will continue to mutate and the genes of the new generations will acquire greater drug resistance.

Processes of gene exchange allow bacteria or ecosystems to become resistant by acquiring single or multiple genes during an event (sometimes, these mutations can be harmful to the species as well). The three types of bacterial gene exchange mechanisms are:

1. Transformation: The bacteria that undergo this process are naturally transformable and develop mosaic genes which have a higher level of resistance.

2. Transduction: Wherein phage transfers DNA from the host cell to another.

3. Conjugation: In this process, a cell-to-cell mediated gene transfer occurs.

Transformation and transduction only occur in closely related strains, but conjugation can occur in both closely related and not-so-closely related species.

In viruses, the main process for acquiring resistance is random point mutations. Additionally, in viruses which have segmented genomes, genetic reassortment as a mechanism for resistance has also been observed.

These pathogens present a grim future for us as a species. We will need to find ways to stop pathogens from acquiring resistance to our medicines if we are desirous of a safe and peaceful future.