Sputum is disinfected by –
**Core Concept**
Sputum disinfection is a critical step in the laboratory diagnosis of respiratory infections, particularly tuberculosis. The goal is to eliminate Mycobacterium tuberculosis and other pathogens without damaging the sputum sample, which is essential for microbiological analysis.
**Why the Correct Answer is Right**
The correct answer is formaldehyde. Formaldehyde is a potent disinfectant that effectively kills M. tuberculosis and other bacteria, viruses, and fungi. It works by coagulating proteins and disrupting cellular membranes, ultimately leading to cell death. Formaldehyde is commonly used in sputum processing for smear microscopy and culture.
**Why Each Wrong Option is Incorrect**
**Option A:** Cresol is a phenolic disinfectant, but it is not the primary choice for sputum disinfection due to its potential to damage the sputum sample and interfere with microbiological analysis.
**Option B:** Glutaraldehyde is a strong disinfectant, but it is not typically used for sputum disinfection due to its high toxicity and potential for tissue damage.
**Option C:** Ethanol is a common disinfectant, but it is not effective against M. tuberculosis and would not be suitable for sputum disinfection.
**Clinical Pearl / High-Yield Fact**
When processing sputum samples, it is essential to use a disinfection method that effectively kills M. tuberculosis without damaging the sample. Formaldehyde is the preferred choice for this purpose.
**Correct Answer:** C. Formaldehyde.