Ulcerative skin lesions among children in Cameroon: It is not always Yaws

A high-resolution view of the immune and stromal cell response to Haemophilus ducreyi infection in human volunteers

Haemophilus ducreyi causes the genital ulcer disease chancroid and cutaneous ulcers in children. To study its pathogenesis, we developed a human challenge model in which we infect the skin on the upper arm of human volunteers with H. ducreyi to the pustular stage of disease. The model has been used to define lesional architecture, describe the immune infiltrate into the infected sites using flow cytometry, and explore the molecular basis of the immune response using bulk RNA-seq. Here, we used single cell RNA-seq (scRNA-seq) and spatial transcriptomics to simultaneously characterize multiple cell types within infected human skin and determine the cellular origin of differentially expressed transcripts that we had previously identified by bulk RNA-seq. We obtained paired biopsies of pustules and wounded (mock infected) sites from five volunteers for scRNA-seq. We identified 13 major cell types, including T- and NK-like cells, macrophages, dendritic cells, as well as other cell types typically found in the skin. Immune cell types were enriched in pustules, and some subtypes within the major cell types were exclusive to pustules. Sufficient tissue specimens for spatial transcriptomics were available from four of the volunteers. T- and NK-like cells were highly associated with multiple antigen presentation cell types. In pustules, type I interferon stimulation was high in areas that were high in antigen presentation-especially in macrophages near the abscess-compared to wounds. Together, our data provide a high-resolution view of the cellular immune response to the infection of the skin with a human pathogen.IMPORTANCEA high-resolution view of the immune infiltrate due to infection with an extracellular bacterial pathogen in human skin has not yet been defined. Here, we used the human skin pathogen Haemophilus ducreyi in a human challenge model to identify on a single cell level the types of cells that are present in volunteers who fail to spontaneously clear infection and form pustules. We identified 13 major cell types. Immune cells and immune-activated stromal cells were enriched in pustules compared to wounded (mock infected) sites. Pustules formed despite the expression of multiple pro-inflammatory cytokines, such as IL-1β and type I interferon. Interferon stimulation was most evident in macrophages, which were proximal to the abscess. The pro-inflammatory response within the pustule may be tempered by regulatory T cells and cells that express indoleamine 2,3-dioxygenase, leading to failure of the immune system to clear H. ducreyi.

Infections caused by Haemophilus ducreyi: one organism, two stories

SUMMARYChancroid, a sexually transmitted infection caused by Haemophilus ducreyi, is characterized by painful genital ulcers (GU) and inguinal lymphadenitis. H. ducreyi was recently described as a major cause of non-sexually transmitted cutaneous ulcers (CU) on the lower legs in children in yaws-endemic regions. This review explores the relationship between CU and GU strains of H. ducreyi; their clinical presentation, diagnosis, epidemiology, and treatment; and how findings from a human challenge model relate to GU and CU. We contrast the decline of GU with the persistence of CU caused by H. ducreyi. Factors such as transmission dynamics, control, and elimination efforts are discussed. Syndromic management and targeted treatment of sex workers can eradicate chancroid, while skin colonization by CU strains and environmental factors may necessitate topical treatments or vaccination for CU eradication. Efforts should focus on identifying additional reservoirs of CU strains, improving hygiene, and eliminating asymptomatic colonization to eradicate this painful infection in children.

Sequence typing of Haemophilus ducreyi isolated from patients in the Namatanai region of Papua New Guinea: Infections by Class I and Class II strain types differ in ulcer duration and resurgence of infection after azithromycin treatment

