Friday, April 13, 2018

Facebook: Microbiology Candida.

So, this post is the answer to our previous question asked on medicowesome facebook page. Question was

#Medicowesome #Microbiology

A vitreous aspirate from a case of metastatic endopthalmitis on culture yields Gram-positive round to oval cells, 12-14 mm in size. The aspirate on Gram staining show the presence of pseudohyphae. Which of the following is the most likely aetiological agent?

1)  Aspergillus.
2)  Rhizopus.
3)  Candida.
4)  Fusarium.

Answer: Option 3) Candida.

Let's analyse the question and extract the information one by one.
So, we get two things from the question.
a) The causative organism has pseudohyphae and
b) It is stained by gram stains.

Among the given options, only Candida can form pseudohyphae. All other options are filamentous fungi forming true mycelia and Candia is the only fungi that are usually gram positive on smears.

Some awesome points that must be known on Candida infections.

1) Candida is unicellular organism belonging to yeast like fungus categories. All Candida species are commensals of humans. So, their mode of transmission is endogenous while most of the fungus have mode of transmission as inhalation.
2) They form pseudohyphae.
3) Candida albicans is different from other candida because :-
   a) It forms true hyphae or germ tubes when grown in serum.
   b) It forms thick walled large spores called chlamydospores.
   c) It is dimorphic. It means it grows as yeast at 37°C and as molds at 25°C.

4) Test to differentiate between C. Albicans and other Candida is called germ tube test or Reynolds Braude phenomenon.
-C. Albicans when placed at 37°C in human serum forms germ cell tubes within 2 hours.
5)Candida albicans is the most common cause of mucosal candidiasis.
6) Candidiasis is the most common systemic mycosis. It is also the most common fungal infection in neutropenic and immunocompetent patients.
7) It causes oral thrush, oesophageal candidasis, cerebral candidasis and pulmonary candidiasis.

Extra information:

Their is one test which I learned online and some people consider it as diagnosis of candida infections.

The Spittle Test:
When you get up in the morning, and before you brush your teeth, eat or drink anything, fill a glass with bottled water at room temperature.
Spit some saliva gently into the glass.
Come back every 20 minutes for the next hour and check for some of these signs.

1) Strings coming down through the water from the saliva at the top.
2) Cloudy saliva sitting at the bottom of the glass.
3) Opaque specks of saliva.

Also, in above question we deducted that the given pathogenic organism is gram stain so we get to learn about stains as well.
Normally, fungi are stained by PAS and methenamine silver but some fungi are stained by special stains like :-

Candida is stained by gram stain.
Cryptococcus is stained by mucicarmine, India ink.
Histoplasma is stained by Giemsa stain.

Thanks for reading!
Ojas Gite.

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