The significance of Candida in the human respiratory tract: our evolving understanding

The impact of Candida spp airway colonization on clinical outcomes in patients with ventilator-associated pneumonia: A systematic review and meta-analysis

BACKGROUND

Previous studies have drawn different conclusions about the impact of Candida airway colonization on clinical outcomes in patients with ventilator-associated pneumonia (VAP).

METHODS

We searched PubMed, the Cochrane Library, Embase (via OVID), and Web of Science database. We included both retrospective and prospective observational studies. The mean difference (MD) or risk ratio (RR) with 95% confidence intervals (CI) were applied to assess the association between Candida colonization and clinical outcomes.

RESULTS

A total of 8 studies with 1,661 patients were pooled in our final studies. Compared with patients with VAP without Candida colonization, patients with Candida colonization had significantly longer durations of mechanical ventilation (MD, 1.93; 95% CI, 0.53-3.33). The intensive care unit (ICU) length of stay seems to be longer among Candida colonized patients than noncolonized patients, although the results were not so significant (MD, 1.15; 95% CI, -1.04 to 3.34). Patients with colonization had higher 28-day mortality and ICU mortality than those without colonization (28-day mortality: RR, 1.64; 95% CI, 1.27-2.12; ICU mortality: RR, 1.57; 95% CI, 1.26-1.94).

CONCLUSIONS

The presence of Candida spp airway colonization is associated with longer durations of mechanical ventilation, higher 28-day mortality, higher ICU mortality, and probably longer ICU length of stay compared with the absence of colonization in patients with VAP.

Opportunistic invasive fungal disease in patients with type 2 diabetes mellitus from Southern China: Clinical features and associated factors

AIMS/INTRODUCTION

A retrospective study was carried out to investigate the clinical characteristics and associated factors for invasive fungal disease in patients with type 2 diabetes mellitus.

MATERIALS AND METHODS

Demographic and clinical data were recorded. Associated factors were analyzed by logistic regression analysis.

RESULTS

Invasive fungal disease was diagnosed in 120 patients with type 2 diabetes mellitus (prevalence, 0.4%). Yeast infection (56/120, 46.7%), including candidiasis (31/56, 55.4%) and cryptococcosis (25/56, 44.6%), was the most common. The urinary tract was mainly involved in candidiasis (12/31, 38.7%). More than half of the cryptococcosis (16/25, 64.0%) presented as pneumonia. Mold infection accounted for 40.8% of the cases, and predominantly involved the lung (34/49, 69.4%). A total of 15 (12.5%) patients had mixed fungal infection. Candida albicans (24/111, 21.6%), Cryptococcus neoformans (19/111, 17.1%) and Aspergillus fumigatus (14/111, 12.6%) were the leading agents. Co-infection occurred in 58 (48.3%) patients, mainly presenting as pneumonia caused by Gram-negative bacteria. The inpatient mortality rate of invasive fungal disease was 23.3% (28/120). Glycated hemoglobin levels were higher in non-survivors than survivors (8.8 ± 2.5 vs 7.7 ± 2.1%, P = 0.02). Anemia (adjusted odds ratio, 3.50, 95% confidence interval 1.95-6.27, P < 0.001), hypoalbuminemia (adjusted odds ratio, 5.42, 95% confidence interval 3.14-9.36, P < 0.001) and elevated serum creatinine (adjusted odds ratio, 2.08, 95% confidence interval 1.07-4.04, P = 0.03) were associated with invasive fungal disease in type 2 diabetes mellitus patients.

CONCLUSIONS

Invasive fungal disease is a life-threatening complication in type 2 diabetes mellitus patients. C. a albicans, C. neoformans, and A. fumigatus are the leading agents. Prolonged hyperglycemia results in unfavorable outcomes. Correction of anemia and hypoalbuminemia might improve prognosis.

Implications of the presence of yeasts in tracheobronchial secretions of critically ill intubated patients

