Published 2026-04-23
Dr. Siska Widya Dewi Kusumah defended her dissertation in ITB’s Doctoral Program in Environmental Engineering on 16 April 2026. Using a One Health approach and integrated risk modelling, the research examined the distribution and health risks of antibiotic-resistant Escherichia coli (AREc) in the Upper Citarum watershed, from pollution sources to human exposure.
The source article presents the study as an integrated quantification of the aquatic environment’s role in transmitting resistant bacteria from multiple sources to people in Indonesia. It places this work within the wider challenge of antibiotic resistance and inappropriate antibiotic use.
Tracing Sources, Exposure, and Risk
The study adopted the DPSEEA framework—Driving forces, Pressure, State, Exposure, Effect, and Action—within One Health, recognising the interdependence of human, animal, and environmental health. National antibiotic consumption data for 2014–2023 were dominated by amoxicillin (45.9%), ciprofloxacin (16.2%), and cefixime (13.6%). Residues including ofloxacin, sulfamethoxazole, and erythromycin were detected in the Upper Citarum during 2016–2025.
The article reports negative inlet-to-outlet AREc reduction ratios across domestic, hospital, livestock, and pharmaceutical wastewater treatment plants, indicating higher resistant-bacteria proportions in effluent than influent. Hospital plants showed the highest reported AREc ratios and broadest resistance spectra.
In receiving waters, mean total E. coli concentrations were reported as 2,558 ± 360 CFU/mL during high rainfall, compared with 1,621 ± 300 CFU/mL in dry conditions. Field-based quantitative microbial risk assessment (QMRA) in Saguling’s floating fish-cage communities, which rely on reservoir water and groundwater, found annual gastrointestinal infection risks exceeding the WHO benchmark used in the study for the three measured groups: total E. coli, ESBL-Ec, and CREc. Exposed individuals were reported to be 1.6 times more likely to become asymptomatic carriers of resistant bacteria.
An integrated SWAT–QMRA model used tetracycline-resistant E. coli (TREc) as an indicator to project risk across space and time. The original article reports a gastrointestinal disease burden estimate of 223,000–296,000 disability-adjusted life years per 100,000 people per year. This figure is reproduced as reported; its magnitude and units require confirmation against the dissertation before further use.
Methodological Contributions
- TREc was proposed as an indicator of single-resistant AREc and ESBL-Ec as an indicator of multi-resistant AREc for routine Upper Citarum monitoring.
- A β-D-glucuronidase method using a microplate reader offered a faster and more accessible detection alternative, with reported accuracy of 87.2%, sensitivity of 67.4%, and specificity of 94%.
- The integrated SWAT–QMRA approach supported spatiotemporal risk mapping and the prioritisation of interventions.
The public defence was chaired by Prof. Emenda Sembiring. Supervisors included Prof. Herto Dwi Ariesyady, Prof. Nuning Nuraini, and Prof. Hisashi Satoh of Hokkaido University, Japan. Examiners included Prof. Indah Rachmahtiah Siti Salami, Prof. Dwina Roosmini, and Dr. Suphia Rahmawati of UII Yogyakarta.
Joint supervision with Hokkaido University supported the research. The work is intended to inform environmental policies addressing antibiotic resistance, particularly in the heavily polluted Citarum watershed.