Question

Acid Fast & Endospore Stain:

1. Does the presence of an acid-fast organism in a clinical specimen always suggest serious clinical disease?

2. To check for active tuberculosis, what type of clinical specimen should be taken from a patient?

3. Why is it important to know whether or not bacterial cells form endospores?

Answer 1

1.

Yes.

Acid fast stain recognizes mycolic acid which is mostly present in mycobacterium bacterial species and Nocardia. Mycobacterium species cause highly infectious diseases like tuberclosis or leprosy whereas Nocardia species may or may not be pathogenic.

2.

Sputum of patients suffering from pulmonary tuberclosis: An early morning, deep cough sputum samples, obtained on three separate days, should be used for AFB smears and cultures.

[Note: For extrapulmonary TB----- gastric aspirates, cerebrospinal fluid, pleural fluid, exudates from abscesses, bone marrow and urine can be used].

3.

Endospore formation mostly occurs in gram positive bacteria that can survive under unfavourable conditions like desiccation, starvation, exposure to chemicals, high temperature and radiation. Once favourable conditions return, the endospore can reactivate and function as vegetative bacterial cell.