Optimizing diagnosis of Acanthamoeba Keratitis : A comparative study of Microscopy , Culture and PCR from a tertiary care centre of South India

Acanthamoeba, a genus of free-living amoebae, inhabits diverse environments such as soil, freshwater, air, sewage, chlorinated water, medical equipment, and contact lens cases. These amoebae exist as trophozoites, actively feeding and proliferating under favorable conditions, but transform into highly resistant cysts under stress. While primarily bacterivorous, certain species, including Acanthamoeba castellanii, A. polyphaga, and A. hatchetti, exhibit pathogenic potential, causing keratitis and granulomatous amoebic encephalitis (GAE), particularly in immunocompromised individuals. GAE occurs when amoebae enter through wounds and disseminate to the brain. Acanthamoeba has also been detected on human skin, in the respiratory and gastrointestinal tracts, and in other hosts, highlighting its ecological adaptability and clinical significance.

Acanthamoeba castellanii, A. polyphaga, and A. hatchetti are among the primary species implicated in Acanthamoeba keratitis (AK), a severe corneal infection that predominantly affects contact lens users due to improper lens hygiene. Hydrogen peroxide-based disinfectants effectively eliminate Acanthamoeba, whereas multipurpose solutions are largely ineffective. AK is often misdiagnosed due to its nonspecific symptoms, delaying treatment and increasing the risk of vision loss. First identified in 1973, its incidence rose in the 1980s with the widespread use of contact lenses, which account for 80–93% of cases globally. In contrast, in rural areas of developing countries, corneal trauma from vegetative matter is the primary risk factor, highlighting distinct epidemiological patterns.

The incidence of Acanthamoeba keratitis (AK) has risen significantly, with cases in the United States increasing tenfold from 2 million per year in 1988 to 20 million in 2003 among contact lens wearers. A study in South India analyzing over 38,000 infectious keratitis cases attributed 0.9% to AK. Despite this growing burden, global prevalence data remain limited, with most knowledge derived from localized studies and case reports, particularly those linked to contact lens use.

With the increasing incidence of Acanthamoeba keratitis (AK), along with diagnostic challenges and limited treatment options, further research is crucial. This study compares two diagnostic methods— Polymerase Chain Reaction (PCR) and culture isolation—for detecting Acanthamoeba species in AK cases. PCR is a highly sensitive technique that can identify even small amounts of Acanthamoeba DNA, making it particularly useful for early diagnosis. In contrast, culture isolation allows for species identification and provides biological insights by growing the amoeba from clinical samples. This study aims to evaluate the accuracy, effectiveness, and practical use of PCR versus culture isolation in AK diagnosis. Identifying the most reliable method will improve diagnostic protocols, enhance patient outcomes, and support public health strategies for better prevention.