Secondary bacterial isolates from previously untreated Buruli ulcer lesions and their antibiotic susceptibility patterns in Southern Nigeria

Mycobacterium ulcerans-Bordetella trematum chronic tropical cutaneous ulcer: A four-case series, Côte d'Ivoire

BACKGROUND

Chronic tropical cutaneous ulcers remain a neglected medical condition in West Africa, particularly Buruli ulcer, which is caused by mycolactone cytotoxin-secreting Mycobacterium ulcerans (M. ulcerans). Medical management of this highly debilitating and necrotising skin infection may be modified by colonisation and co-infection of the ulcer by opportunistic and pathogenic microorganisms, which considerably delays and increases the cost of treatment.

METHODOLOGY/PRINCIPAL FINDING

We diagnosed chronic tropical cutaneous ulcers in nine patients in Côte d'Ivoire using M. ulcerans-specific PCRs and culturomics. This revealed M. ulcerans in 7/9 ulcer swabs and 5/9 control swabs as well as an additional 122 bacterial species, 32 of which were specific to ulcers, 61 specifics to the controls, and 29 which were shared, adding 40 bacterial species to those previously reported. Whole genome sequencing of four Bordetella trematum (B. trematum) isolates in four Buruli ulcer swabs and no controls indicated cytolethal distending toxins, as confirmed by cytotoxic assay.

CONCLUSIONS/SIGNIFICANCE

In four cases of Buruli ulcer in Côte d'Ivoire, B. trematum was a co-pathogen which was resistant to rifampicin and clarithromycin, unmatching M. ulcerans antibiotic susceptibility profile and counteracting the current treatment of Buruli ulcer in West Africa and Australia. Thus, we report here chronic mixed M. ulcerans-B. trematum chronic tropical ulcer as a specific form of Buruli ulcer in West Africa.

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.

Responses to chemical cross-talk between the Mycobacterium ulcerans toxin, mycolactone, and Staphylococcus aureus

Buruli ulcer is a neglected tropical disease caused by the environmental pathogen, Mycobacterium ulcerans whose major virulence factor is mycolactone, a lipid cytotoxic molecule. Buruli ulcer has high morbidity, particularly in rural West Africa where the disease is endemic. Data have shown that infected lesions of Buruli ulcer patients can be colonized by quorum sensing bacteria such as Staphylococcus aureus, S. epidermidis, and Pseudomonas aeruginosa, but without typical pathology associated with those pathogens' colonization. M. ulcerans pathogenesis may not only be an individual act but may also be dependent on synergistic or antagonistic mechanisms within a polymicrobial network. Furthermore, co-colonization by these pathogens may promote delayed wound healing, especially after the initiation of antibiotic therapy. Hence, it is important to understand the interaction of M. ulcerans with other bacteria encountered during skin infection. We added mycolactone to S. aureus and incubated for 3, 6 and 24 h. At each timepoint, S. aureus growth and hemolytic activity was measured, and RNA was isolated to measure virulence gene expression through qPCR and RNASeq analyses. Results showed that mycolactone reduced S. aureus hemolytic activity, suppressed hla promoter activity, and attenuated virulence genes, but did not affect S. aureus growth. RNASeq data showed mycolactone greatly impacted S. aureus metabolism. These data are relevant and significant as mycolactone and S. aureus sensing and response at the transcriptional, translational and regulation levels will provide insight into biological mechanisms of interspecific interactions that may play a role in regulation of responses such as effects between M. ulcerans, mycolactone, and S. aureus virulence that will be useful for treatment and prevention.

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.

Assessment of community knowledge, attitude, and stigma of Buruli ulcer disease in Southern Nigeria

Background

Poor knowledge can influence timely care-seeking among persons with Buruli ulcer disease (BUD).

Objectives

To assess community knowledge, attitude and stigma towards persons with BUD in endemic settings of Southern Nigeria.

Methods

This was a cross-sectional survey conducted among adult community members in four States of Southern Nigeria. A semi-structured interviewer-administered questionnaire was administered to all participants.

Results

Of 491 adults who completed the survey, 315 (64.2%) belonged to the ≤40 years age group, 257 (52.3%) were males and 415 (84.5%) had some formal education. The overall mean (SD) knowledge score was 5.5±2.3 (maximum 10). Only 172 (35.0%) of the participants had a good knowledge of BUD. A total of 327 (66.6%) considered BUD as a very serious illness. Also, there was a high-level of stigma against BUD patients; 372 (75.8%) of the participants felt compassion for and desire to help them, 77 (15.7%) felt compassion but tended to stay away from them, and 53 (10.8%) feared them because they may infect them with the disease. Having a formal education and ethnicity were independent predictors of good knowledge of BUD.

