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Antimicrobial Agents and Chemotherapy, November 2007, p. 4029-4035, Vol. 51, No. 11
0066-4804/07/$08.00+0     doi:10.1128/AAC.00175-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Promising Clinical Efficacy of Streptomycin-Rifampin Combination for Treatment of Buruli Ulcer (Mycobacterium ulcerans Disease)

Annick Chauty,¹ Marie-Françoise Ardant,¹ Ambroise Adeye,¹ Hélène Euverte,¹ Augustin Guédénon,³ Christian Johnson,² Jacques Aubry,⁴ Eric Nuermberger,⁵ and Jacques Grosset^5*

Centre de Dépistage et de Traitement de l'ulcère de Buruli, Pobè, Bénin,¹ Buruli Ulcer Control Programme, Cotonou, Bénin,² Fondation Raoul Follereau, Paris, France,³ University Nantes, Faculty of Pharmacy, F-44093, Inserm, U601, Nantes, France,⁴ Johns Hopkins University School of Medicine, Center for Tuberculosis Research, Baltimore, Maryland⁵

Received 6 February 2007/ Returned for modification 23 March 2007/ Accepted 16 May 2007

Top ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
According to recommendations of the 6th WHO Advisory Committee on Buruli ulcer, directly observed treatment with the combination of rifampin and streptomycin, administered daily for 8 weeks, was recommended to 310 patients diagnosed with Buruli ulcer in Pobè, Bénin. Among the 224 (72%) eligible patients for whom treatment was initiated, 215 (96%) were categorized as treatment successes, and 9, including 1 death and 8 losses to follow-up, were treatment failures. Of the 215 successfully treated patients, 102 (47%) were treated exclusively with antibiotics and 113 (53%) were treated with antibiotics plus surgical excision and skin grafting. The size of lesions at treatment initiation was the major factor associated with surgical intervention: 73% of patients with lesions of >15 cm in diameter underwent surgery, whereas only 17% of patients with lesions of <5 cm had surgery. No patient discontinued therapy for side effects from the antibiotic treatment. One year after stopping treatment, 208 of the 215 patients were actively retrieved to assess the long-term therapeutic results: 3 (1.44%) of the 208 retrieved patients had recurrence of Mycobacterium ulcerans disease, 2 among the 107 patients treated only with antibiotics and 1 among the 108 patients treated with antibiotics plus surgery. We conclude that the WHO-recommended streptomycin-rifampin combination is highly efficacious for treating M. ulcerans disease. Chemotherapy alone was successful in achieving cure in 47% of cases and was particularly effective against ulcers of less than 5 cm in diameter.

Top ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Buruli ulcer (Mycobacterium ulcerans disease) is an emerging chronic ulcerative skin disease that may lead to extensive destruction of the skin and soft tissues and occasionally of bones (16). The disease has been reported from more than 30 countries worldwide, mainly in tropical and subtropical regions (25). It is caused by soluble polyketide toxins named mycolactones that are produced by pathogenic strains of M. ulcerans (7, 8, 11) and are responsible for tissue damage and local immunosuppression. Although several antibiotics have demonstrated activity against M. ulcerans in vitro (15, 22), no consensus about their clinical efficacy for treatment of M. ulcerans disease has been reached. Consequently, wide surgical excision of necrotic tissue followed by skin grafting has long been considered to be the only effective treatment (14, 19, 23).

Recently, based on the results of several experimental studies performed in the mouse footpad model (2, 4, 5, 12), a pilot clinical trial conducted in Ghana under the auspices of WHO demonstrated that after daily treatment with rifampin and streptomycin for at least 4 weeks, M. ulcerans could no longer be cultured from the lesions (6). In addition, the antibiotic treatment reduced the surface area of most lesions by more than 50%, thus allowing less-extensive surgical excision. Encouraged by these promising results, the 6th WHO Advisory Committee on M. ulcerans disease recommended in March 2003 the daily administration of rifampin and an aminoglycoside, usually streptomycin, for 8 weeks as the first-line treatment for all forms of M. ulcerans disease (25). The two antibiotics should always be given in combination and under supervision so as to prevent the selection of resistant mutants (13). While it was anticipated that antibiotics alone might be curative in some patients with early lesions (i.e., nodules, papules, plaques, and ulcers of less than 5 cm in diameter), the primary aims of chemotherapy for more-advanced lesions were to reduce the extent of surgical excision and to prevent recurrence.

