Characterization of Enterococcus species in surface drinking water from Akoko Edo Nigeria reveals contamination levels and risks to public health – Nature

Report on the Characterization of Enterococcus Species in Surface Drinking Water in Akoko Edo, Nigeria

Executive Summary

This report details the findings of a year-long investigation into the microbiological quality of surface drinking water in Akoko Edo, Nigeria, with a specific focus on the presence and characteristics of Enterococcus species. The study highlights significant challenges to achieving Sustainable Development Goal 6 (SDG 6: Clean Water and Sanitation) and reveals direct threats to Sustainable Development Goal 3 (SDG 3: Good Health and Well-being). The presence of fecal indicator bacteria, including Enterococcus, confirms contamination of water sources vital to local communities. A high prevalence of multidrug-resistant (MDR) strains, coupled with virulence factors and biofilm-forming capabilities, indicates a severe public health risk. The detection of numerous antibiotic resistance and virulence genes underscores the role of these water bodies as reservoirs for clinically significant pathogens. These findings provide critical data for public health officials to conduct risk assessments and implement targeted interventions to safeguard community health and advance progress toward the SDGs.

1.0 Introduction: Water Quality and Sustainable Development Goals

1.1 The Critical Role of Water in Achieving SDG 3 and SDG 6

Access to safe and affordable drinking water is a fundamental human right and a cornerstone of public health, central to the United Nations’ 2030 Agenda for Sustainable Development. SDG 6 explicitly calls for ensuring the availability and sustainable management of water and sanitation for all. However, in many rural communities, such as Akoko Edo, Nigeria, surface water bodies serve multiple purposes, including drinking, irrigation, and domestic use, making them highly susceptible to contamination. This contamination directly undermines progress toward SDG 6 and poses a significant risk of waterborne diseases, thereby impeding the achievement of SDG 3, which aims to ensure healthy lives and promote well-being for all at all ages.

1.2 Public Health Implications of Enterococcus Contamination

Enterococcus species are established indicators of fecal pollution in water. Their presence signals the potential for other pathogenic organisms and presents a direct health threat. Certain species, such as E. faecalis and E. faecium, are opportunistic pathogens capable of causing severe infections. A critical concern for SDG 3 is the rise of antimicrobial resistance (AMR), a global health crisis that threatens the effective treatment of infections. Environmental reservoirs, including contaminated surface water, are increasingly recognized as hotspots for the development and dissemination of AMR. This study investigates the prevalence, virulence, and AMR profiles of Enterococcus species to evaluate the public health risks associated with these water sources and provide data to inform strategies aligned with achieving SDG 3 and SDG 6.

2.0 Key Findings on Water Contamination in Akoko Edo, Nigeria

2.1 Bacterial Population Density and Fecal Contamination

The investigation revealed significant fecal contamination in the surface water samples, a clear failure to meet the standards required by SDG 6. Bacterial densities varied seasonally, with higher counts observed during the wet season, likely due to increased runoff from anthropogenic activities.

• Fecal Coliforms: Densities ranged from 0.60 to 3.18 log10 CFU/100mL.
• Total Coliforms: Densities ranged from 1.59 to 3.51 log10 CFU/100mL.
• Enterococcus species: Densities ranged from 0.52 to 1.92 log10 CFU/100mL.

A total of 97 Enterococcus isolates were identified, with E. faecium (29.9%) being the most prevalent species, followed by E. faecalis (21.7%). The high counts of these fecal indicator bacteria confirm that the water is unfit for human consumption without treatment and poses a direct risk to community health.

2.2 Antimicrobial Resistance (AMR) Profile: A Threat to SDG 3

The high levels of AMR detected among Enterococcus isolates represent a serious threat to public health and the efficacy of essential medicines, a core component of SDG 3. The findings indicate that the environment is a significant reservoir for resistance determinants.

• Multidrug Resistance (MDR): An alarming 63.9% of isolates were identified as multidrug-resistant, showing resistance to at least three different classes of antibiotics.
• High Resistance Rates: Significant resistance was observed against commonly used antibiotics, including penicillin (74.2%), ampicillin (71.1%), and erythromycin (59.8%).
• MAR Index: 62.9% of isolates had a Multiple Antibiotic Resistance (MAR) index greater than 0.2, indicating their origin from a high-risk environment with significant antibiotic pressure.

