Characteristics And Varieties Of Culture Media For The Growth Of Fungal Microorganisms

Characteristics and varieties of culture media for the growth of fungal microorganisms

General components of cultivation media

Fungi grow, varying their morphology and physiological behavior according to the nutritional elements that we provide. In general, culture media have solid media agar (being a support element), some carbohydrates as a source of energy (glucose, lactose, others), extracts (meat, brain, heart, liver, others), peptone as Nitrogen source, jet water (which provides minerals) or distilled water, pH indicator, selective agents (antibiotics, antifungals, others) and a damping system. Each culture medium has a unique recipe where an established amount of certain components mentioned above is added and is restricted from others, depending on the end we need.

CULTURE MEDIA CLASSIFICATION

The culture media can be classified in many ways but this time they will be addressed according to their consistency, composition and function, in which they stand out:

According to its consistency:

• Liquids: They are commonly known as broths, they have all components in an aqueous solution.
• Solids: It is prepared by adding grip to the broth, this agar is a substance extracted from algae and is totally inert whose consistency is solid jelly and is not digested by microorganisms.
• SEMISOLIDS: It has a established broth/agency established to obtain this consistency.

According to its composition and function:

• General: They are means designed for the growth of most fungal microorganisms. In mycology the best known is the Sabouraud Dextrose (SDA) agar for its easy preparation, it is used daily and is a basic means for the isolation and growth of fungal agents from clinical samples for future identification.
• Selective: They are means that allow the growth of pathogenic fungi that affect the human being and that are of importance for the study in clinical cases, these are due to the fact that they allow the growth of pathogenic fungal agents and prevent the growth of the majority of environmental fungi and bacteria that have no clinical importance. This is achieved because in their composition they have inhibitory substances such as antibiotics, in the case of antifungics we have the audition and in the cases of antibacterial we have chloramphenicol and gentamicin that are the most used. In this case the known media par excellence and that provides good results is the Micosel Agar.
• Enriching: They are means used for certain microorganisms that require certain additional substrates to develop and grow (these means do not necessarily inhibit the growth of other fungi). Here we have as an example the infusion cerebro heart (BHI) that allows good isolation in the case of fungi causing deep mycosis as is the case with histoplasmosis.
• Differential: These are means that allow differentiating and classify. For example, chromogenic ages for Candid.
• Specials: These are specifically designed for the growth of a genus or kind of fungi. A clear example is the converse medium to obtain the coccidioides spp Levaduriform phase. Because it has unique specifications to obtain the growth of this fungus.
• Homemade media of Borelli: These are means whose form of preparation is based on using “house” nutrients such as carrot, potato, corn, changur, honey, milk, wheat flour, oatmeal and others that are for everyday use. These means are useful because they provide the microorganism with the necessary substrates to favor the sporulation and production of conidia that are part of their morphology, being important and indispensable for the identification of fungi. As an example we have the lactrimel media that mainly has milk, wheat flour and honey.

In all, the ideal conditions required by each microorganism, temperature, pH, O2, CO2, others must be provided.

Note: There are media that can present several of the forms above at the same time, that is, they can be enriched and differential or enriched and selective, among others, among others.

Presentation of cultivation media

Tube culture:

It is a method used in mycology laboratories, where tubes are used whose diameter and size depend on the need for the bioanalist or researcher. In these tubes, the prepared agar that this liquid phase is taken to the autoclave for a certain time to sterilize, then it is placed at room temperature in an inclined way to form a kind of bevel, once it is solidified and that there is Completed with the sterility protocol, it is used to sow clinical samples or pieces of fungal material and then show the growth of the microorganism.

Petri plate cultivation:

It is a method used in mycology laboratories, where Petri plates are used, in this case, unlike the tube method, the agar in the autoclave must be sterilized before serving in the plates, when the material is container works in the extraction bell to maintain sterility, it is expected that it is solidified and that it has complied with the sterility protocol and then proceed to sow the clinical samples or a piece of fungal material and wait to show growth.

Note: The tube culture medium is much safer than in Petri plates due to the reduced shape of the mouth of the tubes and their easy manipulation when compared to the Petri plates that are easier to open and much more difficult to handle , this increases the possibilities of occupational accidents when fungal material in the laboratory environment.

Note: Due to the shortage of materials in the country, other types of containers have been taken for the elaboration of cultivation media with various forms that are comfortable and facilitate work in the laboratory, taking into account that they must be easy to handle and that they comply with With the standards of biosafety and sterility.

Microculture

There are other variants on the use of agar when you have already prepared, the microculture also known as sheet culture, is a technique of great use in clinical mycology and consists of sowing the fungus in a small portion of the culture medium that is over A slide, this is done in order to obtain the sporulation of the sown microorganism, and thus evidence more precise and efficient way. From the microcultures two traditional methods are highlighted that are:

• Ridell or square method: a square between 1-1.5cm of agar is cut and placed on a slide, a small piece (a small piece) of the fungus that you want to identify and sowing on the four sides of the four sides of the square, then a lamella is placed at the top as a kind of a lid.
• Rivalier or gout method: in this case the solid agar is based applying heat and with a sterile pasteur pipette you take a bit of the agar and drops on drop, this taking into account a time interval between each drop, Where the previous one has solidified, so that several layers with each drop are left, once solid the fungus is sowing to identify on this agar surface.

Note: Both are carried out on a Petri plate, with an internal support for the slide sheet, and sterile water is added, without the amount of the same exceeding the support, and thus keep the environment wet. All this must be sterile.

Clinical utility and importance of cultivation media

The culture means allow to isolate a fungal agent from clinical samples by providing the necessary elements for their development and good growth, thus allowing the correct identification of both gender and species of the pathogen and subsequently to be able to apply the necessary treatment in a timely manner to eliminate that infectious agent of the patient as soon as possible.

Preparation of culture media

At present, most culture media are marketed; normally in the form of lyophilized to which it is necessary to rehydrate. In these cases the preparation of the culture medium is simply reduced in weighing the desired amount of the same and dissolved in distilled water following the manufacturer’s instructions. The therper substances are sterilized by filtration and are added to the rest of the components after they have previously been sterilized in the autoclave and cooled at room temperature or at 40-50ºC if it is means of means with agar with.