Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. 
Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. What was reviewed?
This review article systematically examines the use of the class 1 integron-integrase gene (intI1) as a proxy indicator of anthropogenic pollution, with a specific focus on heavy metals, antibiotics, disinfectants, and other pollutants. The authors analyze the evolutionary history, distribution, and genetic characteristics of intI1, highlighting its association with resistance genes for various contaminants. The review collates evidence from environmental and laboratory studies to demonstrate the correlation between intI1 abundance and human activities, especially those resulting in environmental contamination by heavy metals and other pollutants. Methodological considerations for monitoring intI1 in environmental samples are discussed, along with recommendations for standardization and application in pollution surveillance frameworks.
Who was reviewed?
The review synthesizes findings from numerous original research studies that investigated the prevalence and dynamics of intI1 and associated resistance genes in environmental, agricultural, and clinical contexts. Studies included in the review encompass bacterial populations from wastewater, river catchments, agricultural soils, farm manure, biopurification systems, estuaries, and industrially contaminated sites across various countries. Both commensal and pathogenic bacteria, as well as environmental bacterial communities exposed to anthropogenic pressures, are discussed. The review integrates data on bacterial isolates, microbial communities, and gene prevalence from diverse geographic regions, reflecting a global perspective on the spread and utility of intI1 as a pollution marker.
Most important findings
| Critical Points | Details |
|---|---|
| intI1 is a robust proxy for anthropogenic pollution, including heavy metal contamination. | The review demonstrates that the clinical intI1 gene is consistently linked to resistance genes for heavy metals, antibiotics, and disinfectants, and its abundance rises with anthropogenic impact. Its presence in diverse bacteria and mobile genetic elements makes it a sensitive marker for pollution stemming from human activities, including heavy metal exposure. |
| Co-selection between heavy metal and antibiotic resistance is widespread and often causal. | Numerous studies reviewed show that environments polluted with heavy metals frequently contain high levels of intI1 and associated resistance genes. This co-selection occurs due to the physical linkage of resistance determinants on mobile genetic elements, allowing selection for metal resistance to simultaneously increase antibiotic resistance gene prevalence. |
| intI1 abundance increases downstream of wastewater treatment and with industrial, agricultural, or urban impact. | The review details that intI1 is poorly removed by conventional water treatment and often increases in effluent. Its abundance also correlates with industrial discharges, farming practices (e.g., manure application), and urbanization, indicating its utility for monitoring pollution gradients and identifying contamination sources. |
| intI1 detection methods are established and amenable to standardization for environmental monitoring. | The authors provide practical guidance for sampling, DNA extraction, and quantitative PCR (qPCR) targeting intI1, including primer design for distinguishing clinical variants. They stress the importance of normalization and replication, and highlight the compatibility of these methods with existing environmental monitoring protocols, making intI1 suitable for routine surveillance in certification programs. |
| intI1 is a universal, quantifiable, and functionally relevant marker, directly relevant to heavy metal certification. | Because intI1 is linked to resistance genes for metals and other pollutants, its monitoring not only signals pollution but also the broader risk of resistance gene dissemination. Its genetic uniformity in clinical contexts allows for precise quantification and comparability across sites and studies, which is crucial for certification and regulatory purposes in programs such as HTMC. |
Key implications
The review establishes that class 1 integron-integrase (intI1) is a scientifically validated, practical biomarker for monitoring anthropogenic pollution, especially heavy metals, across diverse environments. Its adoption would enable heavy metal certification programs to track contamination and resistance gene spread efficiently, supporting robust regulatory oversight and risk management in agricultural, industrial, and water treatment sectors.
Citation
Gillings MR, Gaze WH, Pruden A, Smalla K, Tiedje JM, Zhu Y-G. Using the class 1 integron-integrase gene as a proxy for anthropogenic pollution. ISME J. 2015
Heavy metals are high-density elements that accumulate in the body and environment, disrupting biological processes. Lead, cadmium, arsenic, mercury, nickel, tin, aluminum, and chromium are of greatest concern due to persistence, bioaccumulation, and health risks, making them central to the HMTC program’s safety standards.
