A tertiary care laboratory processing several hundred sputum specimens daily switches its primary acid-fast screening from Ziehl-Neelsen staining to auramine O staining with light-emitting diode fluorescence microscopy. What is the principal justification for this switch?
- A Auramine-stained bacilli can be identified to species level by their fluorescence pattern
- B Slides can be scanned at low magnification, increasing sensitivity and throughput per hour ✓
- C Fluorescence staining eliminates the need for decontamination of specimens
- D Auramine staining distinguishes viable from dead bacilli on direct smear
Correct answer: B. Slides can be scanned at low magnification, increasing sensitivity and throughput per hour
Explanation
Auramine O binds mycolic acids and fluoresces bright yellow-green, allowing the reader to scan the entire smear field rapidly at 200x magnification instead of oil immersion at 1000x, so more area is screened per unit time and sensitivity improves, particularly for paucibacillary and HIV-associated samples. Fluorescence gives no information on species identity or viability, and specimen decontamination with sodium hydroxide is still mandatory before concentration and staining. These limitations keep culture or molecular methods necessary for confirmation.
Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 12th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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