A case of cutaneous tuberculosis in a Buruli ulcer-endemic area

Cutaneous tuberculosis-ambiguous transmission, bacterial diversity with biofilm formation in humoral abnormality: case report illustration

Background

Cutaneous tuberculosis (CTB) and its paucibacillary forms are rare and difficult to diagnose, especially in immunocompromised patients with significant comorbidity. The aim of the study was to introduce the modern concept of the microbiome and diagnostic chain into clinical practice (patient-centered care) with the presentation of an atypical form of cutaneous tuberculosis with necrotizing non-healing ulcers leading to polymicrobial infection.

Methods

The study material included samples from sputum, broncho-alveolar lavage and skin ulcer, taken from a patient developing cutaneous tuberculosis. The microbiological investigation was performed, and identification of the isolates was carried out using genotyping and the matrix-assisted laser desorption ionization-time of flight mass spectrometry.

Results

The immunocompromised patient with humoral abnormality (plasma cell dyscrasia) and severe paraproteinemia developed multiorgan tuberculosis. Although cutaneous manifestation preceded systemic and pulmonary symptoms (approximately half a year), the mycobacterial genotyping confirmed the same MTB strain existence in skin ulcers and the respiratory system. Therefore, the infectious chain: transmission, the portal of entry, and bacterial spreading in vivo, were unclear. Microbial diversity found in wound microbiota (among others Gordonia bronchialis, Corynebacterium tuberculostearicum, Staphylococcus haemolyticus, and Pseudomonas oryzihabitans) was associated with the spread of a skin lesion. The in vitro biofilm-forming capacity of strains isolated from the wound may represent the potential virulence of these strains. Thus, the role of polymicrobial biofilm may be crucial in ulcer formation and CTB manifestation.

Conclusions

Severe wound healing as a unique biofilm-forming niche should be tested for Mycobacterium (on species and strain levels) and coexisting microorganisms using a wide range of microbiological techniques. In immunodeficient patients with non-typical CTB presentation, the chain of transmission and MTB spread is still an open issue for further research.

Skin wounds in a rural setting of Côte d'Ivoire: Population-based assessment of the burden and clinical epidemiology

Background

Data on the burden and clinical epidemiology of skin wounds in rural sub-Saharan Africa is scant. The scale of the problem including preventable progression to chronic wounds, disability and systemic complications is largely unaddressed.

Methods

We conducted a cross-sectional study combining active (household-based survey) and passive case finding (health services-based survey) to determine the burden and clinical epidemiology of wounds within the Taabo Health and Demographic Surveillance System (HDSS) in rural Côte d’Ivoire. Patients identified with wounds received free care and were invited to participate in the wound management study simultaneously carried out in the survey area. The data were analysed for wound prevalence, stratified by wound and patient characteristics.

Results

3842 HDSS-registered persons were surveyed. Overall wound prevalence derived from combined active and passive case finding was 13.0%. 74.1% (403/544) of patients were below the age of 15 years. Most frequent aetiologies were mechanical trauma (85.3%), furuncles (5.1%), burns (2.9%) and Buruli ulcer (2.2%). Most wounds were acute and smaller than 5 cm² in size. 22.0% (176/799) of wounds showed evidence of secondary bacterial infection. 35.5% (22/62) of chronic wounds had persisted entirely neglected for years. Buruli ulcer prevalence was 2.3 per 1000 individuals and considerably higher than expected from an annual incidence of 0.01 per 1000 individuals as reported by WHO for Côte d’Ivoire at the time of the study.

Conclusions

Skin wounds are highly prevalent in rural West Africa, where they represent a widely neglected problem. The HDSS-based survey with combined active and passive case finding adopted in this study provides a better estimate than school- and health institution-based surveys which underestimate the frequency of skin wounds and, particularly, of neglected tropical diseases of the skin, such as Buruli ulcer and yaws. A comparison with country-specific WHO data suggests underreporting of Buruli ulcer cases.

Trial registration

Registration at ClinicalTrials.gov NCT03957447.

Data on the burden and clinical epidemiology of skin wounds in rural sub-Saharan Africa is scant. The scale of the problem including preventable progression to chronic wounds, disability and systemic complications is largely unaddressed.

We conducted a cross-sectional study combining active (household-based survey) and passive case finding (health services-based survey) to determine the burden and clinical epidemiology of wounds within the Taabo Health and Demographic Surveillance System (HDSS) in rural Côte d’Ivoire. Patients identified were invited to participate in the wound management study simultaneously carried out in the survey area.

We surveyed approximately 4000 HDSS-registered persons and found a high overall wound prevalence (13.0%), predominately in children. Mechanical trauma was the leading cause, followed by furuncles, burns and Buruli ulcer. Most wounds were acute and had a size of less than 5 cm², but a substantial proportion was large, complicated, or chronic, some of the latter persisting neglected for years.

The HDSS-based survey with combined active and passive case finding adopted in this study provides a better estimate than school- and health institution-based surveys which underestimate the frequency of skin wounds and, particularly, of neglected tropical diseases of the skin, such as Buruli ulcer and yaws. A comparison with country-specific WHO data suggests underreporting of Buruli ulcer cases.

