Ann Clin Microbiol.  2024 Dec;27(4):271-277. 10.5145/ACM.2024.27.4.7.

Cutaneous infection caused by Prototheca wickerhamii identified using VITEK MS following pretreatment with a moldextraction protocol: a case report

• Shin DH
• Kim J
• Lee WG

• KMID: 2566093
• DOI: http://doi.org/10.5145/ACM.2024.27.4.7

Abstract

Prototheca wickerhamii is an achlorophyllic algae that rarely acts as an opportunistic pathogen in humans. We report the case of a 66-year-old female patient with a history of diabetes mellitus who presented with a pus-like discharge from face, facial redness, and swelling. The patient was admitted to the emergency room with worsening facial pain. Gram staining from pus-like discharge revealed yeast like features; however, an isolated colony on a blood agar plate was not identified using VITEK 2 (Biomerieux) or matrix-assisted laser desorption/ionization time-of flight mass spectrometry (MALDI-TOF) using VITEK MS (Biomerieux). Lactophenol cotton blue staining of the colony revealed characteristic sporangia and endospore features. After performing the protein extraction procedure for filamentous fungi (mold) isolates using ethanol and formic acid, MALDI-TOF MS identified the colony as Prototheca wickerhamii, with 99.9% confidence. This case indicates that Prototheca spp. require specialized sample preparation steps, such as the ethanol/formic acid extraction procedure, for identification using MALDI-TOF MS.

Keyword

Matrix-assisted laser desorption-ionization mass spectrometry; Mycology; Protein; Prototheca

Figure

• 

  Fig. 1. Colony and microscopic morphology of Prototheca wickerhamii. (A) White dry colonies on BAP after 24 hours of incubation at 35⁹ with 5% CO2 . (B) Lactophenol cotton blue stain of P. wickerhamii showing endospore and sporangia features (oil immersion, × 1000 magnification). BAP, blood agar plate.

• 

  Fig. 2. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry Prototheca wickerhamii spectrum. (A) Spectrum of P. wickerhamii after yeast sample preparation with formic acid showing ambiguous identification. (B) Spectrum of P. wickerhamii after mold sample preparation using ethanol/formic acid extraction.

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