Microscopy for Acid Fast Bacilli: A Useful but Neglected Tool in Routine Laboratory Diagnosis of Buruli Ulcer

Abstract

Background: Laboratory diagnosis of Buruli ulcer disease has become vital with the introduction of antibiotic treatment. Polymerase chain reaction (PCR) for the IS2404 repeat sequence of Mycobacterium ulcerans is the gold standard for laboratory diagnosis. This is expensive and only carried out in reference laboratories in endemic countries in Africa. In order to improve the efficiency of diagnosis at the point of care and reduce the total cost of patient management, we decided to evaluate Ziehl-Neelsen (ZN) staining for acid-fast bacilli (AFB) as an inexpensive diagnostic tool. Methods: Two smears directly prepared at the point of care were examined under oil-immersion microscopy after ZN staining for AFB and compared the results to PCR samples from the same patients. Results: Good quality smears were obtained from all subjects and our results showed that when a second smear was added the sensitivity of microscopy for AFB was increased from 52 to 55% for FNA samples and from 51 to 57 % for swabs. Conclusion: If PCR were to be omitted in all patients with suspected Buruli ulcer disease when AFB were detected it would result in a considerable saving.