Ulcera del Buruli: la "nuova lebbra" Africana. Isolamento e identificazione di M. ulcerans in prelievi bioptici provenienti da pazienti del Benin

Abstract

Buruli ulcer, caused by Mycobacterium ulcerans, a slow growing mycobacterium which classically infects the skin and the subcutaneous tissues generating indolent ulcers, is, after tuberculosis and leprosy, the third most common mycobacterial infection and has emerged as an important cause of human disease in at least 32 tropical and subtropical countries.The disease initially manifests a painless swelling in the skin and progresses to skin ulceration. Because of the lack of a specific vaccine and the inefficacy of antibiotic therapies, the current treatment is surgical excision. Early diagnosis and treatment prevent complications and therefore, a prompt and accurate diagnosis is crucial, but difficult to perform in countries with limited resources. In this paper we describe the mycobacteriological diagnosis on samples obtained from patients who underwent plastic-reconstructive surgery in a hospital in Zinvie, Benin (West Africa). M. ulcerans was isolated from 19/32 subjects at the mycobacteriology laboratory of the Institute of Hygiene, University of Bari, Italy, 10-15 days after sampling. The identification of M. ulcerans was performed with a panel of tests for conventional identification, including biochemical analyses (niacin, nitrate reduction, catalase at 68°C, Tween hydrolysis, and urease), cultures (growth at 32, 37, and 45°C), and inhibition studies (tolerance of 5% NaCl and thiophenecarboxylic acid) as well as with INNO-LiPA MYCOBACTERIA v2 and confirmed with Chromatographic Analysis of Cell Wall Mycolic Acid (high-performance liquid chromatography). Our results demonstrate that, even on samples collected in distant sites and analyzed after 10-15 days, the conventional phenoptype identification confirmed by molecular testing and HPLC resulted in an accurate identification of such a devastating and relatively rare mycobacterium as M. ulcerans which had never been previously isolated in Italy.