Scientists have discovered that although different harmful bacteria dominate in different Indian cities, the genes that enable them to resist antibiotics remain largely similar. This finding suggests that antimicrobial resistance (AMR) follows a shared pattern across urban India.
In a study published in Nature Communications, researchers from the CSIR–Centre for Cellular and Molecular Biology (CCMB) in Hyderabad, along with partner institutions, analysed 447 wastewater samples collected from 19 sites across Delhi, Mumbai, Kolkata, and Chennai. The samples were gathered between March 2022 and March 2024.
The researchers concluded that sewage-based surveillance can serve as an effective tool for detecting disease outbreaks early and monitoring the spread of drug-resistant pathogens in real time.
Different Bacteria Across Cities, Similar Resistance Genes
Antimicrobial resistance occurs when bacteria develop the ability to survive antibiotic treatments that would normally kill them. Although data on local AMR prevalence in India remains limited, wastewater monitoring offers a broader understanding of resistance patterns within communities.
To investigate this, the researchers used shotgun metagenomics to analyse bacterial genetic material present in urban wastewater. This approach allowed them to study the mechanisms through which bacteria develop resistance to antibiotics.
The analysis revealed that microbial communities varied significantly between cities, largely due to local environmental conditions. For instance, Klebsiella pneumoniae appeared more frequently in Chennai and Mumbai, while Pseudomonas aeruginosa was more abundant in Kolkata.
However, despite these differences in bacterial populations, the genes responsible for antibiotic resistance remained largely consistent across all four metropolitan cities.
How Bacteria Develop and Share Resistance
The study also examined how bacteria use resistance genes to survive antibiotic exposure. Some of these genes strengthen bacterial cell walls, preventing antibiotics from entering the cell. Others enable bacteria to break down, expel, or chemically modify antibiotic molecules.
Importantly, bacteria can transfer these resistance genes not only to their offspring but also to neighbouring bacteria. This gene-sharing process allows resistance to spread rapidly across microbial communities and environments.
Differences in the Spread of Resistance Genes
As reported by TOI, the researchers further observed differences in how easily resistance genes spread among bacteria. Genes that confer resistance to tetracyclines and beta-lactam antibiotics were found to transfer more easily between bacteria compared with genes associated with macrolide resistance.
Understanding these variations is crucial, as it helps scientists predict how antibiotic resistance may spread across populations and environments.
Expanding the Role of Wastewater Surveillance
Beyond mapping resistance patterns, the researchers emphasised the importance of expanding wastewater-based pathogen surveillance across the country. According to the study, this approach can be particularly valuable in resource-limited settings.
The researchers also developed a standard operating procedure that allows wastewater samples to be stored at 4°C for up to seven days without compromising data quality. This makes it possible for samples collected in different regions to be transported to centralised testing laboratories.
A Tool for Early Detection of Outbreaks
Dr. Vinay K. Nandicoori, Director of CSIR-CCMB, highlighted the importance of wider participation in sewage-based monitoring.
According to him, expanding wastewater surveillance could enable scientists and public health authorities to detect outbreaks earlier and track the spread of drug-resistant pathogens in real time, strengthening India’s capacity to respond to emerging health threats.