Coralie L’Ollivier

Assessment of various parameters to improve MALDI-TOF MS reference spectra libraries constructed for the routine identification of filamentous fungi

BackgroundThe poor reproducibility of matrix-assisted desorption/ionization time-of-flight (MALDI-TOF) spectra limits the effectiveness of the MALDI-TOF MS-based identification of filamentous fungi with highly heterogeneous phenotypes in routine clinical laboratories. This study aimed to enhance the MALDI-TOF MS-based identification of filamentous fungi by assessing several architectures of reference spectrum libraries.ResultsWe established reference spectrum libraries that included 30 filamentous fungus species with various architectures characterized by distinct combinations of the following: i) technical replicates, i.e., the number of analyzed deposits for each culture used to build a reference meta-spectrum (RMS); ii) biological replicates, i.e., the number of RMS derived from the distinct subculture of each strain; and iii) the number of distinct strains of a given species. We then compared the effectiveness of each library in the identification of 200 prospectively collected clinical isolates, including 38 species in 28 genera.Identification effectiveness was improved by increasing the number of both RMS per strain (p<10-4) and strains for a given species (p<10-4) in a multivariate analysis.ConclusionAddressing the heterogeneity of MALDI-TOF spectra derived from filamentous fungi by increasing the number of RMS obtained from distinct subcultures of strains included in the reference spectra library markedly improved the effectiveness of the MALDI-TOF MS-based identification of clinical filamentous fungi.

Opportunistic fungal pathogen Candida glabrata circulates between humans and yellow-legged gulls.

The opportunistic pathogenic yeast Candida glabrata is a component of the mycobiota of both humans and yellow-legged gulls that is prone to develop fluconazole resistance. Whether gulls are a reservoir of the yeast and facilitate the dissemination of human C. glabrata strains remains an open question. In this study, MLVA genotyping highlighted the lack of genetic structure of 190 C. glabrata strains isolated from either patients in three hospitals or fecal samples collected from gull breeding colonies located in five distinct areas along the French Mediterranean littoral. Fluconazole-resistant isolates were evenly distributed between both gull and human populations. These findings demonstrate that gulls are a reservoir of this species and facilitate the diffusion of C. glabrata and indirect transmission to human or animal hosts via environmental contamination. This eco-epidemiological view, which can be applied to other vertebrate host species, broadens our perspective regarding the reservoirs and dissemination patterns of antifungal-resistant human pathogenic yeast.

Intestinal Cell Tight Junctions Limit Invasion of Candida albicans through Active Penetration and Endocytosis in the Early Stages of the Interaction of the Fungus with the Intestinal Barrier

C. albicans is a commensal yeast of the mucous membranes in healthy humans that can also cause disseminated candidiasis, mainly originating from the digestive tract, in vulnerable patients. It is necessary to understand the cellular and molecular mechanisms of the interaction of C. albicans with enterocytes to better understand the basis of commensalism and pathogenicity of the yeast and to improve the management of disseminated candidiasis. In this study, we investigated the kinetics of tight junction (TJ) formation in parallel with the invasion of C. albicans into the Caco-2 intestinal cell line. Using invasiveness assays on Caco-2 cells displaying pharmacologically altered TJ (i.e. differentiated epithelial cells treated with EGTA or patulin), we were able to demonstrate that TJ protect enterocytes against invasion of C. albicans. Moreover, treatment with a pharmacological inhibitor of endocytosis decreased invasion of the fungus into Caco-2 cells displaying altered TJ, suggesting that facilitating access of the yeast to the basolateral side of intestinal cells promotes endocytosis of C. albicans in its hyphal form. These data were supported by SEM observations of differentiated Caco-2 cells displaying altered TJ, which highlighted membrane protrusions engulfing C. albicans hyphae. We furthermore demonstrated that Als3, a hypha-specific C. albicans invasin, facilitates internalization of the fungus by active penetration and induced endocytosis by differentiated Caco-2 cells displaying altered TJ. However, our observations failed to demonstrate binding of Als3 to E-cadherin as the trigger mechanism of endocytosis of C. albicans into differentiated Caco-2 cells displaying altered TJ.

Diagnosis of human nematode infections

Many hundreds of millions of people throughout the world are infected by nematodes found in the intestine or tissues with a high prevalence in developing countries. Despite their frequency and morbidity, these infections, which may affect migrants and travelers, remain difficult to diagnosis even in developed countries. This is primarily due to the variety of clinical signs often associated with a lack of highly sensitive and specific diagnostic tools. Parasitological diagnosis is often difficult to achieve and can neither be applied during the pre-patent period nor for parasitic impasses. Serological diagnosis is frequently hampered by a lack of specificity due to cross-reaction with others helminthes. Molecular biology methods still require optimization. The diagnostic approach applied by a clinician of a suspected nematode infection is based on a vast set of data including patient history and way of life, clinical examination, non-specific biological tests and, when available, specific diagnostic tests.

Epidemiology of human dermatophytoses in Africa

In this critical literature review, we summarize the epidemiological trends of dermatophytoses reported in Africa. Our findings clearly emphasize the heavy burden of dermatophytosis in Africa. Tinea capitis is the primary clinical presentation of dermatophytosis in African children throughout the entire African continent. The disease affects more than 20% of school-age children in West Africa, while the prevalence ranges from 10% to more than 70% in other regions of Africa. In African adults, the presence of tinea corporis is the most frequent indicator of dermatophytosis. However, epidemiological studies have been primarily conducted on particular patient groups that are not representative of the general population. We examined dermatophyte species distribution patterns. We observed a predominance of anthropophilic dermatophytes, mainly T. violaceum, in the North and East of Africa and both T. soudanense and M. audouinii in the Western and Central regions of the continent. Interestingly, the zoophilic species, M. canis, has recently emerged in North and East Africa. Optimization of both mycology diagnosis capacities and epidemiological methodology would provide insight into the role that climate and other global aspects of the human environment play in dermatophyte epidemiology. We advocate that using a multisectoral and collaborative strategy would strengthen such future studies.

Visceral leishmaniasis in acute myeloid leukemia revealed on peripheral blood smear

Images of parasitic forms of Leishmania infantum are typical in the hands of a skilled expert but should be known by biologists of Hematology Department. In an endemic region, the diagnosis of visceral leishmaniasis (VL) must be considered because of its potential role in accelerating hematological malignancy.

Successful Treatment of Pulmonary and Cerebral Toxoplasmosis Associated with Pneumocystis Pneumonia in an HIV Patient

In both the post and pre combination antiretroviral therapy (cART) era, Pneumocystis jirovecii and Toxoplasma gondii remain common opportunistic infectious agents. The common manifestations are pneumonia for P. jirovecii and brain abscess for T. gondii. Nevertheless, co-infection remains rare, and pulmonary toxoplasmosis is scarce, or may be underestimated because of its similarity with Pneumocystis jirovecii pneumonia. We reported an uncommon case of an AIDS patient (6 CD4 + T cells/mm3) with both pulmonary and cerebral toxoplasmosis associated with pneumocystis pneumonia. The patient presented with general weakness, fever and dyspnea. Pulmonary toxoplasmosis and pneumocystis were confirmed by microscopic examination and DNA detection in the bronchoalveolar lavage. Computed tomography imaging of the brain revealed a single characteristic cerebral toxoplasmosis lesion of the left capsular area. He was successful treated by trimethoprim/sulfamethoxaxole in conjunction with an early reintroduction of cART, and without IRIS development. During a 3-year follow-up, HIV viral load remained undetectable, and the patient did not relapse for toxoplasmosis or Pneumocystis pneumonia.