The objective of the present work is to report the results obtained in Pobè, Bénin, where the WHO recommendations have been implemented since 2003.

Top ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Study population. Among the 1,137,888 inhabitants of the Ouémé-Plateau Department, 310 patients with M. ulcerans disease were diagnosed in the years 2003 (145 patients) and 2004 (165 patients) at 1 of 12 clinics in the region. The great majority of these patients were living in the villages located along the national "Road 4" between the cities of Bonou and Dangbo and on the left bank of the Ouémé River. Among the inhabitants of Ouémé-Plateau, 45% are below 15 years of age, 49% are between 15 and 59, and only 6% are above 60 years of age. The male/female ratio is 0.91.

Inclusion criteria. Patients suspected of having M. ulcerans disease by 1 of the 12 clinics in Ouémé-Plateau Department were further evaluated by the physician of the CDTUB at Pobè, where a presumptive diagnosis of M. ulcerans disease ulcer was made on the basis of the following epidemiological and clinical features: (i) residence in an area of endemicity and (ii) presentation with an ulcerative or nonulcerative lesion consistent with M. ulcerans disease. Nonulcerative lesions included (i) firm, painless, and possibly pruritic subcutaneous nodules of 1 to 2 cm in diameter; (ii) firm, painless, well-demarcated, and elevated plaques of more than 2 cm in diameter; and (iii) diffuse, poorly demarcated, and possibly painful edema or cellulitis. Ulcerative lesions were considered if they were painless or only minimally painful, with characteristic undermined edges and a whitish-yellow necrotic base surrounded by edematous skin.

Exclusion criteria. Pregnant patients or patients receiving traditional treatment at the time of diagnosis and who wanted to carry on with it concurrently were excluded, as were patients with a history of leprosy, tuberculosis, liver problems (hepatomegaly, jaundice, serum amino aspartate transferase concentrations of more than three times the upper limit of normal), kidney problems (oligoanuria with lower-extremity edema, serum creatinine concentration of more than two times the upper limit of normal), or hearing problems (audiograms were not available before the year 2005).

Procedures. (i) Pretreatment assessment. A thorough history was taken and a thorough physical examination performed to assess the form and severity of the M. ulcerans disease, to rule out tuberculosis, and to detect auditory, hepatic, and renal disorders. Radiological examination of the affected limb was performed for patients with symptoms suggestive of bone involvement, e.g., disabilities and painful lesions with fever. Radiological investigation was also performed for patients with ulcerative lesions of durations of 4 months or more, because they were considered at higher risk of bone involvement.

Swabs were collected from the undermined edges of ulcerative lesions for smearing and Ziehl-Neelsen staining and for PCR to detect M. ulcerans DNA (18). No bacteriological investigation was performed for nonulcerated lesions. However, as none of the laboratory examinations were performed in 2003 and 2004 at the local site, their results were not used to support or refute the initial clinical diagnosis of M. ulcerans disease or to make decisions about treatment.

Upon treatment initiation, a photograph of the lesion(s) was taken with the oral consent of the patient or parent, and the size (i.e., the mean value of the longest and shortest diameters) and features (edema, necrotic base and edges of ulcer, induration) of the lesion(s) were recorded.

(ii) Treatment and on-treatment assessment. All enrolled patients, regardless of age and the clinical form of the disease exhibited, were treated daily with a combination of rifampin at 10 mg/kg body weight by the oral route and streptomycin at 15 mg/kg body weight by intramuscular injection. Local dressings were also provided for patients with ulcerative lesions. Patients who were able to return each day to the clinic were treated on an ambulatory basis under the direct observation of the clinic nurse. Patients who were unsuitable for ambulatory treatment, either because of the distance from their home to the clinic or because of the severity of the disease, were hospitalized in the CDTUB. Antibiotic treatment and dressings were provided free of charge, but an "all-inclusive" one-time symbolic payment of 30 euros or $40 was charged for surgical intervention(s). Hospitalized patients were provided with free morning breakfast and lunch but had to take care of their dinner by themselves.

