Evaluation of quantitative real-time PCR and Platelia galactomannan assays for the diagnosis of disseminated Talaromyces marneffei infection.

Talaromyces (Penicillium) marneffei is an emerging pathogen that causes significant morbidity and mortality in immunocompromised patients in endemic regions such as southeast Asia. The diagnosis of disseminated T. marneffei infection remains challenging in clinical practice. In the study, a well-validated real-time quantitative polymerase chain reaction (qPCR) target region of ITS1-5.8S-ITS2 and a Platelia galactomannan (GM) assay were compared for their diagnostic performance using serum samples from patients with or without human immunodeficiency virus (HIV). The results showed that this novel qPCR method is highly sensitive and specific for T. marneffei DNA detection in serum samples, and the limit of detection and species-specificity of qPCR were five copies of DNA and 100%, respectively. For detection in serum samples from 36 talaromycosis patients, the sensitivity of qPCR was 86.11% (31/36), including 20/20 (100%) patients with fungemia and 11/16 (68.75%) patients without fungemia. For the GM assay, the sensitivity was 80.56% (29/36) when the GM optical density cutoff index was ≥0.5, including 19/20 (95%) patients with fungemia and 10/16 (62.5%) patients without fungemia. These results indicate that the novel qPCR and GM assays can be used as a valuable tool in the diagnosis of T. marneffei infection. Serum samples are convenient hematological specimens for T. marneffei DNA quantification. Combining the GM assay and qPCR is more scientific and appropriate for diagnosing T. marneffei infection in endemic areas.

Calcineurin A Is Essential in the Regulation of Asexual Development, Stress Responses and Pathogenesis in Talaromyces marneffei.

Talaromyces marneffei is a common cause of infection in immunocompromised patients in Southeast Asia and Southern China. The pathogenicity of T. marneffei depends on the ability of the fungus to survive the cytotoxic processes of the host immune system and grow inside host macrophages. These mechanisms that allow T. marneffei to survive macrophage-induced death are poorly understood. In this study, we examined the role of a calcineurin homolog (cnaA) from T. marneffei during growth, morphogenesis and infection. Deletion of the cnaA gene in T. marneffei resulted in a strain with significant defects in conidiation, germination, morphogenesis, cell wall integrity, and resistance to various stressors. The ΔcnaA mutant showed a lower minimal inhibitory concentration (MIC) against caspofungin (16 µg/ml to 2 µg/ml) and micafungin (from 32 µg/ml to 4 µg/ml) compared with the wild-type. These results suggest that targeting calcineurin in combination with echinocandin treatment may be effective for life-threatening systemic T. marneffei infection. Importantly, the cnaA mutant was incapable of adapting to the macrophage environment in vitro and displayed virulence defects in a mouse model of invasive talaromycosis. For the first time, a role has been shown for cnaA in the morphology and pathogenicity of a dimorphic pathogenic filamentous fungus.