Aka Nguetta^1,, Coulibaly N D¹, Kouamé-Elogne N C¹, Yao Aubin², Apia Basile¹, Yoboué Gontran², Kouadio Kouamé¹, Koffi Aboa³, Kakou-Ngazoa ES¹, Paul Saunderson⁴, Dosso Mireille¹

Background Buruli ulcer is a chronic necrotizing infectious paniculitis caused by Mycobacterium ulcerans which is prevalent in tropical countries with hot and humid climates. In Côte d'Ivoire, there is a problem of biological confirmation despite the availability of an efficient technical platform and well-trained laboratory staff. Biological confirmation tests carried out from 2005 to 2014 revealed the presence of M. ulcerans only in 61% of suspected cases. Conversely, in 39% of cases no etiology was identified. To understand the reasons for this under-reporting, a study was carried out in 3 endemic health districts in Côte d'Ivoire. The objectives were to improve the quality of clinical samples for microbiological and molecular analysis, to optimize the biological confirmation of Buruli ulcer, and to improve results management. Methods Buruli ulcer suspected patients were enrolled in three endemic health districts from 2016 to 2022. Clinical samples were taken in health centers and transferred to the national reference laboratory. Three confirmation methods were carried out: PCR targeting the IS2404 insertion sequence, direct-smear examination by microscopy after Ziehl-Neelsen staining and culture on Löwenstein-Jensen medium. When the first PCR result was negative, a second sample was taken 10 to 15 days later. When the result of the second PCR test was negative, a third sample was taken 10 to 15 days later and analyzed according to the same protocol. Test results were reported to healthcare providers within 3-5 days. An external evaluation of the quality of the PCR tests was carried out by the Institute of Tropical Medicine in Antwerp and by the Swiss Institute of Public and Tropical Health. Results 270 patients with suspected cutaneous lesion were recruited in the health districts of Tiassalé (55.2%), Oumé (21.9%) and Sinfra (22.9%). The study population was divided into four age groups, with a predominance of subjects aged under 17 (53%). Ziehl-Neelsen staining revealed the presence of Acid-fast bacilli in 38.1% of cases. The insertion sequence IS2404 was detected in 80% of the samples and mycobacterial isolates were detected in 44.8% of cases. The combination of the three diagnostic methods gave a positivity rate of 81.5% throughout the study period. The culture-PCR coupling optimized the confirmation rate to 81.5%, with a detection of 3% of cases not diagnosed by PCR. Conclusion During the study 18.5% of suspicious lesions were not confirmed as Buruli ulcer cases. This approach has optimized the biological confirmation of M. ulcerans infection in suspected BU cases. The interaction between the peripheral centers and the reference laboratory was improved in patient follow-up. The delay in reporting results was reduced and the quality of the data collection was improved. At the end of this study, a Buruli ulcer management approach was proposed, which could help endemic countries to strengthen the quality of case management.

M. ulcerans infection control, confirmation rate, insertion sequence, microscopy, culture