2.3 Virulence Factors and Biofilm Formation

The pathogenic potential of the isolated Enterococcus species was confirmed through the detection of virulence factors and a high capacity for biofilm formation. These characteristics enhance the bacteria’s ability to cause disease and persist in water systems, further challenging the objectives of SDG 3 and SDG 6.

1. Virulence Factor Production:
   • β-hemolytic activity was present in 21.6% of isolates.
   • Gelatinase activity was found in 15.5% of isolates.
   • Hyaluronidase activity was detected in 9.3% of isolates.
2. Biofilm Formation: A significant portion of isolates demonstrated the ability to form biofilms, which can protect bacteria from disinfectants and facilitate the transfer of resistance genes.
   • Strong biofilm formation was observed, particularly in E. faecalis (33.3%).
   • Moderate biofilm formation was common across E. faecalis (47.6%) and E. casseliflavus (53.3%).
   • A significant correlation was found between biofilm formation and the MAR index (r = 0.550, p

2.4 Genetic Determinants of Risk: Resistance and Virulence Genes

Polymerase chain reaction (PCR) analysis identified a wide array of genes responsible for antibiotic resistance, virulence, and biofilm formation, providing genetic evidence of the public health threat.

• Efflux Pump Genes: Genes associated with AMR, such as msrC (26.8%) and tetL (25.8%), were widely distributed, contributing to the MDR phenotype.
• Virulence Genes: Key virulence genes were detected, including gelE (43.3%), cylA (29.9%), and hyl (23.7%), confirming the pathogenic potential of the environmental isolates.
• Biofilm-Associated Genes: Genes critical for biofilm formation were highly prevalent, including gcpA (83.5%), csgD (71.1%), and adrA (62.9%).
• Antibiotic Resistance Genes (ARGs): A diverse range of ARGs were identified, conferring resistance to multiple antibiotic classes. Notably, genes conferring resistance to last-resort antibiotics like vancomycin (vanA, vanB, vanC) were present, which is a critical concern for SDG 3.

3.0 Analysis and Implications for Sustainable Development

3.1 Surface Water as a Reservoir for Public Health Threats

The study confirms that the surface water bodies in Akoko Edo are significant reservoirs of virulent and antibiotic-resistant Enterococcus. The combination of high bacterial loads, MDR phenotypes, and pathogenic traits indicates that direct consumption or use of this water poses a substantial risk of difficult-to-treat infections. This situation highlights a critical gap in water management and sanitation infrastructure, directly hindering the attainment of SDG 6. The continuous discharge of untreated waste from human and agricultural activities perpetuates this cycle of contamination, creating a persistent threat to public health.

3.2 The Intersection of AMR, Water Quality, and Global Health Goals

The findings illustrate the interconnectedness of environmental health and human health, a central tenet of the One Health approach and essential for achieving the SDGs. The prevalence of AMR in environmental bacteria is a stark reminder that efforts to combat antibiotic resistance must extend beyond clinical settings. Contaminated water serves as a conduit for the spread of resistance genes into the wider environment and human populations, directly undermining global efforts to preserve the efficacy of antibiotics as outlined in the objectives of SDG 3. Addressing water contamination is therefore not only a matter of sanitation but a critical intervention point for controlling the spread of AMR.

4.0 Conclusion and Recommendations for Public Health Action

The surface drinking water in Akoko Edo, Nigeria, is heavily contaminated with fecal bacteria, including pathogenic and multidrug-resistant Enterococcus species. This presents a severe and immediate threat to public health and stands as a major obstacle to achieving Sustainable Development Goals 3 and 6. The water sources act as environmental reservoirs for virulence and antibiotic resistance determinants, posing a risk of infections that may be difficult to treat.

Based on these findings, the following actions are recommended:

1. Urgent Public Health Advisory: Local health authorities should immediately inform communities of the risks associated with consuming untreated surface water and promote safe water practices, such as boiling or filtration.
2. Implement Water Treatment Solutions: Investment in accessible, low-cost water treatment technologies at the community level is crucial to provide a safe drinking water alternative and make progress toward SDG 6.
3. Enhanced Surveillance and Monitoring: Regular monitoring of water quality and AMR patterns in environmental sources is necessary to inform public health strategies and track progress.
4. Integrated Water and Waste Management: Develop and enforce policies to manage waste from domestic and agricultural sources to prevent further contamination of water bodies, aligning with the integrated approach of SDG 6.

The data from this report should be utilized by policymakers and health professionals to formulate evidence-based risk assessments and interventions that protect consumer safety, improve public health outcomes, and drive progress on the Sustainable Development Goals.