Every 2 weeks during treatment, each patient was evaluated by the study physician. A photograph was taken of the lesion, and its size and aspect were measured and recorded again to document the evolution of the disease. Assessment of clinical improvement or deterioration was based on changes of the size of lesions, the degree of edema, and the appearance of the ulcer base. Any increase in size, persistence of edema, and/or absence of cleaning of the ulcer base was considered as an indication for surgery. In addition, patients were questioned about symptoms of vertigo and abnormal hearing and examined for scleral icterus, and they were removed from the study if there was indication of toxic side effects. Radiological examinations were performed for patients with painful lesions and hemoglobin tests were performed for patients just before surgery.

Unless there was a clear indication of drug toxicity or clinical deterioration (defined as lesions increasing in size), all patients received at least 4 weeks of antibiotic therapy. On completion of 4 weeks of treatment, patients with evidence of clinical improvement and no sign of retraction or contracture received 4 additional weeks of antibiotic treatment. Adjunctive surgical excision and skin grafting were recommended for those patients who were then considered unlikely to be cured by chemotherapy alone, primarily due to the size of the ulcer or involvement of the joint. According to the WHO protocol, patients with evidence of deterioration would also have been recommended for surgical excision, but in reality, no deterioration of lesions was observed for any patient by the end of 4 weeks of chemotherapy alone.

Upon completion of 8 weeks of antibiotic treatment, patients whose lesions had been healed (i.e., formation of a scar and disappearance of inflammation) were released from treatment. Patients with lesions that had improved but not yet healed were continued on dressings but discontinued from chemotherapy. Finally, surgical excision of the lesion was recommended to those patients whose lesions had not improved or had even worsened between weeks 4 and 8 of chemotherapy.

(iii) Posttreatment follow-up. After completion of treatment, all patients were advised to come back to the clinic in the case of recurrence. One year after the completion of treatment or after defaulting during the course of treatment, patients were actively retrieved to assess the relapse rate or the treatment outcome.

(iv) Survival analysis of the need for surgical treatment. Survival analysis was performed using patients treated initially with antibiotics alone and receiving at least 4 weeks of treatment. Subjects were considered successes if cured without surgery and failures if, at either 4 or 8 weeks, surgery was performed if clinical response was insufficient in the opinion of the treating physician. Data from patients lost to follow-up after 4 or more weeks of therapy were censored. Comparisons were made between groups initiating treatment with nonulcerative disease versus those initiating with ulcerative disease and between groups with ulcers of different sizes using the log rank test and the log rank test for trend, respectively (GraphPad Prism v.4.00; GraphPad Software, San Diego, CA).

Definitions of treatment outcome. (i) Successful treatment. Treatment was considered "successful" when the lesions were completely healed (scarred without residual inflammation) upon completion of the 8-week antibiotic treatment or during the next few weeks with or without adjunctive surgical excision.

(ii) Loss to follow-up. Patients were considered as "lost to follow-up" (defaulters) when they abandoned or refused treatment and were not retrieved.

(iii) Failed treatment. Treatment was considered to have "failed" in the event of death related to M. ulcerans disease and/or the persistence of nonscarring lesions despite appropriate medical and/or surgical treatment.

(iv) Recurrence. Recurrence was defined as the reactivation of the disease within 1 year after apparent success upon treatment completion.

Top ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Clinical features at enrollment. As shown in Table 1, among the 310 patients who were clinically diagnosed with M. ulcerans disease between January 2003 and December 2004, 179 (58%) were under 15 years old, 44 (14%) were under 5 years of age, and 5 were under 1 year of age. Both sexes were equally affected among those less than 15 years of age, but there were more females (n = 81; 62%) than males (n = 50; 38%) among the 131 patients aged 15 or more years. The lesions were localized on the limbs for 264 patients (85%), particularly on the lower limb (56%), and 236 patients (76%) had an ulcerative form of the disease. Among the 74 patients without ulcer, 15 (20%) had nodules, 40 (54%) had plaques, and 19 (26%) had extensive edema.

