Invasive candidiasis: from mycobiome to infection, therapy, and prevention.

Candida spp. are commonly found in humans, colonizing most healthy individuals. A high prevalence of invasive candidiasis has been reported in recent years. Here, we assess the relation between Candida spp. as part of the human mycobiome, the host defense mechanisms, and the pathophysiology of invasive disease in critically ill patients. Many hypotheses have been proposed to explain the different immune responses to the process where Candida goes through healthy mycobiome to colonization to invasion; the involvement of other microbiota inhabitants, changes in temperature, low nitrogen levels, and the caspase system activation have been described. Patients admitted to an intensive care unit (ICU) are at the highest risk for invasive candidiasis, mostly due to the severity of their disease, immune-suppressive states, prolonged length of stay, broad-spectrum antibiotics, septic shock, and Candida colonization. The first approach should be using predictive scores as screening, followed by the determination of biomarkers (when available), and, in the near future, probably immune-genomics and analysis of the clinical background in order to initiate prompt and correct treatment. Regarding treatment, the initiation with an echinocandin is strongly recommended in critically ill patients. In conclusion, prompt treatment and adequate source control in the more severe patients remains the ultimate goal, as well as restoration of a healthy microbiota.