A silent danger lurks in water, posing a growing threat to public health.
Imagine a microscopic organism so resilient it can survive in chlorinated swimming pools and tap water, so adaptable it can cause a devastating eye infection that often gets misdiagnosed. This isn't science fiction—it's the reality of Acanthamoeba, a free-living amoeba becoming an increasing public health concern in Poland and worldwide. For contact lens wearers, a group comprising up to 93% of patients, this pathogen poses a particularly serious risk of a sight-threatening condition called Acanthamoeba keratitis (AK)3 .
Up to 93% of Acanthamoeba keratitis patients are contact lens wearers3 .
Recent Polish research is shedding new light on this invisible threat, focusing on evaluating how physical and chemical agents can combat the resilient strains detected in the country. This article explores the cutting-edge science behind these investigations and what they mean for public health.
Acanthamoeba is a genus of free-living amoebae found virtually everywhere in our environment. "The amoebae are common in natural and man-made habitats worldwide. They occur in air, water, soil and dust; they are found in/on vegetables, animals and humans"1 . These microorganisms thrive in diverse locations, from lakes and soil to tap water, swimming pools, and even domestic water systems1 3 .
What makes Acanthamoeba particularly fascinating—and dangerous—is its amphizoic nature, meaning it can live freely in the environment but also act as an opportunistic parasite in human hosts1 . The amoeba exists in two distinct forms:
The active, reproductive form that feeds on bacteria and other microorganisms.
A dormant, highly resistant form that develops under harsh conditions3 .
The cyst form represents a remarkable survival strategy. "Mature cysts are round, measuring 10–25 μm, with thick double-layered walls and minimal metabolic activity"8 . These cysts are incredibly resilient, able to survive for up to 20 years under dry conditions and resist extreme temperatures, pH fluctuations, and many disinfectants and medications8 .
Acanthamoeba causes a severe corneal infection called Acanthamoeba keratitis (AK) that can lead to permanent visual impairment. The infection begins when the amoeba adheres to the corneal surface, then produces enzymes that destroy epithelial cells and penetrate deeper into the cornea8 .
The journey from symptoms to correct diagnosis is often fraught with difficulty. "Overall, 75% to 90% of AK cases are misdiagnosed"3 , frequently as herpetic keratitis, bacterial infection, or fungal keratitis. This diagnostic challenge stems from AK's non-specific early symptoms, which include3 8 :
Misdiagnosis Rate of AK Cases3
| Disease Stage | Clinical Findings |
|---|---|
| Early | Epithelial opacities, microcysts ("dirty epithelium"), pseudo-dendrites, punctuate keratopathy, subepithelial infiltrates |
| Advanced | Ring-like stromal infiltrate, radial keratoneuritis (perineural infiltrates), satellite lesions, anterior uveitis with hypopyon |
| Late | Stromal thinning, corneal ulceration, abscess formation, corneal perforation |
Non-specific symptoms often mistaken for other eye infections. Epithelial changes begin.
Characteristic ring infiltrate appears. Severe pain disproportionate to clinical findings.
Corneal ulceration, potential for perforation. Permanent vision damage likely without treatment.
In Poland, AK has been diagnosed with increasing frequency in recent years1 . Polish researchers have conducted interdisciplinary studies to better understand the local strains and improve diagnosis and treatment.
In 84% of incidents, Acanthamoeba infection was connected to contact lens exposure to tap water or pool water1 .
In many cases, the infection involved not just Acanthamoeba but concomitant bacteria (e.g., Pseudomonas aeruginosa) and fungi1 .
Polish scientists have identified several Acanthamoeba species in corneal isolates, including:
Genotype T4 is the most commonly associated with AK infections globally3 .
A crucial area of Acanthamoeba research involves evaluating the effectiveness of various chemical and physical agents against the resilient cyst form. Recent methodological advances are accelerating this work.
Until recently, determining whether disinfectants successfully killed Acanthamoeba cysts was a time-consuming process. The conventional protocol for quantifying living cysts required 7 days to complete, representing a significant bottleneck in research4 .
This method involved culturing serially diluted samples and observing them for excystment—the process where dormant cysts reactivate into trophozoites. Researchers would then calculate living cyst counts based on which dilutions showed growth4 .
In 2025, Japanese researchers developed an accelerated protocol that reduces the quantification time from 7 days to just 3 days while maintaining accuracy4 . The breakthrough came from optimizing culture conditions to promote faster excystment:
Supplementing the standard PYG medium with 5% or more fetal bovine serum (FBS)
Incubating cultures at 2.5% CO₂ concentration or higher4
The table below shows how these modifications reduced the time needed for living cyst quantification:
| Sample Type | Culture Conditions | Time to Complete Quantification (Days) |
|---|---|---|
| Standard Strain | 0.04% CO₂ (normal air) | 6 |
| Standard Strain | 2.5% CO₂ + 5% FBS | 3 |
| Clinical Strain | 0.04% CO₂ (normal air) | 5 |
| Clinical Strain | 2.5% CO₂ + 5% FBS | 3 |
This accelerated protocol proves particularly valuable for testing disinfectant effectiveness against the cysts. The faster turnaround time means researchers can more rapidly screen potential anti-amoebic agents, bringing us closer to effective treatments and prevention strategies.
Studying resistant pathogens like Acanthamoeba requires specialized laboratory tools and techniques. The table below outlines key components of the scientist's toolkit for this research:
| Tool/Category | Specific Examples | Function/Purpose |
|---|---|---|
| Culture Media | Peptone-Yeast Extract-Glucose (PYG) medium, BSC (Bacto Casitone) medium | Supports amoeba growth and excystment in laboratory conditions |
| Diagnostic Tools | In vivo confocal microscopy, slit-lamp examination, phase-contrast microscopy | Enables visualization and identification of Acanthamoeba in corneal tissue and cultures |
| Molecular Techniques | Polymerase Chain Reaction (PCR), 18S rDNA sequencing, genotyping | Provides species and genotype identification; more accurate than morphological methods alone |
| Viability Assessment | Excystment quantification in 96-well plates, Bürker hemocytometer | Measures living cysts and trophozoite counts to determine disinfectant effectiveness |
Given the challenges in treating AK, prevention remains paramount, especially for contact lens wearers. Key risk factors include3 :
Swimming, showering, or rinsing lenses with tap water
Inadequate cleaning and disinfection practices
Topping off solution instead of replacing it
Followed by exposure to contaminated water
Never expose lenses to any form of water (tap, pool, lake, or sea)
Rub and rinse lenses with fresh disinfecting solution each time they're cleaned
Replace lens cases at least every three months
Unless specifically prescribed by an eye doctor
Shown more effective against Acanthamoeba3
Adhere to recommended lens replacement frequency
The growing threat of Acanthamoeba in Poland and globally underscores the importance of continued research into effective chemical and physical agents against this pathogen. As Polish researchers noted, "In samples from contact lens wearers where microbial keratitis is identified along with some connection with the patient's exposure to contaminated water environments, a risk of Acanthamoeba spp. infections should be considered"1 .
Ongoing studies focus on understanding the complicated relationship between Acanthamoeba and co-occurring pathogens, developing more effective disinfectants, and improving diagnostic methods to reduce the current high rates of misdiagnosis.
For the public, particularly contact lens wearers, awareness and proper hygiene remain the best defense against this invisible threat lurking in water sources. As research continues, the scientific community moves closer to better protecting public health from this resilient pathogen.
For more information on Acanthamoeba prevention, consult your eye care professional and review contact lens hygiene guidelines from public health authorities.