Findings in patients from Benin with osteomyelitis and polymerase chain reaction-confirmed Mycobacterium ulcerans infection

Repurposing of statins for Buruli Ulcer treatment: antimicrobial activity against Mycobacterium ulcerans

Mycobacterium ulcerans causes Buruli Ulcer, a neglected infectious skin disease that typically progresses from an early non-ulcerative lesion to an ulcer with undermined edges. If not promptly treated, these lesions can lead to severe disfigurement and disability. The standard antibiotic regimen for Buruli Ulcer treatment has been oral rifampicin combined with intramuscular streptomycin administered daily for 8 weeks. However, there has been a recent shift toward replacing streptomycin with oral clarithromycin. Despite the advantages of this antibiotic regimen, it is limited by low compliance, associated side effects, and refractory efficacy for severe ulcerative lesions. Therefore, new drug candidates with a safer pharmacological spectrum and easier mode of administration are needed. Statins are lipid-lowering drugs broadly used for dyslipidemia treatment but have also been reported to have several pleiotropic effects, including antimicrobial activity against fungi, parasites, and bacteria. In the present study, we tested the susceptibility of M. ulcerans to several statins, namely atorvastatin, simvastatin, lovastatin and fluvastatin. Using broth microdilution assays and cultures of M. ulcerans-infected macrophages, we found that atorvastatin, simvastatin and fluvastatin had antimicrobial activity against M. ulcerans. Furthermore, when using the in vitro checkerboard assay, the combinatory additive effect of atorvastatin and fluvastatin with the standard antibiotics used for Buruli Ulcer treatment highlighted the potential of statins as adjuvant drugs. In conclusion, statins hold promise as potential treatment options for Buruli Ulcer. Further studies are necessary to validate their effectiveness and understand the mechanism of action of statins against M. ulcerans.

A human model of Buruli ulcer: The case for controlled human infection and considerations for selecting a Mycobacterium ulcerans challenge strain

Critical knowledge gaps regarding infection with Mycobacterium ulcerans, the cause of Buruli ulcer (BU), have impeded development of new therapeutic approaches and vaccines for prevention of this neglected tropical disease. Here, we review the current understanding of host-pathogen interactions and correlates of immune protection to explore the case for establishing a controlled human infection model of M. ulcerans infection. We also summarise the overarching safety considerations and present a rationale for selecting a suitable challenge strain.

The search for a Buruli Ulcer vaccine and the effectiveness of the Bacillus Calmette-Guérin vaccine

Buruli Ulcer is a neglected tropical disease that is caused by Mycobacterium ulcerans. It is not fatal; however, it manifests a range of devastating symptoms on the hosts' bodies. Various drugs and treatments are available for the disease; however, they are often costly and have adverse effects. There is still much uncertainty regarding the mode of transmission, vectors, and reservoir. At present, there are no official vector control methods, prevention methods, or a vaccine licensed to prevent infection. The Bacillus Calmette-Guérin vaccine developed against tuberculosis has some effectiveness against M. ulcerans. However, it is unable to induce long-lasting protection. Various types of vaccines have been developed based specifically against M. ulcerans; however, to date, none has entered clinical trials or has been released for public use. Additional awareness and funding are needed for research in this field and the development of more treatments, diagnostic tools, and vaccines.

Mycobacterium ulcerans-specific immune response after immunisation with bacillus Calmette-Guérin (BCG) vaccine

BACKGROUND

Bacillus Calmette-Guérin (BCG) vaccine provides partial protection against Buruli ulcer caused by Mycobacterium ulcerans in epidemiological studies. This study aimed to quantify M. ulcerans-specific immune responses induced by BCG immunisation.

METHODS

Intracellular cytokine analysis of in-vitro experiments done 10 weeks after BCG immunisation in 130 Australian infants randomised to one of three BCG vaccine strains given either at birth (BCG-Denmark, BCG-Japan, or BCG-Russia) or at two months of age (BCG-Denmark).

