Human Infectious Corneal Ulcer Caused by Pythium Insidiosum

Perry, Henry D.; Pardanani, Bhagwati; Szabo, Katarina; Rahn, Elsa K.; Stone, John H.; Salkin, Ira F.; Dixon, Dennis R.

doi:10.1097/00003226-199301000-00015

Cited by 60 publications

(40 citation statements)

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“…Several cases of human pythiosis (nearly 80% of the total global cases) have been reported in Thailand. The disease has also been reported in other countries, such as Australia (31), New Zealand (22), the United States (10,19,27), Haiti (32), and Malaysia (3). The source of infection and the mode of transmission of the disease are still unknown.…”

Section: Discussionmentioning

confidence: 79%

Identification of Emerging Human-Pathogenic Pythium insidiosum by Serological and Molecular Assay-Based Methods

Vanittanakom¹,

Supabandhu²,

Khamwan

et al. 2004

J Clin Microbiol

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Pythium insidiosum is a pathogen that causes disease in both animals and humans. Human infection is rare; however, when it does occur, most patients, especially those having underlying hemoglobinopathy syndromes, such as thalassemia, exhibit a severe form. We identified four isolates of P. insidiosum. Two were recovered from tissue biopsy specimens from thalassemic and leukemic patients, one was derived from brain tissue from a thalassemic patient, and another was isolated from a corneal ulcer from a fourth patient. Western blotting and an enzyme-linked immunosorbent assay (ELISA) were performed with a serum sample derived from one thalassemic patient. The methods used to identify the P. insidiosum isolates were based on morphology, nucleic acid sequencing, and a PCR assay. To confirm the identification, portions of the 18S rRNA genes of these four isolates were sequenced. The sequences were shown to be homologous to previously described P. insidiosum DNA sequences. In addition, PCR amplification of the internal transcribed spacer region specific for P. insidiosum was positive for all four isolates. The ELISA with the serum sample from the thalassemic patient gave a positive result from a serum dilution of 1:800. Finally, Western immunoblotting with this serum sample showed positive immunoglobulin G recognition for proteins of 110, 73, 56, 42 to 35, 30 to 28, 26, and 23 kDa. The results of this study show that both molecularly based diagnostic and serodiagnostic techniques are useful for the rapid identification of human pythiosis. The predominant antigens recognized by Western blotting may be useful in the development of a more sensitive and specific diagnostic tool for this disease.

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Section: Discussionmentioning

confidence: 79%

Identification of Emerging Human-Pathogenic Pythium insidiosum by Serological and Molecular Assay-Based Methods

Vanittanakom¹,

Supabandhu²,

Khamwan

et al. 2004

J Clin Microbiol

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“…6,10,25 For this reason, isolates of P. insidiosum have traditionally been identified as such on the basis of morphologic hyphal characteristics (broad, hyaline, rarely septate hyphae that are 4-10 m in diameter and branch at right angles), growth at 37 C, and production of motile biflagellate zoospores (asexual reproductive structures) in water cultures in association with plant material. 1,6,28,41 However, although the production of biflagellate zoospores is helpful in identifying isolates as oomycetes in the order Peronosporales, this characteristic is shared by other Pythium species 13,17 as well as by members of the genera Phytophthora 7 and Lagenidium 2,9 and thus is not specific for P. insidiosum. 1 Because of the difficulties associated with the identification of P. insidiosum based on morphologic features alone, supplemental techniques based on antigenic and molecular characteristics have been developed.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of Microbial Culture Techniques for the Isolation of Pythium Insidiosum from Equine Tissues