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TABLE 1. Age distribution of the 310 patients diagnosed in 2003 and 2004 with M. ulcerans disease in relation to sex, localization, and clinical form of the disease

Treatment with the streptomycin-rifampin combination. Only 224 (72%) of the 310 patients, either ambulatory at 1 of the 12 local clinics or hospitalized in the CDTUB, Pobè, received daily treatment with the streptomycin-rifampin combination. The other 86 patients did not receive the recommended treatment because of pregnancy (n = 3), immediate surgical excision of the lesions at another center (n = 36), the patient's decision to receive traditional treatment (n = 6), or refusal of antibiotic and/or surgical treatment (n = 41). Among the 224 patients treated with streptomycin-rifampin, 157 (70%) received their treatment at the local clinic close to their residence, whereas 67 (30%) were hospitalized in CDTUB, Pobè.

Of the 168 patients with ulcers initiated on the recommended treatment, laboratory confirmation of M. ulcerans infection, by acid-fast bacillus smear and/or PCR, was attempted for 145. As shown in Table 2, the smear was positive for 87 (60%) and PCR was positive for 83 (57%). Treatment outcomes were essentially the same among patients with and those without laboratory confirmation.

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TABLE 2. Smear and PCR results for ulcerative cases only

Status after 4 weeks of treatment. Among the 224 patients who were treated with streptomycin-rifampin, 1 (0.4%) died on the third day from cachexia. This patient, a 30-year-old female with an extensive ulcer on the right lower limb, was on treatment for the previous 6 months with a traditional healer; when chemotherapy began, the direct acid-fast bacillus smear was positive. Four (1.8%) patients underwent early surgery to correct painful contractures but continued on antibiotic therapy. Eleven (5%) patients discontinued treatment between the second and fourth weeks of treatment and were lost to follow-up.

By the end of 4 weeks of treatment, various degrees of clinical improvement were observed for the remaining 208 patients: the edema subsided totally in 66% of the cases and partially in the others, and the sizes of the ulcers decreased (usually with total scarring for <5-cm ulcers and by 1 cm on average for large ulcers) or remained unchanged, but the necrotic base of the ulcer cleared up. Among these 208 patients, 91 (43.8%) who had diverse initial lesions (Table 3), including 13 patients with large ulcers (>15 cm in diameter), responded so well (no more inflammation, edema, or undermined edges and clearing of the necrotic base with limited reduction in the lesion size) to the initial 4 weeks of chemotherapy alone that they were continued on dressings and chemotherapy for four more weeks.

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TABLE 3. Treatment of patients and outcome during the 8 weeks of treatment

The remaining 117 patients had, on average, more-extensive lesions (44 had large ulcers of >15 cm in diameter) and were recommended for surgical excision plus continuation of antibiotic therapy for four more weeks. Of these patients, 83 accepted the recommendations, but 31 refused surgery and continued dressings and antibiotic therapy, and 3 refused further treatment and were lost to follow-up.

In summary, among the 208 patients who completed 4 weeks of streptomycin-rifampin treatment, 122 (58.6%) continued antibiotic treatment for another 4-week course without surgical excision of lesions, 83 (39.9%) underwent surgical excision and continued antibiotic treatment, and 3 (1.5%) refused any further treatment.

Status after 8 weeks of treatment. All of the 83 patients who underwent surgery after 4 weeks of antibiotic therapy completed another 4-week course of treatment and were clinically cured by the eighth week, even though some of them still required dressings after surgical excision and/or skin grafting. On average, the length of hospitalization for those having had surgery was 2 months.

Among the 122 patients who began a second 4-week course of chemotherapy without surgery, 3 (2.4%) were lost to follow-up, 90 (73%) successfully completed their antibiotic treatment and were clinically cured, and 29 (24%) failed to completely heal their lesions (Table 3). Thus, including the 4 patients who had early surgery, the lesions in 177 (87.6%) of the 202 patients who had completed 8 weeks of daily streptomycin-rifampin therapy with or without adjunctive surgical excision were considered treatment successes at the 8-week assessment.

Surgical treatment was offered to the 29 patients whose lesions had failed to be completely healed at 8 weeks: 21 patients accepted surgery, but 8 patients refused and were continued on regular dressings alone. In the following 3 months, scarring of the lesions occurred with all of these 29 patients. Because the lesions healed sooner or later for all 202 patients who completed 8 weeks of daily chemotherapy with or without adjunctive surgical excision, the overall treatment success rate was 100%.

