The Emergence of Aquatic Reservoirs: Carbapenemase and Colistin Resistance in Rio de Janeiro

High rates of carbapenemase and colistin-resistance genes have been detected in Rio de Janeiro urban waters, threatening last-line antibiotics and posing an immediate public-health concern.

Sampling focused on urban surface waters in Rio de Janeiro aquatic systems, with cultured isolates assessed phenotypically and by PCR for resistance determinants. Overall, 49.4% of recovered isolates were non-susceptible to carbapenems; testing detected blaKPC, blaTEM, blaVIM, blaSPM and the integron marker intl1. A subset of isolates also showed phenotypic polymyxin B resistance, indicating a substantial environmental reservoir of clinically relevant resistance.

Isolates were predominantly Gram-negative bacilli, and presence of intl1 supports horizontal gene-transfer potential among environmental strains. Urban aquatic networks concentrate fecal inputs and effluents, creating ecological niches where mobile elements and multidrug-resistant organisms can amplify and move across connected waterways—linking directly to elevated risk of transmission through urban water networks.

The authors call for continuous monitoring and outline practical detection approaches consistent with their findings, including sentinel surface-water sampling, wastewater-based epidemiology, culture with targeted qPCR for bla and mcr genes, and periodic metagenomic screens for novel variants as components of robust environmental surveillance. Layered molecular and culture surveillance across sentinel sites will improve early detection of environmental AMR trends.

Waterborne exposure and colonization are plausible routes for community acquisition of resistant Gram-negative organisms, which could raise background prevalence and complicate empiric therapy for serious infections. These patterns also influence infection-prevention priorities for populations using contaminated recreational or municipal waters.

Key Takeaways:

• Nearly 50% of environmental isolates from this one-day urban sampling were carbapenem-non-susceptible, with multiple carbapenemase and colistin-resistance genes detected.
• Detection of intl1 and mobile resistance genes in Gram-negative bacilli indicates horizontal transfer potential and amplification in aquatic hotspots.
• Optimal situational awareness will rely on layered approaches: sentinel surface-water sampling, wastewater-based epidemiology, culture plus targeted qPCR for bla and mcr genes, and periodic metagenomic surveillance.