Environmental amoebae do not support the long‐term survival of virulent mycobacteria

Aims

To test the hypothesis that Mycobacterium bovis can persist in the environment within protozoa.

Methods and Results

In this study, we used a novel approach to detect internalized mycobacteria in environmental protozoa from badger latrines. Acid‐fast micro‐organisms were visualized in isolated amoebae, although we were unable to identify them to species level as no mycobacteria were grown from these samples nor was M. bovis detected by IS6110 PCR. Co‐incubation of Acanthamoeba castellanii with virulent M. bovis substantially reduced levels of bacilli, indicating that the amoebae have a negative effect on the persistence of M. bovis.

Conclusions

The internalization of mycobacteria in protozoa might be a rare event under environmental conditions. The results suggest that amoebae might contribute to the inactivation of M. bovis rather than representing a potential environmental reservoir.

Significance and Impact of the Study

Protozoa have been suggested to act as an environmental reservoir for M. bovis. The current study suggests that environmental amoebae play at most a minor role as potential reservoirs of M. bovis and that protozoa might inhibit persistence of M. bovis in the environment.     

Action mechanisms of probiotics on Candida spp. and candidiasis prevention: an update

Due to the high incidence of fungal infections caused by Candida species and their increasing resistance to antimicrobial treatments, alternative therapies such as probiotics have been studied. It has been show that several species of the genus Lactobacillus have anti-Candida activity, probably by direct inhibition, through competition for adhesion sites or production of secondary metabolites, and by indirect inhibition, through stimulation of the immune system of their host. However, the mechanisms of inhibition of these probiotics on Candida species have not yet been fully elucidated since this effect is related to more than one inhibition pathway. In the literature, several in vitro and in vivo studies have been developed seeking to elucidate the probiotics mechanisms of action. These studies have been focused on C. albicans inhibition assays, including analysis of antimicrobial activity, adherence capacity, biofilms formation, filamentation and interference on virulence genes, as well as assays of experimental candidiasis in invertebrate and vertebrate models. In this context, the purpose of this review was to gather different studies focused on the action mechanism of probiotic strains on Candida sp. and to discuss their impact on the candidiasis prevention.     

Saliva promotes survival and even proliferation of Candida species in tap water

Candida yeasts colonize the human oral cavity as commensals or opportunistic pathogens. They may be isolated from water circulating in dental unit waterlines mixed with traces of saliva mainly because of the dysfunction of antiretraction valves. This study deals with the growth ability of Candida albicans, Candida glabrata and Candida parapsilosis in tap water with saliva (0-20% v/v). Results show that C. glabrata is the most susceptible species in tap water. Furthermore, saliva promotes both survival and proliferation of the three studied Candida species in tap water.     

Biofilm of Candida albicans: formation,regulation and resistance

Candida albicans is the most common human fungal pathogen, causing infections that range from mucous membranes to systemic infections. The present article provides an overview of C. albicans, with the production of biofilms produced by this fungus, as well as reporting the classes of antifungals used to fight such infections, together with the resistance mechanisms to these drugs. Candida albicans is highly adaptable, enabling the transition from commensal to pathogen due to a repertoire of virulence factors. Specifically, the ability to change morphology and form biofilms is central to the pathogenesis of C. albicans. Indeed, most infections by this pathogen are associated with the formation of biofilms on surfaces of hosts or medical devices, causing high morbidity and mortality. Significantly, biofilms formed by C. albicans are inherently tolerant to antimicrobial therapy, so the susceptibility of C. albicans biofilms to current therapeutic agents remains low. Therefore, it is difficult to predict which molecules will emerge as new clinical antifungals. The biofilm formation of C. albicans has been causing impacts on susceptibility to antifungals, leading to resistance, which demonstrates the importance of research aimed at the prevention and control of these clinical microbial communities.     

耳念珠菌的流行病学和生物学研究进展

耳念珠菌Candida auris已成为引起严重院里感染的新兴病原真菌。自2009年第一次报道以来,耳念珠菌在全球迅速传播并导致几次院内感染的暴发。与念珠菌属其他成员相比,耳念珠菌具有诸多特点,比如多重耐药、鉴别困难、死亡率高、易在医院内传播等。关于耳念珠菌的生物学和致病性研究越来越多,我们对耳念珠菌的认识也逐渐增强,本综述详细地介绍了耳念珠菌全球感染的流行病学以及该病原真菌的基本生物学特征,并对其毒力和耐药机制研究进展进行汇总,对未来关于耳念珠菌研究的前景进行了展望。     

