Rate of transmission and endogenous origin of Candida albicans and Candida glabrata on adult intensive care units studied by pulsed field gel electrophoresis

From environmental adaptation to host survival: Attributes that mediate pathogenicity of Candida auris

Candida species are a major cause of invasive fungal infections. While Candida albicans, C. glabrata, C. parapsilosis, and C. tropicalis are the most dominant species causing life-threatening candidiasis, C. auris recently emerged as a new species causing invasive infections with high rates of clinical treatment failures. To mimic initial phases of systemic Candida infections with dissemination via the bloodstream and to elucidate the pathogenic potential of C. auris, we used an ex vivo whole blood infection model. Similar to other clinically relevant Candida spp., C. auris is efficiently killed in human blood, but showed characteristic patterns of immune cell association, survival rates, and cytokine induction. Dual-species transcriptional profiling of C. auris-infected blood revealed a unique C. auris gene expression program during infection, while the host response proofed similar and conserved compared to other Candida species. C. auris-specific responses included adaptation and survival strategies, such as counteracting oxidative burst of immune cells, but also expression of potential virulence factors, (drug) transporters, and cell surface-associated genes. Despite comparable pathogenicity to other Candida species in our model, C. auris-specific transcriptional adaptations as well as its increased stress resistance and long-term environmental survival, likely contribute to the high risk of contamination and distribution in a nosocomial setting. Moreover, infections of neutrophils with pre-starved C. auris cells suggest that environmental preconditioning can have modulatory effects on the early host interaction. In summary, we present novel insights into C. auris pathogenicity, revealing adaptations to human blood and environmental niches distinctive from other Candida species.

ICU-acquired candidemia within selective digestive decontamination studies: a meta-analysis

PURPOSE

To estimate the direct and indirect (contextual) effects of the factorized constituents of selective digestive decontamination and selective oropharyngeal decontamination (SDD/SOD), being topical antibiotic (TA) and protocolized antifungal prophylaxis (PAFP), on ICU-acquired candidemia.

METHODS

A broad range of ICU candidemia incidence studies were sourced to serve as points of reference. The candidemia incidence was extracted from component (control and intervention) groups decanted from studies of various designs (concurrent or non-concurrent) and whether investigating SDD/SOD versus non-TA methods of ICU infection prevention. The candidemia incidences were summarized in regression models using generalized estimating equation (GEE) methods. Groups derived from observational studies (no prevention method under study) provided an overarching external benchmark candidemia incidence for calibration.

RESULTS

Within studies investigating SDD/SOD, the mean (and 95% confidence interval) candidemia incidence among concurrent component groups (40 control; 2.4%; 1.7-3.2% and 43 intervention groups; 2.4%; 1.6-3.1%), but not non-concurrent control groups (11 groups; 1.6%; 0.1-2.7%), is higher than that of the benchmark candidemia incidence derived from 54 observational groups (1.5%; 1.2-1.9%). The TA constituent within SDD/SOD has significant direct and indirect (contextual) effects in GEE models even after adjusting for the publication year and the group-wide presence of either candidemia risk factors or PAFP use.

CONCLUSION

The TA constituent of SDD/SOD is associated with a contextual effect on candidemia incidence which is similar in magnitude to that of the conventional candidemia risk factors and against which PAFP partially attenuates. This increase is inapparent within individual SDD/SOD studies examined in isolation.

A review of molecular techniques to type Candida glabrata isolates

Candida glabrata has emerged as a common cause of fungal infection causing mucosal and systemic infections. This yeast is of concern because of its reduced antifungal susceptibility to azole antifungals such as fluconazole. A clear understanding of the epidemiology of Candida infection and colonisation required a reliable typing system for the evaluation of strain relatedness. In this study, we discuss the different molecular approaches for typing C. glabrata isolates. Recent advances in the use of molecular biology-based techniques have enabled investigators to develop typing systems with greater sensitivities. Several molecular genotypic approaches have been developed for fast and accurate identification of C. glabrata in vitro. These techniques have been widely used to study diverse aspects such as nosocomial transmission. Molecular typing of C. glabrata could also provide information on strain variation, such as microvariation and microevolution.

Multiple-locus variable-number tandem-repeat analysis for rapid typing of Candida glabrata

A multiple-locus variable-number tandem-repeat analysis (MLVA) using six microsatellite markers was assessed in 127 Candida glabrata isolates. Thirty-seven different genotypes, stable both in vitro and in vivo, were observed. The highest discriminatory power (D = 0.902) was reached by using only four markers. MLVA seems to be relevant for C. glabrata typing.

Genotyping of clinical Rhodotorula mucilaginosa isolates by pulsed field gel electrophoresis

Identification and typing of fungal isolates is a prerequisite for control and prevention of nosocomial infections. As the discriminatory power of phenotypic methods is not sufficient for epidemiological purposes, genotyping methods such as DNA fingerprinting, random amplification of polymorphic DNA (RAPD) analysis, or pulsed field gel electrophoresis (PFGE) are preferred. To our knowledge, this study is the first application of PFGE for typing Rhodotorula mucilaginosa strains. The PFGE patterns of six clinical isolates produced two different karyotypes, which were confirmed by RAPD analysis. Five strains isolated from bloodstream infections from three different institutions showed the same karyotype and RAPD patterns, while the urological specimen differed slightly.

Diagnosis of fungal diseases

In this chapter, we focus on diagnostic laboratory methods that are necessary and suitable for providing physicians with a timely and accurate diagnosis of fungal diseases. After discussing some pre-analytical aspects, the complete set of methods, i.e., microscopy, histopathology, culture, antigen detection, DNA detection, and antibody detection, is concisely described. Identification techniques depend on the fungal group involved. Therefore, separate paragraphs are dedicated to the identification of yeasts and filamentous fungi, which include moulds, dermatophytes, and dimorphic fungi.

Use of Fourier-transform infrared spectroscopy for typing of Candida albicans strains isolated in intensive care units

Comparative studies of Candida albicans strains are essential for proving cross-infections in epidemiological investigations. Typing of C. albicans strains is mainly based on genotypic methods. Fourier-transform infrared (FTIR) spectroscopy is described in this study as a novel phenotypic approach to the typing of C. albicans. The first step in the approach was the standardization of sample preparation (culture conditions and sampling parameters) and acquisition and classification parameters (spectral acquisition, spectral window selection, classification algorithm, and heterogeneity threshold). The second step consisted of validating the established parameters with a set of 79 strains of C. albicans isolated over 4 months from nine patients hospitalized in two intensive care units. Strains were isolated from multiple anatomical sites with repeated sampling. FTIR spectroscopy results were compared to randomly amplified polymorphic DNA (RAPD) results; this analysis showed that the amplification patterns of strains isolated from a given patient were identical and that different patients had different profiles. FTIR spectroscopy data were analyzed by hierarchical clustering performed with the second-derivative spectra. This classification revealed nine groups, one per patient. Only one spectrum out of 79 was misclassified by the FTIR spectroscopy method. RAPD and FTIR spectroscopy results were in good agreement, showing that, when nosocomial candidiasis transmission is suspected and urgent information is needed, this technique may be useful as a quick identification tool to give solid clues before confirmation by a genotypic method.