Identification of the Mycobacterium ulcerans protein MUL_3720 as a promising target for the development of a diagnostic test for Buruli ulcer

Buruli ulcer (BU) caused by Mycobacterium ulcerans is a devastating skin disease, occurring mainly in remote West African communities with poor access to health care. Early case detection and subsequent antibiotic treatment are essential to counteract the progression of the characteristic chronic ulcerative lesions. Since the accuracy of clinical BU diagnosis is limited, laboratory reconfirmation is crucial. However, currently available diagnostic techniques with sufficient sensitivity and specificity require infrastructure and resources only accessible at a few reference centres in the African endemic countries. Hence, the development of a simple, rapid, sensitive and specific point-of-care diagnostic tool is one of the major research priorities for BU. In this study, we have identified a previously unknown M. ulcerans protein, MUL_3720, as a promising target for antigen capture-based detection assays. We show that MUL_3720 is highly expressed by M. ulcerans and has no orthologs in other prevalent pathogenic mycobacteria. We generated a panel of anti-MUL_3720 antibodies and used them to confirm a cell wall location for MUL_3720. These antibodies could also specifically detect M. ulcerans in infected human tissue samples as well as in lysates of infected mouse footpads. A bacterial 2-hybrid screen suggested a potential role for MUL_3720 in cell wall biosynthesis pathways. Finally, we demonstrate that a combination of MUL_3720 specific antibody reagents in a sandwich-ELISA format has sufficient sensitivity to make them suitable for the development of antigen capture-based diagnostic tests for BU.

According to the recommendations of the World Health Organization, the clinical diagnosis of BU should be reconfirmed by at least two laboratory techniques. However, out of the four currently available tests, three (PCR, histopathology and cultivation of M. ulcerans) can only be performed at centralized reference laboratories; the fourth (microscopic detection of acid fast bacilli) lacks the required sensitivity and specificity. Therefore, a simple tool for early diagnosis of the disease, which can be implemented in rural health care facilities of the endemic countries, is of urgent need. In this study we aimed at the identification of M. ulcerans proteins as potential targets for the development of a simple and rapid diagnostic antigen detection assay. Among 36 proteins, MUL_3720 best met the predefined criteria of being highly expressed by M. ulcerans and not having orthologs in other pathogenic mycobacterial species prevalent in the endemic regions. Here we generated monoclonal and polyclonal antibodies against this protein and carried out pilot studies for the development of an antigen capture-based diagnostic test.

Cutaneous tuberculosis overview and current treatment regimens

Tuberculosis is one of the oldest diseases known to humankind and it is currently a worldwide threat with 8-9 million new active disease being reported every year. Among patients with co-infection of the human immunodeficiency virus (HIV), tuberculosis is ultimately responsible for the most deaths. Cutaneous tuberculosis (CTB) is uncommon, comprising 1-1.5% of all extra-pulmonary tuberculosis manifestations, which manifests only in 8.4-13.7% of all tuberculosis cases. A more accurate classification of CTB includes inoculation tuberculosis, tuberculosis from an endogenous source and haematogenous tuberculosis. There is furthermore a definite distinction between true CTB caused by Mycobacterium tuberculosis and CTB caused by atypical mycobacterium species. The lesions caused by mycobacterium species vary from small papules (e.g. primary inoculation tuberculosis) and warty lesions (e.g. tuberculosis verrucosa cutis) to massive ulcers (e.g. Buruli ulcer) and plaques (e.g. lupus vulgaris) that can be highly deformative. Treatment options for CTB are currently limited to conventional oral therapy and occasional surgical intervention in cases that require it. True CTB is treated with a combination of rifampicin, ethambutol, pyrazinamide, isoniazid and streptomycin that is tailored to individual needs. Atypical mycobacterium infections are mostly resistant to anti-tuberculous drugs and only respond to certain antibiotics. As in the case of pulmonary TB, various and relatively wide-ranging treatment regimens are available, although patient compliance is poor. The development of multi-drug and extremely drug-resistant strains has also threatened treatment outcomes. To date, no topical therapy for CTB has been identified and although conventional therapy has mostly shown positive results, there is a lack of other treatment regimens.

Mycobacterium ulcerans persistence at a village water source of Buruli ulcer patients

Buruli ulcer (BU), a neglected tropical disease of the skin and subcutaneous tissue, is caused by Mycobacterium ulcerans and is the third most common mycobacterial disease after tuberculosis and leprosy. While there is a strong association of the occurrence of the disease with stagnant or slow flowing water bodies, the exact mode of transmission of BU is not clear. M. ulcerans has emerged from the environmental fish pathogen M. marinum by acquisition of a virulence plasmid encoding the enzymes required for the production of the cytotoxic macrolide toxin mycolactone, which is a key factor in the pathogenesis of BU. Comparative genomic studies have further shown extensive pseudogene formation and downsizing of the M. ulcerans genome, indicative for an adaptation to a more stable ecological niche. This has raised the question whether this pathogen is still present in water-associated environmental reservoirs. Here we show persistence of M. ulcerans specific DNA sequences over a period of more than two years at a water contact location of BU patients in an endemic village of Cameroon. At defined positions in a shallow water hole used by the villagers for washing and bathing, detritus remained consistently positive for M. ulcerans DNA. The observed mean real-time PCR Ct difference of 1.45 between the insertion sequences IS2606 and IS2404 indicated that lineage 3 M. ulcerans, which cause human disease, persisted in this environment after successful treatment of all local patients. Underwater decaying organic matter may therefore represent a reservoir of M. ulcerans for direct infection of skin lesions or vector-associated transmission.

