Antimicrobial treatment for early, limited Mycobacterium ulcerans infection: a randomised controlled trial

Clinical and microbiological predictors of healing in Buruli ulcer disease

Introduction

Wound measurements are relevant in monitoring the rate of healing (RoH) and may predict time to healing. Predicting the time to healing can help improve the management of Buruli ulcer. We examine three methods for the determination of RoH and their use as predictors of time to healing.

Methods

Lesion measurements of Buruli ulcer patients treated from 2007 to 2022 were obtained with acetate sheet tracings (2D) or Aranz software (3D) fortnightly. RoH was determined using the absolute area, percentage area reduction and linear methods at 4 weeks post onset of antibiotic treatment. Predicted time to healing was compared to the actual healing time. Baseline characteristics were assessed for associations with healing.

Results

All three methods for calculating the RoH significantly distinguished between fast and slow healers (p < 0.0001). The predicted healing time using the linear method was comparable to the actual healing time for fast healers (p = 0.34). The RoH was influenced by the form of lesion, with plaques [OR 2.19 5 %CI (1.2-3.6), p = 0.009], and oedemas [OR 8.5; 95 %CI (1.9--36.9), p = 0.004] being associated with delayed healing. The proportion of patients with paradoxical reactions 16 % vs 3 %, p < 0.0001), higher baseline bacterial load (75/104;72 % vs 21/47;45 %, p = 0.001) and delayed clearance of viable organisms (71/104;68 % vs 9/47;19 %, p < 0.0001) was higher in the slow healers than the fast healers.

Conclusion

Predicted healing rates were comparatively lower for slow healers than fast healers. Baseline characteristics associated with healing can be explored for an improved disease management plan to reduce patient and caregiver anxiety.

Mycobacterium ulcerans not detected by PCR on human skin in Buruli ulcer endemic areas of south eastern Australia

INTRODUCTION

Mycobacterium ulcerans (MU) causes Buruli ulcer (Buruli), a geographically restricted infection that can result in skin loss, contracture and permanent scarring. Lesion-location maps compiled from more than 640 cases in south eastern Australia suggest biting insects are likely involved in transmission, but it is unclear whether MU is brought by insects to humans or if MU is already on the skin and inoculation is an opportunistic event that need not be insect dependent.

METHODS

We validated a PCR swab detection assay and defined its dynamic range using laboratory cultured M. ulcerans and fresh pigskin. We invited volunteers in Buruli-endemic and non-endemic areas to sample their skin surfaces with self-collected skin swabs tested by IS2404 quantitative PCR.

RESULTS

Pigskin validation experiments established a limit-of-detection of 0.06 CFU/cm2 at a qPCR cycle threshold (Ct) of 35. Fifty-seven volunteers returned their self-collected kits of 4 swabs (bilateral ankles, calves, wrists, forearms), 10 from control areas and 47 from endemic areas. Collection was timed to coincide with the known peak-transmission period of Buruli. All swabs from human volunteers tested negative (Ct ≥35).

CONCLUSIONS

M. ulcerans was not detected on the skin of humans from highly Buruli endemic areas.

Mycobacterium ulcerans culture results according to duration of prior antibiotic treatment: A cohort study

Mycobacterium ulcerans disease is a necrotising disease of the skin and subcutaneous tissue and is effectively treated with eight-weeks antibiotic therapy. Significant toxicities, however, are experienced under this prolonged regimen. Here, we investigated the length of antibiotic duration required to achieve negative cultures of M. ulcerans disease lesions and evaluated the influence of patient characteristics on this outcome. M. ulcerans cases from an observational cohort that underwent antibiotic treatment prior to surgery and had post-excision culture assessment at Barwon Health, Victoria, from May 25 1998 to June 30 2019, were included. Antibiotic duration before surgery was grouped as <2 weeks, ≥2-<4 weeks, ≥4-<6 weeks, ≥6-<8 weeks, ≥8-<10 weeks and ≥10-20 weeks. Cox regression analyses were performed to assess the association between variables and culture positive results. Ninety-two patients fitted the inclusion criteria. The median age was 60 years (IQR 28-74.5) and 51 (55.4%) were male. Rifampicin-based regimens were predominantly used in combination with clarithromycin (47.8%) and ciprofloxacin (46.7%), and the median duration of antibiotic treatment before surgery was 23 days (IQR, 8.0-45.5). There were no culture positive results after 19 days of antibiotic treatment and there was a significant association between antibiotic duration before surgery and a culture positive outcome (p<0.001). The World Health Organisation category of the lesion and the antibiotic regimen used had no association with the culture outcome. Antibiotics appear to be effective at achieving negative cultures of M. ulcerans disease lesions in less than the currently recommended eight-week duration.

Evaluation of the fluorescent-thin layer chromatography (f-TLC) for the diagnosis of Buruli ulcer disease in Ghana

Background

Buruli ulcer is a tissue necrosis infection caused by an environmental mycobacterium called Mycobacterium ulcerans (MU). The disease is most prevalent in rural areas with the highest rates in West and Central African countries. The bacterium produces a toxin called mycolactone which can lead to the destruction of the skin, resulting in incapacitating deformities with an enormous economic and social burden on patients and their caregivers. Even though there is an effective antibiotic treatment for BU, the control and management rely on early case detection and rapid diagnosis to avert morbidities. The diagnosis of Mycobacterium ulcerans relies on smear microscopy, culture histopathology, and PCR. Unfortunately, all the current laboratory diagnostics have various limitations and are not available in endemic communities. Consequently, there is a need for a rapid diagnostic tool for use at the community health centre level to enable diagnosis and confirmation of suspected cases for early treatment. The present study corroborated the diagnostic performance and utility of fluorescent-thin layer chromatography (f-TLC) for the diagnosis of Buruli ulcer.

Methodology/Principal findings

The f-TLC method was evaluated for the diagnosis of Buruli ulcer in larger clinical samples than previously reported in an earlier preliminary study Wadagni et al. (2015). A total of 449 patients suspected of BU were included in the final data analysis out of which 122 (27.2%) were positive by f-TLC and 128 (28.5%) by PCR. Using a composite reference method generated from the two diagnostic methods, 85 (18.9%) patients were found to be truly infected with M. ulcerans, 284 (63.3%) were uninfected, while 80 (17.8%) were misidentified as infected or noninfected by the two methods. The data obtained was used to determine the discriminatory accuracy of the f-TLC against the gold standard IS2404 PCR through the analysis of its sensitivity, specificity, positive (+LR), and negative (–LR) likelihood ratio. The positive (PPV) and negative (NPV) predictive values, area under the receiver operating characteristic curve Azevedo et al. (2014), and diagnostic odds ratio were used to assess the predictive accuracy of the f-TLC method. The sensitivity of f-TLC was 66.4% (85/128), specificity was 88.5% (284/321), while the diagnostic accuracy was 82.2% (369/449). The AUC stood at 0.774 while the PPV, NPV, +LR, and–LR were 69.7% (85/122), 86.9% (284/327), 5.76, and 0.38, respectively. The use of the rule-of-thumb interpretation of diagnostic tests suggests that the method is good for use as a diagnostic tool.

Conclusions/Significance

Larger clinical samples than previously reported had been used to evaluate the f-TLC method for the diagnosis of Buruli ulcer. A sensitivity of 66.4%, a specificity of 88.5%, and diagnostic accuracy of 82.2% were obtained. The method is good for diagnosis and will help in making early clinical decisions about the patients as well as patient management and facilitating treatment decisions. However, it requires a slight modification to address the challenge of background interference and lack of automatic readout to become an excellent diagnostic tool.

Protective Efficacy of BCG Vaccine against Mycobacterium leprae and Non-Tuberculous Mycobacterial Infections

The genus mycobacterium includes several species that are known to cause infections in humans. The microorganisms are classified into tuberculous and non-tuberculous based on their morphological characteristics, defined by the dynamic relationship between the host defenses and the infectious agent. Non-tuberculous mycobacteria (NTM) include all the species of mycobacterium other than the ones that cause tuberculosis (TB). The group of NTM contains almost 200 different species and they are found in soil, water, animals—both domestic and wild—milk and food products, and from plumbed water resources such as sewers and showerhead sprays. A systematic review of Medline between 1946 and 2014 showed an 81% decline in TB incidence rates with a simultaneous 94% increase in infections caused by NTM. Prevalence of infections due to NTM has increased relative to infections caused by TB owing to the stringent prevention and control programs in Western countries such as the USA and Canada. While the spread of typical mycobacterial infections such as TB and leprosy involves human contact, NTM seem to spread easily from the environment without the risk of acquiring from a human contact except in the case of M. abscessus in patients with cystic fibrosis, where human transmission as well as transmission through fomites and aerosols has been recorded. NTM are opportunistic in their infectious processes, making immunocompromised individuals such as those with other systemic infections such as HIV, immunodeficiencies, pulmonary disease, or usage of medications such as long-term corticosteroids/TNF-α inhibitors more susceptible. This review provides insight on pathogenesis, treatment, and BCG vaccine efficacy against M. leprae and some important NTM infections.

Caregiver burden in Buruli ulcer disease: Evidence from Ghana

BACKGROUND

Buruli ulcer disease (BUD) results in disabilities and deformities in the absence of early medical intervention. The extensive role of caregiving in BUD is widely acknowledged, however, associated caregiver burden is poorly understood. In this paper we assessed the burden which caregivers experience when supporting patients with BUD in Ghana.

