The opportunistic human fungal pathogen Candida albicans promotes the growth and proliferation of commensal Escherichia coli through an iron-responsive pathway

Potential airborne human pathogens: A relevant inhabitant in built environments but not considered in indoor air quality standards

Potential airborne human pathogens (PAHPs) may be a relevant component of the air microbiome in built environments. Despite that PAHPs can cause infections, particularly in immunosuppressed patients at medical centers, they are scarcely considered in standards of indoor air quality (IAQ) worldwide. Here, we reviewed the current information on microbial aerosols (bacteria, fungal and viruses) and PAHPs in different types of built environments (e.g., medical center, industrial and non-industrial), including the main factors involved in their dispersion, the methodologies used in their study and their associated biological risks. Our analysis identified the human occupancy and ventilation systems as the primary sources of dispersal of microbial aerosols indoors. We also observed temperature and relative humidity as relevant physicochemical factors regulating the dispersion and viability of some PAHPs. Our analysis revealed that some PAHPs can survive and coexist in different environments while other PAHPs are limited or specific for an environment. In relation to the methodologies (conventional or molecular) the nature of PAHPs and sampling type are pivotal. In this context, indoors air-borne viruses are the less studies because their small size, environmental lability, and absence of efficient sampling techniques and universal molecular markers for their study. Finally, it is noteworthy that PAHPs are not commonly considered and included in IAQ standards worldwide, and when they are included, the total abundance is the single parameter considered and biological risks is excluded. Therefore, we propose a revision, design and establishment of public health policies, regulations and IAQ standards, considering the interactions of diverse factors, such as nature of PAHPs, human occupancy and type of built environments where they develop.

Fungal Gut Microbiota Dysbiosis and Its Role in Colorectal, Oral, and Pancreatic Carcinogenesis

The association between bacterial as well as viral gut microbiota imbalance and carcinogenesis has been intensively analysed in many studies; nevertheless, the role of fungal gut microbiota (mycobiota) in colorectal, oral, and pancreatic cancer development is relatively new and undiscovered field due to low abundance of intestinal fungi as well as lack of well-characterized reference genomes. Several specific fungi amounts are increased in colorectal cancer patients; moreover, it was observed that the disease stage is strongly related to the fungal microbiota profile; thus, it may be used as a potential diagnostic biomarker for adenomas. Candida albicans, which is the major microbe contributing to oral cancer development, may promote carcinogenesis via several mechanisms, mainly triggering inflammation. Early detection of pancreatic cancer provides the opportunity to improve survival rate, therefore, there is a need to conduct further studies regarding the role of fungal microbiota as a potential prognostic tool to diagnose this cancer at early stage. Additionally, growing attention towards the characterization of mycobiota may contribute to improve the efficiency of therapeutic methods used to alter the composition and activity of gut microbiota. The administration of Saccharomyces boulardii in oncology, mainly in immunocompromised and/or critically ill patients, is still controversial.

Pathways of healthcare and antibiotics use following reported gastrointestinal illness: a cross-sectional study in rural Anhui, China

OBJECTIVE

To document the factors, and their pathways, that influence healthcare and antibiotics use following reported gastrointestinal illnesses in Anhui province, China.

STUDY DESIGN

This study uses cross-sectional design, descriptive statistical analysis, pathway mapping and multivariate logistic regression modelling.

SETTING

Households in 12 villages in Anhui province, China.

PARTICIPANTS

A total of 3659 residents who: (1) held a registered rural residence and were actually living in the sampled villages when this study was conducted; (2) were aged 18 years and older and (3) were willing to participate and able to answer the survey questions.

OUTCOME MEASURES

Planned and measured variables included the occurrence of gastrointestinal illness, professional care seeking and antibiotic use due to the illness and factors influencing these measures.

RESULTS

Of the 3659 informants, 29.0% reported gastrointestinal illness episodes in the past year. Of these episodes, 50.2% led to professional care seeking and 65.4% of antibiotic use. Multivariate logistic modelling identifies that: (1) reported gastrointestinal illnesses were more frequent in north compared with middle (OR 0.569, 95% CI 0.472 to 0.686) and south (OR 0.588, 95% CI 0.492 to 0.702) Anhui, and were positively associated with age (B=0.123, p<0.05), knowledge concerning (B=0.248, p<0.05) and practice of (B=0.184, p<0.05) prevention; (2) seeking professional care and antibiotic use following the illness was linked to the severity of symptoms and geographical locations, rather than to specific pathogenic features.