Importantly, chemotherapy was well tolerated, with no sign of hepatotoxicity or cochleovestibular toxicity, except for three patients who complained of vertigo at the 8-week assessment. The symptoms were mild and disappeared spontaneously once the treatment was completed. None of the patients in this series had discontinued therapy due to side effects.

Follow-up after completion of treatment. (i) Retrieval of patients who were lost to follow-up during chemotherapy. Within the 6 months following the standard duration of treatment, site visits were organized to retrieve the 17 patients lost to follow-up during the first or second month of antibiotic treatment. Among the 11 patients who were lost to follow-up between week 2 and week 4 of antibiotic therapy, 8 were retrieved several months later: by the time of retrieval, the lesions of 4 patients had healed, and for the other 4 patients, unhealed lesions were successfully treated with surgical excision. Among the six patients who were lost to follow-up after completing 1 month of antibiotic therapy because they either refused surgery (n = 3) or abandoned antibiotic therapy (n = 3), only one patient was retrieved; this patient was treated successfully by surgical excision at another center.

Therefore, as shown in the flow chart (Fig. 1), among the 224 patients for whom the streptomycin-rifampin combination was initiated between January 2003 and December 2004, 215 (96%) were ultimately considered as treatment successes and 9 were treatment failures, including 1 who died and 8 who were lost to follow-up. Successful cases included the 4 patients who had initial surgery and completed 8 weeks of chemotherapy, the 202 patients cured after 8 weeks of chemotherapy with (n = 104) or without (n = 98) surgery, the 8 patients retrieved from among the 11 patients who defaulted after 2 weeks of chemotherapy, and the single patient retrieved from the 6 patients who defaulted after 4 weeks of chemotherapy. Among the 215 successfully treated patients, 102 were cured with chemotherapy alone (47.4%), while 113 were cured with chemotherapy plus surgical excision with or without skin grafting (52.6%).

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FIG. 1. Flow chart of the patients. S+R, streptomycin-rifampin.

Lesion size and lesion nature (ulcerative or nonulcerative) at enrollment were the major factors in deciding whether to recommend surgical excision. Table 4 summarizes the results obtained among the 208 patients who were exclusively treated with the streptomycin-rifampin combination during the initial 4 weeks of treatment. In all, 81% of cases with ulcers of less than 5 cm in diameter were cured with chemotherapy alone, whereas only 21% of cases with ulcers larger than 15 cm in diameter were cured with chemotherapy alone. The benefit of chemotherapy is also evident for patients with nonulcerative lesions. Among 53 such cases receiving at least the four initial weeks of chemotherapy, 24 (45%) were cured with chemotherapy alone, a percentage higher than that (29% [5 of 17]) for the patients with small nonulcerated lesions who healed spontaneously in the controlled clinical trial conducted in Uganda between 1968 and 1970 (17). Survival analysis confirmed that ulcer size correlated with the need for surgery (P < 0.0001; log rank test for trend). Overall, nonulcerative disease required surgery just as frequently as ulcerative disease (P = 0.48). However, stratification by ulcer size revealed that ulcers of <5 cm in size were less likely (P = 0.0022), ulcers of 5 to 14 cm were equally likely (P = 0.0735), and ulcers of 15 cm were more likely (P = 0.0146) to require surgery compared to what was seen for nonulcerative lesions (Fig. 2).

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TABLE 4. Outcomes for the 208 patients treated with antibiotics alone for at least 4 weeks

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FIG. 2. Cumulative survival without surgery by lesion type.

(ii) Follow-up 1 year after treatment completion. Within the year following treatment completion, 208 of the 215 patients were actively retrieved for assessment of long-term results. Three (1.4%) had recurrence of M. ulcerans disease: two patients were treated with antibiotics alone, and one patient was treated with antibiotics plus surgery. It is interesting that none of the three relapses were identified by active retrieval. All three patients with relapse, whose clinical histories are given below, presented themselves, suggesting that the health education at the time of release from treatment was useful.