METHOD/ PRINCIPAL FINDINGS

This qualitative study was conducted in 3 districts in Ghana between August and October 2019. 13 semi-structured interviews were conducted on caregivers of BUD patients in the local language of Twi. Data was translated into English, coded into broad themes, and direct content analysis approach was used to analyse results. The results show the caregivers face financial, psychological and health issues as a consequence of their caregiving role.

CONCLUSION/ SIGNIFICANCE

This study found significant caregiver burden on family members. It also highlighted the psychological burden caregivers experience and the limited knowledge of the disease within endemic communities. Further research is needed to quantify the caregiver burden of BUD at different economic levels in order to better understand the impact of possible caregiver interventions on patient outcomes.

Rekindling of a Masterful Precedent; Bacteriophage: Reappraisal and Future Pursuits

Antibiotic resistance is exuberantly becoming a deleterious health problem world-wide. Seeking innovative approaches is necessary in order to circumvent such a hazard. An unconventional fill-in to antibiotics is bacteriophage. Bacteriophages are viruses capable of pervading bacterial cells and disrupting their natural activity, ultimately resulting in their defeat. In this article, we will run-through the historical record of bacteriophage and its correlation with bacteria. We will also delineate the potential of bacteriophage as a therapeutic antibacterial agent, its supremacy over antibiotics in multiple aspects and the challenges that could arise on the way to its utilization in reality. Pharmacodynamics, pharmacokinetics and genetic engineering of bacteriophages and its proteins will be briefly discussed as well. In addition, we will highlight some of the in-use applications of bacteriophages, and set an outlook for their future ones. We will also overview some of the miscellaneous abilities of these tiny viruses in several fields other than the clinical one. This is an attempt to encourage tackling a long-forgotten hive. Perhaps, one day, the smallest of the creatures would be of the greatest help.

Genetics in the Host-Mycobacterium ulcerans interaction

Buruli ulcer is an emerging infectious disease associated with high morbidity and unpredictable outbreaks. It is caused by Mycobacterium ulcerans, a slow-growing pathogen evolutionarily shaped by the acquisition of a plasmid involved in the production of a potent macrolide-like cytotoxin and by genome rearrangements and downsizing. These events culminated in an uncommon infection pattern, whereby M. ulcerans is both able to induce the initiation of the inflammatory cascade and the cell death of its proponents, as well as to survive within the phagosome and in the extracellular milieu. In such extreme conditions, the host is sentenced to rely on a highly orchestrated genetic landscape to be able to control the infection. We here revisit the dynamics of M. ulcerans infection, drawing parallels from other mycobacterioses and integrating the most recent knowledge on its evolution and pathogenicity in its interaction with the host immune response.

Six vs Eight Weeks of Antibiotics for Small Mycobacterium ulcerans Lesions in Australian Patients

BACKGROUND

Antibiotics are highly effective in curing Mycobacterium ulcerans lesions, but are associated with significant toxicity. In those not undergoing surgery, we compared 6 weeks with the currently recommended 8 weeks of combination antibiotic therapy for small M. ulcerans lesions.

METHODS

Mycobacterium ulcerans cases from an observational cohort at Barwon Health, Victoria, treated with antibiotics alone from 1 October 2010 to 31 March 2018 were included. The 6-week antibiotic group received ≥28 days and ≤42 days and the 8-week antibiotic group received ≥56 days of antibiotic therapy, respectively. Only World Health Organization category 1 lesions were included.

RESULTS

207 patients were included; 53 (25.6%) in the 6-week group and 154 (74.4%) in the 8-week group. The median age of patients was 53 years (interquartile range [IQR], 33-69 years) and 100 (48.3%) were female. Lesions were ≤900 mm2 in size in 79.7% of patients and 93.2% were ulcerative. Fifty-three patients (100%) achieved treatment cure in the 6-week group compared with 153 (99.4%) in the 8-week group (P = .56). No patients died or were lost to follow-up during the study. Median time to heal was 70 days (IQR, 60-96 days) in the 6-week group and 128 days (IQR, 95-173 days) in the 8-week group (P < .001). Two (3.8%) patients in the 6-week group experienced a paradoxical reaction compared with 39 (25.3%) patients in the 8-week group (P = .001).

CONCLUSIONS

For selected small M. ulcerans lesions, 6 weeks may be as effective as 8 weeks of combined antibiotic therapy in curing lesions without surgery.

Microbiology of secondary infections in Buruli ulcer lesions; implications for therapeutic interventions

Background

Buruli ulcer (BU) is a skin disease caused by Mycobacterium ulcerans and is the second most common mycobacterial disease after tuberculosis in Ghana and Côte d’Ivoire. M. ulcerans produces mycolactone, an immunosuppressant macrolide toxin, responsible for the characteristic painless nature of the infection. Secondary infection of ulcers before, during and after treatment has been associated with delayed wound healing and resistance to streptomycin and rifampicin. However, not much is known of the bacteria causing these infections as well as antimicrobial drugs for treating the secondary microorganism. This study sought to identify secondary microbial infections in BU lesions and to determine their levels of antibiotic resistance due to the prolonged antibiotic therapy required for Buruli ulcer.

Results

Swabs from fifty-one suspected BU cases were sampled in the Amansie Central District from St. Peters Hospital (Jacobu) and through an active case surveillance. Forty of the samples were M. ulcerans (BU) positive. Secondary bacteria were identified in all sampled lesions (N = 51). The predominant bacteria identified in both BU and Non-BU groups were Staphylococci spp and Bacilli spp. The most diverse secondary bacteria were detected among BU patients who were not yet on antibiotic treatment. Fungal species identified were Candida spp, Penicillium spp and Trichodema spp. Selected secondary bacteria isolates were all susceptible to clarithromycin and amikacin among both BU and Non-BU patients. Majority, however, had high resistance to streptomycin.

Conclusions

Microorganisms other than M. ulcerans colonize and proliferate on BU lesions. Secondary microorganisms of BU wounds were mainly Staphylococcus spp, Bacillus spp and Pseudomonas spp. These secondary microorganisms were less predominant in BU patients under treatment compared to those without treatment. The delay in healing that are experienced by some BU patients could be as a result of these bacteria and fungi colonizing and proliferating in BU lesions. Clarithromycin and amikacin are likely suitable drugs for clearance of secondary infection of Buruli ulcer.

Identification of P218 as a potent inhibitor of Mycobacterium ulcerans DHFR

Mycobacterium ulcerans is the causative agent of Buruli ulcer, a debilitating chronic disease that mainly affects the skin. Current treatments for Buruli ulcer are efficacious, but rely on the use of antibiotics with severe side effects. The enzyme dihydrofolate reductase (DHFR) plays a critical role in the de novo biosynthesis of folate species and is a validated target for several antimicrobials. Here we describe the biochemical and structural characterization of M. ulcerans DHFR and identified P218, a safe antifolate compound in clinical evaluation for malaria, as a potent inhibitor of this enzyme. We expect our results to advance M. ulcerans DHFR as a target for future structure-based drug discovery campaigns.

Risk Factors Associated with Antibiotic Treatment Failure of Buruli Ulcer

Combination antibiotic therapy is highly effective in curing Buruli ulcer (BU) caused by Mycobacterium ulcerans Treatment failures have been uncommonly reported with the recommended 56 days of antibiotics, and little is known about risk factors for treatment failure. We analyzed treatment failures among BU patients treated with ≥56 days of antibiotics from a prospective observational cohort at Barwon Health, Victoria, from 1 January 1998 to 31 December 2018. Treatment failure was defined as culture-positive recurrence within 12 months of commencing antibiotics under the following conditions: (i) following failure to heal the initial lesion or (ii) a new lesion developing at the original or at a new site. A total of 430 patients received ≥56 days of antibiotic therapy, with a median duration of 56 days (interquartile range [IQR], 56 to 80). Seven (1.6%) patients experienced treatment failure. For six adult patients experiencing treatment failure, all were male, weighed >90 kg, did not have surgery, and received combination rifampin-clarithromycin (median rifampin dose, 5.6 mg per kg of body weight per day; median clarithromycin dose, 8.1 mg/kg/day). When compared to those who did not fail treatment on univariate analysis, treatment failure was significantly associated with a weight of >90 kg (P < 0.001), male gender (P = 0.02), immune suppression (P = 0.04), and a first-line regimen of rifampin-clarithromycin compared to a regimen of rifampin-fluoroquinolone (P = 0.05). There is a low rate of treatment failure in Australian BU patients treated with rifampin-based oral combination antibiotic therapy. Our study raises the possibility that treatment failure risk may be increased in males, those with a body weight of >90 kg, those with immune suppression, and those taking rifampin-clarithromycin antibiotic regimens, but future pharmacokinetic and pharmacodynamics studies are required to determine the validity of these hypotheses.

The immunology of other mycobacteria: M. ulcerans, M. leprae

Mycobacterial pathogens can be categorized into three broad groups: Mycobacterium tuberculosis complex causing tuberculosis, M. leprae and M. lepromatosis causing leprosy, and atypical mycobacteria, or non-tuberculous mycobacteria (NTM), responsible for a wide range of diseases. Among the NTMs, M. ulcerans is responsible for the neglected tropical skin disease Buruli ulcer (BU). Most pathogenic mycobacteria, including M. leprae, evade effector mechanisms of the humoral immune system by hiding and replicating inside host cells and are furthermore excellent modulators of host immune responses. In contrast, M. ulcerans replicates predominantly extracellularly, sheltered from host immune responses through the cytotoxic and immunosuppressive effects of mycolactone, a macrolide produced by the bacteria. In the year 2018, 208,613 new cases of leprosy and 2713 new cases of BU were reported to WHO, figures which are notoriously skewed by vast underreporting of these diseases.