Conclusion

There is poor community knowledge of BUD in endemic settings of Southern Nigeria which influenced the attitude and perceptions of community members towards persons with BUD

Rapid detection of Mycobacterium ulcerans with isothermal recombinase polymerase amplification assay

Background

Access to an accurate diagnostic test for Buruli ulcer (BU) is a research priority according to the World Health Organization. Nucleic acid amplification of insertion sequence IS2404 by polymerase chain reaction (PCR) is the most sensitive and specific method to detect Mycobacterium ulcerans (M. ulcerans), the causative agent of BU. However, PCR is not always available in endemic communities in Africa due to its cost and technological sophistication. Isothermal DNA amplification systems such as the recombinase polymerase amplification (RPA) have emerged as a molecular diagnostic tool with similar accuracy to PCR but having the advantage of amplifying a template DNA at a constant lower temperature in a shorter time. The aim of this study was to develop RPA for the detection of M. ulcerans and evaluate its use in Buruli ulcer disease.

Methodology and principal findings

A specific fragment of IS2404 of M. ulcerans was amplified within 15 minutes at a constant 42°C using RPA method. The detection limit was 45 copies of IS2404 molecular DNA standard per reaction. The assay was highly specific as all 7 strains of M. ulcerans tested were detected, and no cross reactivity was observed to other mycobacteria or clinically relevant bacteria species. The clinical performance of the M. ulcerans (Mu-RPA) assay was evaluated using DNA extracted from fine needle aspirates or swabs taken from 67 patients in whom BU was suspected and 12 patients with clinically confirmed non-BU lesions. All results were compared to a highly sensitive real-time PCR. The clinical specificity of the Mu-RPA assay was 100% (95% CI, 84–100), whiles the sensitivity was 88% (95% CI, 77–95).

Conclusion

The Mu-RPA assay represents an alternative to PCR, especially in areas with limited infrastructure.

Current diagnostic methods to detect M. ulcerans suffer from delayed time-to-results in most endemic countries by the prolonged period of time for the shipment and storage of samples to a distant, centralized laboratory. The M. ulcerans recombinase polymerase amplification assay (Mu-RPA) is a new, rapid diagnostic test developed for the detection of M. ulcerans infection, known commonly as Buruli ulcer, a chronic, debilitating, necrotizing disease of the skin and soft tissues. This assay is suitable for use on a portable detection device, with the potential to be used for quick diagnosis at the point of need, providing timely results to health workers at Buruli ulcer treatment clinics.

Assessment of health care workers' knowledge, attitude and risk perception of Buruli ulcer disease in Southern Nigeria

Background

Poor knowledge of health care workers may be responsible for the under-diagnosis and low notification of Buruli ulcer (BU) in high-burden settings. This study assessed health care workers' knowledge, attitude and risk perception of BU in Southern Nigeria.

Methods

We conducted a cross-sectional survey among 186 health care workers recruited from 58 health facilities in four states of Southern Nigeria. A semi-structured interviewer-administered questionnaire was administered to all participants.

Results

The overall mean knowledge score was 8.8±2.7 (maximum 15). Only 29.0% (54/186) of the respondents had a good knowledge of BU. The mean (SD) attitude score was 4.5±1.2 (maximum 6). Also, 61.3% (114/) of the respondents had a good attitude towards BU. The overall mean (SD) risk perception score was 2.6±1.3 (maximum 5). Only 26.3% (49/) of the respondents had a good risk perception of BU disease. Previous training was an independent predictor of good knowledge (aOR 4.6), good attitude (aOR 3.8) and good risk perception (aOR 2.9) to BU.

Conclusions

Health care workers in endemic settings of Nigeria have poor knowledge of and poor risk perception of BU disease. Training of health care workers is recommended to address the identified gaps to ensure earlier diagnosis and referral to specialist centres.

Report of a series of 82 cases of Buruli ulcer from Nigeria treated in Benin, from 2006 to 2016

Background

Nigeria is one of the countries endemic for Buruli ulcer (BU) in West Africa but did not have a control programme until recently. As a result, BU patients often access treatment services in neighbouring Benin where dedicated health facilities have been established to provide treatment free of charge for BU patients. This study aimed to describe the epidemiological, clinical, biological and therapeutic characteristics of cases from Nigeria treated in three of the four treatment centers in Benin.

Methodology/Principal findings

A series of 82 BU cases from Nigeria were treated in three centres in Benin during 2006–2016 and are retrospectively described. The majority of these patients came from Ogun and Lagos States which border Benin. Most of the cases were diagnosed with ulcerative lesions (80.5%) and WHO category III lesions (82.9%); 97.5% were healed after a median hospital stay of 46 days (interquartile range [IQR]: 32–176 days).

Conclusions/Significance

This report adds to the epidemiological understanding of BU in Nigeria in the hope that the programme will intensify efforts aimed at early case detection and treatment.

Buruli ulcer (BU) is a neglected tropical disease that mainly affects the skin. The disease results from infection with Mycobacterium ulcerans, an environmental bacterium. In Benin, the BU treatment centres usually receive patients from Nigeria. In 2014, a study from one of the treatment centres (CDTUB, Pobe) which borders south-western Nigeria reported on a cohort of 127 PCR-confirmed cases between 2005 and 2013. We describe the epidemiological, clinical, biological and therapeutic characteristics of BU cases from Nigeria treated in the three other CDTUBs.