et al. 2002

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Abstract. The purpose of this study was to evaluate the effects of sample handling, storage, and culture techniques on the isolation of Pythium insidiosum from infected equine tissues. Tissue and kunker samples obtained immediately posteuthanasia from a horse with subcutaneous pythiosis were used to assess the effects of sample type (kunkers vs. tissues), media type (selective vs. nonselective), storage technique, and storage time on P. insidiosum isolation rate. Overall, isolation rates were higher from fresh kunkers (94.6%) and stored kunkers (76.4%) than from fresh tissues (8.3%) or stored tissues (4.6%). Isolation of P. insidiosum also occurred more often on antibiotic-containing media than on nonselective media for both fresh and stored samples. For samples that were stored for 1-3 days prior to culture, P. insidiosum isolation rates were highest for the following techniques: kunkers stored at room temperature and plated on selective media (100%), kunkers stored at 4 C and then plated on either nonselective (91.7%) or selective (95.8%) media, kunkers stored on cold packs and then plated on either nonselective (93.8%) or selective (100%) media, kunkers stored in ampicillin solution and plated on selective media (100%), and kunkers stored in ampicillin/gentocin solution and plated on selective media (87.5%). For samples stored for 4-5 days, P. insidiosum isolation rates were highest for kunkers stored at 4 C and then plated on either nonselective (81.3%) or selective (87.5%) media, kunkers stored in ampicillin solution and then plated on selective media (87.5%), and kunkers stored in ampicillin/gentocin solution and plated on selective media (87.5%). Results of this study suggest that optimal isolation rates of P. insidiosum from infected equine tissues are achieved by culturing fresh kunkers on selective media. For samples that cannot be processed immediately, acceptable handling techniques include storage at room temperature for up to 3 days, refrigeration for up to 5 days, shipping on cold packs, and storage in antibiotic solution, each combined with subsequent inoculation on selective media.

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“…In Thailand, this organism causes subcutaneous lesions and chronic inflammation and occlusion of blood vessels (especially of the lower extremities) in thalassemic and nonthalassemic patients (381). Keratitis due to P. insidiosum has been noted in tropical (22,155,244,411) and temperate (260) regions. Two particularly aggressive cases of orbital cellulitis with deep facial tissue involvement have occurred in the United States (244).…”

Section: Rhinosporidium Seeberimentioning

confidence: 99%

Current Perspectives on Ophthalmic Mycoses

2003

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Fungi may infect the cornea, orbit and other ocular structures. Species of Fusarium, Aspergillus, Candida, dematiaceous fungi, and Scedosporium predominate. Diagnosis is aided by recognition of typical clinical features and by direct microscopic detection of fungi in scrapes, biopsy specimens, and other samples. Culture confirms the diagnosis. Histopathological, immunohistochemical, or DNA-based tests may also be needed. Pathogenesis involves agent (invasiveness, toxigenicity) and host factors. Specific antifungal therapy is instituted as soon as the diagnosis is made. Amphotericin B by various routes is the mainstay of treatment for life-threatening and severe ophthalmic mycoses. Topical natamycin is usually the first choice for filamentous fungal keratitis, and topical amphotericin B is the first choice for yeast keratitis. Increasingly, the triazoles itraconazole and fluconazole are being evaluated as therapeutic options in ophthalmic mycoses. Medical therapy alone does not usually suffice for invasive fungal orbital infections, scleritis, and keratitis due to Fusarium spp., Lasiodiplodia theobromae, and Pythium insidiosum. Surgical debridement is essential in orbital infections, while various surgical procedures may be required for other infections not responding to medical therapy. Corticosteroids are contraindicated in most ophthalmic mycoses; therefore, other methods are being sought to control inflammatory tissue damage. Fungal infections following ophthalmic surgical procedures, in patients with AIDS, and due to use of various ocular biomaterials are unique subsets of ophthalmic mycoses. Future research needs to focus on the development of rapid, species-specific diagnostic aids, broad-spectrum fungicidal compounds that are active by various routes, and therapeutic modalities which curtail the harmful effects of fungus- and host tissue-derived factors

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Human Infectious Corneal Ulcer Caused by Pythium Insidiosum

Cited by 60 publications

References 0 publications

Identification of Emerging Human-Pathogenic Pythium insidiosum by Serological and Molecular Assay-Based Methods

Identification of Emerging Human-Pathogenic Pythium insidiosum by Serological and Molecular Assay-Based Methods

Evaluation of Microbial Culture Techniques for the Isolation of Pythium Insidiosum from Equine Tissues

Current Perspectives on Ophthalmic Mycoses

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