Sensitivity and specificity of potassium hydroxide and calcofluor white stain to differentiate between fungal and Pythium filaments in corneal scrapings from patients of Pythium keratitis

Bagga, Bhupesh; Vishwakarma, Pratima; Sharma, Savitri; Jospeh, Joveeta; Mitra, Sanchita; Mohamed, Ashik

doi:10.4103/ijo.ijo_1880_21

Cited by 19 publications

(25 citation statements)

References 21 publications

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“…Grass leaves with water culture has been shown to induce zoospore formation, which is confirmatory for P. insidiosum (Fig. 2 d) [ 11 , 36 ]. The above process can be time-consuming (up to 11 days) and significantly delay the initiation of appropriate pharmacotherapy.…”

Section: Microbiological Laboratory Diagnosissupporting

confidence: 59%

“…Culture positivity with zoospore induction gives a definitive diagnosis but still PCR (polymerase chain reaction) is the gold standard due to high sensitivity and specificity. It is also vital to understand all the existing and evolving modes of lab diagnosis [ 36 ].…”

Section: Microbiological Laboratory Diagnosismentioning

confidence: 99%

“…One or different combinations of the above, along with a trained eye and clinical suspicion, can help in the early detection of PI keratitis. In vivo confocal microscopy (IVCM) has been shown to demonstrate hyperreflective beaded string-like branching structures, but they cannot differentiate Pythium from fungus or Nocardia [ 36 , 42 ].…”

Section: Microbiological Laboratory Diagnosismentioning

confidence: 99%

“…Pythium has been described to grow as a flat colorless or light brown colony with fine radiations in the edges [ 7 , 36 ]. Culture can be obtained either from scraping or inoculation from the corneal button into blood agar, potato dextrose agar (PDA), or Sabouraud dextrose agar (SDA).…”

Section: Microbiological Laboratory Diagnosismentioning

confidence: 99%

“…Apart from positive culture with zoospore formation, PCR tests are the only gold standard, as they typically identify species-specific sequences of the DNA [ 11 , 36 ]. PCR can either be performed as a rapid test from a corneal scraping or the growth on a culture plate.…”

Section: Microbiological Laboratory Diagnosismentioning

confidence: 99%

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Pythium insidiosum Keratitis: Past, Present, and Future

et al. 2022

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Pythium insidiosum (PI) is an oomycete, a protist belonging to the clade Stramenopila. PI causes vision-threatening keratitis closely mimicking fungal keratitis (FK), hence it is also labeled as “parafungus”. PI keratitis was initially confined to Thailand, USA, China, and Australia, but with growing clinical awareness and improvement in diagnostic modalities, the last decade saw a massive upsurge in numbers with the majority of reports coming from India. In the early 1990s, pythiosis was classified as vascular, cutaneous, gastrointestinal, systemic, and ocular. Clinically, morphologically, and microbiologically, PI keratitis closely resembles severe FK and requires a high index of clinical suspicion for diagnosis. The clinical features such as reticular dot infiltrate, tentacular projections, peripheral thinning with guttering, and rapid limbal spread distinguish it from other microorganisms. Routine smearing with Gram and KOH stain reveals perpendicular septate/aseptate hyphae, which closely mimic fungi and make the diagnosis cumbersome. The definitive diagnosis is the presence of dull grey/brown refractile colonies along with zoospore formation upon culture by leaf induction method. However, culture is time-consuming, and currently polymerase chain reaction (PCR) method is the gold standard. The value of other diagnostic modalities such as confocal microscopy and immunohistopathological assays is limited due to cost, non-availability, and limited diagnostic accuracy. PI keratitis is a relatively rare disease without established treatment protocols. Because of its resemblance to fungus, it was earlier treated with antifungals but with an improved understanding of its cell wall structure and absence of ergosterol, this is no longer recommended. Currently, antibacterials have shown promising results. Therapeutic keratoplasty with good margin (1 mm) is mandated for non-resolving cases and corneal perforation. In this review, we have deliberated on the evolution of PI keratitis, covered all the recently available literature, described our current understanding of the diagnosis and treatment, and the potential future diagnostic and management options for PI keratitis.

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Section: Microbiological Laboratory Diagnosissupporting

confidence: 59%

Section: Microbiological Laboratory Diagnosismentioning

confidence: 99%

Section: Microbiological Laboratory Diagnosismentioning

confidence: 99%

Section: Microbiological Laboratory Diagnosismentioning

confidence: 99%

Section: Microbiological Laboratory Diagnosismentioning

confidence: 99%

See 3 more Smart Citations

Pythium insidiosum Keratitis: Past, Present, and Future

et al. 2022

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Diagnostic capacity for fungal keratitis in Africa – Survey in 50 African countries

Makangara Cigolo,

Oladele,

Kennedy

et al. 2023

The Ocular Surface

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The 2023 Doyne Lecture—a cornea care system: evolution

Rao

2024

Eye

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Blindness and visual impairment affect the quality of life of the individual and their family members. Corneal opacities are a key cause of vision loss around the world, especially in low-income and middle-income countries (LMIC). Corneal blindness and vision loss impacts every age group, and the risk factors and the causes are also varied. Socio-economic factors also play a significant role in its prevalence. Preventing, treating, and managing corneal conditions in LMIC contexts can therefore be quite complex and challenging. A model of eye care delivery developed and refined over the past four decades, the L V Prasad Eye Institute’s cornea care system presents an example and a sense of hope. The model takes corneal care from world-class facilities in urban locations to rural locations, overcoming a variety of challenges. The initial breakthrough came with solving and ensuring a steady supply of corneal tissue. Then to training high-quality resources, building capacity, and investing in research that translates from the bench to the bedside. A variety of innovations, both in diagnosis and the operating theatre, have paved for improved outcomes that are tailored for the contexts in which this system operates. The institute envisions a future where its work further narrows the gap in eye care disparities and leads to life-changing impact in ophthalmic care of the cornea.

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Sensitivity and specificity of potassium hydroxide and calcofluor white stain to differentiate between fungal and Pythium filaments in corneal scrapings from patients of Pythium keratitis

Cited by 19 publications

References 21 publications

Pythium insidiosum Keratitis: Past, Present, and Future

Pythium insidiosum Keratitis: Past, Present, and Future

Diagnostic capacity for fungal keratitis in Africa – Survey in 50 African countries

The 2023 Doyne Lecture—a cornea care system: evolution

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