CONCLUSIONS

Reported gastrointestinal illnesses are quite prevalent in the sample population and a large proportion of these have resulted in professional care and antibiotics use. The factors associated with the reported illnesses and pathways of healthcare and antibiotic use, as identified in this study, should inform future research and intervention efforts.

Binary interactions between the yeast Candida albicans and two gut-associated Bacteroides species

The yeast Candida albicans forms part of the natural gut microbiota of healthy human individuals and its interactions with other microbial symbionts can impact host well-being. We therefore studied binary interactions between potentially pathogenic representatives of the gut-associated bacterial genus Bacteroides and C. albicans using anaerobic bacteria/yeast co-cultures prepared with a quarter-strength brain heart infusion (¼ BHI; 9.25 g/l) broth. We found that, except for minor changes observed in the cell numbers of one out of four C. albicans strains tested, yeast growth was largely unaffected by the presence of the bacteria. In contrast, growth of Bacteroides fragilis NCTC 9343 and Bacteroides vulgatus ATCC 8482 was significantly enhanced in the presence of C. albicans. Supplementation of Bacteroides monocultures with dead Candida albicans CAB 392 cells, containing intact outer cell wall mannan layers, resulted in increased bacterial concentrations. Subsequent culturing of the Bacteroides strains in a liquid minimal medium supplemented with candidal mannan demonstrated that B. vulgatus ATCC 8482, unlike B. fragilis NCTC 9343, utilized the mannan. Furthermore, by reducing the initial oxygen levels in monocultures prepared with ¼ BHI broth, bacterial numbers were significantly enhanced compared to in monocultures prepared with ¼ BHI broth not supplemented with the reducing agent l-cysteine hydrochloride. This suggests that C. albicans can stimulate Bacteroides growth via aerobic respiration and/or antioxidant production. The cell-free supernatant of 24-h-old C. albicans CAB 392 monocultures was also found to increase Bacteroides growth and chloramphenicol sensitivity.

The gut mycobiota: insights into analysis, environmental interactions and role in gastrointestinal diseases

The gut microbiota is a dense and diverse ecosystem that is involved in many physiological functions as well as in disease pathogenesis. It is dominated by bacteria, which have been extensively studied in the past 15 years; however, other microorganisms, such as fungi, phages, archaea and protists, are also present in the gut microbiota. Exploration of the fungal component, namely, the mycobiota, is at an early stage, and several specific technical challenges are associated with mycobiota analysis. The number of fungi in the lower gastrointestinal tract is far lower than that of bacteria, but fungal cells are much larger and much more complex than bacterial cells. In addition, a role of the mycobiota in disease, notably in IBD, is indicated by both descriptive data in humans and mechanistic data in mice. Interactions between bacteria and fungi within the gut, their functional roles and their interplay with the host and its immune system are fascinating areas that researchers are just beginning to investigate. In this Review, we discuss the newest data on the gut mycobiota and explore both the technical aspects of its study and its role in health and gastrointestinal diseases.

Cross-Domain and Viral Interactions in the Microbiome

The importance of the microbiome to human health is increasingly recognized and has become a major focus of recent research. However, much of the work has focused on a few aspects, particularly the bacterial component of the microbiome, most frequently in the gastrointestinal tract. Yet humans and other animals can be colonized by a wide array of organisms spanning all domains of life, including bacteria and archaea, unicellular eukaryotes such as fungi, multicellular eukaryotes such as helminths, and viruses. As they share the same host niches, they can compete with, synergize with, and antagonize each other, with potential impacts on their host. Here, we discuss these major groups making up the human microbiome, with a focus on how they interact with each other and their multicellular host.

The X chromosome and sex-specific effects in infectious disease susceptibility

The X chromosome and X-linked variants have largely been ignored in genome-wide and candidate association studies of infectious diseases due to the complexity of statistical analysis of the X chromosome. This exclusion is significant, since the X chromosome contains a high density of immune-related genes and regulatory elements that are extensively involved in both the innate and adaptive immune responses. Many diseases present with a clear sex bias, and apart from the influence of sex hormones and socioeconomic and behavioural factors, the X chromosome, X-linked genes and X chromosome inactivation mechanisms contribute to this difference. Females are functional mosaics for X-linked genes due to X chromosome inactivation and this, combined with other X chromosome inactivation mechanisms such as genes that escape silencing and skewed inactivation, could contribute to an immunological advantage for females in many infections. In this review, we discuss the involvement of the X chromosome and X inactivation in immunity and address its role in sexual dimorphism of infectious diseases using tuberculosis susceptibility as an example, in which male sex bias is clear, yet not fully explored.