Ultraviolet Light Enhances the Bovine Serum Albumin Fixation for Acid Fast Bacilli Stain

Abstract

The use of a liquid culture system such as MGIT broth has greatly improved the sensitivity of isolating mycobacteria in clinical laboratories. Microscopic visualization of acid fast bacilli (AFB) in the culture positive MGIT broth remains the first routine step for rapidly indicating the presence of mycobacteria. We modified an ultraviolet (UV) light fixation process to increase AFB cells adherence to the slide. The retained haze proportion of a 1-cm circle marked area on the smear slide was quantified after the staining procedure indicating the adherence degree of AFB cells. More AFB cells were preserved on the slide after exposure to UV light of either germicidal lamp or UV crosslinker in a time-dependent manner. We demonstrated both the bovine serum albumin (BSA) in MGIT media and UV light exposure were required for enhancing fixation of AFB cells. While applying to AFB stains for 302 AFB positive MGIT broths in clinics, more AFB cells were retained and observed on smear slides prepared by the modified fixation procedure rather than by the conventional method. The modified fixation procedure was thus recommended for improving the sensitivity of microscopic diagnosis of AFB cells in culture positive MGIT broth.

A controlled evaluation of filter paper use during staining of sputum smears for tuberculosis microscopy

“…Investigation into methods to prevent smear removal during staining warrants further research. Adding bovine serum albumin prior to heat fixation with or without the use of added ultraviolet light exposure for further cross-linkage for cell adhesion, the use of poly-L-lysine covered slides, or methanol fixation may reduce washing away of smears but increase the costs and/or the time required for smear microscopy 20 , 21 …”