Using 16s rRNA sequencing to characterize the microbiome of tropical cutaneous ulcer disease: insights into the microbial landscape and implications for diagnosis and treatment.

Cutaneous ulcers are common in yaws-endemic areas. Although often attributed to 'Treponema pallidum subsp. pertenue' and Haemophilus ducreyi, quantitative PCR has highlighted a significant proportion of these ulcers are negative for both pathogens and are considered idiopathic. This is a retrospective analysis utilising existing 16S rRNA sequencing data from two independent yaws studies that took place in Ghana and the Solomon Islands. We characterized bacterial diversity in 38 samples to identify potential causative agents for idiopathic cutaneous ulcers. We identified a diverse bacterial profile, including Arcanobacterium haemolyticum, Campylobacter concisus, Corynebacterium diphtheriae, Staphylococcus spp. and Streptococcus pyogenes, consistent with findings from previous cutaneous ulcer microbiome studies. No single bacterial species was universally present across all samples. The most prevalent bacterium, Campylobacter ureolyticus, appeared in 42% of samples, suggesting a multifactorial aetiology for cutaneous ulcers in yaws-endemic areas. This study emphasizes the need for a nuanced understanding of potential causative agents. The findings prompt further exploration into the intricate microbial interactions contributing to idiopathic yaw-like ulcers, guiding future research toward comprehensive diagnostic and therapeutic strategies.

Diagnostics to support the eradication of yaws-Development of two target product profiles.

BACKGROUND: Yaws is targeted for eradication by 2030, using a strategy based on mass drug administration (MDA) with azithromycin. New diagnostics are needed to aid eradication. Serology is currently the mainstay for yaws diagnosis; however, inaccuracies associated with current serological tests makes it difficult to fully assess the need for and impact of eradication campaigns using these tools. Under the recommendation of the WHO Diagnostic Technical Advisory Group (DTAG) for Neglected Tropical Diseases(NTDs), a working group was assembled and tasked with agreeing on priority use cases for developing target product profiles (TPPs) for new diagnostics tools. METHODOLOGY AND PRINCIPAL FINDINGS: The working group convened three times and established two use cases: identifying a single case of yaws and detecting azithromycin resistance. One subgroup assessed the current diagnostic landscape for yaws and a second subgroup determined the test requirements for both use cases. Draft TPPs were sent out for input from stakeholders and experts. Both TPPs considered the following parameters: product use, design, performance, configuration, cost, access and equity. To identify a single case of yaws, the test should be able to detect an analyte which confirms an active infection with at least 95% sensitivity and 99.9% specificity. The high specificity was deemed important to avoid a high false positive rate which could result in unnecessary continuation or initiation of MDA campaigns. If used in settings where the number of suspected cases is low, further testing could be considered to compensate for imperfect sensitivity and to improve specificity. The test to detect azithromycin resistance should be able to detect known genetic resistance mutations with a minimum sensitivity and specificity of 95%, with the caveat that all patients with suspected treatment failure should be treated as having resistant yaws and offered alternative treatment. CONCLUSIONS: The TPPs developed will provide test developers with guidance to ensure that novel diagnostic tests meet identified public health needs.

Conjunctival Scarring, Corneal Pannus, and Herbert's Pits in Adolescent Children in Trachoma-endemic Populations of the Solomon Islands and Vanuatu.

BACKGROUND: In the Solomon Islands and Vanuatu, the sign trachomatous inflammation-follicular (TF) is common, but ocular infection with Chlamydia trachomatis is not. It is therefore debatable whether azithromycin mass drug administration (MDA), the recommended antibiotic treatment strategy for trachoma's elimination as a public health problem, is necessary in this setting. We set out to estimate what proportion of adolescents were at risk of progression of trachomatous scarring. METHODS: A cross-sectional survey was undertaken of all children aged 10-14 years resident in communities identified as high-TF clusters during previous population-based mapping. Graders examined children for clinical evidence of trachomatous scarring, pannus, and Herbert's pits (HPs) or limbal follicles in both eyes. A dried blood spot was collected from each child and tested for antibodies to C. trachomatis. RESULTS: A total of 492 children in 24 villages of the Solomon Islands and Vanuatu were examined. In total, 35/492 (7%) of children had limbal signs (pannus and/or HPs) plus any conjunctival scarring. And 9/492 (2%) had limbal signs and moderate or severe conjunctival scarring; 22% of children were anti-Pgp3 seropositive. CONCLUSIONS: Few adolescents here are at risk of future complications from trachoma, supporting the conclusion that further antibiotic MDA is not currently required for trachoma elimination purposes in these settings.