Buruli ulcer (BU) is a neglected tropical disease caused by Mycobacterium ulcerans which affects mainly children in West Africa. Although it is commonly believed that the infection originates from an environmental source, both the reservoir of M. ulcerans and the mode of transmission to human patients remain to be elucidated. Previous investigations indicated that transmission likely takes place away from the homes of patients. We therefore screened the farms as well as village and farm water locations of 46 laboratory confirmed BU patients of the Mapé Basin of Cameroon for the presence of M. ulcerans DNA by real-time PCR. In this analysis three positive village water locations were identified. By studying one of these locations in great detail we found that M. ulcerans DNA persists in underwater detritus in one section of the village water location even after all local cases had been treated. The detritus may represent a reservoir of M. ulcerans from where infection could take place through either direct contamination of skin lesions or through contamination or colonization of insect vectors.

The urgent need for clinical, diagnostic, and operational research for management of Buruli ulcer in Africa

Despite great advances in the diagnosis and treatment of Buruli ulcer, it is one of the least studied major neglected tropical diseases. In Africa, major constraints in the management of Buruli ulcer relate to diagnosis and treatment, and accessibility, feasibility, and delivery of services. In this Personal View, we outline key areas for clinical, diagnostic, and operational research on this disease in Africa and propose a research agenda that aims to advance the management of Buruli ulcer in Africa. A model of care is needed to increase early case detection, to diagnose the disease accurately, to simplify and improve treatment, to reduce side-effects of treatment, to deal with populations with HIV and tuberculosis appropriately, to decentralise care, and to scale up coverage in populations at risk. This approach will require commitment and support to strategically implement research by national Buruli ulcer programmes and international technical and donor organisations, combined with adaptations in programme design and advocacy. A critical next step is to build consensus for a research agenda with WHO and relevant groups experienced in Buruli ulcer care or related diseases, and we call on on them to help to turn this agenda into reality.

Geographic distribution, age pattern and sites of lesions in a cohort of Buruli ulcer patients from the Mapé Basin of Cameroon

Buruli ulcer (BU), a neglected tropical disease of the skin, caused by Mycobacterium ulcerans, occurs most frequently in children in West Africa. Risk factors for BU include proximity to slow flowing water, poor wound care and not wearing protective clothing. Man-made alterations of the environment have been suggested to lead to increased BU incidence. M. ulcerans DNA has been detected in the environment, water bugs and recently also in mosquitoes. Despite these findings, the mode of transmission of BU remains poorly understood and both transmission by insects or direct inoculation from contaminated environment have been suggested. Here, we investigated the BU epidemiology in the Mapé basin of Cameroon where the damming of the Mapé River since 1988 is believed to have increased the incidence of BU. Through a house-by-house survey in spring 2010, which also examined the local population for leprosy and yaws, and continued surveillance thereafter, we identified, till June 2012, altogether 88 RT-PCR positive cases of BU. We found that the age adjusted cumulative incidence of BU was highest in young teenagers and in individuals above the age of 50 and that very young children (<5) were underrepresented among cases. BU lesions clustered around the ankles and at the back of the elbows. This pattern neither matches any of the published mosquito biting site patterns, nor the published distribution of small skin injuries in children, where lesions on the knees are much more frequent. The option of multiple modes of transmission should thus be considered. Analyzing the geographic distribution of cases in the Mapé Dam area revealed a closer association with the Mbam River than with the artificial lake.

Buruli ulcer (BU) is an infectious disease caused by Mycobacterium ulcerans that is affecting mostly children in endemic areas of West Africa. Proximity to slow flowing water is a risk factor, but the exact mode of transmission of BU remains unclear. Man-made environmental changes, such as sand mining, damming of rivers and irrigation have been implicated with increases in disease incidence. Here, we report findings from a survey for BU and continued case detection thereafter in the Bankim Health District of Cameroon. In this area, the local population believed that the damming of the Mapé River has led to the emergence of BU. In 28 months we identified 88 laboratory confirmed cases of BU. Studying these cases, we found that the age adjusted cumulative incidence of BU in the elderly is similar to that in children and that the distribution pattern of BU lesions neither matches mosquito biting patterns nor the distribution of small skin injuries. Multiple modes of transmission should therefore be considered. Our data further showed that the patients appear to have closer contact to the local Mbam River than to the artificial Mapé dam reservoir.