Toxoplasma gondii: uptake and survival of oocysts in free-living amoebae

Waterborne transmission of the oocyst stage of Toxoplasma gondii can cause outbreaks of clinical toxoplasmosis in humans and infection of marine mammals. In water-related environments and soil, free-living amoebae are considered potential carriers of various pathogens, but knowledge on interactions with parasitic protozoa remains elusive. In the present study, we assessed whether the free-living Acanthamoebacastellanii, due to its phagocytic activity, can interact with T. gondii oocysts. We report that amoebae can internalize T. gondii oocysts by active uptake. Intracellular oocysts in amoebae rarely underwent phagocytic lysis, retained viability and established infection in mice. Interaction of T. gondii with amoebae did not reduce the infectivity and pathogenicity of oocysts even after prolonged co-cultivation. Our results show that uptake of oocysts by A. castellanii does not restrain the transmission of T. gondii in a murine infection model.     

Clade-specific chromosomal rearrangements and loss of subtelomeric adhesins in Candida auris

Candida auris is an emerging fungal pathogen of rising concern due to global spread, the ability to cause healthcare-associated outbreaks, and antifungal resistance. Genomic analyses revealed that early contemporaneously detected cases of C. auris were geographically stratified into four major clades. While Clades I, III, and IV are responsible for ongoing outbreaks of invasive and multidrug-resistant infections, Clade II, also termed the East Asian clade, consists primarily of cases of ear infection, is often susceptible to all antifungal drugs, and has not been associated with outbreaks. Here, we generate chromosome-level assemblies of twelve isolates representing the phylogenetic breadth of these four clades and the only isolate described to date from Clade V. This Clade V genome is highly syntenic with those of Clades I, III, and IV, although the sequence is highly divergent from the other clades. Clade II genomes appear highly rearranged, with translocations occurring near GC-poor regions, and large subtelomeric deletions in most chromosomes, resulting in a substantially different karyotype. Rearrangements and deletion lengths vary across Clade II isolates, including two from a single patient, supporting ongoing genome instability. Deleted subtelomeric regions are enriched in Hyr/Iff-like cell-surface proteins, novel candidate cell wall proteins, and an ALS-like adhesin. Cell wall proteins from these families and other drug-related genes show clade-specific signatures of selection in Clades I, III, and IV. Subtelomeric dynamics and the conservation of cell surface proteins in the clades responsible for global outbreaks causing invasive infections suggest an explanation for the different phenotypes observed between clades.     

Chlamydia trachomatis targets mitochondrial dynamics to promote intracellular survival and proliferation

Chlamydia trachomatis is an obligate intracellular bacterium that scavenges host metabolic products for its replication. Mitochondria are the power plants of eukaryotic cells and provide most of the cellular ATP via oxidative phosphorylation. Several intracellular pathogens target mitochondria as part of their obligatory cellular reprogramming. This study was designed to analyse the mitochondrial morphological changes in response to C. trachomatis infection in HeLa cells. Mitochondrial elongation and fragmentation were found at the early stages and late stages of C. trachomatis infection, respectively. C. trachomatis infection‐induced mitochondrial elongation was associated with the increase of mitochondrial respiratory activity, ATP production, and intracellular growth of C. trachomatis. Silencing mitochondrial fusion mediator proteins abrogated the C. trachomatis infection‐induced elevation in the oxygen consumption rate and attenuated chlamydial proliferation. Mechanistically, C. trachomatis induced the elevation of intracellular cAMP at the early phase of infection, followed by the phosphorylation of fission‐inactive serine residue 637 (S637) of Drp1, resulting in mitochondrial elongation. Accordingly, treatment with adenylate cyclase inhibitor diminished mitochondrial elongation and bacterial growth in infected cells. Collectively, these results strongly indicate that C. trachomatis promotes its intracellular growth by targeting mitochondrial dynamics to regulate ATP synthesis via inhibition of the fission mediator Drp1.     