Barriers to Buruli ulcer treatment completion in the Ashanti and Central Regions, Ghana

BACKGROUND

Buruli ulcer is a chronic ulcerating skin condition, with the highest burden found in Central and West Africa where it disproportionately affects the most vulnerable populations. Treatment is demanding, comprising eight-weeks of daily antibiotics, regular wound care and possible surgical intervention. Treatment completion is key to optimising outcomes, however the degree of and barriers to this are not well understood. Recent change from injectable treatment (SR8) to oral treatment (CR8) has made it feasible to further decentralise care, potentially improving treatment access and completion. However, the impact of this and of other demographic and clinical influences on treatment completion must be explored first to ensure appropriate models of care are developed.

METHODOLOGY/PRINCIPAL FINDINGS

A retrospective clinical notes review and secondary data analysis of records from patients diagnosed between 1 January 2006-31 December 2018 at four district hospital clinics in the Ashanti and Central Regions, Ghana. Univariable analyses and multivariable logistic regression were performed to assess the association between explanatory variables and treatment completion. There were 931 patient episodes across the four clinics with overall treatment completion of 84.4%. CR8 was associated with higher treatment completion compared to SR8 (OR 4.1, P = 0.001). There was no statistically significant association found between distance from patient residence to clinic and treatment completion.

CONCLUSIONS/SIGNIFICANCE

Improved treatment completion with CR8 supports its use as first line therapy and may enable decentralisation to fully community-based care. We did not find an association between distance to care and treatment completion, though analyses were limited by data availability. However, we did find evidence that distance to care continues to be associated with more severe forms of disease, which may reflect the higher costs of accessing care and lower awareness of the condition the further a patient lives. Decentralised care must therefore also continue to support community engagement and active outreach to identify cases early.

Pharmacologic management of Mycobacterium ulcerans infection

INTRODUCTION

Pharmacological treatment of Buruli ulcer (Mycobacterium ulcerans infection; BU) is highly effective, as shown in two randomized trials in Africa.

AREAS COVERED

We review BU drug treatment - in vitro, in vivo and clinical trials (PubMed: '(Buruli OR (Mycobacterium AND ulcerans)) AND (treatment OR therapy).' We also highlight the pathogenesis of M. ulcerans infection that is dominated by mycolactone, a secreted exotoxin, that causes skin and soft tissue necrosis, and impaired immune response and tissue repair. Healing is slow, due to the delayed wash-out of mycolactone. An array of repurposed tuberculosis and leprosy drugs appears effective in vitro and in animal models. In clinical trials and observational studies, only rifamycins (notably, rifampicin), macrolides (notably, clarithromycin), aminoglycosides (notably, streptomycin) and fluoroquinolones (notably, moxifloxacin, and ciprofloxacin) have been tested.

EXPERT OPINION

A combination of rifampicin and clarithromycin is highly effective but lesions still take a long time to heal. Novel drugs like telacebec have the potential to reduce treatment duration but this drug may remain unaffordable in low-resourced settings. Research should address ulcer treatment in general; essays to measure mycolactone over time hold promise to use as a readout for studies to compare drug treatment schedules for larger lesions of Buruli ulcer.

Rifampicin and clarithromycin (extended release) versus rifampicin and streptomycin for limited Buruli ulcer lesions: a randomised, open-label, non-inferiority phase 3 trial

BACKGROUND

Buruli ulcer is a neglected tropical disease caused by Mycobacterium ulcerans infection that damages the skin and subcutis. It is most prevalent in western and central Africa and Australia. Standard antimicrobial treatment with oral rifampicin 10 mg/kg plus intramuscular streptomycin 15 mg/kg once daily for 8 weeks (RS8) is highly effective, but streptomycin injections are painful and potentially harmful. We aimed to compare the efficacy and tolerability of fully oral rifampicin 10 mg/kg plus clarithromycin 15 mg/kg extended release once daily for 8 weeks (RC8) with that of RS8 for treatment of early Buruli ulcer lesions.

METHODS

We did an open-label, non-inferiority, randomised (1:1 with blocks of six), multicentre, phase 3 clinical trial comparing fully oral RC8 with RS8 in patients with early, limited Buruli ulcer lesions. There were four trial sites in hospitals in Ghana (Agogo, Tepa, Nkawie, Dunkwa) and one in Benin (Pobè). Participants were included if they were aged 5 years or older and had typical Buruli ulcer with no more than one lesion (caterories I and II) no larger than 10 cm in diameter. The trial was open label, and neither the investigators who took measurements of the lesions nor the attending doctors were masked to treatment assignment. The primary clinical endpoint was lesion healing (ie, full epithelialisation or stable scar) without recurrence at 52 weeks after start of antimicrobial therapy. The primary endpoint and safety were assessed in the intention-to-treat population. A sample size of 332 participants was calculated to detect inferiority of RC8 by a margin of 12%. This study was registered with ClinicalTrials.gov, NCT01659437.

FINDINGS

Between Jan 1, 2013, and Dec 31, 2017, participants were recruited to the trial. We stopped recruitment after 310 participants. Median age of participants was 14 years (IQR 10-29) and 153 (52%) were female. 297 patients had PCR-confirmed Buruli ulcer; 151 (51%) were assigned to RS8 treatment, and 146 (49%) received oral RC8 treatment. In the RS8 group, lesions healed in 144 (95%, 95% CI 91 to 98) of 151 patients, whereas lesions healed in 140 (96%, 91 to 99) of 146 patients in the RC8 group. The difference in proportion, -0·5% (-5·2 to 4·2), was not significantly greater than zero (p=0·59), showing that RC8 treatment is non-inferior to RS8 treatment for lesion healing at 52 weeks. Treatment-related adverse events were recorded in 20 (13%) patients receiving RS8 and in nine (7%) patients receiving RC8. Most adverse events were grade 1-2, but one (1%) patient receiving RS8 developed serious ototoxicity and ended treatment after 6 weeks. No patients needed surgical resection. Four patients (two in each study group) had skin grafts.

INTERPRETATION

Fully oral RC8 regimen was non-inferior to RS8 for treatment of early, limited Buruli ulcer and was associated with fewer adverse events. Therefore, we propose that fully oral RC8 should be the preferred therapy for early, limited lesions of Buruli ulcer.

FUNDING

WHO with additional support from MAP International, American Leprosy Missions, Fondation Raoul Follereau France, Buruli ulcer Groningen Foundation, Sanofi-Pasteur, and BuruliVac.

Global Epidemiology of Buruli Ulcer, 2010-2017, and Analysis of 2014 WHO Programmatic Targets

Buruli ulcer is a neglected tropical disease caused by Myocobacterium ulcerans; it manifests as a skin lesion, nodule, or ulcer that can be extensive and disabling. To assess the global burden and the progress on disease control, we analyzed epidemiologic data reported by countries to the World Health Organization during 2010–2017. During this period, 23,206 cases of Buruli ulcer were reported. Globally, cases declined to 2,217 in 2017, but local epidemics seem to arise, such as in Australia and Liberia. In 2013, the World Health Organization formulated 4 programmatic targets for Buruli ulcer that addressed PCR confirmation, occurrence of category III (extensive) lesions and ulcerative lesions, and movement limitation caused by the disease. In 2014, only the movement limitation goal was met, and in 2019, none are met, on a global average. Our findings support discussion on future Buruli ulcer policy and post-2020 programmatic targets.

In Vivo Imaging of Bioluminescent Mycobacterium ulcerans: A Tool to Refine the Murine Buruli Ulcer Tail Model

Buruli ulcer (BU) is a neglected tropical disease caused by infection with Mycobacterium ulcerans. Unclear transmission, no available vaccine, and suboptimal treatment regimens hamper the control of this disease. Carefully designed preclinical research is needed to address these shortcomings. In vivo imaging (IVIS^®, Perkin Elmer, Waltham, MA) of infection is an emerging tool that permits monitoring of disease progression and reduces the need to using large numbers of mice at different time-points during the experiment, as individual mice can be imaged at multiple time-points. We aimed to further describe the use of in vivo imaging (IVIS) in BU. We studied the detection of M. ulcerans in experimentally infected BALB/c mouse tails and the subsequent histopathology and immune response in this pilot study. IVIS-monitoring was performed weekly in ten infected BALB/c mice to measure light emitted as a proxy for bacterial load. Nine of 10 (90%) BALB/c mice infected subcutaneously with 3.3 × 10⁵ M. ulcerans JKD8049 (containing pMV306 hsp16+luxG13) exhibited light emission from the site of infection, indicating M. ulcerans growth in vivo, whereas only five of 10 (50%) animals developed clinical signs of the disease. Specific antibody titers were detected within 2 weeks of the infection. Interferon (IFN)-γ and interleukin (IL)-10 were elevated in animals with pathology. Histopathology revealed clusters of acid-fast bacilli in the subcutaneous tissue, with macrophage infiltration and granuloma formation resembling human BU. Our study successfully showed the utility of M. ulcerans IVIS monitoring and lays a foundation for further research.

