Occult Talaromyces marneffei Infection Unveiled by the Novel Mp1p Antigen Detection Assay

Abstract

Talaromyces marneffei causes fatal invasive mycosis in Southeast Asia. Diagnosis by culture has limited sensitivity and can result in treatment delay. We describe the use of a novel Mp1p enzyme immunoassay (EIA) to identify blood culture-negative talaromycosis, subsequently confirmed by bone marrow cultures. This EIA has the potential to speed diagnosis, enabling early therapy initiation.

Keywords: Mp1p EIA; Penicillium marneffei; Talaromyces marneffei; penicilliosis; talaromycosis.

Figure 1.

Wright’s stained smear of the bone marrow aspirate of Patient 1 showing numerous yeast cells measuring 5–6 µm inside an engorged histiocyte. The arrows show the actively dividing yeast cells, revealing a midline septum characteristic of Talaromyces marneffei.

Figure 2.

Talaromyces marneffei subcultures from the bone marrow of Patient 2. At 25°C, T. marneffei produces powdery greenish mold colonies and a bright red pigment that diffuses into Sabouraud Dextrose Agar (SDA) medium. Tape preparation of the mold colonies shows septate hyphae with conidiophores bearing phialides and round conidia under the microscope. At 37°C, T. marneffei produces white yeast colonies on SDA media without the red pigmentation. Microscopic examination shows oval yeast cells, 1 with a central septum (arrow).