Galápagos wastewater is creating new reservoirs of antibiotic-resistant bacteria

By Dr. Priyom Bose, Ph.D.Reviewed by Lauren HardakerAug 6 2026

A mobile microbiology laboratory deployed in the Galápagos archipelago reveals that wastewater-contaminated marine sites have substantially higher densities of antimicrobial resistance genes and drug-resistant bacteria, raising concerns about potential risks to human, animal, and ecosystem health.

Study: Human wastewater contamination drives the emergence of multidrug-resistant bacteria in the Galápagos marine ecosystem. Image Credit: Ezume Images / Shutterstock

A recent Nature Communications study evaluated how human wastewater contamination may promote the introduction, persistence, and diversification of multidrug-resistant bacteria in the Galápagos marine environment, using mobile laboratory-based metagenomic surveillance.

AMR Surveillance Challenges

Antimicrobial resistance (AMR) occurs when microorganisms, including bacteria, viruses, fungi, and parasites, acquire the ability to withstand drugs intended to kill or inhibit them. This phenomenon is a critical global health concern, with bacterial AMR associated with approximately five million deaths worldwide in 2021 and a burden projected to increase further.

The impact of AMR is especially acute in lower- and middle-income countries (LMICs), where factors such as insufficient surveillance, inadequate infrastructure, rapid urbanization, and misuse of antimicrobials accelerate the spread of resistance.

Relatively few studies have explored how environmental mechanisms and pathways contribute to AMR dissemination, particularly in LMICs where surveillance is constrained by limited resources. This knowledge gap hinders effective interventions and risk assessments.

Recent advances in mobile sequencing technologies, such as Oxford Nanopore, offer promising tools for addressing the AMR surveillance deficit in remote and resource-constrained settings, including LMICs. These platforms support rapid, field-based genomic analysis and real-time detection of AMR genes and resistant organisms.

However, targeted sequencing alone cannot capture the full complexity of environmental AMR, underscoring the need for complementary approaches such as quantitative polymerase chain reaction (qPCR) surveillance, culture-based phenotyping, and metagenomic sequencing. Current “mini-lab” systems often rely on culture-based methods and require extensive setup, underscoring the need for flexible, multimodal solutions.

Mobile Laboratory Surveillance of Environmental AMR in the Galápagos Archipelago

The Galápagos archipelago offers a unique setting for studying antimicrobial resistance (AMR) in marine ecosystems. Most islands remain uninhabited, but Santa Cruz and San Cristóbal face rapid population growth and rising tourism. Persistent discharge of untreated wastewater, especially at coastal sites around Puerto Baquerizo Moreno on San Cristóbal, raises concerns for environmental and public health. Enhanced AMR surveillance is vital for safeguarding both residents and marine life.

The researchers developed a mobile microbiology laboratory to identify contamination hotspots and link bacterial taxa, AMR genes, and resistance profiles. On-site molecular and microbiological assays, including fecal qPCR and untargeted shotgun metagenomic sequencing, were performed on the island using a mobile field laboratory. Fecal qPCR assays detected and mapped hotspots of untreated wastewater contamination, helping map likely wastewater-contamination hotspots. Metagenomic sequencing enabled comprehensive analysis of microbial community composition, identification of antimicrobial resistance genes, and detection of taxa associated with human fecal contamination. Long-read metagenomic analysis was conducted on a subset of ten samples collected during 2022 and 2023.

Lactose-fermenting Enterobacteriaceae were selectively cultured to assess resistance phenotypes, while whole-genome sequencing of Escherichia coli strains revealed the genetic context and plasmid-mediated mobility of AMR genes.

Environmental surveillance for enteric and fecal bacterial contamination in the marine environment around San Cristóbal involved 2 years of sampling at 16 marine sites, 2 freshwater sites, and 2 municipal wastewater treatment facilities that contained raw sewage. Sampling sites were distributed across the island.

Sewage-Driven Fecal and Antimicrobial Resistance Contamination in San Cristóbal’s Coastal Waters

Extensive water sampling over two years revealed pervasive fecal pollution in San Cristóbal’s marine environment, originating from both animal and human sources. A universal stool marker was detected at all sites, while a human-specific marker, indicative of untreated sewage, showed consistently high levels at Punta Carola Pipe, a major sewage outfall. In contrast, several recreational and remote beaches exhibited low or sporadic human contamination, while observations at some nearby sites suggested that local physical barriers, currents, weather, and discharge patterns may influence contaminant dispersal.

High counts of viable coliform bacteria were detected at locations with strong human marker signals, strengthening the evidence of human-derived wastewater contamination. More than 3,000 colony-forming units per milliliter (CFU/mL) of coliforms were found at Punta Carola Pipe and Laguna, with similarly elevated counts observed at Muelle de Pescadores and Playa de Oro during certain periods.

Long-read metagenomic sequencing highlighted significant microbial and AMR gene contamination in wastewater-affected sites. Sewage and Punta Carola Pipe samples contained abundant enteric and potentially pathogenic bacteria, with the highest density and diversity of AMR genes, including those conferring resistance to tetracyclines, beta-lactams, and macrolides. Remote, less-impacted sites harbored typical marine bacteria and few AMR genes.

Phenotypic testing of 183 environmental coliform isolates revealed that multidrug resistance (MDR) was common at sewage and outfall sites, with 38–42% of isolates displaying resistance to three or more antibiotic classes.

The researchers identified globally distributed, high-risk E. coli lineages, including ST10, ST58, ST69, and ST155. Many acquired resistance genes, particularly those affecting aminoglycosides, tetracyclines, sulfonamides, and macrolides, were primarily located on plasmids. Strain-level analysis showed evidence consistent with recent plasmid sharing, recombination, and dynamic acquisition or loss of resistance genes, including three isolates with meropenem resistance, a concerning finding given the importance of carbapenems as last-resort antibiotics.

Conclusions

The findings indicate that untreated sewage discharge near San Cristóbal is a major source of the fecal and AMR contamination detected at affected coastal sites. The detection of multidrug-resistant bacteria and high-risk E. coli strains raises concern about potential risks to human, animal, and environmental health.

This study shows that deployment of a portable, multimodal mobile laboratory incorporating a rapid “lab-free” qPCR workflow enabled on-site detection of fecal contamination and field-based characterization of AMR genes and resistant bacterial isolates, demonstrating a powerful tool for environmental surveillance and supporting the need for improved wastewater management and further risk assessment.