Talaromyces marneffei
 | This article needs additional citations for verification. (September 2014) |
| Talaromyces marneffei | |
|---|---|
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Eurotiomycetes |
| Order: | Eurotiales |
| Family: | Trichocomaceae |
| Genus: | Talaromyces |
| Species: | T. marneffei
|
| Binomial name | |
| Talaromyces marneffei Segretain[citation needed]
| |
Talaromyces marneffei, formerly called Penicillium marneffei,
When it was classified as a Penicillium, it was the only known
Epidemiology
There is a high incidence of
Discovered in
Although both the
Talaromyces marneffei has been found in bamboo rat
One study of 550 AIDS patients showed that the incidence was higher during the
Another study could not establish contact with bamboo rats as a risk factor, but exposure to the soil was the critical risk factor. However, soil samples failed to yield much of the fungus.
It is not known whether people get the disease by eating infected rats, or by inhaling fungi from their faeces.
One HIV-positive physician is known to have been infected while attending a course on tropical
Clinical presentation
Patients commonly present with symptoms and signs of infection of the reticuloendothelial system, including generalized lymphadenopathy, hepatomegaly, and splenomegaly. The respiratory system is commonly involved as well; cough, fever, dyspnea, and chest pain may be present, reflecting the probable inhalational route of acquisition. Approximately one-third of patients may also exhibit gastrointestinal symptoms, such as diarrhea.[7][8][9]
Laboratory diagnosis
The fact that Talaromyces marneffei is thermally dimorphic is a relevant clue when trying to identify it. However, it should be kept in mind that other
Plating samples out onto two Sabouraud agar plates, then incubating one at 30 °C and the other at 37 °C, should result in two different morphologies. A mold-form will grow at 30 °C, and a yeast-form at 37 °C.
Mycelial colonies will be visible on the 30 °C plate after two days. Growth is initially fluffy and white and eventually turns green and granular after sporulation has occurred. A soluble red pigment is produced, which diffuses into the agar, causing the reverse side of the plate to appear red or pink. The periphery of the mold may appear orange-coloured, and radial sulcate folds will develop.
Under the microscope, the mold phase will look like a typical
On the 37 °C plate, the colonies grow as yeasts. These colonies can be cerebriform, convoluted, or smooth. There is a decreased production in pigment, the colonies appearing cream/light-tan/light-pink in colour. Microscopically, sausage-shaped cells are mixed with hyphae-like structures. As the culture ages, segments begin to form. The cells divide by
The patient's history also is a diagnostic help. If they have traveled to Southeast Asia and are HIV-positive, then there is an increased risk of them having talaromycosis.
Treatment
Treatment of talaromycosis depends on the degree of immunosuppression and organ involvement, but most isolates of Talaromyces marneffei display low MIC's to amphotericin B as well as itraconazole, posaconazole and voriconazole.[10]
Research
Genomics
Sexual reproduction
T. marneffei had been assumed to reproduce exclusively by asexual means based on the highly clonal population structure of this species. However, studies by Henk et al.[11] (2012) revealed that the genes required for meiosis are present in T. marneffei. In addition, they obtained evidence for mating and genetic recombination in this species. Henk et al.[11] concluded that T. marneffei is sexually reproducing, but recombination in natural populations is most likely to occur across spatially and genetically limited distances resulting in a highly clonal population structure. It appears that sex can be maintained in this species even though very little genetic variability is produced.
Mycovirology
The study by Lau et al [12] (2018) described the first evidence of a mycovirus in a thermally dimorphic fungus. Talaromyces marneffei partitivirus-1 (TmPV1), a dsRNA mycovirus, was detected in 12.7% (7 out of 55) of clinical T. marneffei isolates. Phylogenetic analysis showed that TmPV1 occupied a distinct clade among the members of the genus Gammapartitivirus. Two virus-free isolates were successfully infected by purified TmPV1 using protoplast transfection. Mice challenged with TmPV1-infected T. marneffei isolates showed significantly shortened survival time and higher fungal burden in organs than mice challenged with isogenic TmPV1-free isolates. Transcriptomic analysis showed that TmPV1 causes aberrant expression of various genes in T. marneffei, with upregulation of potential virulence factors and suppression of RNA interference (RNAi)-related genes.
MicroRNA-like RNAs
Talaromyces marneffei dicer-dependent microRNA-like RNAs (milRNAs) were identified and these milRNAs were found to be differentially expressed in different growth phases of T. marneffei. Furthermore, the phylogeny of RNAi genes of T. marneffei were also described in the same study.[13] Phylogenetic analysis of both ITS and dcl-1 gene showed that the corresponding sequences in T. marneffei were most closely related to Penicillium emmonsii, Penicillium chrysogenum and Aspergillus spp. However, phylogenetic analysis of dcl-2 and qde-2 genes showed a different evolutionary topology. The dcl-2 of T. marneffei and its homologue in T. stipitatus are more closely related to those of the thermal dimorphic pathogenic fungi, Histoplasma capsulatum, Blastomyces dermatitidis, Paracoccidioides brasiliensis and Coccidioides immitis than to P. chrysogenum and Aspergillus spp., suggesting the co-evolution of dcl-2 among the thermal dimorphic fungi. On the other hand, qde-2 of T. marneffei is most closely related to its homologues in other thermal dimorphic fungi than to that in T. stipitatus, P. chrysogenum and Aspergillus spp.
References
- PMID 26956447.
- S2CID 53248512.
- S2CID 26045334.
- PMID 29621346.
- PMID 10897365.
- ^ Capponi M, Segretain G, Sureau P (1956). "Pénicillose de Rhizomys sinensis". Bull Soc Pathol Exot. 49 (3): 418–21. Archived from the original on 2020-03-28. Retrieved 2017-09-08.
- PMID 8000744.
- PMID 8816141.
- S2CID 38451183.
- ^ "Talaromyces marneffei". Mycology Online. The University of Adelaide. Archived from the original on 5 November 2019. Retrieved 5 November 2019.
- ^ PMID 23055919.
- PMID 29895639..
Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License - PMID 23991243.
Further reading
- Vanittanakom N, Cooper CR, Fisher MC, Sirisanthana T (January 2006). "Penicillium marneffei infection and recent advances in the epidemiology and molecular biology aspects". Clinical Microbiology Reviews. 19 (1): 95–110. PMID 16418525.