First cases of fungal infections in man from Fereydounia khargensis
June 13 2016
The number of new fungal pathogens is increasing due to a growing population of immunocompromised patients and advanced identification techniques. Fereydounia khargensis is a newly discovered yeast, first isolated in 2014 from plant remnants in Iran. Tap et al. (2015) report the first two cases of fungal infections associated with Fereydounia khargensis in humans.
Patient 1, a 33 year old HIV positive male was admitted to hospital due to episodes of fever associated with chills and rigours lasting 2 weeks. There were no other associated symptoms except weight loss. Chest X-ray did not reveal the cause of the fever. On admission, blood culture was negative; however, after several repeats, it was positive on the 6th day of hospitalisation.
Patient 2, a 59 year-old male with end-stage renal failure, hypertension, diabetes mellitus and hep B, was admitted to hospital after nausea and dizziness prior to a fall at home. On the 6th day of admission, patient 2 demonstrated signs indicative of an infection, including an increased white blood cell count of the peritoneal fluid. After incubation, the Gram stain exhibited a mixed growth of gram-negative bacterium and yeast-like cells.
Fig. 2 LPCB stain of F. khargensis at 9100 magnification showing bipolar budding of blastospores
Isolates from both patients were misidentified by conventional systems as the microscopic characteristics from LPCB staining and slide culture were unfamiliar. Furthermore, the commercial yeast identification systems (API 20C and VITEK 2) were also unable to accurately identify the isolate due to database limitations. Identification was therefore by polymerase chain reaction (PCR) of the internal transcribed space (ITS) and LSU regions in the rRNA gene. This method resulted in a 99.7 and 100% match to the reference strain respectively.
Patient 1 was initially treated with amphotericin B, switching to itraconazole after 7 days due to lack of clinical improvement. Patient 2 was treated with fluconazole and showed clinical improvement after 10 days of treatment. Antifungal treatment is a challenge for patients with unusual yeast infections. Many of the available drugs are associated with serious side effects and some species have developed antifungal resistance. in vitro susceptibility tests of the isolates demonstrated sensitivity to azole agents, but multi-drug resistance against amphotericin B, anidulafungin and caspofungin.
The authors highlight the growing number of new and uncommon disease-causing yeasts and the challenge presented for accurate identification. In addition, the number of resistant species is also increasing, posing challenges for antifungal treatment and patient management. Molecular techniques such as PCR-sequencing may succeed where traditional methods fail.