RESULTS

Proportions of polyfunctional CD4⁺ T-cells were higher in M. ulcerans-stimulated compared to unstimulated control samples. These proportions were not influenced by the vaccine strain or timing of the immunisation. The M. ulcerans-specific immune responses showed similar patterns to those observed in M. tuberculosis-stimulated samples, although they were of lower magnitude.

CONCLUSIONS

Our data show that BCG immunisation induces M. ulcerans-specific immune responses in infants, likely explaining the cross-protective effect observed in epidemiological studies. (ACTRN12608000227392).

Individual and clinical variables associated with the risk of Buruli ulcer acquisition: A systematic review and meta-analysis

BACKGROUND

Buruli ulcer (BU) is a necrotizing skin disease, caused by Mycobacterium ulcerans, with poorly understood acquisition risk factors. This review aims at evaluating the importance of individual-sex, age, family ties with history of BU, gene variants-and clinical-Bacillus Calmette-Guérin (BCG) immunization, Human Immunodeficiency Virus (HIV) infection-variables in this process.

METHODS

A systematic review was performed considering the following databases: ClinicalTrials.gov, Cochrane Controlled Register of Trials (CENTRAL), Current Contents Connect, Embase, MEDLINE, SciELO, Scopus and Web of Science. Eligible studies were critically appraised with The Joanna Briggs Institute checklists and heterogeneity was assessed with Cochran Q-test and I2 statistic. Published demographic data was descriptively analysed and clinical data pooled within random-effects modelling for meta-analysis.

RESULTS

A total of 29 studies were included in the systematic review. Two randomized controlled trials (RCTs) and 21 case-control studies were selected for meta-analysis. Studies show that BU mainly affects age extremes, more preponderately males among children. Data pooled from RCTs do not reveal BCG to be protective against BU (odds ratio (OR) = 0.63; 95% CI = 0.38-1.05; I2 = 56%), a finding case-control studies appear to corroborate. HIV infection (OR = 6.80; 95% CI = 2.33-19.85; I2 = 0%) and SLC11A1 rs17235409 A allele (OR = 1.86; 95% CI = 1.25-2.77; I2 = 0%) are associated with increased prevalence of the disease. No definite conclusions can be drawn regarding the influence of previous family history of BU.

DISCUSSION

While available evidence warrants further robustness, these results have direct implications on current interventions and future research programs, and foster the development of more cost-effective preventive and screening measures.

REGISTRATION

The study was registered at PROSPERO with number CRD42019123611.

PCR detection of Mycobacterium ulcerans-significance for clinical practice and epidemiology

Introduction: Buruli ulcer (BU) is a neglected disease which has been reported from mostly impoverished, remote rural areas from 35 countries worldwide. BU affects skin, subcutaneous tissue, and bones, and may cause massive tissue destruction and life-long disabilities if not diagnosed and treated early. Without laboratory confirmation diagnostic and treatment errors may occur. This review describes the application of IS2404 PCR, the preferred diagnostic test, in the area of individual patient management and clinico-epidemiological studies. Areas covered: A Medline search included publications on clinical sample collection, DNA extraction, and PCR detection formats of the past and present, potential and limitations of clinical application, as well as clinico-epidemiological studies. Expert commentary: A global network of reference laboratories basically provides the possibility for PCR confirmation of 70% of all BU cases worldwide as requested by the WHO. Keeping laboratory confirmation on a constant level requires continuous outreach activities. Among the potential measures to maintain sustainability of laboratory confirmation and outreach activities are decentralized or mobile diagnostics available at point of care, such as IS2404-based LAMP, which complement the standard IS2404-based diagnostic tools available at central level.

