Affordable Dipstick Test to Combat Antimicrobial Resistance

Antimicrobial resistance (AMR) refers to the ability of microorganisms such as bacteria, viruses, fungi, and parasites to survive exposure to medicines that were previously effective against them. This resistance emerges due to genetic mutations or the acquisition of resistance genes, often accelerated by excessive or inappropriate use of antibiotics in human health, animal husbandry, and agriculture. AMR is a major global public health threat because it renders common infections harder to treat, increases treatment costs, prolongs illness, and raises mortality, particularly in low- and middle-income countries like India.

Sewage is increasingly recognised as a critical surveillance point because it acts as a composite mirror of antibiotic use and resistance patterns within a population. Wastewater aggregates biological material from households, hospitals, pharmaceutical industries, and animal farms, capturing both antibiotic residues and resistance genes circulating upstream. Unlike clinical surveillance, which only records patients who access healthcare, sewage-based monitoring provides a population-level snapshot, including asymptomatic carriers and unreported antibiotic use.

The study by THSTI demonstrates how sewage surveillance can serve as an early warning system for emerging resistance. For example, detecting carbapenem or colistin resistance genes in wastewater can alert authorities before resistant infections become widespread in hospitals. Internationally, countries like the Netherlands and the UK have used wastewater surveillance for polio and COVID-19, showing its value as a public health intelligence tool. In the AMR context, sewage surveillance allows preventive interventions rather than reactive crisis management.

The development of an affordable dipstick assay is significant because AMR surveillance has traditionally relied on expensive and technically demanding methods such as shotgun metagenomic sequencing, which cost upwards of Rs 9,000 per sample and require advanced laboratory infrastructure. Such approaches are unsuitable for routine, large-scale monitoring in countries with constrained public health budgets and uneven laboratory capacity. As a result, AMR surveillance in many LMICs remains sporadic and hospital-centric, missing early community-level signals.

The THSTI dipstick assay, costing around Rs 400–550 per unit, addresses this gap by combining affordability, speed, and scalability. It can detect up to 16 resistance genes within two hours and produces a visual readout that does not require highly specialised expertise. This makes it feasible for deployment in district laboratories, municipal bodies, and even minimal-resource settings, thereby democratising access to surveillance technology.

For India, which is a global hotspot for AMR due to high antibiotic consumption and environmental contamination, this innovation aligns with national priorities under the National Action Plan on AMR. Affordable surveillance enables targeted interventions such as regulating antibiotic sales, upgrading wastewater treatment plants, and monitoring pharmaceutical effluents. More broadly, it reflects the principle of appropriate technology—solutions tailored to local constraints rather than imported high-cost models.

The dipstick-based assay works through a multi-step but streamlined process. First, sewage samples are collected and processed to extract genetic material. Specific resistance genes are then amplified using methods such as polymerase chain reaction (PCR) to increase detectability. The amplified genetic material is applied to a dipstick along with a detection reagent. If targeted AMR genes are present, they bind to probes on the dipstick and generate visible coloured bands, allowing results to be interpreted with the naked eye.

The key strengths of this approach include speed, affordability, and adaptability. Results are available within two hours, each dipstick can detect multiple resistance genes simultaneously, and the assay can be updated within days to include newly discovered genes. This makes it well-suited for rapid, large-scale surveillance and early risk identification, particularly in urban sewage hotspots where resistance is known to concentrate.

However, the assay also has limitations. As experts caution, the presence of a resistance gene does not necessarily indicate an active infection or a viable pathogen. Genes act as indicators of potential risk rather than definitive proof of disease transmission. Therefore, dipstick results must be interpreted in context and complemented by deeper genomic and microbiological studies. In this sense, the assay functions best as a screening and prioritisation tool rather than a standalone diagnostic solution.

Sewage-based AMR surveillance offers several strategic advantages as a public health policy tool. It is ethically non-intrusive, cost-effective, and capable of covering large populations without individual testing. By identifying resistance hotspots early, it enables upstream interventions such as regulating antibiotic use, improving sanitation, and targeting healthcare inspections. The THSTI study illustrates how such surveillance can guide evidence-based decision-making rather than reactive crisis responses.

However, there are policy and scientific challenges. Sewage data can be complex to interpret because resistance genes may originate from multiple sources, including non-pathogenic bacteria. Without adequate contextual data, there is a risk of misattribution or overreaction. Moreover, surveillance alone does not reduce AMR unless linked to enforceable regulatory and behavioural interventions, such as prescription audits and effluent treatment norms.

Therefore, sewage-based surveillance should be viewed as a complementary pillar within a broader AMR strategy that includes clinical surveillance, antibiotic stewardship, environmental regulation, and public awareness. Its greatest value lies in prioritisation and early warning, not in replacing conventional microbiological investigation.

India’s AMR governance framework, anchored in the National Action Plan on AMR (NAP-AMR), emphasises surveillance, rational antibiotic use, and environmental controls. The THSTI dipstick assay can be integrated as a frontline surveillance tool at municipal and state levels, particularly in urban centres where wastewater infrastructure exists. Regular sewage monitoring could identify localities with unusually high resistance signals, triggering targeted investigations and corrective action.

For instance, if resistance genes linked to last-resort antibiotics are detected downstream of pharmaceutical clusters, regulators could audit effluent treatment plants and enforce compliance. Similarly, persistent signals near large hospitals could prompt reviews of antibiotic stewardship practices. This approach mirrors international experiences, such as wastewater monitoring for polio resurgence, where environmental signals guide immunisation drives.

As a case study, the dipstick assay illustrates how indigenous innovation can bridge the gap between policy intent and operational capacity. By embedding affordable science into governance structures, India can move from reactive AMR management to anticipatory and preventive public health action, setting an example for other LMICs facing similar challenges.