Vaccine-Specific Immune Responses against Mycobacterium ulcerans Infection in a Low-Dose Murine Challenge Model

The neglected tropical disease Buruli ulcer (BU) is an infection of subcutaneous tissue with Mycobacterium ulcerans There is no effective vaccine. Here, we assessed an experimental prime-boost vaccine in a low-dose murine tail infection model. We used the enoyl reductase (ER) domain of the M. ulcerans mycolactone polyketide synthases electrostatically coupled with a previously described Toll-like receptor 2 (TLR-2) agonist-based lipopeptide adjuvant, R₄Pam₂Cys. Mice were vaccinated and then challenged via tail inoculation with 14 to 20 CFU of a bioluminescent strain of M. ulcerans Mice receiving either the experimental ER vaccine or Mycobacterium bovis bacillus Calmette-Guérin (BCG) were equally protected, with both groups faring significantly better than nonvaccinated animals (P < 0.05). To explore potential correlates of protection, a suite of 29 immune parameters were assessed in the mice at the end of the experimental period. Multivariate statistical approaches were used to interrogate the immune response data to develop disease-prognostic models. High levels of interleukin 2 (IL-2) and low gamma interferon (IFN-γ) produced in the spleen best predicted control of infection across all vaccine groups. Univariate logistic regression revealed vaccine-specific profiles of protection. High titers of ER-specific IgG serum antibodies together with IL-2 and IL-4 in the draining lymph node (DLN) were associated with protection induced by the ER vaccine. In contrast, high titers of IL-6, tumor necrosis factor alpha (TNF-α), IFN-γ, and IL-10 in the DLN and low IFN-γ titers in the spleen were associated with protection following BCG vaccination. This study suggests that an effective BU vaccine must induce localized, tissue-specific immune profiles with controlled inflammatory responses at the site of infection.

Buruli ulcer treatment: Rate of surgical intervention differs highly between treatment centers in West Africa

Background

Antibiotic treatment proved itself as the mainstay of treatment for Buruli ulcer disease. This neglected tropical disease is caused by Mycobacterium ulcerans. Surgery persists as an adjunct therapy intended to reduce the mycobacterial load. In an earlier clinical trial, patients benefited from delaying the decision to operate. Nevertheless, the rate of surgical interventions differs highly per clinic.

Methods

A retrospective study was conducted in six different Buruli ulcer (BU) treatment centers in Benin and Ghana. BU patients clinically diagnosed between January 2012 and December 2016 were included and surgical interventions during the follow-up period, at least one year after diagnosis, were recorded. Logistic regression analysis was carried out to estimate the effect of the treatment center on the decision to perform surgery, while controlling for interaction and confounders.

Results

A total of 1193 patients, 612 from Benin and 581 from Ghana, were included. In Benin, lesions were most frequently (42%) categorized as the most severe lesions (WHO criteria, category III), whereas in Ghana lesions were most frequently (44%) categorized as small lesions (WHO criteria, category I). In total 344 (29%) patients received surgical intervention. The percentage of patients receiving surgical intervention varied between hospitals from 1.5% to 72%. Patients treated in one of the centers in Benin were much more likely to have surgery compared to the clinic in Ghana with the lowest rate of surgical intervention (RR = 46.7 CI 95% [17.5–124.8]). Even after adjusting for confounders (severity of disease, age, sex, limitation of movement at joint at time of diagnosis, ulcer and critical sites), rates of surgical interventions varied highly.

Conclusion

The decision to perform surgery to reduce the mycobacterial load in BU varies highly per clinic. Evidence based guidelines are needed to guide the role of surgery in the treatment of BU

Buruli ulcer is a necrotizing and disabling skin infection, caused by Mycobacterium ulcerans. The infection, a skin-related Neglected Tropical Diseases, affects mostly people living in limited resources settings. Since the introduction of rifampicin based combination antibiotic therapy as standard care, the role of surgery as adjunct therapy to kill M. ulcerans is less defined and understood. A randomized controlled trial showed benefit from delaying the decision to operate. Nevertheless, the rate of surgical interventions differs highly per clinic. We present the differences in rate of surgical interventions in six different Buruli ulcer treatment centers in Ghana and Benin. We demonstrate that these differences mainly depend on the opinion of the health care workers working in the treatment centers even after adjusting for disease severity.

Phage therapy as a renewed therapeutic approach to mycobacterial infections: a comprehensive review

Mycobacterial infections are considered to a serious challenge of medicine, and the emergence of MDR and XDR tuberculosis is a serious public health problem. Tuberculosis can cause high morbidity and mortality around the world, particularly in developing countries. The emergence of drug-resistant Mycobacterium infection following limited therapeutic technologies coupled with the serious worldwide tuberculosis epidemic has adversely affected control programs, thus necessitating the study of the role bacteriophages in the treatment of mycobacterial infection. Bacteriophages are viruses that are isolated from several ecological specimens and do not exert adverse effects on patients. Phage therapy can be considered as a significant alternative to antibiotics for treating MDR and XDR mycobacterial infections. The useful ability of bacteriophages to kill Mycobacterium spp has been explored by numerous research studies that have attempted to investigate the phage therapy as a novel therapeutic/diagnosis approach to mycobacterial infections. However, there are restricted data about phage therapy for treating mycobacterial infections. This review presents comprehensive data about phage therapy in the treatment of mycobacterial infection, specifically tuberculosis disease.

Antimicrobial activity of Mycobacteriophage D29 Lysin B during Mycobacterium ulcerans infection

Buruli Ulcer (BU) is a cutaneous disease caused by Mycobacterium ulcerans. The pathogenesis of this disease is closely related to the secretion of the toxin mycolactone that induces extensive destruction of the skin and soft tissues. Currently, there are no effective measures to prevent the disease and, despite availability of antibiotherapy and surgical treatments, these therapeutic options are often associated with severe side effects. Therefore, it is important to develop alternative strategies for the treatment of BU. Endolysins (lysins) are phage encoded enzymes that degrade peptidoglycan of bacterial cell walls. Over the past years, lysins have been emerging as alternative antimicrobial agents against bacterial infections. However, mycobacteria have an unusual outer membrane composed of mycolylarabinogalactan-peptidoglycan. To overcome this complex barrier, some mycobacteriophages encode a lipolytic enzyme, Lysin B (LysB). In this study, we demonstrate for the first time that recombinant LysB displays lytic activity against M. ulcerans isolates. Moreover, using a mouse model of M. ulcerans footpad infection, we show that subcutaneous treatment with LysB prevented further bacterial proliferation, associated with IFN-γ and TNF production in the draining lymph node. These findings highlight the potential use of lysins as a novel therapeutic approach against this neglected tropical disease.

Buruli Ulcer (BU) is a necrotizing skin disease caused by Mycobacterium ulcerans. Although the current antibiotic treatment for BU is effective, daily administrations for a prolonged period of time, combined with potential risk of severe side effects, negatively impact on patient adherence. In that sense, we tested the efficacy of an alternative strategy based on Lysin B (LysB), a phage encoded lipolytic enzyme that degrades the mycolylarabinogalactan-peptidoglycan complex present in the mycobacterial cell wall. In this study, we show that LysB not only displays lytic activity against M. ulcerans isolates in vitro, but also leads to a decrease of M. ulcerans proliferation in infected mouse footpads. These findings highlight the potential use of lysins as a novel therapeutic approach against this neglected tropical disease.

A case of squamous cell carcinoma occurring on a scar of Buruli ulcer in Bouake, Ivory Coast

Buruli ulcer is infectious necrotizing panniculitis due to Mycobacterium ulcerans. Buruli ulcer is healed by leaving dystrophic, fibrous and retractile scars. On these scars can occur long-term squamous cell carcinoma. We report the first case of squamous cell carcinoma occurring on healing of Buruli ulcer. A 32-year-old woman with Buruli ulcer who has been cured for about 10 years is seen for ulcero-bulging knee swelling. The examination had revealed a large swelling of about ten centimeters in diameter, ulcero-budding, with an easily bleeding cauliflower appearance. The diagnosis of squamous cell carcinoma being retained without metastasis, resection of the tumor with scarring after one month without chemotherapy. There was no recurrence after six months of decline. The epidemiology of Buruli ulcer, responsible for scarring, explains the young age of our patient and the localization of carcinoma on the limb. The carcinomatous degeneration of scars, especially the scars of old burns, is constantly reported. The characteristics of Buruli ulcer scars, which bring them closer to burn scars, may explain why they are particularly affected by carcinomatous degeneration. One could also mention the chronicity of the wound in this infection, or wonder if the mycobacteria itself could play a role in carcinogenesis. This observation is, in our opinion, an alarm signal. We must fear an outbreak of cases in the years to come. To this end, preventive measures should already be taken by sensitizing the patients for an early consultation before any modification of their scars. After recovery, Buruli ulcer seems to present a risk of long-term evolution to a cancer. The scars of this condition, which could be considered precancerous lesions.

