Drug-Resistant Bacteria Found in Hospital Wastewater

Untreated hospital wastewater in Gabon may be contributing to the environmental spread of multidrug-resistant bacteria, according to a new study published in BMC Microbiology. Researchers found high concentrations of antibiotic-resistant Enterobacteriaceae in hospital effluent, raising concerns about the role of wastewater in antimicrobial resistance (AMR) transmission and reinforcing the importance of a One Health approach.

Antimicrobial resistance is recognised as one of the greatest threats to global public health, with resistant bacteria capable of spreading between humans, animals, and the environment. Hospitals are considered important reservoirs of resistant organisms, yet in many low- and middle-income countries, wastewater is discharged without adequate treatment, allowing these pathogens to enter surrounding ecosystems.

High Bacterial Loads Found in Hospital Effluent

To investigate the extent of environmental contamination, researchers collected 98 water samples between 2023 and 2024 from 11 hospitals across Gabon. The study included 52 samples from hospital wastewater and 46 from nearby environmental waters.

Physical characteristics of the water, including pH, temperature, colour, foam, and debris, were recorded before laboratory analysis. Following bacterial culture and identification, 113 Enterobacteriaceae isolates were recovered and tested against 19 commonly used antibiotics.

Hospital wastewater contained substantially higher bacterial loads than surrounding surface waters, with concentrations reaching up to 1.68 × 10⁸ colony-forming units per millilitre.

Multidrug Resistance Was Widespread

All 113 confirmed Enterobacteriaceae isolates demonstrated multidrug-resistant phenotypes.

Resistance to beta-lactam antibiotics exceeded 95%, indicating that many of the recovered bacteria would likely be difficult to treat using commonly prescribed antimicrobial agents. The researchers identified Escherichia species as the most frequently isolated genus, accounting for 45 of the bacterial isolates.

The widespread occurrence of multidrug-resistant Enterobacteriaceae in untreated hospital effluent highlights the potential for resistant bacteria to disseminate into rivers, streams, and other environmental reservoirs where they may persist and spread further.

Visual Indicators May Help Identify Contaminated Sites

In addition to microbiological analyses, the researchers examined whether simple environmental observations could help identify areas with higher levels of contamination.

The presence of debris, foam, and grey or brown water discolouration was significantly associated with higher bacterial loads. Although these visual features cannot confirm microbiological contamination on their own, the authors suggest they could serve as practical indicators for identifying locations that warrant further environmental monitoring.

Such low-cost surveillance tools may be particularly valuable in regions where laboratory resources are limited.

Findings Support a One Health Response

The authors conclude that untreated hospital wastewater represents an important environmental source of antimicrobial-resistant bacteria in Gabon. They argue that improving wastewater treatment infrastructure should become a public health priority to reduce the release of resistant organisms into the environment.

The findings also reinforce the importance of adopting a One Health strategy, recognising the interconnected roles of human health, environmental protection, and infection control in tackling antimicrobial resistance.

While the study was observational and did not directly assess transmission to humans or animals, it provides further evidence that environmental reservoirs should be considered an integral component of national and global AMR surveillance programmes.

Reference

Chandja WBE et al. Dissemination of antibiotic-resistant enterobacteriaceae from hospital wastewater in Gabon: implications for the one health strategy. BMC Microbiol. 2026;DOI: 10.1186/s12866-026-05384-y.

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