Pseudallescheria boydii

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Pseudallescheria boydii
Crushed
dextrinoid
reaction of ascospores
Scientific classification
Kingdom:
Fungi
Division:
Ascomycota
Class:
Sordariomycetes
Order:
Microascales
Family:
Microascaceae
Genus:
Pseudallescheria
Species:
P. boydii
Binomial name
Pseudallescheria boydii
(Shear) McGinnis, A.A.Padhye & Ajello (1982)
Synonyms[1]
  • Allescheria boydii Shear (1922)
  • Petriellidium boydii (Shear) Malloch (1970)
  • Verticillium graphii Harz & Bezold (1889)
  • Sporocybe chartoikoon Beij. (1913)
  • Acladium castellanii Pinoy (1916)
  • Pseudallescheria shearii Negroni & I.Fisch. (1944)
  • Scedosporium boydii

Pseudallescheria boydii is a species of

antifungal agents normally used to treat infections by filamentous fungi.[4]

Fungal pneumonia caused by this mold was the cause of death in three athletes submerged in the Yarkon River after a bridge collapsed during the 1997 Maccabiah Games.[5]

Taxonomy

The fungus was originally

Phytopathologist from Florence.[8] The species was then transferred to the genus Pseudallescheria in 1982 when examination of the type specimens of Petriellidium and Pseudallescheria revealed that they were the same genus.[9]

Ecology

An ability to tolerate minimal aeration and high

oxygen pressure.[10] Growth of P. boydii can be seen in environments where nitrogen-containing compounds are common, usually due to human pollution. Its ability to use natural gas and other volatile organic compounds suggests a capacity for bioremediation.[10]

Growth and morphology

Pseudallescheria boydii is a

L-arabinitol.[16] It cannot assimilate maltose or lactose; however, it is able to assimilate urea, asparagine, potassium nitrate and ammonium nitrate.[10] The optimal temperature for growth is 25 °C (77 °F) and the fungus is generally considered to be mesophilic,[13] although it can grow at higher temperatures (up to 37 °C (99 °F)) as well.[10] Asexual reproduction manifests in one of two forms: the Scedosporium type (the most common type) and the Graphium type. Scedosporium apiospermum forms greyish-white colonies with a grey-black reverse. The conidia are single-celled, pale brown and oval in form. Their size ranges from 4–9 x 6–10 μm and their development is annellidic.[15]

Pathogenicity

Pseudallescheria boydii is an emerging

pseudallescheriasis, which includes all other forms of the disease commonly presented in the central nervous system, lungs, joints and bone.[18] The former can also be distinguished by the presence of sclerotia, or granules, which are typically absent in pseudallescheriasis-type infections.[15] Infection is initiated via inhalation or traumatic implantation in the skin.[18] Infection can lead to arthritis,[11] otitis,[11] endocarditis,[11] sinusitis, and other manifestations.[11] Masses of hyphae can form "fungus balls" in the lungs.[11] While "fungus balls" can also form in other organs, they are commonly derived from host necrotic tissue resulting from nodular infarction and thrombosis of lung vessels following infection.[10]

This species is second in prevalence after

lymphopenia, steroid treatment, serum albumin levels of < 3 mg/dL and neutropenia.[22]

Diagnosis

Detection and diagnosis of S. apiospermum is possible through isolation of the fungus in culture or through cytology and histopathology in the tissues of diseased individuals.

H&E, periodic acid–Schiff stain, Tissue Gram or Grocott's methenamine silver stain.[10] A radiological diagnosis may be helpful in elucidating the extent of the disease in terms of bone and soft tissue involvement. Scedosporium-caused eumycetomas have been found to have thick-walled cavities and grains appearing as hyperreflective echoes on scans, while actinomycetomas show fine echoes at the bottom of cavities.[10]

