The Unseen Invader: Acanthamoeba in Tap Water

A silent and unseen organism inhabits water supplies in various regions, capable of causing serious infections and posing a significant challenge to public health.

Explore the Research

What is Acanthamoeba?

A microscopic free-living amoeba found widely in our environment, capable of causing serious infections in humans.

Trophozoite Stage

The active, vegetative form where the amoeba feeds on bacteria, yeasts, and other organisms, and reproduces ² ⁶ .

Cyst Stage

A dormant, resilient form with a double wall, making it highly resistant to disinfection, extreme temperatures, and antibiotics ² ⁶ .

Acanthamoeba Keratitis (AK)

A severe, painful infection of the cornea that is sight-threatening and predominantly associated with contact lens wearers ⁴ ⁶ .

Granulomatous Amebic Encephalitis (GAE)

A rare but almost always fatal infection of the brain and spinal cord, typically occurring in immunocompromised individuals ² ⁹ .

A Closer Look at the Hormozgan Study

The warm climate of Hormozgan province in southern Iran, combined with local water storage practices, created an ideal environment to investigate the presence of this pathogen. A pivotal 2017 study sought to evaluate the contamination of tap water sources in selected cities of this region ¹ .

Methodology: Tracking the Amoeba

Sample Collection

Fifty water samples (approximately 500 mL each) were collected directly from tap water resources. These were split between two common sources: 25 samples from water tanks and 25 from wells ¹ .

Filtration and Culturing

Each sample was passed through a filter to concentrate any microorganisms present. The material from the filter was then cultured on a special 1.5% non-nutrient agar medium ¹ .

Incubation and Cloning

The cultures were incubated at room temperature and monitored daily for the growth of amoebae. To ensure pure samples for identification, successful cultures were cloned ¹ .

Identification

The final step involved using a microscope to identify the distinctive features of Acanthamoeba, such as its spiky acanthopodia in the trophozoite stage and its double-walled cysts ¹ .

Key Findings and Results

The results of the study were striking, revealing significant contamination of the water supply.

Acanthamoeba Contamination in Tap Water Sources

Water Source	Number of Samples Tested	Number of Positive Samples (%)
Well Water	25	9 (36%)
Tank Water	25	5 (20%)
Total	50	14 (28%)

Data adapted from ¹

The data clearly showed that well water was more frequently contaminated (36%) than water from tanks (20%), leading to an overall contamination rate of over one-quarter of all samples tested ¹ . This high prevalence highlights a substantial public health exposure, especially considering the ubiquity of tap water in daily life.

The Scientist's Toolkit: How We Detect Acanthamoeba

Identifying this elusive organism requires specific tools and techniques.

Tool or Reagent	Function in Research
Non-Nutrient Agar (NNA)	A growth medium that does not feed the amoebae directly, forcing them to prey on the added bacteria.
Escherichia coli	A layer of this bacteria is spread on the NNA to serve as a food source for the amoebae, encouraging their growth.
Cellulose Acetate Filters	Used to concentrate amoebae from large volumes of water by trapping them as the sample is poured through.
Polymerase Chain Reaction (PCR)	A molecular technique that amplifies specific DNA sequences, allowing for highly sensitive detection and genotyping of Acanthamoeba beyond what microscopy can see ⁵ ⁸ .
JDP1 & JDP2 Primers	Specific DNA primers used in PCR to target a unique region of the Acanthamoeba 18S rRNA gene, enabling accurate identification ⁷ ⁸ .

Detection Methods Comparison

Later studies in the same region, such as one in Bandar Abbas, have employed these molecular methods. For instance, one such study found that while the culture method identified Acanthamoeba in 6% of samples, the more sensitive PCR method detected it in 9.6% of samples ⁵ ⁸ .

Why the T4 Genotype is a Major Concern

Aspect	Description
Prevalence	It is the most frequently identified genotype in both environmental and clinical samples across the globe ⁶ ⁸ .
Pathogenicity	It is the genotype most often isolated from patients with Acanthamoeba keratitis and other infections ⁶ .
Environmental Hardiness	Its success is attributed to a high degree of adaptability to various environments, allowing it to thrive in diverse conditions.

Genotype Distribution

Protecting Public Health: Significance and Prevention

The discovery of a high occurrence of Acanthamoeba in tap water sources is a clear warning sign for public health ¹ . For the residents of Hormozgan and similar regions, it means that a common daily resource could be a potential source of exposure.

Low Risk 28% Contamination High Risk

Primary Risk Group: Contact Lens Wearers

The primary risk for the serious eye infection, Acanthamoeba keratitis, is for contact lens wearers who might rinse their lenses or storage cases with tap water, or who swim or shower while wearing lenses ⁴ ⁶ .

Prevention and Protection Strategies

Simple yet effective steps to protect health from these unseen invaders.

Avoid Water Contact with Lenses

The single most important preventive measure is to never allow contact lenses to come into contact with unsterilized water.

Use Effective Disinfectants

Not all water treatment methods are equally effective against the resilient cyst form of Acanthamoeba ¹ .

Monitor Water Systems

Regular surveillance of water supplies, especially stored water in tanks and wells, is crucial to assess risk and guide treatment efforts ¹ ⁷ .

Protect Vulnerable Populations

For the broader population, especially those who are immunocompromised, proper water treatment is essential.

A Clear Signal for Vigilance

The research in Hormozgan province provides a compelling and concrete example of how a widespread environmental organism can translate into a direct local health concern. The 28% contamination rate of tap water with Acanthamoeba is more than just a statistic; it is a clear signal of the exposure risk faced by the community.

It highlights the critical need for public awareness, particularly among contact lens users, and reinforces the importance of robust water monitoring and disinfection practices. As science continues to unveil the hidden life in our water, it empowers us to take simple yet effective steps to protect our health from these unseen invaders.