TY - JOUR
T1 - Pythium insidiosum Keratitis
T2 - Past, Present, and Future
AU - Gurnani, Bharat
AU - Kaur, Kirandeep
AU - Agarwal, Shweta
AU - Lalgudi, Vaitheeswaran G.
AU - Shekhawat, Nakul S.
AU - Venugopal, Anitha
AU - Tripathy, Koushik
AU - Srinivasan, Bhaskar
AU - Iyer, Geetha
AU - Gubert, Joseph
N1 - Funding Information:
The authors want to thank Dr. Joseph Gubert for providing microbiological images for the article. They also wish to thank Aravind Eye Hospital and Postgraduate Institute of Ophthalmology, Pondicherry, India; Sankara Nethralaya, Chennai; The Ottawa Hospital, University of Ottawa Eye Institute, Ontario, Canada; Wilmer Eye Institute, Johns Hopkins University School of Medicine, United States of America; Aravind Eye Hospital and Postgraduate Institute of Ophthalmology Tirunelveli, Tamil Nadu, India; and ASG Eye Hospital, BT Road, Kolkata, India. No funding or sponsorship was received for this article. All named authors meet the International Committee of Medical Journal Editors (ICMJE) criteria for authorship for this article, take responsibility for the integrity of the work as a whole, and have given their approval for this version to be published. Concept and design: BG, KK, SA; drafting manuscript: BG, KK, SA, NS, VL, AV, KT, GI, BS, JG; critical revision of manuscript: BG, KK, SA, NS, AV, VL, KT; supervision: BG, SA, VL, NS GI, BS. All authors read and approved the final manuscript. Bharat Gurnani, Kirandeep Kaur, Shweta Agarwal, Vaitheeswaran G Lalgudi, Nakul S. Shekhawat, Anitha Venugopal, Koushik Tripathy, Geetha Iyer and Joseph Gubert have nothing to disclose. This review article is based on previously conducted studies. The article does not contain any studies with human participants or animals performed by any of the authors.
Publisher Copyright:
© 2022, The Author(s).
PY - 2022/10
Y1 - 2022/10
N2 - Pythiuminsidiosum (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.
AB - Pythiuminsidiosum (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.
KW - Azithromycin
KW - Keratitis
KW - Leaf incarnation method
KW - Linezolid
KW - Parafungus
KW - Pythiuminsidiosum
KW - Therapeutic keratoplasty
KW - Zoospore
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U2 - 10.1007/s40123-022-00542-7
DO - 10.1007/s40123-022-00542-7
M3 - Review article
C2 - 35788551
AN - SCOPUS:85133508337
SN - 2193-8245
VL - 11
SP - 1629
EP - 1653
JO - Ophthalmology and Therapy
JF - Ophthalmology and Therapy
IS - 5
ER -