A 13-month-old infant who had in July 2003 immediate surgical excision of two small facial ulcers and skin grafting without antibiotic treatment in another center presented 5 months later, on 25 November 2003, with a small edematous plaque localized on the left cheek along the scar of the previous surgical excision. PCR was positive for M. ulcerans. Daily treatment with streptomycin-rifampin combination was initiated but discontinued 2 weeks later, on 9 December 2003, for a nonmedical reason. One month later, antibiotic treatment was resumed for 8 weeks, from 10 January to 9 March 2004, with apparent success. Four months later, on July 29, the patient presented again with a nodule and an edematous reaction at the margin of the scar. No bone lesion was detected by X-ray. A second treatment of 2 months in duration with daily streptomycin-rifampin was initiated and successfully completed. Two years later, in March 2006, the patient was well, without apparent hearing loss but with a peripheral facial nerve palsy related to the initial surgical procedure.

The second patient was a 6-year-old girl with a 4- by 5-cm plaque on the right thigh. She successfully completed an 8-week course of antibiotics. However, a small nodule appeared in the ipsilateral inguinal region 2 months after treatment completion. The two lesions were treated with excision followed by another 8-week course of antibiotics. She eventually healed without any clinical signs of toxicity.

The third patient was a 60-year-old woman treated for a large plaque on the left thigh. She received 2 weeks of daily rifampin-streptomycin and then discontinued the treatment for 2 weeks before resuming treatment for another 6 weeks followed by excision and skin grafting. Two months after treatment completion, she experienced a relapse with a small ulcerative plaque close to the scar. A second 8-week course of antibiotic therapy resulted in an apparent cure. More than 2 years later, she was still healed, with no sign of hearing loss.

Top ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
While we acknowledge that the Ghana trial (6) was indeed the first clinical trial to demonstrate that chemotherapy with the combination of streptomycin-rifampin was active for treating early lesions of M. ulcerans disease, we should not ignore its limitations. The trial had a small sample size, focused only on patients with preulcerative lesions, and included surgical excision for all patients at the end of chemotherapy. It did not address several important issues, namely, (i) whether chemotherapy is also effective for ulcerative lesions, including moderate-to-large lesions, (ii) whether or not chemotherapy alone may cure M. ulcerans disease, and (iii) the optimal duration of chemotherapy. The present report, based on a field study of the implementation of the WHO recommendations (25), offers answers to these issues. Remarkably, close to one half of the patients for whom treatment was initiated were cured with antibiotic therapy alone, including 81% of those with small ulcers, 56% of those with ulcers of between 5 and 15 cm in diameter, and even 21% of those with larger ulcers, contradicting the long-held dogma that surgical excision is the only effective therapy (19). Based on these results, antibiotic treatment alone seems appropriate for ulcers smaller than 5 cm. Even for the other half of the patients who were cured with antibiotic therapy plus surgical excision, the antibiotic therapy was clearly beneficial. For many, it reduced the size of the lesions and made the surgical excision easier to perform. In addition, the 0.9% recurrence rate among patients treated with antibiotics plus surgical excision and the 1.9% recurrence rate for patients treated only with antibiotics compare quite favorably with recurrence rates of 10 to 20% previously described for patients treated with surgical excision alone (1, 3, 10, 17, 23, 24). Overall, these findings confirm the potent bactericidal activity of the 2-month course of streptomycin-rifampin demonstrated experimentally in the mouse footpad model (2, 4, 5, 12) and in the clinical trial conducted in Ghana (6).

Although our results are very promising for the treatment of M. ulcerans disease in countries of endemicity, they should be viewed in the appropriate context. Treatment according to the WHO recommendations was implemented in the Ouémé-Plateau Department, Bénin, by a full-time medical team supported by the National Program and a nongovernmental organization (Fondation Raoul Follereau). Antibiotics and wound care were delivered under direct nurse supervision through a dedicated network of 12 clinics, thus making ambulatory treatment possible for a majority of patients, 157 out of 224 (70%). In addition, 25 beds were available in the CDTUB for patients who could not receive ambulatory treatment or required surgical excision and skin grafting.