Shortening Buruli Ulcer Treatment with Combination Therapy Targeting the Respiratory Chain and Exploiting Mycobacterium ulcerans Gene Decay

Buruli ulcer is treatable with antibiotics. An 8-week course of rifampin (RIF) and either streptomycin (STR) or clarithromycin (CLR) cures over 90% of patients. However, STR requires injections and may be toxic, and CLR shares an adverse drug-drug interaction with RIF and may be poorly tolerated. Studies in a mouse footpad infection model showed that increasing the dose of RIF or using the long-acting rifamycin rifapentine (RPT), in combination with clofazimine (CFZ), a relatively well-tolerated antibiotic, can shorten treatment to 4 weeks. CFZ is reduced by a component of the electron transport chain (ETC) to produce reactive oxygen species toxic to bacteria. Synergistic activity of CFZ with other ETC-targeting drugs, the ATP synthase inhibitor bedaquiline (BDQ) and the bc ₁:aa ₃ oxidase inhibitor Q203 (now named telacebec), was recently described against Mycobacterium tuberculosis Recognizing that M. tuberculosis mutants lacking the alternative bd oxidase are hypersusceptible to Q203 and that Mycobacterium ulcerans is a natural bd oxidase-deficient mutant, we tested the in vitro susceptibility of M. ulcerans to Q203 and evaluated the treatment-shortening potential of novel 3- and 4-drug regimens combining RPT, CFZ, Q203, and/or BDQ in a mouse footpad model. The MIC of Q203 was extremely low (0.000075 to 0.00015 μg/ml). Footpad swelling decreased more rapidly in mice treated with Q203-containing regimens than in mice treated with RIF and STR (RIF+STR) and RPT and CFZ (RPT+CFZ). Nearly all footpads were culture negative after only 2 weeks of treatment with regimens containing RPT, CFZ, and Q203. No relapse was detected after only 2 weeks of treatment in mice treated with any of the Q203-containing regimens. In contrast, 15% of mice receiving RIF+STR for 4 weeks relapsed. We conclude that it may be possible to cure patients with Buruli ulcer in 14 days or less using Q203-containing regimens rather than currently recommended 56-day regimens.

Oxazolidinones Can Replace Clarithromycin in Combination with Rifampin in a Mouse Model of Buruli Ulcer

Rifampin (RIF) plus clarithromycin (CLR) for 8 weeks is now the standard of care for Buruli ulcer (BU) treatment, but CLR may not be an ideal companion for rifamycins due to bidirectional drug-drug interactions. The oxazolidinone linezolid (LZD) was previously shown to be active against Mycobacterium ulcerans infection in mice but has dose- and duration-dependent toxicity in humans. Sutezolid (SZD) and tedizolid (TZD) may be safer than LZD. Here, we evaluated the efficacy of these oxazolidinones in combination with rifampin in a murine BU model. Mice with M. ulcerans-infected footpads received control regimens of RIF plus either streptomycin (STR) or CLR or test regimens of RIF plus either LZD (1 of 2 doses), SZD, or TZD for up to 8 weeks. All combination regimens reduced the swelling and bacterial burden in footpads after two weeks of treatment compared with RIF alone. RIF+SZD was the most active test regimen, while RIF+LZD was also no less active than RIF+CLR. After 4 and 6 weeks of treatment, neither CLR nor the oxazolidinones added significant bactericidal activity to RIF alone. By the end of 8 weeks of treatment, all regimens rendered footpads culture negative. We conclude that SZD and LZD warrant consideration as alternative companion agents to CLR in combination with RIF to treat BU, especially when CLR is contraindicated, intolerable, or unavailable. Further evaluation could prove SZD superior to CLR in this combination.

Spontaneous healing of Mycobacterium ulcerans disease in Australian patients

Background

Mycobacterium ulcerans causes necrotising infections of skin and soft tissue mediated by the polyketide exotoxin mycolactone that causes cell apoptosis and immune suppression. It has been postulated that infection can be eradicated before the development of clinical lesions but spontaneous resolution of clinical lesions has been rarely described.

Methodology/Principal findings

We report a case series of five Australian patients who achieved healing of small M. ulcerans lesions without antibiotics or surgery. The median age of patients was 47 years (IQR 30–68 years) and all patients had small ulcerative lesions (median size 144mm², IQR 121-324mm²). The median duration of symptoms prior to diagnosis was 90 days (IQR 90–100 days) and the median time to heal from diagnosis without treatment was 68 days (IQR 63–105 days). No patients recurred after a median follow-up of 16.6 months (IQR 16.6–17.9 months) from the development of symptoms and no patients suffered long-term disability from the disease.

Conclusions

We have shown that healing without specific treatment can occur for small ulcerated M. ulcerans lesions suggesting that in selected cases a robust immune response alone can cure lesions. Further research is required to determine what lesion and host factors are associated with spontaneous healing, and whether observation alone is an effective and safe form of management for selected small M. ulcerans lesions.

Mycobacterium ulcerans causes a destructive infection of skin and soft tissue known as Buruli ulcer that when severe can lead to serious long-term deformity and disability. It is currently not well documented whether people with Mycobacterium ulcerans disease can cure themselves without treatment. In our study we describe five people with small ulcers who cured their disease without specific medical or surgical treatment. This suggests that a proportion of people can develop an immune response sufficient enough to eradicate the disease without the help of medical intervention. This is an important step, as recognition of this possibility provides important further insights into the human immune response against the disease. It also opens the possibility to further studies that may determine characteristics of the organism and hosts that favour spontaneous healing of lesions. This knowledge may in turn improve efforts to prevent and control the disease which are currently lacking.

Mycobacterium ulcerans Population Genomics To Inform on the Spread of Buruli Ulcer across Central Africa

Buruli ulcer is a neglected tropical disease of skin and subcutaneous tissue caused by infection with the pathogen Mycobacterium ulcerans Many critical issues for disease control, such as understanding the mode of transmission and identifying source reservoirs of M. ulcerans, are still largely unknown. Here, we used genomics to reconstruct in detail the evolutionary trajectory and dynamics of M. ulcerans populations at a central African scale and at smaller geographical village scales. Whole-genome sequencing (WGS) data were analyzed from 179 M. ulcerans strains isolated from all Buruli ulcer foci in the Democratic Republic of the Congo, The Republic of Congo, and Angola that have ever yielded positive M. ulcerans cultures. We used both temporal associations and the study of the mycobacterial demographic history to estimate the contribution of humans as a reservoir in Buruli ulcer transmission. Our phylogeographic analysis revealed one almost exclusively predominant sublineage of M. ulcerans that arose in Central Africa and proliferated in its different regions of endemicity during the Age of Discovery. We observed how the best sampled endemic hot spot, the Songololo territory, became an area of endemicity while the region was being colonized by Belgium (1880s). We furthermore identified temporal parallels between the observed past population fluxes of M. ulcerans from the Songololo territory and the timing of health policy changes toward control of the Buruli ulcer epidemic in that region. These findings suggest that an intervention based on detecting and treating human cases in an area of endemicity might be sufficient to break disease transmission chains, irrespective of other reservoirs of the bacterium.IMPORTANCE Buruli ulcer is a destructive skin and soft tissue infection caused by Mycobacterium ulcerans The disease is characterized by progressive skin ulceration, which can lead to permanent disfigurement and long-term disability. Currently, the major hurdles facing disease control are incomplete understandings of both the mode of transmission and environmental reservoirs of M. ulcerans As decades of spasmodic environmental sampling surveys have not brought us much closer to overcoming these hurdles, the Buruli ulcer research community has recently switched to using comparative genomics. The significance of our research is in how we used both temporal associations and the study of the mycobacterial demographic history to estimate the contribution of humans as a reservoir in Buruli ulcer transmission. Our approach shows that it might be possible to use bacterial population genomics to assess the impact of health interventions, providing valuable feedback for managers of disease control programs in areas where health surveillance infrastructure is poor.

High-Dose Rifamycins Enable Shorter Oral Treatment in a Murine Model of Mycobacterium ulcerans Disease

Buruli ulcer (BU), caused by Mycobacterium ulcerans, is a neglected tropical skin and soft tissue infection that is associated with disability and social stigma. The mainstay of BU treatment is an 8-week course of rifampin (RIF) at 10 mg/kg of body weight and 150 mg/kg streptomycin (STR). Recently, the injectable STR has been shown to be replaceable with oral clarithromycin (CLR) for smaller lesions for the last 4 weeks of treatment. A shorter, all-oral, highly efficient regimen for BU is needed, as the long treatment duration and indirect costs currently burden patients and health systems. Increasing the dose of RIF or replacing it with the more potent rifamycin drug rifapentine (RPT) could provide such a regimen. Here, we performed a dose-ranging experiment of RIF and RPT in combination with CLR over 4 weeks of treatment in a mouse model of M. ulcerans disease. A clear dose-dependent effect of RIF on both clinical and microbiological outcomes was found, with no ceiling effect observed with tested doses up to 40 mg/kg. RPT-containing regimens were more effective on M. ulcerans All RPT-containing regimens achieved culture negativity after only 4 weeks, while only the regimen with the highest RIF dose (40 mg/kg) did so. We conclude that there is dose-dependent efficacy of both RIF and RPT and that a ceiling effect is not reached with the current standard regimen used in the clinic. A regimen based on higher rifamycin doses than are currently being evaluated against tuberculosis in clinical trials could shorten and improve therapy of Buruli ulcer.

Triple oral beta-lactam containing therapy for Buruli ulcer treatment shortening

The potential use of clinically approved beta-lactams for Buruli ulcer (BU) treatment was investigated with representative classes analyzed in vitro for activity against Mycobacterium ulcerans. Beta-lactams tested were effective alone and displayed a strong synergistic profile in combination with antibiotics currently used to treat BU, i.e. rifampicin and clarithromycin; this activity was further potentiated in the presence of the beta-lactamase inhibitor clavulanate. In addition, quadruple combinations of rifampicin, clarithromycin, clavulanate and beta-lactams resulted in multiplicative reductions in their minimal inhibitory concentration (MIC) values. The MIC of amoxicillin against a panel of clinical isolates decreased more than 200-fold within this quadruple combination. Amoxicillin/clavulanate formulations are readily available with clinical pedigree, low toxicity, and orally and pediatric available; thus, supporting its potential inclusion as a new anti-BU drug in current combination therapies.

