What are the common pathogenic fungal tests used in microbiology rooms

1, fungal microscopy

is the simplest and valuable laboratory diagnostic method. Its advantage lies in the simplicity, rapidity, and the positive result of the sterile site can directly determine the fungal infection. However, due to the low rate of positivity, a negative result cannot exclude the diagnosis. Direct microscopy is most helpful for superficial and subcutaneous fungal infections. The presence of S. dermatitidis, Candida, and Malassezia components in skin scrapings, hair, or nail specimens provides a reliable diagnosis of the corresponding fungal disease. The diagnosis of deep-seated fungal disease can often be established by direct microscopic examination of sterile body fluids, e.g., detection of Cryptococcus neoformans yeast cells with podocytes in cerebrospinal fluid or Histoplasma capsulatum cells in peripheral blood smears. However, in general, in the fungus site is only found in a large number of fungal mycelium is meaningful, through direct microscopic examination can generally distinguish between Candida, Cryptococcus, dark fungi, Trichoderma (splicing) and other fungal infections, and further clarification of the identification of strains need to be identified through the culture of the identification of the completion.

2, fungal culture

Fungal culture is an important part of the laboratory examination, the culture of pathogenic fungi is a prerequisite for the further identification of strains. The first step of fungal culture is to cultivate the primary culture of fungi from clinical specimens, and after the primary culture, further isolation and purification culture and identification culture are carried out. The culture medium, incubation time and temperature used for each step of the culture of different pathogenic fungi are somewhat different. Conventional fungal culture requires 3-4 weeks of incubation at 28-30°C. Generally, SDA or PDA is used for primary culture, and two tubes are used for culture, one of which can be supplemented with antibiotics (chloramphenicol or gentamicin is acceptable). During 1 week of incubation, it should be observed daily for fungal growth. Generally, after 4 weeks of incubation, if there is no fungal growth, it can be reported as negative. If fungi are found in the culture, pick a small amount of organisms directly or after a small culture, use lactophenol cotton wool to make a smear for microscopic observation, combined with the colony's general morphology, the typical species can be reported directly to the species. Atypical strains of bacteria according to the basic performance, the use of appropriate standard identification medium, standard culture conditions, if necessary, combined with physiology and molecular biology methods for identification.

3, fungal identification

The identification of common pathogenic fungi to master the principle of identification is the first distinction between yeast and mold.

If yeast-like colonies are cultured on the primary medium, they should be isolated and purified before identification. After removing bacterial and other fungal contamination and distinguishing mixed infections, pure colonies are identified. Yeast identification is based on morphological and physiological characteristics, and is carried out according to a certain procedure. First, colonies are classified according to their color. The most common clinical colonies are white or creamy white colonies, which are further identified by the germ tube test, if the germ tube test is positive, then Candida albicans, if negative, then by the morphological characteristics of the culture on Vitek YBC or API20C and corn tween agar. In addition, tests such as Candida chromogenic agar and urease test can be applied to aid in identification.

TestZone.com

The identification of mycobacteria is very complex, with a number of criteria including morphological features, temperature tolerance, actinomycin resistance, biphasicity, nutritional requirements, proteolytic activity, and the ability to hydrolyze urea. Modern taxonomic identification is based on the process of individual conidiation in combination with other characteristics. After the primary culture, according to the morphological characteristics can be generally identified to the level of the genus, and then according to the identification requirements of different fungi, the use of standard media and culture conditions to further complete the identification of strains. For example: Aspergillus genus identification requires the use of standard media, that is, the Cha's medium and malt agar, 25 ℃ culture for 7 days with Aspergillus morphology identification of the retrieval table corresponds to get the correct results.