Ephemeral-habitat colonization and neotropical species richness of Caenorhabditis nematodes

Background

The drivers of species co-existence in local communities are especially enigmatic for assemblages of morphologically cryptic species. Here we characterize the colonization dynamics and abundance of nine species of Caenorhabditis nematodes in neotropical French Guiana, the most speciose known assemblage of this genus, with resource use overlap and notoriously similar external morphology despite deep genomic divergence.

Methods

To characterize the dynamics and specificity of colonization and exploitation of ephemeral resource patches, we conducted manipulative field experiments and the largest sampling effort to date for Caenorhabditis outside of Europe. This effort provides the first in-depth quantitative analysis of substrate specificity for Caenorhabditis in natural, unperturbed habitats.

Results

We amassed a total of 626 strain isolates from nine species of Caenorhabditis among 2865 substrate samples. With the two new species described here (C. astrocarya and C. dolens), we estimate that our sampling procedures will discover few additional species of these microbivorous animals in this tropical rainforest system. We demonstrate experimentally that the two most prevalent species (C. nouraguensis and C. tropicalis) rapidly colonize fresh resource patches, whereas at least one rarer species shows specialist micro-habitat fidelity.

Conclusion

Despite the potential to colonize rapidly, these ephemeral patchy resources of rotting fruits and flowers are likely to often remain uncolonized by Caenorhabditis prior to their complete decay, implying dispersal-limited resource exploitation. We hypothesize that a combination of rapid colonization, high ephemerality of resource patches, and species heterogeneity in degree of specialization on micro-habitats and life histories enables a dynamic co-existence of so many morphologically cryptic species of Caenorhabditis.

Electronic supplementary material

The online version of this article (10.1186/s12898-017-0150-z) contains supplementary material, which is available to authorized users.

Comparison of molecular and serological assays on cerebrospinal fluid for the diagnosis of neurosyphilis

BACKGROUND

Many assays are available on cerebrospinal fluid (CSF) for the diagnosis of neurosyphilis (NS) but there is no 'gold standard'.

OBJECTIVES

The aim of this study was to evaluate different molecular and serological assays used in NS.

METHODS

We evaluated two PCR assays and three serological techniques in parallel on CSF samples collected between 2019 and 2020 from patients suspected of NS.

RESULTS

The study included 143 patients comprising 30 early NS, 7 late NS and 106 patients without a diagnosis of NS. All patients with NS were symptomatic and had either neurological (67.6%) or ophthalmological signs (54.1%). The qPCR and nPCR assays had overall sensitivities (Se) of 41% and 27%, respectively; with each an overall specificity (Sp) of 100%. VDRL had a Se of 51% and a Sp of 92%. Immunoblot had a Se of 62% and a Sp of 85%. Finally, treponemal tests (TT) had a Se of 96% and a Sp of 69%.

CONCLUSIONS

Our study confirms the excellent specificity of molecular techniques allowing to avoid overdiagnosis of NS, and thus, unjustified intensive antibiotic therapy protocols. CSF TT, although not very specific, has an excellent Se confirming that there is almost never NS with negative CSF TT. VDRL and immunoblot tests have better overall diagnostic performance. However, none of these techniques has sufficient diagnostic performance to represent a 'gold standard'. Thus, the diagnosis of NS relies on a combination of clinical and biological parameters with the association of PCR with serology, associating VDRL and immunoblot, in CSF.

Psoriasis and sexuality: Patients express their feelings

Background

In France, psoriasis is a chronic inflammatory skin disease. For several years now, particular attention has been given to the quality of life (Qol) of psoriasis patients. Sexual dysfunction (SD) defined as not wanting or enjoying sexual experience is an important component of Qol. Psoriasis through its physical symptoms and psychological consequences can thus be responsible for SD.

Method

The survey participants were recruited through the national psoriasis dermatitis patient association.

