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Trichosporon fungus– An emerging opportunistic blood stream infection

Trichosporon fungus– An emerging opportunistic blood stream infection

Trichosporon species are the major emerging opportunistic pathogen in immunocompromised patients. They are known to be inhabitants of soil and may colonize human skin, upper respiratory tract and gastrointestinal tract. Its diverse refractoriness to conventional antifungal drugs and association with high mortality rate is worrisome.

Previously, all pathogenic members of the genus Trichosporon were referred as a single species, T. beigelii.3 Biochemical and morphologic differences within the genus had led to new nomenclature of T. beigelii into 9 distinct species, amongst them Trichosporon asahii is the most common cause of disseminated disease. Phenotypic identification of Trichosporon species usually gives very inconsistent results, so molecular methods are required for accurate identification, but they are still expensive and not suitable for most laboratories.

In the past, amphotericin B was recommended for treatment but the response was poor and the failure rate was high. Even MICs of echinocandins are very high and multiple incidences of breakthrough infections have been reported. Trichosporon species are usually susceptible to azoles thus, treatment should be done using one of these azoles.

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Dr Meera Challapilla and colleagues at PD Hinduja Hospital, Mumbai, Maharashtra conducted a study to determine the risk factors, treatment outcome and antifungal susceptibility pattern of Trichosporon species in bloodstream infections. The Study has appeared in the Journal of Association of Physicians of India.

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The researchers evaluated all patients with blood culture positive for Trichosporon species from January 2012 to August 2016 at PD Hinduja National Hospital and research centre retrospectively. Species identification and antifungal susceptibility by broth microdilution method for various drugs were determined using Vitek2 compact automated system.

They found  12 patients to have Trichosporon bloodstream infection. 9 isolates that were speciated all were T. asahii. All patients had a central venous catheter and received prior antibiotics. The overall mortality rate was 50%.

The researchers concluded that higher mortality was associated with central venous catheter and voriconazole should be used as a drug of choice for treatment. Identification of Trichosporon species along with its sensitivity and proper treatment of patients is of utmost importance.

Trichosporon species is an emerging fungal infection which can be easily misidentified as Candida. But dry wrinkled colonies, LCB mount showing arthroconidia & blastoconidia and positive urease test help in its identification. In our study, the major risk factors for trichoporonosis were used central venous catheters and multiple antibiotics. Hence, strict infection control measures should be followed while handling patients with invasive medical devices. Higher mortality rate was observed because of its refractoriness to conventional antifungal drugs. Voriconazole should be used as drug of choice for treatment.

Figures 1-3 and Tables 1 and 2

Courtesy Journal of Associationof Physicians of India

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