Microdeletion on chromosome 8p23.1 in a familial form of severe Buruli ulcer

Buruli ulcer (BU), the third most frequent mycobacteriosis worldwide, is a neglected tropical disease caused by Mycobacterium ulcerans. We report the clinical description and extensive genetic analysis of a consanguineous family from Benin comprising two cases of unusually severe non-ulcerative BU. The index case was the most severe of over 2,000 BU cases treated at the Centre de Dépistage et de Traitement de la Lèpre et de l’Ulcère de Buruli, Pobe, Benin, since its opening in 2003. The infection spread to all limbs with PCR-confirmed skin, bone and joint infections. Genome-wide linkage analysis of seven family members was performed and whole-exome sequencing of both patients was obtained. A 37 kilobases homozygous deletion confirmed by targeted resequencing and located within a linkage region on chromosome 8 was identified in both patients but was absent from unaffected siblings. We further assessed the presence of this deletion on genotyping data from 803 independent local individuals (402 BU cases and 401 BU-free controls). Two BU cases were predicted to be homozygous carriers while none was identified in the control group. The deleted region is located close to a cluster of beta-defensin coding genes and contains a long non-coding (linc) RNA gene previously shown to display highest expression values in the skin. This first report of a microdeletion co-segregating with severe BU in a large family supports the view of a key role of human genetics in the natural history of the disease.

Buruli ulcer (BU) is a tropical infectious disease caused by Mycobacterium ulcerans. Although being the third most common mycobacterial disease in the world after tuberculosis and leprosy, BU remains a neglected tropical disease and an emerging health emergency in several developing countries. It causes profound skin ulcerations and eventually bone infections. Life-long functional sequelae are observed in more than 20% of patients, most of whom are children. Several observations, in particular the large variability in the clinical severity of the disease after infection, suggested the role of human genetic factors in the development of BU. We report the case of a 5-year old girl from Benin, born of consanguineous parents, who suffered from extensive dissemination of the mycobacterium in the skin, bones and joints. One of her siblings was also affected. The deep genetic exploration of this family led to the identification of a small deletion on chromosome 8 in both patients but absent from unaffected siblings. Interestingly, the deletion is located within a region containing genes encoding for beta-defensins, a family of antimicrobial peptides involved in both innate immunity and healing process of skin wounds. This first report of a microdeletion associated with severe BU in a large family supports the view of a key role of human genetics in the natural history of the disease.

Mycobacterium ulcerans infection (Buruli ulcer) in French Guiana, South America, 1969-2013: an epidemiological study

BACKGROUND

Mycobacterium ulcerans infection is the third most common mycobacterial disease in the world after tuberculosis and leprosy. To date, transmission pathways from its environmental reservoir to humans are still unknown. In South America, French Guiana has the highest reported number of M ulcerans infections across the continent. This empirical study aimed to characterise the epidemiology of M ulcerans infection in French Guiana between 1969 and 2013.

METHODS

Data were collected prospectively mainly by two dermatologists at Cayenne Hospital's dermatology department between Jan 1, 1969, and Dec 31, 2013, for age, date of diagnosis, sex, residence, location of the lesion, type of lesion, associated symptoms, and diagnostic method (smear, culture, PCR, or histology) for all confirmed and suspected cases of M ulcerans. We obtained population data from censuses. We calculated mean M ulcerans infection incidences, presented as the number of cases per 100 000 person-years.

FINDINGS

245 patients with M ulcerans infections were reported at Cayenne Hospital's dermatology department during the study period. M ulcerans infection incidence decreased over time, from 6·07 infections per 100 000 person-years (95% CI 4·46-7·67) in 1969-83 to 4·77 infections per 100 000 person-years (3·75-5·79) in 1984-98 and to 3·49 infections per 100 000 person-years (2·83-4·16) in 1999-2013. The proportion of children with infections also declined with time, from 42 (76%) of 55 patients in 1969-83 to 26 (31%) of 84 in 1984-98 and to 22 (21%) of 106 in 1999-2013. Most cases occurred in coastal areas surrounded by marshy savannah (incidence of 21·08 per 100 000 person-years in Sinnamary and 21·18 per 100 000 person-years in Mana). Lesions mainly affected limbs (lower limbs 161 [66%] patients; upper limbs 60 [24%] patients). We diagnosed no bone infections.

INTERPRETATION

The decrease of M ulcerans infection incidence and the proportion of children with infections over a 45 year period in this ultra-peripheral French territory might have been mostly driven by improving living conditions, prophylactic recommendations, and access to health care.