Buruli ulcer (BU) is a chronic debilitating disease of the skin and soft tissue, mainly affecting children and young adults in tropical regions. Before 2004, the only treatment option was surgery; a major breakthrough was the discovery that BU could be cured in most cases with a standard treatment that involved 8 weeks of combination therapy with rifampicin and streptomycin. However, the use of streptomycin is often associated with severe side effects such as ototoxicity, or nephrotoxicity. More recently, a clinical trial demonstrated equipotency of replacing the injectable streptomycin by the clarithromycin, which is orally available and associated with fewer side effects. BU treatment is now moving toward a full orally available treatment of clarithromycin-rifampicin. Although effective and mostly well tolerated, this new treatment is still associated with side effects and only moxifloxacin is additionally recommended by WHO for BU therapy. New drugs are thus needed to increase the number of available treatments, reduce side effects, and improve efficacy with treatments shorter than 8 weeks. In this work, we describe for the first time the potential inclusion of beta-lactams in BU therapy. More specifically, we propose the use of amoxicillin/clavulanate since it is oral, suitable for the treatment of children, and readily available with a long track record of clinical pedigree. Its inclusion in a triple oral therapy complementing current combinatorial rifampicin-clarithromycin treatment has the potential to counteract resistance development and to reduce length of treatment and time to cure.

Targeting the Mycobacterium ulcerans cytochrome bc1:aa3 for the treatment of Buruli ulcer

Mycobacterium ulcerans is the causative agent of Buruli ulcer, a neglected tropical skin disease that is most commonly found in children from West and Central Africa. Despite the severity of the infection, therapeutic options are limited to antibiotics with severe side effects. Here, we show that M. ulcerans is susceptible to the anti-tubercular drug Q203 and related compounds targeting the respiratory cytochrome bc₁:aa₃. While the cytochrome bc₁:aa₃ is the primary terminal oxidase in Mycobacterium tuberculosis, the presence of an alternate bd-type terminal oxidase limits the bactericidal and sterilizing potency of Q203 against this bacterium. M. ulcerans strains found in Buruli ulcer patients from Africa and Australia lost all alternate terminal electron acceptors and rely exclusively on the cytochrome bc₁:aa₃ to respire. As a result, Q203 is bactericidal at low dose against M. ulcerans replicating in vitro and in mice, making the drug a promising candidate for Buruli ulcer treatment.

Mycobacterium ulcerans is the causative agent of Buruli ulcer (BU). Existing anti-tubercular drugs have been used to treat the condition with varying success. Here, the authors show that a clinical-stage drug candidate for tuberculosis, Q203, is effective at killing M. ulcerans and is a promising therapeutic candidate for BU.

Cutaneous Infections Due to Nontuberculosis Mycobacterium: Recognition and Management

Nontuberculous mycobacteria (NTM) are a diverse group of organisms that are ubiquitous in the environment, and the incidence of cutaneous infections due to NTM has been steadily increasing. Cutaneous infections due to NTM can be difficult to diagnose, due to their wide spectrum of clinical presentations and histopathological findings that are often nonspecific. A variety of modalities including tissue culture and polymerase chain reaction (PCR) assays may be necessary to identify the organism. Treatment can also be challenging, as it can depend on multiple factors, including the causative organism, the patient's immunological status, and the extent of disease involvement. In this review, we discuss the common presentations of cutaneous NTM infections, diagnostic tools, and treatment recommendations. A multi-disciplinary approach that involves good communication between the clinician, the histopathologist, the microbiologist, and infectious disease specialists can help lead to successful diagnosis and management.

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.

Cutaneous Mycobacterial Infections

Humans encounter mycobacterial species due to their ubiquity in different environmental niches. In many individuals, pathogenic mycobacterial species may breach our first-line barrier defenses of the innate immune system and modulate the activation of phagocytes to cause disease of the respiratory tract or the skin and soft tissues, sometimes resulting in disseminated infection. Cutaneous mycobacterial infections may cause a wide range of clinical manifestations, which are divided into four main disease categories: (i) cutaneous manifestations of Mycobacterium tuberculosis infection, (ii) Buruli ulcer caused by Mycobacterium ulcerans and other related slowly growing mycobacteria, (iii) leprosy caused by Mycobacterium leprae and Mycobacterium lepromatosis, and (iv) cutaneous infections caused by rapidly growing mycobacteria. Clinically, cutaneous mycobacterial infections present with widely different clinical presentations, including cellulitis, nonhealing ulcers, subacute or chronic nodular lesions, abscesses, superficial lymphadenitis, verrucous lesions, and other types of findings. Mycobacterial infections of the skin and subcutaneous tissue are associated with important stigma, deformity, and disability. Geography-based environmental exposures influence the epidemiology of cutaneous mycobacterial infections. Cutaneous tuberculosis exhibits different clinical phenotypes acquired through different routes, including via extrinsic inoculation of the tuberculous bacilli and dissemination to the skin from other sites, or represents hypersensitivity reactions to M. tuberculosis infection. In many settings, leprosy remains an important cause of neurological impairment, deformity, limb loss, and stigma. Mycobacterium lepromatosis, a mycobacterial species related to M. leprae, is linked to diffuse lepromatous leprosy of Lucio and Latapí. Mycobacterium ulcerans produces a mycolactone toxin that leads to subcutaneous tissue destruction and immunosuppression, resulting in deep ulcerations that often produce substantial disfigurement and disability. Mycobacterium marinum, a close relative of M. ulcerans, is an important cause of cutaneous sporotrichoid nodular lymphangitic lesions. Among patients with advanced immunosuppression, Mycobacterium kansasii, the Mycobacterium avium-intracellulare complex, and Mycobacterium haemophilum may cause cutaneous or disseminated disease. Rapidly growing mycobacteria, including the Mycobacterium abscessus group, Mycobacterium chelonei, and Mycobacterium fortuitum, are increasingly recognized pathogens in cutaneous infections associated particularly with plastic surgery and cosmetic procedures. Skin biopsies of cutaneous lesions to identify acid-fast staining bacilli and cultures represent the cornerstone of diagnosis. Additionally, histopathological evaluation of skin biopsy specimens may be useful in identifying leprosy, Buruli ulcer, and cutaneous tuberculosis. Molecular assays are useful in some cases. The treatment for cutaneous mycobacterial infections depends on the specific pathogen and therefore requires a careful consideration of antimicrobial choices based on official treatment guidelines.

The changing epidemiology worldwide of Mycobacterium ulcerans

Mycobacterium ulcerans is recognised as the third most common mycobacterial infection worldwide. It causes necrotising infections of skin and soft tissue and is classified as a neglected tropical disease by the World Health Organization (WHO). However, despite extensive research, the environmental reservoir of the organism and mode of transmission of the infection to humans remain unknown. This limits the ability to design and implement public health interventions to effectively and consistently prevent the spread and reduce the incidence of this disease. In recent years, the epidemiology of the disease has changed. In most endemic regions of the world, the number of cases reported to the WHO are reducing, with a 64% reduction in cases reported worldwide in the last 9 years. Conversely, in a smaller number of countries including Australia and Nigeria, reported cases are increasing at a rapid rate, new endemic areas continue to appear, and in Australia cases are becoming more severe. The reasons for this changing epidemiology are unknown. We review the epidemiology of M. ulcerans disease worldwide, and document recent changes. We also outline and discuss the current state of knowledge on the ecology of M. ulcerans, possible transmission mechanisms to humans and what may be enabling the spread of M. ulcerans into new endemic areas.

Mycobacterium ulcerans disease management in Australian patients: the re-emergence of surgery as an important treatment modality

With the demonstration of the effectiveness of antibiotic treatment, the management of Mycobacterium ulcerans disease has changed from a predominantly surgically to a predominantly medically treated disease. However, research among Australian patients has revealed that antibiotic treatment alone is associated with prolonged wound healing times, high rates of treatment toxicity, and the potential for significant tissue destruction associated with severe paradoxical reactions. We present the current state of M. ulcerans management in Barwon Health, Australia, where a close working relationship exists between the Plastic Surgical and Infectious Diseases units. Here treatment has evolved based on nearly 20 years of experience gained from managing more around 600 patients from a M. ulcerans epidemic on the nearby Bellarine and Mornington Peninsulas. In our experience, surgery has re-emerged to play an important role in the treatment of M. ulcerans in improving the rate of wound healing, minimizing antibiotic associated toxicity and preventing further tissue loss associated with severe paradoxical reactions. For selected small lesions surgery without antibiotics may also be an effective treatment option, however aggressive surgical resection of lesions with wide margins through uninvolved tissue should no longer be performed. Furthermore, extensive excisional surgery that will require the use of split skin grafts and vascularized tissue flaps to repair skin defects should be avoided if possible.

Drugs for treating Buruli ulcer (Mycobacterium ulcerans disease)

BACKGROUND

Buruli ulcer is a necrotizing cutaneous infection caused by infection with Mycobacterium ulcerans bacteria that occurs mainly in tropical and subtropical regions. The infection progresses from nodules under the skin to deep ulcers, often on the upper and lower limbs or on the face. If left undiagnosed and untreated, it can lead to lifelong disfigurement and disabilities. It is often treated with drugs and surgery.