Direct detection is possible in samples histochemically stained in 20% KOH followed by fluorescence microscopy with antibody. The characteristic shape, texture and colour of tissues can help identify S. apiospermum grains, which are often surrounded by an eosinophilic zone.[10] Histopathologically, hyalohyphomycotic fungi like Scedosporium spp., Aspergillus spp., Fusarium spp. and Petriella spp. are similar in that they show septation of hyphae at regular intervals, have dichotomous branching and invade blood vessels. However, Scedosporium presents more irregular branching, sometimes with terminal or intercalary chlamydospores.[10] In serum, Scedosporium infections can be detected by counterimmunoelectrophoresis.[23] Molecular diagnostics appear to be promising in complementing current conventional diagnostic methods.[10]

Culture detection is accomplished by rinsing "grains" in 70% ethanol and sterile saline solution to avoid bacterial contamination prior to inoculation on growth medium. Selection of Scedosporium growth can be achieved on Leonian's agar supplemented with 10 g/mL benomyl, or on media containing cycloheximide or amphotericin B.[10] Optimal incubation is at a temperature of 25–35 °C (77–95 °F).[10]

Treatment

Pseudallescheria boydii is resistant to amphotericin B[18] and nearly all other antifungal drugs. Consequently, there is currently no consistently effective antifungal therapy for this agent.[18] Miconazole has shown the best in vivo activity; however, itraconazole, fluconazole, ketoconazole and voriconazole have also been used in treatment, albeit with less success.[15][20] In an in vitro environment, terbinafine has been found to work in synergy with azoles against P. boydii. Echinocandins, such as caspofungin and sordarins, have shown promise in in vitro assays. CMT-3, a chemically modified tetracycline, has also shown to be active in vitro against P. boydii.[13]

Epidemiology

In the United States, P. boydii is the most common causal agent of eumycetoma, and tends to be more common in men than in women, particularly in the 20- to 45-year-old age group.[10] In the United States, the incidence of infection by S. apiospermum between 1993 and 1998 was 0.82 per 100,000 patient-inpatient days; this figure increased to 1.33 per 100,000 patient-inpatient days by 2005.[10] In Thailand, 18 people died of the fungus between 1953 and 2004 [2].

Society and culture

Pseudallescheria boydii infection was implicated in the deaths of three athletes injured during the opening ceremony of the 1997 Maccabiah Games when the Maccabiah bridge collapsed in the Yarkon River.[5]

In 2003, Thai singer Apichet Kittikorncharoen suffered brain infection with Pseudallescheria boydii after a car accident in which he fell in a canal in Bangkok, Thailand. This event has sparked a public outcry over pollution in Bangkok's canals [2].

References

  1. ^ "Pseudallescheria boydii (Shear) McGinnis, A.A. Padhye & Ajello, Mycotaxon 14 (1): 97 (1982)". MycoBank. International Mycological Association. Retrieved 2014-11-23.
  2. ^ a b c Pseudallescheria at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
  3. PMID 18581978
    . Retrieved 2024-02-11.
  4. PMID 19058049
    .
  5. ^
    ISBN 978-0-520-23428-4
    .
  6. JSTOR 3753469
    .
  7. JSTOR 3757662
    .
  8. S2CID 246307410
    . Retrieved January 27, 2022.
  9. ^ McGinnis, M.R.; Padhye, A.A.; Ajello, L. (1982). "Pseudallescheria Negroni et Fischer, 1943 and its later synonym Petrielldium Malloch, 1970". Mycotaxon. 14 (1): 94–102.
  10. ^
    PMID 18202441
    .
  11. ^
    ISBN 978-90-70351-43-4
    .
  12. ISBN 978-0792389354
    .
  13. ^ a b c d e Patterson, Thomas F.; McGinnis, Michael R. "Pseudallescheria spp". www. doctorfungus.org. Archived from the original on 28 October 2014. Retrieved 28 October 2014.
  14. PMID 16207945
    .
  15. ^
    ISBN 9781437727029
    .
  16. ^
    S2CID 22605873
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  17. PMID 22507831
    .
  18. ^
    ISBN 978-0-443-07593-3
    .
  19. PMID 2181980
    .
  20. ^
    PMID 9356805
    .
  21. ISBN 978-0721624440
    .
  22. ^ Ajello, L.; Hay, R. J. (1997). Medical Mycology Vol 4 Topley & Wilson's Microbiology and Infectious Infections (9th ed.). London: Arnold.
  23. PMID 19321690
    .
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