Browsing by Author "Duah, Mabel Sarpong"

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    Detection of viability markers of mycobacterium ulcerans and their association with healing in buruli ulcer patients
    (NOVEMBER, 2016) Duah, Mabel Sarpong
    Buruli ulcer (BU) is a neglected tropical disease caused by Mycobacterium ulcerans (M. ulcerans), an infection common in rural parts of West Africa including Ghana. It affects predominantly children between the ages of 5-15 years. Treatment of BU has changed over the past 11 years with the introduction of antibiotics (rifampicin and streptomycin) as an alternative to surgery. The aim of antibiotic treatment is that each patient receives the minimum appropriate therapy needed to achieve recurrent free cure. The current duration of antibiotic therapy (8 weeks) was based on observations in patients with early M. ulcerans which were excised after treatment. Thus it is likely that a shorter course of antibiotic treatment may be successful in some patients. To characterise the viability of M. ulcerans in BU and to ascertain its association with time to/ rate of healing of lesions. Fine needle aspirates and swabs were obtained from patients confirmed with active BU using IS2404 PCR as a gold standard. Samples were obtained at baseline (week 0), during treatment (week 4), end of treatment (week8) and after treatment (weeks 12 and 16) for detection of viable M. ulcerans using combined assay 16S rRNA/IS2404 RT qPCR and culture. Patients were followed up 2 weekly with wound measurements using Silhouette required for determination of rate of healing. Of one hundred and twenty-nine patients, viable M ulcerans could be detected in 65% at baseline. By week 4, 20 (15.5%) of lesions had healed or 29 (22%) had undetectable viable organisms. At week 8 viable M. ulcerans were still detected in 43 (33%) lesions of unhealed, 15 (12%) of unhealed at week 12 and 3 (2%) of unhealed at week 16. Patients with detectable viable organisms after antibiotic treatment had significantly higher bacterial load, vii longer healing time and lower healing rate at week 4 compared with those with undetectable viable organisms at baseline or by week 4. We demonstrated that current antibiotic therapy for BU disease is highly successful in most patients but it may be possible to abbreviate the treatment to 4 weeks in patients with a low initial bacterial load. On the other hand, evidence has been presented that persistent infection with viable M. ulcerans contributes to slow healing in other patients, suggesting that those with a high bacterial load, may need antibiotics for longer than 8 weeks.
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    IFN-g and IL-5 whole blood response directed against mycolactone polyketide synthase domains in patients with Mycobacterium ulcerans infection
    (PeerJ, 2018-07-31) Phillips, Richard Odame; Loglo, Aloysius D.; Frimpong, Michael; Duah, Mabel Sarpong; Sarfo, Fred Stephen; et. al
    Background: Buruli ulcer is a disease of the skin and soft tissues caused by infection with a slow growing pathogen, Mycobacterium ulcerans. A vaccine for this disease is not available but M. ulcerans possesses a giant plasmid pMUM001 that harbours the polyketide synthase (PKS) genes encoding a multi-enzyme complex needed for the production of its unique lipid toxin called mycolactone, which is central to the pathogenesis of Buruli ulcer. We have studied the immunogenicity of enzymatic domains in humans with M. ulcerans disease, their contacts, as well as non-endemic areas controls. Methods: Between March 2013 and August 2015, heparinized whole blood was obtained from patients confirmed with Buruli ulcer. The blood samples were diluted 1 in 10 in Roswell Park Memorial Institute (RPMI) medium and incubated for 5 days with recombinant mycolactone PKS domains and mycolyltransferase antigen 85A (Ag85A). Blood samples were obtained before and at completion of antibiotic treatment for 8 weeks and again 8 weeks after completion of treatment. Supernatants were assayed for interferon-g (IFN-g) and interleukin-5 (IL-5) by enzyme-linked immunosorbent assay. Responses were compared with those of contacts and non-endemic controls. Results: More than 80% of patients and contacts from endemic areas produced IFN-g in response to all the antigens except acyl carrier protein type 3 (ACP3) to which only 47% of active Buruli ulcer cases and 71% of contacts responded. The highest proportion of responders in cases and contacts was to load module ketosynthase domain (Ksalt) (100%) and enoylreductase (100%). Lower IL-5 responses were induced in a smaller proportion of patients ranging from 54% after ketoreductase type B stimulation to only 21% with ketosynthase type C (KS C). Among endemic area contacts, the, highest proportion was 73% responding to KS C and the lowest was 40% responding to acyltransferase with acetate specificity type 2. Contacts of Buruli ulcer patients produced significantly higher IFN-g and IL-5 responses compared with those of patients to PKS domain antigens and to mycolyltransferase Ag85A of M. ulcerans. There was low or no response to all the antigens in non-endemic areas controls. IFN-g and IL-5 responses of patients improved after treatment when compared to baseline results. Discussion: The major response to PKS antigen stimulation was IFN-g and the strongest responses were observed in healthy contacts of patients living in areas endemic for Buruli ulcer. Patients elicited lower responses than healthy contacts, possibly due to the immunosuppressive effect of mycolactone, but the responses were enhanced after antibiotic treatment. A vaccine made up of the most immunogenic PKS domains combined with the mycolyltransferase Ag85A warrants further investigation.
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    Paradoxical reactions in Buruli ulcer after initiation of antibiotic therapy: Relationship to bacterial load
    (PLOS Neglected Tropical Diseases, 2019-08-26) Phillips, Richard Odame; Frimpong, Michael; Agbavor, Bernadette; Duah, Mabel Sarpong; Loglo, Aloysius; et. al
    Background We investigated the relationship between bacterial load in Buruli ulcer (BU) lesions and the development of paradoxical reaction following initiation of antibiotic treatment. Methods This was a longitudinal study involving BU patients from June 2013 to June 2017. Fine needle aspirates (FNA) and swab samples were obtained to establish the diagnosis of BU by PCR. Additional samples were obtained at baseline, during and after treatment (if the lesion had not healed) for microscopy, culture and combined 16S rRNA reverse transcriptase/ IS2404 qPCR assay. Patients were followed up at regular intervals until complete healing. Results Forty-seven of 354 patients (13%) with PCR confirmed BU had a PR, occurring between 2 and 42 (median 6) weeks after treatment initiation. The bacterial load, the proportion of patients with positive M. ulcerans culture (15/34 (44%) vs 29/119 (24%), p = 0.025) and the proportion with positive microscopy results (19/31 (61%) vs 28/90 (31%), p = 0.003) before initiation of treatment were significantly higher in the PR compared to the no PR group. Plaques (OR 5.12; 95% CI 2.26–11.61; p<0.001), oedematous (OR 4.23; 95% CI 1.43–12.5; p = 0.009) and category II lesions (OR 2.26; 95% CI 1.14–4.48; p = 0.02) were strongly associated with the occurrence of PR. The median time to complete healing (28 vs 13 weeks, p <0.001) was significantly longer in the PR group. Conclusions Buruli ulcer patients who develop PR are characterized by high bacterial load in lesion samples taken at baseline and a higher rate of positive M. ulcerans culture. Occurrence of a PR was associated with delayed healing.