1. Which SDGs are addressed or connected to the issues highlighted in the article?

• SDG 3: Good Health and Well-being

  The article directly connects to SDG 3 by investigating the public health risks associated with contaminated drinking water. It focuses on the presence of pathogenic bacteria (Enterococcus species), their virulence factors, and, most significantly, their antimicrobial resistance (AMR). The study highlights how multidrug-resistant (MDR) bacteria in a primary water source pose a “potential public health threat” and can lead to “difficult-to-treat infection,” which directly impacts community health and well-being.

• SDG 6: Clean Water and Sanitation

  This is the most central SDG to the article. The study is an “assessment of drinking surface water” and explicitly mentions that its work is relevant to “Sustainable Development Goals (SDGs 6), which seeks to guarantee that by 2030, everyone will have equitable access to safe, affordable drinking water.” The research assesses water quality by measuring fecal contamination, which is a core component of ensuring “clean water.” The findings that the water is “fecally polluted and unfit for drinking” underscore the challenges in achieving this goal in the studied rural community.

2. What specific targets under those SDGs can be identified based on the article’s content?

• Target 3.3: End epidemics and combat water-borne diseases

  The article’s focus on identifying bacteria that are “indicative of water contamination and pose potential health risks to consumers” directly relates to combating water-borne diseases. The investigation into “virulence genes” and the potential of Enterococcus species to “cause diseases” provides critical data for understanding and preventing the spread of such illnesses through contaminated water sources.

• Target 3.d: Strengthen the capacity for early warning, risk reduction and management of national and global health risks

  The study’s extensive analysis of antimicrobial resistance (AMR), including the finding that “63.9% of the isolates displayed multidrug resistance (MDR),” serves as an early warning for a significant global health risk. The article states that its findings “provide crucial data for health professionals to conduct risk assessments, reducing the risk of health issues.” This aligns perfectly with strengthening the capacity to identify, assess, and manage public health threats like AMR originating from environmental sources.

• Target 6.1: Achieve universal and equitable access to safe and affordable drinking water for all

  The article explicitly references this goal. The entire study is premised on the fact that the “surface water serves as a drinking water source for local communities” in a rural area. By assessing the water’s safety and concluding it is “unfit for drinking” due to high counts of fecal indicator bacteria, the study highlights the gap in achieving safe drinking water access for this population.

• Target 6.3: Improve water quality by reducing pollution

  The research identifies significant water pollution, attributing it to “anthropogenic activities and the deposition of wastes into the water.” The presence of fecal coliforms, total coliforms, and Enterococcus species are direct measures of pollution. The study’s conclusion that surface waters “serve as reservoirs to fecal bacteria due to indiscriminate pollution” directly addresses the need to improve water quality by tackling pollution sources.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

• Concentration of fecal indicator bacteria (Enterococcus, fecal coliforms)

  This is a direct indicator mentioned and used throughout the study to assess water safety (Target 6.1) and quality (Target 6.3). The article provides specific measurements: “bacterial densities measured in log10 CFU/100mL, with fecal coliforms, total coliforms, and Enterococcus species all present.” It notes that the “high count of enterococci, as it exceeds the WHO standards, suggests that the surface water is fecally polluted and unfit for drinking.” This quantitative data serves as a clear metric for water quality.

• Prevalence of antimicrobial resistance (AMR) and multidrug resistance (MDR)

  This is a key indicator for assessing health risks (Target 3.d). The article quantifies this by stating, “63.9% of the isolates displayed multidrug resistance (MDR).” It also details resistance rates to specific antibiotics like penicillin (74.2%) and ampicillin (71.1%). The calculation of the “Multiple antibiotic resistance (MAR) index” is another specific metric used to identify high-risk environments.

• Presence of virulence and antibiotic resistance genes (ARGs)

  This is an implied indicator for measuring the potential for water-borne disease outbreaks (Target 3.3) and the management of health risks (Target 3.d). The study uses polymerase chain reaction (PCR) to detect specific “virulence genes” (e.g., gelE, cylA, esp) and a wide array of ARGs (e.g., tetM, ermB, vanA, vanC, qnrS). The prevalence of these genes in the water source is a direct measure of the potential danger it poses to public health.

4. Create a table with three columns titled ‘SDGs, Targets and Indicators” to present the findings from analyzing the article. In this table, list the Sustainable Development Goals (SDGs), their corresponding targets, and the specific indicators identified in the article.

Source: nature.com