FUNDING

Agence Nationale de la Recherche.

Primary subacute epiphyseal osteomyelitis caused by Mycobacterium species in young children: a modern diagnostic approach

Primary epiphyseal subacute osteomyelitis (PESAO) caused by Mycobacterium species in young children is poorly recognized. We aimed to define the spectrum of this uncommon condition and to propose a novel diagnostic approach. We performed a systematic review of the literature on the PubMed website by selecting all reports of isolated infantile PESAO caused by Mycobacterium species since 1975. We identified 350 citations, of which 174 were assessed for eligibility based on title and abstract. The full text of 81 eligible citations was screened, and relevant data of 15 children under 4 years of age with mycobacterial PESAO were extracted. These data were pooled with those from our Institution. Data from 16 children were reviewed. The median age was 16 ± 7 months and the male:female ratio 1.7. The knee was the most common infection site (94%). The diagnosis of mycobacterial disease was delayed in all cases (range, 2 weeks to 6 months), and initially presumed by histology in 15 children (94%). Microbiologically proven diagnosis was confirmed by bone cultures in 8 of the 15 children (53%), and by specific PCR in 2 of the 3 culture-negative bone specimens (67%). Three children experienced long-term orthopedic complications despite surgical drainage and prolonged antimycobacterial regimens. All recently reported cases came from high-burden tuberculosis areas. Mycobacterium species contribute to the burden of infantile PESAO in endemic tuberculosis areas and may cause growth disturbances. We argue in favor of the early recognition of mycobacterial disease by specific molecular assays in children with infantile PESAO living in high-burden areas.

Clinical Features of Spontaneous Partial Healing During Mycobacterium ulcerans Infection

Background.  Buruli ulcer, caused by Mycobacterium ulcerans, is a necrotizing skin disease leading to extensive cutaneous and subcutaneous destruction and functional limitations. Spontaneous healing in the absence of medical treatment occurs in rare cases, but this has not been well described in the literature. Methods.  In a retrospective case study in an area of Benin where this disease is highly endemic, we selected 26 Buruli ulcer patients presenting features of spontaneous healing from a cohort of 545 Buruli ulcer patients treated between 2010 and 2013. Results.  The 26 patients studied had a median age of 13.5 years and were predominantly male (1.4:1). Three groups of patients were defined on the basis of their spontaneous healing characteristics. The first group (12 patients) consisted of patients with an ulcer of more than 1 year's duration showing signs of healing. The second (13 patients) group contained patients with an active Buruli ulcer lesion some distance away from a first lesion that had healed spontaneously. Finally, the third group contained a single patient displaying complete healing of lesions from a nodule, without treatment and with no relapse. Conclusions.  We defined several features of spontaneous healing in Buruli ulcer patients and highlighted the difficulties associated with diagnosis and medical management. Delays in consultation contributed to the high proportion of patients with permanent sequelae and a risk of squamous cell carcinoma. Early detection and antibiotic treatment are the best ways to reduce impairments.

Clinical Epidemiology of Buruli Ulcer from Benin (2005-2013): Effect of Time-Delay to Diagnosis on Clinical Forms and Severe Phenotypes

