Enhanced detection of Mycobacteria stained with rhodamine auramine at 37 degrees C

Sputum smear microscopy is the most efficient and rapid technique for detection of acid-fast bacilli (AFB). Fluorochrome method of staining is preferred for Mycobacteria in the overburdened laboratories as the fluorescing bacilli are more readily detected than the fuchsin stained bacilli in shorter period of time. A total of 300 sputum samples obtained from suspected cases of Tuberculosis were collected and were subjected to staining by rhodamine auramine at 37 degrees C and also at room temperature (conventional method). The smears were then blindly evaluated. Fifty-eight samples were positive by both methods and 5 were positive at 37 degrees C only. Staining at 37 degrees C increased the smear positivity by 8.6% over conventional staining at room temperature. No smears were positive only with staining at room temperature alone. Out of 58 smears positive by both methods, 25 had equal number of AFB in both smears, 22 had more AFB in smear stained at 37 degrees C and 11 had greater number of AFB in smears stained at room temperature. Our study, therefore, indicates that rhodamine auramine staining at 37 degrees C is superior to conventional auramine method at room temperature for detecting AFB in sputum smears.