Pseudohyphae

Detailed article on Pseudohyphae in medical mycology

Pseudohyphae are a type of cellular structure found in certain fungi, particularly in the yeast form of Candida species. They are characterized by elongated cells that remain attached after cell division, forming a chain-like structure. Pseudohyphae are an important morphological feature that can be observed in the laboratory and are often associated with the pathogenicity of certain fungi.

Structure and Formation

Pseudohyphae are formed when yeast cells undergo a process of elongation and remain attached to each other. Unlike true hyphae, which are found in molds and are characterized by continuous cytoplasm and septa, pseudohyphae consist of individual yeast cells that are elongated and connected end-to-end. The formation of pseudohyphae is often triggered by environmental conditions such as nutrient limitation or changes in temperature and pH.

Comparison with True Hyphae

While both pseudohyphae and true hyphae are filamentous structures, they differ in several key aspects:

• Cellular Structure: True hyphae have septa with pores that allow cytoplasmic streaming, whereas pseudohyphae consist of individual cells with constrictions at the septa.
• Growth Pattern: True hyphae grow by apical extension, while pseudohyphae grow by budding and elongation of yeast cells.
• Function: True hyphae are primarily involved in nutrient absorption and growth, whereas pseudohyphae are often associated with pathogenicity and tissue invasion.

Role in Pathogenicity

Pseudohyphae play a significant role in the pathogenicity of certain fungi, particularly in Candida albicans, a common opportunistic pathogen. The ability to switch between yeast and pseudohyphal forms is known as dimorphism, and it is a key virulence factor. Pseudohyphae can penetrate host tissues more effectively than yeast cells, facilitating invasion and infection.

Laboratory Identification

In the laboratory, pseudohyphae can be identified using various staining techniques and microscopy. Common methods include:

• Gram Stain: Pseudohyphae appear as elongated, Gram-positive structures.
• Calcofluor White Stain: This fluorescent stain binds to chitin in the cell walls, highlighting the pseudohyphal structure under a fluorescence microscope.
• Culture on Cornmeal Agar: This medium promotes the formation of pseudohyphae, allowing for easy observation.

Clinical Significance

The presence of pseudohyphae in clinical specimens, such as vaginal swabs or blood cultures, can indicate a fungal infection, particularly with Candida species. It is important for clinicians to recognize and differentiate pseudohyphae from other fungal structures to ensure accurate diagnosis and treatment.

Also see

• Candida albicans
• Hypha
• Yeast
• Fungal morphology
• Dimorphism (mycology)