SeminarMycobacterium ulcerans infection
Section snippets
Bacteriology
M ulcerans belongs to the large group of environmental mycobacteria. It is a slowly growing acid-fast and alcohol-fast microorganism that is best cultured in egg-yolk-enriched Löwenstein-Jensen medium at 32°C (pH 5·4–7·4, pO2<2·5 kPa). Attempts to culture the microrganism from clinical specimens fail in over half of all cases. Standard techniques require much time for isolation and identification. If carbon-14 is added to the culture medium, a radiometric assay (BACTEC system) may detect growth
Epidemiology and transmission
Most researchers believe that M ulcerans infection is acquired from the natural environment, and that small, penetrating injuries transmit the bacterium to the subcutaneous fat of exposed parts of the body.3 Patients may have forgotten such injuries by the time they develop overt disease. Children outnumber adults in almost all reported large case series, and this fact may partly explain why many affected individuals have no recollection of any previous injury.
Support for the theory that M
Clinical features
In most African patients with Buruli-ulcer disease, the subcutaneous tissue is the primary focus of infection (figure 2). A firm, non-tender nodule indicates the first stage of disease, but preulcerative lesions also include plaques, which consist of larger areas of indurated skin, and oedema (figure 3). In the second stage, ulceration takes place (figure 4). Coalescent necrosis of the subcutaneous fat with vascular occlusion results in sloughing and secondary ulceration of the overlying skin,
Diagnosis
In endemic areas, the clinical diagnosis of ulcerating lesions is straightforward. The painless ulcer with undermined edges, with a necrotic slough can be recognised easily (figure 4). Most lesions are on the limbs, although they may also be present on the trunk or face; facial lesions may be mistaken for cancrum oris (noma). Patients with Buruli ulcer have no clinically detectable lymphadenitis, and have no systemic symptoms such as fever or malaise, which would suggest staphylococcal or
Surgery
Early excision of small preulcerative lesions (papules and nodules) is curative. After excision, the skin can be closed. Extensive preulcerative lesions (plaques and oedema) require surgery also, but effective surgical treatment can be delayed because of diagnostic uncertainty. Necrotic ulcers are easily recognised and should be excised. All necrotic tissue should be carefully removed, with excision extending into healthy tissue, so as to prevent persistent subcutaneous infection from residual
Prevention
BCG vaccination had an incomplete but significant protective effect against Buruli ulcer in two controlled clinical trials in Uganda.25, 26 The potential role of other available mycobacterial vaccines in the prevention of M ulcerans infection is unknown. M vaccae, an environmental mycobacterium, seems to induce a protective cell-mediated immune response, switching the immune system from a predominantly Th-2-like immune response into a Th-1 immune response pattern in mice.27 The first studies in
Yamoussoukro meeting
The first International Conference on Buruli Ulcer Control and Research was held during July 6–8, 1998, in Yamoussoukro, Cote d'lvoire. The primary objectives of the conference were to raise awareness of the importance of the disease, and to increase recognition of M ulcerans infection. Representatives from Benin, Ghana, Togo, and Cote d'lvoire reported substantial increases in numbers of patients,12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 and emphasised the
Conclusions
50 years after its first description in the medical literature,1 and 100 years after Cook first observed Buruli ulcer in Uganda,5 the time is right for action to alleviate and control the suffering inflicted by this disease. A strong combined effort, both by the International M ulcerans Study Team, and by sponsor organisations, is needed to find answers to basic scientific questions. Modern molecular tools can be used to confirm modes of transmission, and contaminated reservoirs should be
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