Result

41% (577) patients reported having SD related to their psoriasis. Women reported significantly more SD than men (387 [44.7%] vs. 190 [35%], p < 0.001). For 396 (28.1%) patients SD due to their psoriasis manifested as a reduction in the frequency of sexual activity, for 207 (14.7%) as change in their sexual practice, and for 284 (27.4%) as an absence of sexual activity without significant difference between women and men. The main consequence of sexual difficulties for patients was loss of self-confidence in 627 (44.5%) cases, guilt in 209 (14.8%) cases, couple life impairment in 214 (15.2%) cases, isolation in 260 (18.5%) cases and frustration.

Discussion

In this study investigating SD related to psoriasis, we found that the disease impact sexual relations of 41% of patients of both gender. The main causes of SD were both physical alone and psychological alone, in the same proportions. The physical symptoms of psoriasis are therefore not the only ones responsible for the sexual discomfort reported from patients in their sexual relations. This may be due to a discomfort of the patient or the physician when talking about sexuality because they can't find the terms to talk about this subject often considered taboo and the age or gender difference. This aspect of the disease should be considered by physicians who care for patients with psoriasis, especially dermatologists. Finally, other strategies should be implemented, such as patient talk groups, referral guides or personalised therapeutic education.

Specific detection of Treponema pallidum in clinical samples: validation of a qPCR assay combining two genomic targets

OBJECTIVES

We evaluated a real-time quantitative PCR (qPCR) for detection of the Treponema pallidum (TP) genome in clinical samples through simultaneous detection of two genomic targets.

METHODS

We performed qPCR with TaqMan technology using two TP genes, polA and tpp47, as targets, with an internal positive control. The qPCR assay was compared with syphilis diagnosis based on a combination of clinical examination, serological results and inhouse nested PCR (nPCR). Samples were analysed at the National Reference Center for STIs at Cochin Hospital in Paris.

RESULTS

In total, from October 2010 to December 2016, 320 documented clinical samples (mucosal and cutaneous swabs) were collected from patients with or without syphilis attending STI centres in France. The qPCR had an overall sensitivity of 89% (95% CI 85.1% to 92.1%), a specificity of 100%, a positive predictive value of 100% and a negative predictive value of 88% (95% CI 84.3% to 91.5%). The agreement between qPCR and nPCR results was 94% (κ=0.88, 95% CI 0.83 to 0.93). Calibration of the qPCR assay, by cloning both the polA and tpp47 genes, defined the detection threshold as 1 copy/µL of DNA elution.

CONCLUSIONS

We validated a new qPCR for detecting the TP genome in clinical samples with excellent sensitivity and specificity. The cloning of polA and tpp47 genes for calibration would be interesting in the evaluation of bacterial loads in samples.

Secondary Bacterial Infections in Patients with Atopic Dermatitis or Other Common Dermatoses

Secondary bacterial infections of common dermatoses such as atopic dermatitis, ectoparasitosis, and varicella zoster virus infections are frequent, with Staphylococcus aureus and Streptococcus pyogenes being the bacteria most involved. There are also Gram-negative infections secondary to common dermatoses such as foot dyshidrotic eczema and tinea pedis. Factors favoring secondary bacterial infections in atopic dermatitis, ectoparasitosis, and varicella zoster virus infections mainly include an epidermal barrier alteration as well as itch. Mite-bacteria interaction is also involved in scabies and some environmental factors can promote Gram-negative bacterial infections of the feet. Furthermore, the bacterial ecology of these superinfections may depend on the geographical origin of the patients, especially in ectoparasitosis. Bacterial superinfections can also have different clinical aspects depending on the underlying dermatoses. Subsequently, the choice of class, course, and duration of antibiotic treatment depends on the severity of the infection and the suspected bacteria, primarily targeting S. aureus. Prevention of these secondary bacterial infections depends first and foremost on the management of the underlying skin disorder. At the same time, educating the patient on maintaining good skin hygiene and reporting changes in the primary lesions is crucial. In the case of recurrent secondary infections, decolonization of S. aureus is deemed necessary, particularly in atopic dermatitis.