Excision of pre-ulcerative forms of Buruli ulcer disease: a curative treatment?

BACKGROUND: Previous investigations have revealed that Mycobacterium ulcerans is extensively distributed spatially throughout ulcerative lesions, including in the margins of excised tissue. In contrast, bacilli in pre-ulcerative lesions are assumed to be concentrated in the center of the lesion. In order to assess the extent to which the surgical excision of pre-ulcerative lesions is capable of removing all infected tissue, we subjected the excision margins of pre-ulcerative lesions to laboratory analysis. PATIENTS AND METHODS: Eleven patients with laboratory-confirmed pre-ulcerative lesions were included in the study. The diameter of the lesion and excised tissue and the "surgical distance" between the border of the lesion and excision margin were measured. The entire excision margin was cut into segments and subjected to IS2404 PCR. RESULTS: The results from the PCR analysis on the samples of excision margins were highly significantly associated with the surgical distance (p < 0.001). The margin samples of nodules were significantly more often PCR positive than the plaques (p = 0.025). The size of the lesion and the size of the excised tissue did not significantly influence the PCR results. Statistically, a surgical distance of more than 9 mm was found to reduce the risk of remaining infected tissue to less than 10%, that of 13 mm to reduce the risk to less than 5%, and that of 25 mm to reduce the risk to nearly 0%. CONCLUSION: The results of this study show that in preulcerative Buruli ulcer disease, bacilli may extend beyond the actual size of the lesion and that there is a strong correlation between the presence of M. ulcerans in the margin samples and the surgical distance. Excision with a surgical distance of 25 mm avoided the risk of remaining mycobacteria in this study. However, no recurrences occurred in the patients with M. ulcerans-positive excision margins. The need of postoperative antimycobacterial treatment in these patients remains to be determined.

A stepwise approach to the laboratory diagnosis of Buruli ulcer disease.

OBJECTIVE: In view of technical and financial limitations in areas of endemicity, the current practice and recommendations for the laboratory diagnosis of Buruli ulcer disease (BUD) may have to be reconsidered. We reviewed diagnostic results in order to explore options for a modified, more practicable, cost-effective and timely approach to the laboratory diagnosis of BUD. METHODS: Diagnostic specimens from 161 clinically diagnosed BUD patients from four different treatment centres in Ghana were subjected to laboratory analysis. The positivity rates of the laboratory assays were compared. RESULTS: The number of laboratory-confirmed clinically diagnosed BUD cases with one positive confirmative test was 20% higher than that with two positive confirmative tests. The specificity of microscopy (MIC) and PCR was 96.6% and 100%, respectively. Subsequent analysis of specimens from surgically excised pre-ulcerative tissue-by-tissue MIC and tissue PCR rendered 65% laboratory-confirmed BUD cases. Subsequent analysis of diagnostic swabs from ulcerative lesions by swab smear MIC and swab PCR rendered 70% of laboratory-confirmed BUD cases. CONCLUSIONS: The specificity of the diagnostic tests used in this study suggests that one positive diagnostic test may be considered sufficient for the laboratory confirmation of BUD. Subsequent application of different diagnostic tests rendered a laboratory confirmation of 65% pre-ulcerative and of 70% ulcerative lesions. Implementation of a stepwise, subsequent analysis of diagnostic specimens will result in considerable cost saving compared with simultaneous testing of specimens by several diagnostic assays.

Susceptibility to Buruli ulcer is associated with the SLC11A1 (NRAMP1) D543N polymorphism.

Similar to other mycobacterial diseases, susceptibility to Buruli ulcer (Mycobacterium ulcerans infection) may be determined by host genetic factors. We investigated the role of SLC11A1 (NRAMP1) in Buruli ulcer because of its associations with both tuberculosis and leprosy. We enrolled 182 Buruli ulcer patients (102 with positive laboratory confirmation) and 191 healthy neighbourhood-matched controls in Ghana, and studied three polymorphisms in the SLC11A1 gene: 3' UTR TGTG ins/del, D543N G/A, and INT4 G/C. Finger prick blood samples from study subjects were dried on filter papers (FTA) and processed. D543N was significantly associated with Buruli ulcer: the odds ratio (adjusted for gender, age, and region of the participant) of the GA genotype versus the GG genotype was 2.89 (95% confidence intervals (CI): 1.41-5.91). We conclude that a genetic polymorphism in the SLC11A1 gene plays a role in susceptibility to develop Buruli ulcer, with an estimated 13% population attributable risk.

Dry-reagent-based PCR as a novel tool for laboratory confirmation of clinically diagnosed Mycobacterium ulcerans-associated disease in areas in the tropics where M. ulcerans is endemic.

After tuberculosis and leprosy, Buruli ulcer (BU), caused by Mycobacterium ulcerans, is the third most common mycobacterial disease in immunocompetent humans. The disease occurs in tropical countries, with foci in West Africa, Central Africa, and the western Pacific. BU is defined as an infectious disease involving the skin and the subcutaneous adipose tissue characterized by a painless nodule, papule, plaque, or edema, evolving into a painless ulcer with undermined edges and often leading to invalidating sequelae. Due to the fundamental lack of understanding of modes of transmission, disease control in endemic countries is limited to early case detection through improved active surveillance and surgical treatment. The laboratory confirmation of BU is complicated by the absence of a diagnostic "gold standard." Therefore, misclassification and delayed diagnosis of BU may occur frequently, causing a considerable socioeconomic impact in terms of treatment costs due to prolonged hospitalization. In order to respond to the urgent need to develop reliable tools for early case detection and to overcome technical difficulties accompanying the implementation of diagnostic PCR procedures in tropical countries, a dry-reagent-based PCR formulation for the detection of M. ulcerans in diagnostic specimens has been developed at the Bernhard Nocht Institute for Tropical Medicine. Following technical and clinical validation, the assay has been successfully installed and field tested at the Kumasi Centre for Collaborative Research in Tropical Medicine, Kumasi, Ghana. Preliminary results show an excellent diagnostic sensitivity of >95%.

Buruli ulcer: differences in treatment outcome between two centres in Ghana.

OBJECTIVES: Assess treatment effects by following up patients treated for Buruli ulcer in two hospitals with different treatment aspects, including widely differing surgical practices. PATIENTS/METHODS: Treated patients were retrospectively identified from hospital records. Between 1994 and July 2000, 136 patients had been admitted for Buruli ulcer in both hospitals, and lived in areas covered in the research period. 78 (57%) Patients were included in the study. Treatment and status of the patient were analysed. RESULTS: 27 (35%) Patients were not healed. Of the 33 patients treated in hospital A, six (18%) were not healed at follow-up, whereas of the 45 patients treated in hospital B, 21 (47%) were not healed. The length of stay in hospital A was significantly longer (P=0.002), and more operations on average were done per patient (P=0.002). In a univariate analysis, treatment in hospital A; the use of rifampicin (P=0.013); and BCG vaccination status (P=0.04) were all significantly associated with ulcer healing. Using a logistic regression model for multivariate analysis, only treatment as given in hospital A, with standard practice of wide surgical excision, appeared to predict ulcer healing independently (P=0.02). CONCLUSIONS: This study shows large differences in treatment outcome between the two hospitals; the results support the hypothesis that extent of surgical treatment influences the chance of healing of Buruli ulcer.