OBJECTIVES

To summarize the evidence of drug treatments for treating Buruli ulcer.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register; the Cochrane Central Register of Controlled Trials (CENTRAL), published in the Cochrane Library; MEDLINE (PubMed); Embase (Ovid); and LILACS (Latin American and Caribbean Health Sciences Literature; BIREME). We also searched the US National Institutes of Health Ongoing Trials Register (clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en/). All searches were run up to 19 December 2017. We also checked the reference lists of articles identified by the literature search, and contacted leading researchers in this topic area to identify any unpublished data.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that compared antibiotic therapy to placebo or alternative therapy such as surgery, or that compared different antibiotic regimens. We also included prospective observational studies that evaluated different antibiotic regimens with or without surgery.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied the inclusion criteria, extracted the data, and assessed methodological quality. We calculated the risk ratio (RR) for dichotomous data with 95% confidence intervals (CI). We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We included a total of 18 studies: five RCTs involving a total of 319 participants, ranging from 12 participants to 151 participants, and 13 prospective observational studies, with 1665 participants. Studies evaluated various drugs usually in addition to surgery, and were carried out across eight countries in areas with high Buruli ulcer endemicity in West Africa and Australia. Only one RCT reported adequate methods to minimize bias. Regarding monotherapy, one RCT and one observational study evaluated clofazimine, and one RCT evaluated sulfamethoxazole/trimethoprim. All three studies had small sample sizes, and no treatment effect was demonstrated. The remaining studies examined combination therapy.Rifampicin combined with streptomycinWe found one RCT and six observational studies which evaluated rifampicin combined with streptomycin for different lengths of treatment (2, 4, 8, or 12 weeks) (941 participants). The RCT did not demonstrate a difference between the drugs added to surgery compared with surgery alone for recurrence at 12 months, but was underpowered (RR 0.12, 95% CI 0.01 to 2.51; 21 participants; very low-certainty evidence).An additional five single-arm observational studies with 828 participants using this regimen for eight weeks with surgery (given to either all participants or to a select group) reported healing rates ranging from 84.5% to 100%, assessed between six weeks and one year. Four observational studies reported healing rates for participants who received the regimen alone without surgery, reporting healing rates ranging from 48% to 95% assessed between eight weeks and one year.Rifampicin combined with clarithromycinTwo observational studies administered combined rifampicin and clarithromycin. One study evaluated the regimen alone (no surgery) for eight weeks and reported a healing rate of 50% at 12 months (30 participants). Another study evaluated the regimen administered for various durations (as determined by the clinicians, durations unspecified) with surgery and reported a healing rate of 100% at 12 months (21 participants).Rifampicin with streptomycin initially, changing to rifampicin with clarithromycin in consolidation phaseOne RCT evaluated this regimen (four weeks in each phase) against continuing with rifampicin and streptomycin in the consolidation phase (total eight weeks). All included participants had small lesions, and healing rates were above 90% in both groups without surgery (healing rate at 12 months RR 0.94, 95% CI 0.87 to 1.03; 151 participants; low-certainty evidence). One single-arm observational study evaluating the substitution of streptomycin with clarithromycin in the consolidation phase (6 weeks, total 8 weeks) without surgery given to a select group showed a healing rate of 98% at 12 months (41 participants).Novel combination therapyTwo large prospective studies in Australia evaluated some novel regimens. One study evaluating rifampicin combined with either ciprofloxacin, clarithromycin, or moxifloxacin without surgery reported a healing rate of 76.5% at 12 months (132 participants). Another study evaluating combinations of two to three drugs from rifampicin, ciprofloxacin, clarithromycin, ethambutol, moxifloxacin, or amikacin with surgery reported a healing rate of 100% (90 participants).Adverse effects were reported in only three RCTs (158 participants) and eight prospective observational studies (878 participants), and were consistent with what is already known about the adverse effect profile of these drugs. Paradoxical reactions (clinical deterioration after treatment caused by enhanced immune response to M ulcerans) were evaluated in six prospective observational studies (822 participants), and the incidence of paradoxical reactions ranged from 1.9% to 26%.

AUTHORS' CONCLUSIONS

While the antibiotic combination treatments evaluated appear to be effective, we found insufficient evidence showing that any particular drug is more effective than another. How different sizes, lesions, and stages of the disease may contribute to healing and which kind of lesions are in need of surgery are unclear based on the included studies. Guideline development needs to consider these factors in designing practical treatment regimens. Forthcoming trials using clarithromycin with rifampicin and other trials of new regimens that also address these factors will help to identify the best regimens.

Sec61 blockade by mycolactone: A central mechanism in Buruli ulcer disease

Infection with Mycobacterium ulcerans results in a necrotising skin disease known as a Buruli ulcer, the pathology of which is directly linked to the bacterial production of the toxin mycolactone. Recent studies have identified the protein translocation machinery of the endoplasmic reticulum (ER) membrane as the primary cellular target of mycolactone, and shown that the toxin binds to the core subunit of the Sec61 complex. Mycolactone binding strongly inhibits the capacity of the Sec61 translocon to transport newly synthesised membrane and secretory proteins into and across the ER membrane. Since the ER acts as the entry point for the mammalian secretory pathway, and hence regulates initial access to the entire endomembrane system, mycolactone-treated cells have a reduced ability to produce a range of proteins including secretory cytokines and plasma membrane receptors. The global effect of this molecular blockade of protein translocation at the ER is that the host is unable to mount an effective immune response to the underlying mycobacterial infection. Prolonged exposure to mycolactone is normally cytotoxic, since it triggers stress responses activating the transcription factor ATF4 and ultimately inducing apoptosis.

Shorter-course treatment for Mycobacterium ulcerans disease with high-dose rifamycins and clofazimine in a mouse model of Buruli ulcer

Starting in 2004, the standard regimen for treatment of Buruli ulcer (BU) recommended by the World Health Organization has been daily treatment for eight weeks with rifampin (RIF) and streptomycin. Based on recent clinical trials, treatment with an all-oral regimen of RIF and clarithromycin (CLR) may be an effective alternative. With the achievement of an all-oral regimen, a new goal is to find a regimen that can shorten the duration of treatment without compromising efficacy. We recently observed that increasing the dose of RIF from the standard 10 mg/kg dose to 20 or 40 mg/kg, or replacing RIF with the more potent long-acting rifamycin, rifapentine (RPT) at 10 mg/kg or 20 mg/kg increased the bactericidal activity of the RIF+CLR regimen in a mouse model of BU. We also recently showed that replacing CLR with clofazimine(CFZ) at 25 mg/kg may have greater sterilizing activity than the RIF+CLR regimen. Here, we demonstrate that combining high-dose rifamycins with CFZ at a lower dose of 12.5 mg/kg results in similar reductions in swelling, bacterial burden and mycolactone concentrations in mouse footpads compared to the standard regimens and more rapid sterilization of footpads as determined by the proportions of footpads harboring viable bacteria three months after completion of treatment. The potential of these high-dose rifamycin and CFZ combinations to shorten BU treatment to four weeks warrants evaluation in a clinical trial.

Buruli ulcer, a neglected tropical skin disease caused by Mycobacterium ulcerans, is treatable since 2004 with antibiotics instead of surgery. Treatment with either rifampin plus streptomycin or, more recently, rifampin plus clarithromycin requires taking the drugs daily for 8 weeks. Streptomycin is administered by injection and may result in hearing loss. Clarithromycin often causes gastrointestinal discomfort. Our goal is to identify a regimen that is both shorter and associated with fewer side effects. Rifampin, previously an expensive drug, is well tolerated not only at the standard dose of 10 mg/kg but at doses of 20 and 40 mg/kg. The related rifamycin, rifapentine, has a longer half-life and is also well tolerated. We tested in a mouse model of Buruli ulcer whether higher doses of these rifamycins together with clofazimine, a drug that has transient skin pigmentation side effects but no toxicities, could effectively reduce lesion size, the number of bacteria, and production of the mycolactone toxin, in a shorter time than that for the existing drug regimens. We found that treatment for 4 weeks with a high dose rifamycin plus clofazimine is as effective as 8 weeks of the current standard regimens of rifampin plus streptomycin or rifampin plus clarithromycin.

Low incidence of recurrent Buruli ulcers in treated Australian patients living in an endemic region

We examined recurrent Buruli ulcer cases following treatment and assumed cure in a large cohort of Australian patients living in an endemic area. We report that while the recurrence rate was low (2.81 cases/year/1000 population), it remained similar to the estimated risk of primary infection within the general population of the endemic area (0.85–4.04 cases/year/1,000 population). The majority of recurrent lesions occurred in different regions of the body and were separated by a median time interval of 44 months. Clinical, treatment and epidemiological factors combined with whole genome sequencing of primary and recurrent isolates suggests that in most recurrent cases a re-infection was more likely as opposed to a relapse of the initial infection. Additionally, all cases occurring more than 12 months after commencement of treatment were likely re-infections. Our study provides important prognostic information for patients and their health care providers concerning the nature and risks associated with recurrent cases of Buruli ulcer in Australia.

Mycobacterium ulcerans (M. ulcerans) causes a necrotising infection of skin and soft-tissue known as Buruli ulcer. Since the regular use of antibiotics for Buruli ulcer treatment in Australian populations was introduced at the turn of the century, treatment success rates have been very high. However there is no information from the Australian setting on the risk of recurrent disease following treatment and assumed cure, despite this being important prognostic information for patients, their families and health-care providers. Furthermore, it is also not known if recurrent disease represents late relapse of the initial treated infection or a subsequent new infection. In our study we have shown for the first time in Australian patients living in an endemic area that the incidence of recurrent Buruli ulcer following treatment and healing is low, and that this risk is similar to the estimated risk of primary infection within the general population of the endemic area. Furthermore, we have used clinical, treatment and epidemiological data supported by genomic information of M. ulcerans organisms to determine that the majority of recurrent lesions appear to result from re-infection. This suggests that for a proportion of treated patients’ acquired protective immunity against the development of recurrent M. ulcerans disease does not develop from their initial infection.

