Biology subjects

Bosshard, P. P.

Publications and source records attributed to Bosshard, P. P..

3 recordsLinked to original sources

bioRxiv2026

Microbial community profiles of genital and non-genital skin lesions from Ghana

Skin ulcers, such as those observed in cases of the non-venereal disease yaws and the venereal disease syphilis, are traditionally diagnosed based on their anatomical location and visible appearance. Yet various evidence suggests that the pathogens that cause these ulcers may not be restricted to genital or non-genital body sites. We explored this by profiling the bacterial communities of genital and non-genital skin ulcers collected in Ghana using 16S rRNA gene amplicon sequencing. Swab samples were collected from 156 clinically diagnosed skin lesions (110 non-genital and 46 genital). The V1-V2 region of the 16S rRNA gene was sequenced to characterize bacterial communities. Microbial diversity, community composition, differential abundance, and associations between lesion diversity and common skin bacteria were analysed using bioinformatics and statistical methods. Following quality filtering, 135 samples were retained, revealing 23 bacterial phyla, 143 families, and 406 genera. Alpha diversity indicated similar bacterial richness and diversity in genital and non-genital skin lesions. Beta diversity analyses indicated differences between genital and non-genital lesions, accompanied by significant differences in within group dispersion. A log2 fold change analysis evidenced genital lesions were enriched in Gardnerella, whereas non-genital lesions showed more abundance of Staphylococcus, Streptococcus, Corynebacterium, Bradyrhizobium, and Pelomonas. Clinically important genera, including Treponema, Haemophilus, and Mycobacterium, were also detected, even in samples with low sequencing depths. Statistical modelling indicated that greater microbial diversity was associated with intermediate abundances of common skin taxa, particularly Corynebacteriaceae, Micrococcaceae, Cutibacterium, and Staphylococcaceae, thereby attesting the presence of polymicrobial communities in skin ulcers. Overall, genital and non-genital skin lesions showed similar microbial diversity but differed in composition. Our findings support the view of skin lesions as ecological niches containing diverse bacterial communities rather than being consistently dominated by a single bacterial taxon. They provide a basis for investigating possible polymicrobial interactions in skin ulcers.

microbiology↗

bioRxiv2025

A new typing scheme demonstrates high discriminatory power for Treponema pallidum subspecies

The global resurgence of treponematoses, particularly syphilis, poses a growing public health challenge. Despite recent advances in sequencing technologies, obtaining complete Treponema pallidum genome sequences for epidemiological studies remains time-consuming and challenging due to the difficulty related to procuring clinical samples with sufficient treponemal burden to fulfil the sequencing requirements. There is an urgent need for rapid, cost-effective and accessible typing methods suitable for laboratories with Sanger sequencing resources. Based on the analysis of 121 T. pallidum genomes from geographically diverse regions, we selected seven highly variable genes to form the basis of this new typing system. These seven genes show high discrimination capacity, identifying many allelic profiles among T. pallidum isolates. Importantly, the scheme employs a single-step PCR protocol for the amplification and sequencing of all seven targets enabling straightforward implementation in standard laboratory settings. The MLST was validated using a diverse set of T. pallidum clinical samples from across the globe. A significant proportion of the tested samples showed macrolide resistance, emphasizing the need for epidemiological surveillance. Utilizing this new tool, we have analyzed the genetic variation within and between populations of T. pallidum, considering the geographical origin of the samples. Population structure analysis revealed distinct genetic clusters, underlining complex transmission dynamics of T. pallidum, shaped by local epidemiological factors. The MLST scheme is publicly accessible through the PubMLST database, encouraging widespread adoption in standard laboratories due to this database being user-friendly, intuitive, and fast to implement. The novel MLST scheme offers a promising tool to advance the study of the molecular epidemiology of T. pallidum, facilitate tracking transmission, and establish a global surveillance network with the overall goal of strengthening public health interventions for syphilis control.

microbiology↗

bioRxiv2020

Systemic and mucosal antibody secretion specific to SARS-CoV-2 during mild versus severe COVID-19

BackgroundInfection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes an acute illness termed coronavirus disease 2019 (COVID-19). Humoral immune responses likely play an important role in containing SARS-CoV-2, however, the determinants of SARS-CoV-2-specific antibody responses are unclear. MethodsUsing immunoassays specific for the SARS-CoV-2 spike protein, we determined SARS-CoV-2-specific immunoglobulin A (IgA) and immunoglobulin G (IgG) in sera and mucosal fluids of two cohorts, including patients with quantitative reverse-transcriptase polymerase chain reaction (RT-qPCR)-confirmed SARS-CoV-2 infection (n = 56; median age 61 years) with mild versus severe COVID-19, and SARS-CoV-2-exposed healthcare workers (n = 109; median age 36 years) with or without symptoms and tested negative or positive by RT-qPCR. FindingsOn average, SARS-CoV-2-specific serum IgA titers in mild COVID-19 cases became positive eight days after symptom onset and were often transient, whereas serum IgG levels remained negative or reached positive values 9-10 days after symptom onset. Conversely, patients with severe COVID-19 showed a highly significant increase of SARS-CoV-2-specific serum IgA and IgG titers as a function of duration since symptom onset, independent of patient age and comorbidities. Very high levels of SARS-CoV-2-specific serum IgA correlated with severe acute respiratory distress syndrome (ARDS). Interestingly, some of the SARS-CoV-2-exposed healthcare workers with negative SARS-CoV-2-specific IgA and IgG serum titers had detectable SARS-CoV-2-specific IgA antibodies in their nasal fluids and tears. Moreover, SARS-CoV-2-specific IgA levels in nasal fluids of these healthcare workers were inversely correlated with patient age. InterpretationThese data show that systemic IgA and IgG production against SARS-CoV-2 develops mainly in severe COVID-19, with very high IgA levels seen in patients with severe ARDS, whereas mild disease may be associated with transient serum titers of SARS-CoV-2-specific antibodies but stimulate mucosal SARS-CoV-2-specific IgA secretion. The findings suggest four grades of antibody responses dependent on COVID-19 severity.

immunology↗