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Phialemonium Curvatum

Phialemonium curvatum is a pathogenic fungus which is part of the Ascomycota phylum and the Phialemonium genus. The philemonium genus was created to account for the difference between the Acremonium and Phialophora. This genus is characterized by its abundance of adelophialides and few discrete phialides with no signs of collarettes. Specifically P. curvatum, is characterized by its grayish white colonies and its allantoid conidia. P. curvatum is typically found in molds however, isolets have been found in a variety of environments including: air, soil, industrial water and sewage. Furthermore, P. curvatum affects mainly immunocomprimised and is rarely seen in immunocompetent patients. P. curvatum has been known to cause peritonitis, endocarditis , endovascular infections , osteomyelitis as well as cutaneous infections of wounds and burns.

Description and Identification:
P. curvatum was first described by W. Gans et McGinnis in 1983. It is often described as being phaeoid although it lacks any form of dark pigmentation. By incubating a sample of P. curvatum at 23-24 °C for one week in a Sabouraub agar, it is possible for a colony of P. curvatum to form. The colony’s appearance is flat and glabrous with a white turning yellowish-gray colouration and yellow pigment surrounding the colony. Furthermore, the conidia of P. curvatum can be described as being uniformly cylindrical to allantoid with their length ranging from 3.5- 6.0 μm and their width varying from 1.0 to 1.4 μm. A key feature of P. curvatum is that its condia have no signs of chlamydoconidia which is key in distinguishing between P. curvatum and P. obovatum. As well, the conidiophores of P. curvatum contain phialides with little or no collarettes with their dimensions varying from 1-7μm in length and 0.5-1.0μm in width. The range in temperature in which P. curvatum can vary between 10 and 36 °C. Another way of identifying P. curvatum is through the use of PCR and DNA sequencing of the ITS. By incubating a suspected culture in a GEPD medium at 30°C, a culture can be grown to allow for the isolation and extraction of genomic DNA. Then through the use ITS1 primers and ITS4, the samples can be amplified, sequenced and analyzed to allow for the identification of P. curvatum.

Arthritis:
Case studies have shown that P. curvatum is capable of causing arthritis. The source of the infection has often been traced to a penile or intra-articular injection of a corticosteroid. The course of treatment has been to prescribe the patient with amphotericin B and voriconazole.

Endocarditis:
P. curvatum rarely causes heart infections, however immunosuppressed patients are far more likely to become infected due to their lower immune function. Endocarditis is an infection of the heart valves and P. curvatum has been linked to this infection through penile injections or through the transplantation of a prosthetic aortic valve. In the case of endocarditis, P. curvatum forms a mass on the heart valve which if left untreated can lead to the impairment of the heart valve and in turn cause a brain infract and consequently death. The key to treating endocarditis caused by P. curvatum is to treat the patient as soon as possible with antifungal medications such as amphotericin B and vorioconazole.

Endophthalmitis:
P. curvatum has been found to be capable of causing endopthalmitis particularly in immune compromised patients. Endophthalmitis is an inflammatory response typically due to an infection of the intraocular cavities. In reference specifically to P. curvatum, hypopyon (an accumulation of pus) as well as virtreous opacities are visible in patients with endophthalmitis. Reported sources of infection can include self intracavernous injections to treat erectile dysfunction as well as phacoemulsification. Histological findings documented in the case study by Weinberger et al. include: necrotizing granulomata, chronic lymphocytic infiltration and fine septate hyphae. Treatment options vary depending on the severity of the infection however treatment usually consists of antifungal medication such as amphotericin B. Furthermore, the patient may undergo a cataract extraction (if present) and a pars plana vitrectomy. If the patient remains unresponsive to the treatment, then enucleation of the infected eye may be necessary.

Peritonitis:
P. curvatum has been known to peritonitis, which is a phaeohyphomycosis affecting the peritoneal cavity, and is responsible for 1-10% of infections in patients undergoing peritoneal dialysis. , This type of phaehophomycosis is associated with a high morbidity and mortality rate. To treat patients with this type of infection, they are put on antifungal medications such as: amphotericin B, ketoconazole, flucytosine and fluconazole until repeeated peritoneal fluid cultures show no fungal growth.

Subcutaneous infection:
The subcutaneous infection caused by P. curvatum commences by forming a small cyst, less than one centimeter in diameter, which is not normally fixed to the skin. As the mass enlarges, the middle of the cyst is filled with purulent material containing most of the fungal hyphae (some hyphae may also be present on the wall of the cyst). As the cyst continues to grow, the mass becomes more dense and can eventually ulcerate. This type of granulomatous infection caused by P. curvatum is characterized by the presence of a number of Langhan-type giant cells, fibroblasts, macrophages surrounded by lymphocytes, as well as a decrease in the number of polymorphonuclear leukocytes. At the centre of the granulomata, it is also possible to identify microabsecesses, collagen tissue as well as necrotic debris caused by the fungal hyphae. The typical course of treatment is to surgically remove the cyst and may include antifungal medications.

Other infections:
P. curvatum, has also been found to affect patients undergoing hemodialysis which caused an endovascular infection. One of the claimed sources of contamination was found to be contaminated water while other sources may have been due to grafts renal and bone marrow transplants. There was also a report of P. curvatum affecting the lower spine and respiratory and causing an abscess with purulent material in the middle. The course of treatment included antifungal medication such amphotericin B, flucytosine, fluconazole, itraconazole, variconzale and caspofungin as well as removal of the cyst.