Nutritional immunity is a process whereby an infected host manipulates essential micronutrients to defend against an invading pathogen. We reveal a dynamic aspect of nutritional immunity during infection that involves copper assimilation. Using a combination of laser ablation inductively coupled mass spectrometry (LA-ICP MS) and metal mapping, immunohistochemistry, and gene expression profiling from infected tissues, we show that readjustments in hepatic, splenic and renal copper homeostasis accompany disseminated Candida albicans infections in the mouse model. Localized host-imposed copper poisoning manifests itself as a transient increase in copper early in the kidney infection. Changes in renal copper are detected by the fungus, as revealed by gene expression profiling and fungal virulence studies. The fungus responds by differentially regulating the Crp1 copper efflux pump (higher expression during early infection and down-regulation late in infection) and the Ctr1 copper importer (lower expression during early infection, and subsequent up-regulation late in infection) to maintain copper homeostasis during disease progression. Both Crp1 and Ctr1 are required for full fungal virulence. Importantly, copper homeostasis influences other virulence traits—metabolic flexibility and oxidative stress resistance. Our study highlights the importance of copper homeostasis for host defence and fungal virulence during systemic disease.

Some Candida species are common commensals, which can become opportunistic pathogens in susceptible hosts. In severely ill patients, Candida species, particularly Candida albicans, can cause life-threatening systemic infections. These infections are difficult to diagnose, as symptoms are similar to those of systemic bacterial infections. These difficulties can lead to delays in initiation in antifungal therapy, which contributes to the high mortality rates (> 40%) associated with these infections. In order to investigate systemic Candida infection, mouse models have been developed that mimic human disease, the most common being the intravenous infection model and the gastrointestinal colonization and dissemination model. This review discusses the two models and the contributions that they have made to our understanding of fungal virulence, host response to infection and the development of novel antifungal therapies and diagnostics.

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Introduction : Data suggests that invasive fungal infections (IFI) might complicate COVID-19. Our goal was to describe characteristics of IFI among critically ill COVID-19 adults. Methods : A retrospective observational case-series analysis was done between March–July 2020. Consecutive patients with critical COVID-19 were eligible, and have been included when proven or putative/probable IFI could be confirmed during their course. For COVID-19 diagnosis, ECDC definitions and WHO severity criteria were followed. Candidaemia was diagnosed according to the ESCMID 2012 guideline. Invasive pulmonary aspergillosis (IPA) was defined following EORTC/MSG, ECMM/ISHAM and modified AspICU criteria. Outcome variables were rates of IFIs, in-hospital all-cause mortality, rate and time to negative respiratory SARS-CoV-2 PCR. Results : From 90 eligible patients, 20 (22.2%) fulfilled criteria for IFI. Incidence rate for IFI was 2.02 per 100 patient-days at ICU. Patients were mostly elderly males with significant comorbidities, requiring mechanical ventilation because of ARDS. IFI could be classified as candidaemia in 7/20 (40%), putative/probable IPA in 16/20 (80.0%). Isolated species of candidaemia episodes were Candida albicans (4/9, 44.4%), Candida glabrata (3/9, 33.3%), Candida parapsilosis (1/9, 11.1%), Candida metapsilosis (1/9, 11.1%). Mold isolates from lower respiratory tract were Aspergillus fumigatus , BAL galactomannan positivity was prevalent (16/20, 80.0%). Mortality was 12/20 (60.0%) with a median time to death of 31.0±37.0 (5–89) days. Only 9/20 (45.0%) patients reached SARS-CoV-2 PCR negativity after a median time of 20.0±12.0 (3–38) days. Conclusion : In this small cohort of critically ill COVID-19 adults, morbidity and mortality related to invasive fungal infections proved to be significant.

One hundred and four enterotoxin producing Escherichia coli strains of wide geographical origin were tested for the expression of curli fimbriae by transmission electronmicroscopy and by ELISA using curli-specific antibodies, as well as for the presence of curli-specific gene sequences by PCR. All isolates, irrespective of the production of the fimbriae, carried sequences specific for the structure (csgA) and for one of the regulator genes (crl) of curli expression, respectively. Curli fimbriae were detected in 56 strains (53.8 %). Thirty-six strains expressed curli only when growing at 30 degrees C, 4 isolates were weakly curliated at 37 degrees C only, while on 16 strains curli was observed at both temperatures. On isolates carrying curli at both temperatures the expression of the fimbria was significantly stronger at 30 degrees C than at 37 degrees C. Curli proficiency significantly, but not completely, correlated with the binding of the Congo Red dye. The expression of curli did not confer epithelial cell invasiveness to ETEC strains but, once expressed at 30 degrees C, it facilitated the adherence of the bacteria to plastic surfaces. Curli present in more than half of the ETEC strains and expressed preferentially at low temperatures could be a factor facilitating the environmental survival of this food- and water-borne pathogen.