Optimising the use of molecular tools for the diagnosis of yaws.

BACKGROUND: Yaws is a neglected tropical disease and results in lesions of skin, soft tissues and bones. PCR plays an important part in surveillance. METHODS: Children suspected to have yaws were enrolled. From the largest lesion, paired swabs were collected, one in transport medium and one as a dry swab. In children with multiple lesions we collected additional swabs from up to four subsequent lesions. Swabs in transport medium were maintained in a cold chain while dry swabs were stored at ambient temperature. Swabs were tested by PCR for Treponema pallidum and Haemophilus ducreyi. RESULTS: Of 55 individuals, 10 (18%) had at least one positive PCR for T. pallidum and 12 (22%) had at least one positive result for H. ducreyi. Concordance was 100% between swabs in transport medium and dry swabs. One patient had PCR-confirmed yaws on the swab of a third lesion when both the first and second lesions were PCR-negative. CONCLUSIONS: Storing swabs in transport medium and transporting in a cold chain did not improve yield, however, detection of T. pallidum is increased by swabbing additional lesions. As the target for yaws is eradication, approaches to sample collection need revisiting to ensure cases are not missed.

Absence of Serological Evidence of Exposure to Treponema pallidum among Children Suggests Yaws Is No Longer Endemic in Kiribati.

Yaws is a neglected tropical disease targeted for eradication by 2020. Kiribati, a Pacific Island nation, was previously endemic for yaws but lacks recent data from which its current endemicity status could be determined. This study tested antibody responses to Treponema pallidum to determine if transmission of yaws is taking place among children in Kiribati. Using a commercially available T. pallidum particle agglutination kit (Serodia®, Fujirebio Inc., Tokyo, Japan), we tested dried blood spots, collected during population-based trachoma prevalence surveys on Tarawa Atoll and Kiritimati Island, for long-lived treponemal antibodies. Dried blood spots from 1,420 children aged 1-9 years were tested. Only two were positive, suggesting T. pallidum is not being widely transmitted among children in the settings sampled. These data require support from additional surveys to demonstrate the absence of clinical signs of disease and molecular evidence of infection, to confirm that yaws is no longer endemic in Kiribati.

A systematic review of historical and contemporary evidence of trachoma endemicity in the Pacific Islands.

INTRODUCTION: Trachoma is endemic in several Pacific Island countries. The aims of this study were to (a) identify future trachoma mapping needs in the Pacific and (b) to examine whether any temporal trends in trachoma prevalence could be ascertained from the historical literature on trachoma in the Pacific Islands. METHODS: Human studies of trachoma and eye care in the Pacific Islands were identified from a systematic search of PubMed, EMbase, Scopus and Web of Science databases. A published quality assessment system for disease prevalence studies was modified to assess studies for quality and transparency. RESULTS: Few general ophthalmic studies in the Pacific mention trachoma. In targeted studies of trachoma, cases have consistently been identified throughout the Pacific since the early twentieth century. The largest number of studies come from Papua New Guinea and Fiji, whereas some countries have no published data on trachoma. The majority of studies identified were published before the Alliance for the Global Elimination of Trachoma 2020 was convened, so lack the standardisation of population-based mapping which has been implemented in the past decade. CONCLUSIONS: Population-based trachoma prevalence estimates have been recently generated in Papua New Guinea, Solomon Islands, Vanuatu, Kiribati and Fiji. There is insufficient evidence to assess whether there has been temporal change in trachoma prevalence in these countries over the past century. Cases of trachoma have been identified in some countries (for example, Nauru and Samoa) which have no recent population-based mapping data, but may be at risk of trachoma endemcitiy. Deployment of appropriate mapping strategies is warranted to identify whether interventions are required.