Haemophilus ducreyi (HD) is an important cause of cutaneous ulcers in several endemic regions, including the Western Pacific Region, especially among children. An HD sequence typing on swab samples taken from 1,081 ulcers in the Namatanai district of Papua New Guinea, during the pilot study for treatment of yaws, has been performed using the Grant typing system. Of the 363 samples that tested positive for the 16S rDNA of HD, the dsrA sequences of 270 samples were determined. Altogether they revealed 8 HD strain types circulating in Namatanai, including seven strain types of Class I (I.3, I.4, I.5, I.9, I.10, I.11, I.12) and one strain of Class II (II.3); four Class I types (I.9, I.10, I.11, I.12) were novel. The southern region of Namatanai (Matalai Rural) was identified as the region with the lowest genotype diversity and with most infections caused by HD Class II. The middle and northern subdistricts were affected mainly by HD Class I. Analysis of patient characteristics revealed that Class II HD infections were more often represented by longer-lasting ulcers than Class I HD infections. An increase in the prevalence of the I.10 strain was found after azithromycin administration compared to the untreated population at baseline likely reflecting higher infectivity of HD Class I, and more specifically strain type I.10.

A Haemophilus ducreyi strain lacking the yfeABCD iron transport system is virulent in human volunteers

Haemophilus ducreyi causes the genital ulcer disease chancroid and painful cutaneous ulcers in children who live in the tropics. To acquire heme from the host, H. ducreyi expresses a TonB-dependent hemoglobin receptor, HgbA, which is necessary and sufficient for H. ducreyi to progress to the pustular stage of disease in a controlled human infection model. HgbA transports hemoglobin across the outer membrane; how heme is transported across the cytoplasmic membrane is unclear. In previous studies, transcripts encoding the YfeABCD heme transporter were upregulated in experimental lesions caused by H. ducreyi in human volunteers, suggesting the latter may have a role in virulence. Here we constructed a double deletion mutant, 35000HPΔyfeABΔyfeCD, which exhibited growth defects relative to its parent 35000HP in media containing human hemoglobin as an iron source. Five human volunteers were inoculated at three sites on the skin overlying the deltoid with each strain. The results of the trial showed that papules formed at 100% (95% CI, 71.5, 100) at both 35000HP and 35000HPΔyfeABΔyfeCD-inoculated sites (P = 1.0). Pustules formed at 60% (95% CI, 25.9, 94.1) at parent-inoculated sites and 53% (95% CI, 18.3, 88.4) at mutant-inoculated sites (P = 0.79). Thus, the ABC transporter encoded by yfeAB and yfeCD was dispensable for H. ducreyi virulence in humans. In the absence of YfeABCD, H. ducreyi likely utilizes other periplasmic binding proteins and ABC-transporters such as HbpA, SapABCDF, and DppBCDF to shuttle heme from the periplasm into the cytoplasm, underscoring the importance of redundancy of such systems in gram-negative pathogens.

Implementation of an integrated control programme for neglected tropical diseases of the skin in Ghana: The essential role of the laboratory

Introduction

In this study, we report on findings from approaches used, the outcomes and the lessons learnt from the laboratory support provided for integrated control of skin NTDs including Buruli ulcer (BU), and yaws in seven selected districts in Ghana.

Methods

Actions implemented from July 2018 to October 2022 included; training district-level health workers on specimen collection, storage, and transport to laboratories, integrated case searches, continual monitoring and supervision for trained health workers, laboratory confirmation of BU and yaws samples and providing results of the analysed samples to guide decision making. Descriptive analysis of data was performed.

Results

A total of 18,683 (including suspected BU 976; suspected yaws 10,995) individuals were screened for BU and yaws. Of 976 suspected BU cases, 16.8% [median (IQR) age 24 (12.0-37.8) years] were confirmed positive by IS2404 PCR; BU mostly presented as ulcers (78.7%); category I (37.2%) and category II (36%). 480 individuals (4.4%) had DPP positive yaws. Multiplex PCR analysis of 75 selected DPP positive cases identified; 7 DPP positive yaws cases as Treponema pallidum, 28 as Haemophilus ducreyi and 7 as Treponema pallidum/Haemophilus ducreyi coinfection. Laboratory results were sent to the districts within a median (IQR) of 5 (3 - 9) days.

Conclusion

The implementation of integrated diagnostic confirmation for skin NTDs is feasible with provision of timely results within a week. Multiplex diagnostic tools differentiated Treponema pallidum and Haemophilus ducreyi. There is a need to sustain active case search activities, enhance health worker training, and improve laboratory confirmation of cases as part of the overall strategy for the integrated control of skin neglected tropical diseases.