Overview of Cutaneous Mycobacterial Infections

Purpose of Review

Mycobacterial infections may affect any human organ and produce disseminated disease in immunocompromised individuals. Their most common clinical presentations include pulmonary, cutaneous (skin and soft tissues), and disseminated forms. The skin and soft tissues are frequent targets of affection by mycobacterial pathogens manifesting as localized or diffuse disease.

Recent Findings

Overall, infections due to Mycobacterium leprae, Mycobacterium ulcerans, and Mycobacterium tuberculosis are the most frequently recognized mycobacterial pathogens involving the skin and soft tissues. Additionally, all mycobacterial species of the nontuberculous group may also produce cutaneous disease. Of these, the most commonly identified organisms causing localized infections of the skin and subcutaneous tissues are the rapidly growing species (Mycobacterium fortuitum, Mycobacterium chelonae, and Mycobacterium abscessus complex), Mycobacterium marinum, and M. ulcerans. Since the skin and soft tissues are important protective barriers for environmental pathogens, their disruption often represents the portal of entry of nontuberculous environmental mycobacteria (soil, natural water systems, engineered water networks, etc.). Additionally, some mycobacterial diseases affecting cutaneous structures occur after exposure to infected animals or their products (i.e., Mycobacterium bovis). Mycobacterial infections of the skin and soft tissues may manifest with a broad range of clinical phenotypes such as cellulitis, single or multiple abscesses, subacute or chronic nodular lesions, macules, superficial lymphadenitis, plaques, nonhealing ulcers, necrotic plaques, verrucous lesions, and many other dermatologic manifestations.

Summary

Geography and environmental exposure play an important role in the epidemiology of cutaneous mycobacterial infections. Mycobacterial infection of the skin and subcutaneous tissue is an important cause of human suffering in terms of morbidity, deformity, dysfunction, and stigma. The diagnosis of cutaneous mycobacterial infections is challenging requiring a low threshold of clinical suspicion for obtaining skin biopsies of cutaneous lesions for acid-fast staining and cultures, and molecular probe assays to detect the presence of mycobacterial pathogens. The choice of antibacterial therapy combinations and length of therapy for cutaneous mycobacterial infections is species-specific.

Antibiotic complications during the treatment of Mycobacterium ulcerans disease in Australian patients

BACKGROUND

Antibiotics are the recommended first-line treatment for Mycobacterium ulcerans disease. Antibiotic toxicity is common in Australian patients, yet antibiotic complication rates and their risk factors have not been determined.

AIM

To determine the incidence rate and risk factors for antibiotic toxicity in Australian patients treated for M. ulcerans disease.

METHODS

An analysis of severe antibiotic complications was performed using data from a prospective cohort of M. ulcerans cases managed at Barwon Health from 1 January 1998 to 30 June 2016. A severe antibiotic complication was defined as an antibiotic adverse event that required its cessation. Antibiotic complication rates and their associations were assessed using a Poisson regression model.

RESULTS

A total of 337 patients was included; 184 (54.6%) males and median age 57 years (interquartile range (IQR) 36-73 years). Median antibiotic treatment duration was 56 days (IQR 49-76 days). Seventy-five (22.2%) patients experienced severe antibiotic complications after a median 28 days (IQR 17-45 days) at a rate of 141.53 per 100 person-years (95% confidence interval (CI) 112.86-177.47). Eleven (14.7%) patients required hospitalisation. Compared with rifampicin/clarithromycin combinations, severe complication rates were not increased for rifampicin/ciprofloxacin (rate ratio (RR) 1.49, 95% CI 0.89-2.50, P = 0.13) or rifampicin/moxifloxacin (RR 2.54, 95% CI 0.76-8.50, P = 0.13) combinations, but were significantly increased for 'other' combinations (RR 2.53, 95% CI 1.13-5.68, P = 0.03). In a multivariable analysis, severe complication rates were significantly increased with reduced estimated glomerular filtration rates (EGFR) (adjusted rate ratio (aRR) 2.65, 95% CI 1.24-5.65 for EGFR 60-89 mL/min and aRR 1.31, 95% CI 0.49-3.53 for EGFR 0-59 mL/min compared with EGFR ≥90 mL/min, P < 0.01) and female gender (aRR 2.15, 95% CI 1.38-3.30, P < 0.01).

CONCLUSIONS

Severe antibiotic complications during M. ulcerans treatment are high with increased rates independently associated with reduced renal function and female gender.

Delayed versus standard assessment for excision surgery in patients with Buruli ulcer in Benin: a randomised controlled trial

BACKGROUND

Surgical intervention was once the mainstay of treatment for Buruli ulcer disease, a neglected tropical disease caused by Mycobacterium ulcerans. Since the introduction of streptomycin and rifampicin for 8 weeks as standard care, surgery has persisted as an adjunct therapy, but its role is uncertain. We investigated the effect of delaying the decision to operate to 14 weeks on rates of healing without surgery.

METHODS

In this randomised controlled trial, we enrolled patients aged 3 years or older with confirmed disease at one hospital in Lalo, Benin. Patients were randomly assigned (1:1) to groups assessing the need for excision surgery 8 weeks (standard care) or 14 weeks after initiation of antimicrobial treatment. The primary endpoint was the number of patients healed without the need for surgery (not including skin grafting), assessed in all patients in follow-up at 50 weeks (or last observation for those healed for >10 weeks). A doctor masked to treatment assignment checked the indications for surgery according to predefined criteria. This study is registered with ClinicalTrials.gov, number NCT01432925.

FINDINGS

Between July 1, 2011, and Jan 15, 2015, 119 patients were enrolled, with two patients per group lost to follow-up. 55 (96%) of 57 participants in the delayed-decision group and 52 (90%) of 58 participants in the standard-care group had healed lesions 1 year after start of antimicrobial treatment (relative risk [RR] 1·08, 95% CI 0·97-1·19). 37 (67%) of 55 patients in the delayed-decision group had their lesions healed without surgical intervention, as did 25 (48%) of 52 in the standard-care group (RR 1·40, 95% CI 1·00-1·96). The time to heal and residual functional limitations did not differ between the two groups (median time to heal 21 weeks [IQR 10-27] in the delayed-decision group and 21 weeks [10-39] in the standard-care group; functional limitations in six [11%] of 57 and three [5%] of 58 patients; p=0·32). Postponing the decision to operate resulted in reduced median duration of hospitalisation (5 days [IQR 0-187] vs 131 days [0-224]; p=0·024) and wound care (153 days [IQR 56-224] vs 182 days [94-307]; p=0·036).

INTERPRETATION

In our study, patients treated for Buruli ulcer benefited from delaying the decision to operate. Even large ulcers can heal with antibiotics alone, without delaying healing rate and without an increase in residual functional limitations.

FUNDING

NWO-VENI grant 241500, BUG Foundation, and UBS OPTIMUS.

Wound healing: Natural history and risk factors for delay in Australian patients treated with antibiotics for Mycobacterium ulcerans disease

BACKGROUND

Healing times following treatment with antibiotics, and factors that influence healing, have not been reported in Australian patients with Mycobacterium ulcerans.

METHODOLOGY/PRINCIPAL FINDINGS

Healing times were determined for all M. ulcerans cases treated by a single physician with antibiotics at Barwon Health, Victoria, from 1/1/13-31/12/16. Lesions were categorised by induration size: category A ≤ 400mm2, Category B 401-1600mm2 and Category C ≥1601mm2. A logistic regression analysis was performed to determine risk factors for prolonged wound healing (>150 days from antibiotic commencement). 163 patients were included; 92 (56.4%) were male and median age was 58 years (IQR 39-73 years). Baseline lesion size [available in 145 (89.0%) patients] was categorised as A in 46 (31.7%), B in 67 (46.2%) and C in 32 (22.1%) patients. Fifty (30.7%) patients had surgery. In those treated with antibiotics alone, 83.0% experienced a reduction in induration size after 2 weeks, then 70.9% experienced an increase in induration size from the lowest point, and 71.7% experienced an increase in ulceration size. A linear relationship existed between the time induration resolved and wound healing began. Median time to heal was 91 days (IQR 70-148 days) for category A lesions; significantly shorter than for category B lesions (128 days, IQR 91-181 days, p = 0.05) and category C lesions (169 days, IQR 159-214 days, p<0.001). Fifty-seven (35.0%) patients experienced a paradoxical reaction. Of those treated with antibiotics alone, lesions experiencing a paradoxical reaction had longer healing times [median time to heal 177 days (IQR 154-224 days) compared to 107 days (IQR 79-153 days), p<0.001]. On multivariable logistic regression, lesion size at baseline (p<0.001) and paradoxical reactions (p<0.001) were independently associated with prolonged healing times. For category A and B lesions, healing time was significantly shorter with antibiotics plus excision and direct closure compared with antibiotics alone [Category A lesions median 55 days (IQR 21-63 days) compared with 91 days (IQR 70-148 days), p<0.001; Category B lesions median 74 days (IQR 21-121 days) compared to 128 days (IQR 97-181 days), p<0.001].

CONCLUSIONS

In Australian patients treated with antibiotics M. ulcerans lesions usually initially improve, then clinically deteriorate with increased induration and ulceration, before healing after the inflammation associated with lesions resolves. The time to complete healing of lesions is generally long, and is further prolonged in those with larger initial lesion size or who develop paradoxical reactions. For small lesions (<4cm2), excisional surgery may reduce healing times.