The presence of some microorganisms in the respiratory tract is a known risk factor for the infection of air passages; however, it is not clear whether this holds true for Candida spp. Thus, our objective was to determine the frequency of yeast colonization in the tracheobronchial secretions of critically ill intubated patients and to assess the presence of these yeasts in the infra-cuff region of the endotracheal tube (ET). Patients aged 18 years or older who had been using an endotracheal tube for 48 hours were recruited. Tracheal secretions were collected; after extubation, the ETs were cut into two fragments in the infra-cuff region. One of these fragments was placed in a solution containing antibiotics and sent to the lab for culture and identification of yeasts. The remaining fragment was fixed and subjected to scanning electron microscopy (SEM). In total, 20 patients with an average age of 73.3 years (± 13.1) participated in this study. These patients remained under endotracheal intubation and invasive mechanical ventilation for an average of 6.4 (± 1.8) and 13.5 days (± 15), respectively. Of these patients, 45 % showed respiratory tract colonization by yeasts of the Candida genus, with C. albicans being the most frequently isolated species (66.7 %). Moreover, in almost 90 % of these patients, blastoconidia of the same yeast were found in the infra-cuff portion of the ET, as evidenced by SEM, strongly fixed on the ET surface. Yeasts isolated from both the infra-cuff region and the tracheobronchial secretions were susceptible to amphotericin B and fluconazole. In conclusion, our results show that the frequency of colonization by yeasts of the Candida genus in the tracheobronchial secretions of intubated patients within 48 hours is high, and that these species can also be found as a biofilm on the ET surface.

The Inhalable Mycobiome of Sawmill Workers: Exposure Characterization and Diversity

Exposure to fungal spores has been associated with respiratory symptoms and allergic alveolitis among sawmill workers, but the complexity of sawmill workers' fungal exposure has been poorly studied. We characterized the fungal diversity in air samples from sawmill workers' breathing zones and identified differences in the richness, diversity, and taxonomic composition between companies, departments, wood types, and seasons. Full-shift personal inhalable dust samples (n = 86) collected from 11 industrial sawmill, sorting mill, and planer mill companies processing spruce and/or pine were subjected to DNA metabarcoding using the fungal internal transcribed spacer (ITS) region 2. The workers were exposed to a higher total number of operational taxonomic units (OTUs) in summer than in winter and when processing spruce than when processing pine. Workers in the saw department had the richest fungal exposure, followed by workers in the planing department and sorting of dry timber department. Sawmills explained 11% of the variation in the fungal community composition of the exposure, followed by season (5%) and department (3%). The fungal compositions of the exposures also differed between seasons, sawmills, wood types, and departments at the taxonomic level, ranging from the phylum to the species level. The differences in exposure diversity suggest that the potential health effects of fungal inhalation may also be different; hence, a risk assessment based on the fungal diversity differences should be performed. This study may serve as a basis for establishing a fungal profile of signature species that are specific for sawmills and that can be measured quantitatively in future risk assessments of sawmill workers.IMPORTANCE To gain more knowledge about exposure-response relationships, it is important to improve exposure characterization by comprehensively identifying the temporal and spatial fungal composition and diversity of inhalable dust at workplaces. The variation in the diverse fungal communities to which individuals are exposed in different seasons and sawmills suggests that variations in exposure-related health effects between seasons and companies can be expected. More importantly, the distinct fungal profiles between departments across companies indicate that workers in different job groups are differently exposed and that health risks can be department specific. DNA metabarcoding provides insight into a broad spectrum of airborne fungi that may serve as a basis for obtaining important knowledge about the fungi to which workers are exposed.

A Higher Rate of Pulmonary Fungal Infection in Chronic Obstructive Pulmonary Disease Patients with Influenza in a Large Tertiary Hospital

BACKGROUND

Influenza is considered a self-limiting disease. However, in patients with chronic obstructive pulmonary disease (COPD), it may result in serious outcomes during the flu season.

OBJECTIVES

The aims of this retrospective study were to explore the characteristics of hospitalized patients with COPD complicated by influenza and determine the factors affecting the prognosis of these patients.

METHOD

Demographic and clinical data were collected for 278 patients totally from the West China Hospital between January 1, 2016 and February 28, 2018.

RESULTS

Among the patients with influenza, the positive fungal culture rate, and the rates of antifungal drug and systemic corticosteroids use were higher for those with COPD than for those without COPD. Respiratory failure was more common in patients with influenza and COPD than in patients with influenza only, while the proportion of severe cases was higher among the former than among the latter. Among the patients with COPD, the positive fungal culture rate, particularly for Aspergillus, and the rate of systemic corticosteroids use were higher for those with influenza than for those without influenza. Multivariate analysis revealed that a COPD history of >20 years and smoking for >20 pack-years were independent factors for susceptibility of COPD patients to influenza.

CONCLUSIONS

Aspergillus infection seems to be more common in patients with influenza and COPD. In addition, COPD complicated by influenza during the seasonal outbreak can easily progress to a severe disease state. Heavy smokers and patients with a prolonged COPD history are more likely to be infected by influenza.