Combination of ARAD microfibre filtration and LAMP methodology for simple, rapid and cost-effective detection of human pathogenic Giardia duodenalis and Cryptosporidium spp. in drinking water

Aims:  In this study, we report a new, simple methodology for the monitoring of Cryptosporidium oocysts and Giardia cysts in drinking water samples, ranging from 10- to 1000-l, which combines a new ARAD microfibre filtration of the (oo)cysts from drinking water and loop-mediated isothermal amplification (LAMP) of a human pathogenic Cryptosporidium parvum , Cryptosporidium hominis , Cryptosporidium meleagridis and Giardia duodenalis Assemblage A and B specific DNA sequence.
Methods and Results:  During the evaluation of the new concentration and detection technique, spiked reagent and matrix water samples plus blank samples were filtered and tested. In total, 27 samples have been investigated. The results clearly demonstrate that the methodology of using a new ARAD filter, which passed through 1000 l of drinking water with high turbidity (2 NTU), and followed by the LAMP assay was able to detect at least one (oo)cyst in 10 l of drinking water based on a 1000-l sample, taken over a 24-h period.
Conclusions:  The described protozoa detection methodology is sensitive, rapid and cost-effective.
Significance and Impact of the Study:  This effective procedure will be useful for small waterworks to achieve continuous monitoring and is also of value for screening catchments to identify those that require further treatment and more detailed microscopic counts.     

Prevalence of dermatophytes and yeasts (Candida spp., Malassezia furfur) in HIV patients

The prevalence of dermatophytes and yeasts (Candida spp. and Pityrosporum spp.) was studied in 40 former drug-addicts, all of whom were HIV seropositive but otherwise had no other symptoms (2nd Stage CDC Atlanta, 1987). We considered 7 skin areas for dermatophytes and Pityrosporum spp. (scalp, forehead, nose, back, chest, groin, toe webs) and the mouth for yeasts. Dermatophytes were found in 8 (20%) and tinea pedis was the most common dermatophytosis: Tricophyton rubrum was the fungus most frequently isolated (6 cases or 15%). The HIV + group showed almost the same rate of dermatophytes colonisation compared to a group of 121 athletes and to the control group. Candida spp. was present in 27 cases (67.5%) but clinical oral lesions were evident only in 5 patients (12.5%). Statistically significant differences were found in the presence of Candida spp. in HIV patients and controls (p<0.05). The lipophilic yeast Pityrosporum ovale was evaluated with quantitative and qualitative methods. Quantitative variations were evident between HIV patients and controls. P. ovale was present in 10 cases: 3 (7.5%) of them showed dischromic lesions while in 7 cases (17.5%) no clinical symptoms were evident.     

Candida ratchasimensis sp. nov. and Candida khaoyaiensis sp. nov., two anamorphic yeast species isolated from flowers in Thailand

Two yeast strains of the genus Candida were isolated from wild flowers collected in Khao Yai National Park, Nakhonratchasima Province, Thailand. Based on morphological, physiological and chemotaxonomic characteristics and sequence analysis of the D1/D2 domain of the 26S rRNA gene, strains BCC 7722^T (=NBRC 102563^T=CBS 10611^T) and BCC 7729^T (=NBRC 102565^T=CBS 10839^T) were found to represent two distinct novel Candida species, for which the names Candida ratchasimensis sp. nov. and Candida khaoyaiensis sp. nov. are proposed, respectively. In the phylogenetic tree constructed according to the neighbour-joining method based on sequences of the D1/D2 domain of the 26S rRNA gene, strains BCC 7722^T (GenBank accession no. AY228492 ) and BCC 7729^T (accession no. DQ400367 ) constituted a cluster with Candida cellae that was connected with a clade with Starmerella meliponinorum and Candida etschellsii . Within the D1/D2 domain, C. ratchasimensis and C. khaoyaiensis differ from C. cellae in 25 nucleotide substitutions with five gaps and 29 nucleotide substitutions with one gap, respectively.     

Vertical micro-distribution and response to nitrogen deposition of testate amoebae in Sphagnum

Previous studies have shown the existence of a vertical micro-distribution of testate amoebae in the first centimeters of Sphagnum and their response to nutrient enrichment. In order to test the response of testate amoebae to depth and N addition in dry moss carpets recolonizing cutover peatlands, we sampled Sphagnum that had received 0, 1, 3, or 10g N m(-2) yr(-1) for three years. The mosses were cut into three segments: 0-1cm, 1-3cm and 3-5cm and analyzed for testate amoebae. The overall diversity (22 taxa) was high considering the dryness of the site, but the species richness of individual samples was low (mean 6.6). The presence of several species characteristic of wetter conditions suggests that they have a broader tolerance than usually believed and/or have a high colonization potential. Species richness increased with depth. Assulina muscorum was most abundant in the top segment, while Phryganella acropodia, Heleopera rosea and Nebela militaris were most abundant in the deepest segment. Neither the metabolism type nor the shell characteristics significantly explained the vertical distribution of species. There was no overall response of testate amoebae to N, although one species, Bullinularia indica, was significantly more abundant in the fertilized than in the control plots.