Buruli Ulcer (BU) is a neglected infectious disease caused by Mycobacterium ulcerans that is responsible for severe necrotizing cutaneous lesions that may be associated with bone involvement. Clinical presentations of BU lesions are classically classified as papules, nodules, plaques and edematous infiltration, ulcer or osteomyelitis. Within these different clinical forms, lesions can be further classified as severe forms based on focality (multiple lesions), lesions' size (>15 cm diameter) or WHO Category (WHO Category 3 lesions). There are studies reporting an association between delay in seeking medical care and the development of ulcerative forms of BU or osteomyelitis, but the effect of time-delay on the emergence of lesions classified as severe has not been addressed. To address both issues, and in a cohort of laboratory-confirmed BU cases, 476 patients from a medical center in Allada, Benin, were studied. In this laboratory-confirmed cohort, we validated previous observations, demonstrating that time-delay is statistically related to the clinical form of BU. Indeed, for non-ulcerated forms (nodule, edema, and plaque) the median time-delay was 32.5 days (IQR 30.0-67.5), while for ulcerated forms it was 60 days (IQR 20.0-120.0) (p = 0.009), and for bone lesions, 365 days (IQR 228.0-548.0). On the other hand, we show here that time-delay is not associated with the more severe phenotypes of BU, such as multi-focal lesions (median 90 days; IQR 56-217.5; p = 0.09), larger lesions (diameter >15 cm) (median 60 days; IQR 30-120; p = 0.92) or category 3 WHO classification (median 60 days; IQR 30-150; p = 0.20), when compared with unifocal (median 60 days; IQR 30-90), small lesions (diameter ≤15 cm) (median 60 days; IQR 30-90), or WHO category 1+2 lesions (median 60 days; IQR 30-90), respectively. Our results demonstrate that after an initial period of progression towards ulceration or bone involvement, BU lesions become stable regarding size and focal/multi-focal progression. Therefore, in future studies on BU epidemiology, severe clinical forms should be systematically considered as distinct phenotypes of the same disease and thus subjected to specific risk factor investigation.

Nontuberculous mycobacterial osteomyelitis

Osteomyelitis caused by nontuberculous mycobacteria (NTM) can have severe consequences and a poor prognosis. Physicians therefore need to be alert to this condition, especially in immunocompromised patients. Although the pathogenesis of NTM osteomyelitis is still unclear, studies in immunodeficient individuals have revealed close relationships between NTM osteomyelitis and defects associated with the interleukin-12-interferon-γ-tumor necrosis factor-α axis, as well as human immunodeficiency virus infection, various immunosuppressive conditions, and diabetes mellitus. Culture and species identification from tissue biopsies or surgical debridement tissue play crucial roles in diagnosing NTM osteomyelitis. Suitable imaging examinations are also important. Adequate surgical debridement and the choice of appropriate, combined antibiotics for long-term anti-mycobacterial chemotherapy, based on in vitro drug susceptibility tests, are the main therapies for these bone infections. Bacillus Calmette-Guerin vaccination might have limited prophylactic value. The use of multiple drugs and long duration of treatment mean that the therapeutic process needs to be monitored closely to detect potential side effects. Adequate duration of anti-mycobacterial chemotherapy together with regular monitoring with blood and imaging tests are key factors determining the recovery outcome in patients with NTM osteomyelitis.

Exploration of a standard treatment for Buruli ulcer through a comprehensive analysis of all cases diagnosed in Japan

Buruli ulcer (BU) is a refractory skin ulcer caused by Mycobacterium ulcerans or M. ulcerans ssp. shinshuense, a subspecies thought to have originated in Japan or elsewhere in Asia. Although BU occurs most frequently in tropical and subtropical areas such as Africa and Australia, the occurrence in Japan has gradually increased in recent years. The World Health Organization recommends multidrug therapy consisting of a combination of oral rifampicin (RFP) and i.m. streptomycin (SM) for the treatment of BU. However, surgical interventions are often required when chemotherapy alone is ineffective. As a first step in developing a standardized regimen for BU treatment in Japan, we analyzed detailed records of treatments and prognoses in 40 of the 44 BU cases that have been diagnosed in Japan. We found that a combination of RFP (450 mg/day), levofloxacin (LVFX; 500 mg/day) and clarithromycin (CAM; at a dose of 800 mg/day instead of 400 mg/day) was superior to other chemotherapies performed in Japan. This simple treatment with oral medication increases the probability of patient adherence, and may often eliminate the need for surgery.

Establishment of quantitative PCR (qPCR) and culture laboratory facilities in a field hospital in benin: 1-year results

No simple diagnostic tool is available to confirm Mycobacterium ulcerans infection, which is an emerging disease reported in many rural areas of Africa. Here, we report the 1-year results of a hospital laboratory that was created in an area of endemicity of Benin to facilitate the diagnosis of M. ulcerans infection.