Bug sleuthing gets a boost

There is a dictum among infectious disease doctors, says V. Ramasubramanian, Senior Consultant in Infectious Diseases at Chennai's Apollo Hospitals: "Diagnosis is not everything: it is the only thing!" Yet, in the intensive care unit (ICU), doctors battling life-threatening infections rely not so much on diagnostics but on clinical judgement — and the liberal use of broad-spectrum antibiotics. The last unwittingly abets anti-microbial resistance (AMR). "We are looking for an accurate test which is not expensive, gives quick results, and is reliable and that is a very tall order."

Lately though, he's been feeling hopeful. The reason is Next-Generation Sequencing (NGS).

Sequencing deciphers the order of nucleotides or alphabets in the DNA, an organism's biological blueprint. Next-generation sequencers perform high-throughput sequencing faster than before. There are also different types of NGS sequencers: those that can read short pieces of DNA in depth and those that can rapidly read much longer sequences.

In cancers, NGS identifies mutations in tumour cells to target treatment. In pre-natal screening, it detects abnormalities in foetal DNA from the mother's blood. Infectious disease is its next frontier. Ramasubramanian sent tissue from a patient's diseased heart valve for one such test. Where the standard culture test yielded nothing, NGS showed a bacterium that, if untreated, could have infected the new, surgically replaced valve.

The use of NGS in infectious disease heralds "a paradigm shift from empirical medicine to evidence-based medicine," says Aneesh Nair, Principal Scientist and Head, NIMS Centre for Genomic Medicine, Thiruvananthapuram. This potentially also impacts India's growing AMR problem. "A reliable diagnostic methodology, where we get an answer in a matter of few hours, will revolutionise our approach in the use of antibiotics," says Ramasubramanian.