What if the real warning signs about our health are not coming from hospitals, but from what we flush away every day? Across India, a quiet and worrying pattern is beginning to surface.
Antimicrobial resistance (AMR) happens when bacteria stop responding to antibiotics that once worked effectively. It is already a growing global crisis, responsible for millions of deaths each year. In India, the challenge is even more complex due to limited local data, making it difficult to identify which bacteria are the most dangerous and how they are evolving.
So where are the early signals coming from, and are we already falling behind in the fight against antimicrobial resistance?
To bridge this critical data gap, a large-scale study analysing 447 samples from 19 sites across Delhi, Mumbai, Kolkata, and Chennai set out to track what is actually circulating across cities at a ground level.
Conducted between March 2022 and March 2024, the study revealed a layered but consistent pattern. While each city had its own dominant bacterial strains, the way they developed resistance remained strikingly similar.
To understand this more deeply, the team turned to an unconventional but revealing source: urban wastewater. Using an advanced gene-mapping approach known as shotgun metagenomics, they moved beyond traditional lab methods to trace how bacteria evolve and resist antibiotics at a genetic level. The work was carried out by researchers from CSIR-Centre for Cellular and Molecular Biology (CCMB) and partner institutions.
What the data shows is both varied and connected. Certain bacteria were more dominant in specific cities. Klebsiella pneumoniae appeared more frequently in Chennai and Mumbai, while Pseudomonas aeruginosa was more common in Kolkata. At first glance, this suggests that each city has its own microbial profile shaped by local conditions.
But a closer look reveals a more concerning link. Despite these differences, the genes that help bacteria survive antibiotics were largely the same across all four cities.
These resistance genes work in multiple ways. Some help bacteria build stronger cell walls, preventing antibiotics from entering. Others allow them to break down or push out the drugs before they can act. More concerning is how easily these traits spread, not just to the next generation but also between neighbouring bacteria.
The study also points to differences in how resistance spreads across drug types. Genes linked to commonly used antibiotics such as tetracyclines and beta-lactams were found to spread more easily than those linked to macrolides, suggesting some treatments may lose effectiveness faster than others.
The findings, published in Nature Communications, also highlight a practical way forward. Wastewater surveillance, the researchers suggest, can act as an early warning system.
“We have developed and validated a Standard Operating Procedure that allows for effective sample storage at 4 degrees Celsius for up to seven days without compromising data quality. The samples can be sent to common testing hubs, which suits resource-limited settings. A broader participation in wastewater-based surveillance will help to detect early outbreaks and track the spread of drug-resistant pathogens in real time,” said Vinay K. Nandicoori, Director of CCMB.
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