In spite of these favorable conditions, the present study still suffers from a shortcoming that is commonly observed for rural areas where M. ulcerans disease is endemic, i.e., the inability to obtain laboratory confirmation of the diagnosis in a timely manner. This is particularly important for the nonulcerative forms of the disease, namely, nodules, plaques, and edema, which lack the pathognomonic features of the ulcerative forms. PCR confirmation of the presence of M. ulcerans (18, 20, 21) was not yet available, and there were not adequate facilities for acid-fast smearing and culture. Therefore, we have concentrated our present efforts on confirming a posteriori the maximum possible number of clinical diagnoses of M. ulcerans infection by smear and PCR using the expertise of national and international reference laboratories. Given the burden and cost of laboratory confirmation and the characteristic clinical features of ulcerative forms of M. ulcerans disease, laboratory confirmation is unlikely to be necessary, feasible, and cost-effective for all cases in areas of high endemicity. Priority should be given to the laboratory diagnosis of nonulcerative cases.

The implementation of the WHO-recommended treatment in the Ouémé-Plateau Department could be improved in several ways. First, it should have been possible to initiate antibiotic therapy for more than 72% of the 310 patients diagnosed with M. ulcerans disease. While we clearly could not have offered streptomycin-rifampin to pregnant women, perhaps we could have convinced more patients to accept the antibiotic treatment rather than turning to traditional medicine. We certainly hope that the efficacy of antibiotic treatment will encourage the detection of lesions at an earlier stage and the acceptance of antibiotic treatment and expand the role of nonsurgical management of M. ulcerans disease.

Second, we would have liked to have lost fewer patients to follow-up during treatment. However, the patients that were lost to follow-up and subsequently retrieved taught us that (i) some patients can be cured with antibiotic treatment for as little as 2 to 4 weeks, and (ii) a fair proportion of patients, 64 of 105 (60.9%), with ulcers of 5 to 15 mm in diameter and even 16 out of 63 (25.4%) with ulcers larger than 15 mm in diameter who refused surgery eventually healed without serious handicaps after receiving antibiotic treatment. Both findings raise important questions. What is the optimal duration of antibiotic therapy? Which clinical and/or laboratory parameters could indicate that the antibiotic therapy can be discontinued safely? Although there are no simple answers to these questions, one may speculate on the role of antibiotic therapy. For many if not most patients, it would appear that antibiotic therapy is able to completely halt the growth of M. ulcerans and the secretion of mycolactone, allowing the infected host to mount an effective immune response that eventually results in scarring of the lesions. For some patients, it is also possible that the antibiotics have a bactericidal action that succeeds in eradicating the organism altogether. Either way, the essential role of antibiotic therapy may be to speed up the natural process of spontaneous scarring, making it possible to postpone the decision regarding excisional surgery well beyond the first 4 weeks of antibiotic therapy for patients that show initial signs of improvement.

Third, we would have liked to have seen the patients at an earlier state of their disease to reduce still more not only patient suffering but also the need for surgery. One may hope that the overall successful implementation of WHO recommendations will in the coming years encourage patients to seek earlier medical advice.

Finally, the lack of alternatives to the streptomycin-rifampin combination will undoubtedly hamper the rapid expansion of antibiotic therapy for M. ulcerans disease. Although the two-month course of therapy has been well tolerated in our experience, the risk of cochleovestibular or renal toxicity with streptomycin and the difficulties associated with the prevention of blood-borne pathogen dissemination by the administration of this injectable drug complicate its use in rural areas. Furthermore, the combination regimen cannot be considered safe for pregnant women. It is hoped that the encouraging results presented here will stimulate further scientific inquiries to develop new orally administered drugs and drug regimens active against M. ulcerans and to simplify the delivery of the current regimen by defining the optimal treatment duration and the prospects for intermittent ambulatory therapy (9).

 
The present study would not have been possible without the full funding support of the Fondation Raoul Follereau, Paris, France, and the support of the Buruli Ulcer Control Programme, Cotonou, Bénin.

 
* Corresponding author. Mailing address: Center for Tuberculosis Research, Johns Hopkins University School of Medicine, 1550 Orleans Street, Baltimore, MD 21231-1001. Phone: (410) 502-8234. Fax: (410) 614-8173. E-mail: jgrosse4{at}jhmi.edu

Published ahead of print on 25 May 2007.

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Antimicrobial Agents and Chemotherapy, November 2007, p. 4029-4035, Vol. 51, No. 11
0066-4804/07/$08.00+0     doi:10.1128/AAC.00175-07
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