Alternative Method for Histopathological Detection of Mycobacterium Tuberculosis and Mycobacterium Leprae using a Modified Acid-Fast Technique

Abstract

Introduction. Mycobacterium tuberculosis and Mycobacterium leprae are acid-fast organisms with lipid-rich cell walls that resist decolorization with acidified alcohol after application of a dye with heat. The Ziehl-Neelsen and Fite Faraco staining technique, which are diagnostic tools for identification of acid-fast bacilli (AFB) found in histopathologic samples, are based on this principle. A modification of the Ziehl-Neelsen technique is described as an alternative rapid and reliable method of diagnosis for prompt detection and treatment.Methodology. One hundred and seven (107) archived tissue specimens from autopsy and dermatology cases interpreted as positive for M. tuberculosis and M. leprae were stained using the proposed modified acid-fast (MAF) technique compared with Fite Faraco (FF) staining method as reference standard. Each specimen was read by two independent evaluators.Results. The degree of diagnostic agreement of the MAF with FF was calculated. For autopsy (n=16) and dermatology (n=91) samples, the Cohen's kappas are 0.765 (substantial) and 0.397 (fair), respectively. Overall, the Cohen's kappa is 0.458 (moderate). Conclusion.The proposed modified Acid-Fast staining method may be considered as an alternative to the conventional Ziehl-Neelsen method and the Fite Faraco method in identifying positive acid-fast bacilli in tissue samples taken from clinical cases of M. tuberculosis and M. leprae.

Intramedullary Tuberculoma of the Spinal Cord: A Case Report

“…Moreover, it requires at least 5,000 – 10,000 bacilli per mL of specimen and requires larger volumes of CSF for spinal TB detection to be feasible. 11 , 12 For this reason, the Fite staining method may be a more prudent choice for spinal TB diagnosis.…”

“…13 This staining technique utilizes a xylene/peanut oil deparaffinizing solvent to minimize the exposure of the bacterial cell wall to organic solvents, thus preserving its acid fast nature. 12 , 13 This method is useful in identifying more delicate acid-fast organisms. While the Fite stain’s sensitivity has been reported to range from 40 – 70% in the detection of mycobacterium leprae , its sensitivity for the detection of mycobacterium tuberculosis has not been studied to date.…”

“…While the Fite stain’s sensitivity has been reported to range from 40 – 70% in the detection of mycobacterium leprae , its sensitivity for the detection of mycobacterium tuberculosis has not been studied to date. 12 , 14 One can speculate that the Fite stain would have greater sensitivity for the detection of any acid fast bacteria than the Ziehl-Neelsen method, based on its ability to preserve the acid-fast nature of more delicate species. 12 In our patient, both TB spot testing and initial staining of the CSF and biopsy specimens with the Ziehl-Neelsen acid-fast bacilli stain were negative.…”

“… 12 , 14 One can speculate that the Fite stain would have greater sensitivity for the detection of any acid fast bacteria than the Ziehl-Neelsen method, based on its ability to preserve the acid-fast nature of more delicate species. 12 In our patient, both TB spot testing and initial staining of the CSF and biopsy specimens with the Ziehl-Neelsen acid-fast bacilli stain were negative. The Fite stain technique proved useful in diagnosis and it helped to guide clinical management in our case.…”

Evolution of tuberculosis diagnostics: From molecular strategies to nanodiagnostics

“…The staining of Mtb is dependent on the acid-resistant property of its high lipid content cell wall. The most common staining technique is the Ziehl-Neelsen method [ 27 ]. Other techniques include the cold staining method.…”