Prospecting for yaws in the Mbaïki Health District in the Central African Republic

Introduction

yaws is endemic in the Central African Republic. The last cases of yaws notified by CAR to WHO date back to 2012. The objective of this study was to measure the prevalence of yaws in the health district of Mbaïki and to describe its clinical and epidemiological characteristics.

Methods

this is a descriptive cross-sectional study, conducted from April 10 to 18, 2020 in the Mbaïki health district. Yaws cases were sought in 570 households in the 38 selected villages of the district. Any consenting individual over the age of one year with yaws-like skin lesions was a suspected case of yaws and included in the study. Blood was taken from suspected cases for serological testing (TDR, RPR and TPHA). Any suspected case of yaws with positive RPR and TPHA was considered a confirmed case.

Results

a total of 1967 people were examined, of whom 113 were considered suspected cases of yaws. All suspected cases were RPR-positive, 41 TPHA-positive and 13 RDT-positive. Forty-one cases of yaws were confirmed in 18 (47.37%) villages. The prevalence of yaws in the Mbaïki health district was 2.08%. Among the cases, 38.94% were children aged 1 to 14. The sex ratio was 1.69. Lesions clinically suggestive of yaws were papilloma-like in 77.00% of cases, followed by micropapules (8.00%) and ulcerations (5.00%).

Conclusion

eight of the nine communes in the Mbaïki health district are yaws-endemic. This result suggests the need to implement the Morges strategy in the Mbaïki health district.

Trial of Three Rounds of Mass Azithromycin Administration for Yaws Eradication

BACKGROUND

Treponema pallidum subspecies pertenue causes yaws. Strategies to better control, eliminate, and eradicate yaws are needed.

METHODS

In an open-label, cluster-randomized, community-based trial conducted in a yaws-endemic area of Papua New Guinea, we randomly assigned 38 wards (i.e., clusters) to receive one round of mass administration of azithromycin followed by two rounds of target treatment of active cases (control group) or three rounds of mass administration of azithromycin (experimental group); round 1 was administered at baseline, round 2 at 6 months, and round 3 at 12 months. The coprimary end points were the prevalence of active cases of yaws, confirmed by polymerase-chain-reaction assay, in the entire trial population and the prevalence of latent yaws, confirmed by serologic testing, in a subgroup of asymptomatic children 1 to 15 years of age; prevalences were measured at 18 months, and the between-group differences were calculated.

RESULTS

Of the 38 wards, 19 were randomly assigned to the control group (30,438 persons) and 19 to the experimental group (26,238 persons). A total of 24,848 doses of azithromycin were administered in the control group (22,033 were given to the participants at round 1 and 207 and 2608 were given to the participants with yaws-like lesions and their contacts, respectively, at rounds 2 and 3 [combined]), and 59,852 doses were administered in the experimental group. At 18 months, the prevalence of active yaws had decreased from 0.46% (102 of 22,033 persons) at baseline to 0.16% (47 of 29,954 persons) in the control group and from 0.43% (87 of 20,331 persons) at baseline to 0.04% (10 of 25,987 persons) in the experimental group (relative risk adjusted for clustering, 4.08; 95% confidence interval [CI], 1.90 to 8.76). The prevalence of other infectious ulcers decreased to a similar extent in the two treatment groups. The prevalence of latent yaws at 18 months was 6.54% (95% CI, 5.00 to 8.08) among 994 children in the control group and 3.28% (95% CI, 2.14 to 4.42) among 945 children in the experimental group (relative risk adjusted for clustering and age, 2.03; 95% CI, 1.12 to 3.70). Three cases of yaws with resistance to macrolides were found in the experimental group.

CONCLUSIONS

The reduction in the community prevalence of yaws was greater with three rounds of mass administration of azithromycin at 6-month intervals than with one round of mass administration of azithromycin followed by two rounds of targeted treatment. Monitoring for the emergence and spread of antimicrobial resistance is needed. (Funded by Fundació "la Caixa" and others; ClinicalTrials.gov number, NCT03490123.).