Beyond Antagonism: The Interaction Between Candida Species and Pseudomonas aeruginosa

There are many examples of the interaction between prokaryotes and eukaryotes. One such example is the polymicrobial colonization/infection by the various opportunistic pathogenic yeasts belonging to the genus Candida and the ubiquitous bacterium, Pseudomonas aeruginosa. Although this interaction has simplistically been characterized as antagonistic to the yeast, this review highlights the complexity of the interaction with various factors influencing both microbes. The first section deals with the interactions in vitro, looking specifically at the role of cell wall components, quorum sensing molecules, phenazines, fatty acid metabolites and competition for iron in the interaction. The second part of this review places all these interactions in the context of various infection or colonization sites, i.e., lungs, wounds, and the gastrointestinal tract. Here we see that the role of the host, as well as the methodology used to establish co-infection, are important factors, influencing the outcome of the disease. Suggested future perspectives for the study of this interaction include determining the influence of newly identified participants of the QS network of P. aeruginosa, oxylipin production by both species, as well as the genetic and phenotypic plasticity of these microbes, on the interaction and outcome of co-infection.

Respiratory Tract Colonization by Candida species Portends Worse Outcomes in Immunocompromised Patients

Background

The significance and clinical management of Candida colonization of the respiratory tract are ill-defined. We now report the frequency of Candida species from the lower respiratory tract in hematopoietic stem cell transplant recipients (HSCT) undergoing bronchoscopy with broncheoalveolar lavage (BAL) for pneumonitis post-HSCT.

Methods

The University of Michigan Clinical Microbiology Lab Database was queried for all respiratory cultures positive for Candida species between 2000-2012. We concurrently performed a retrospective analysis of 515 HSCT recipients with pneumonitis at our institution between 2001-2012.

Results

During this twelve-year period, there were 2524 unique Candida isolates (78% Candida albicans). Of the 515 HSCT patients with suspected pneumonitis,127 (24.7%) HSCT subjects were culture positive for a fungal pathogen, with Candida species identified in 27 cases (5.2%). When compared with other HSCT subjects, those cultures positive for Candida had significantly increased mortality (p=0.04).

Conclusions

Candida sp. are commonly cultured from the respiratory tract of HSCT recipients, with increased mortality in affected patients. While there is insufficient evidence for anti-fungal treatment of Candida species colonization, the presence of the yeast may be useful as a surrogate marker of disease severity.

Essential oils and their components are a class of antifungals with potent vapour-phase-mediated anti-Candida activity

Multi-resistant microorganisms continue to challenge medicine and fuel the search for new antimicrobials. Here we show that essential oils and their components are a promising class of antifungals that can have specific anti-Candida activity via their vapour-phase. We quantify the vapour-phase-mediated antimicrobial activity (VMAA) of 175 essential oils and 37 essential oil components, representing more than a 1,000 unique molecules, against C. albicans and C. glabrata in a novel vapour-phase-mediated susceptibility assay. Approximately half of the tested essential oils and their components show growth-inhibitory VMAA. Moreover, an average greater activity was observed against the intrinsically more resistant C. glabrata, with essential oil component citronellal having a highly significant differential VMAA. In contrast, representatives of each class of antifungals currently used in clinical practice showed no VMAA. The vapour-phase-mediated susceptibility assay presented here thus allows for the simple detection of VMAA and can advance the search for novel (applications of existing) antimicrobials. This study represents the first comprehensive characterisation of essential oils and their components as a unique class of antifungals with antimicrobial properties that differentiate them from existing antifungal classes.

Candida albicans and Pseudomonas aeruginosa Interact To Enhance Virulence of Mucosal Infection in Transparent Zebrafish

Polymicrobial infections often include both fungi and bacteria and can complicate patient treatment and resolution of infection. Cross-kingdom interactions among bacteria, fungi, and/or the immune system during infection can enhance or block virulence mechanisms and influence disease progression. The fungus Candida albicans and the bacterium Pseudomonas aeruginosa are coisolated in the context of polymicrobial infection at a variety of sites throughout the body, including mucosal tissues such as the lung. In vitro, C. albicans and P. aeruginosa have a bidirectional and largely antagonistic relationship. Their interactions in vivo remain poorly understood, specifically regarding host responses in mediating infection. In this study, we examine trikingdom interactions using a transparent juvenile zebrafish to model mucosal lung infection and show that C. albicans and P. aeruginosa are synergistically virulent. We find that high C. albicans burden, fungal epithelial invasion, swimbladder edema, and epithelial extrusion events serve as predictive factors for mortality in our infection model. Longitudinal analyses of fungal, bacterial, and immune dynamics during coinfection suggest that enhanced morbidity is associated with exacerbated C. albicans pathogenesis and elevated inflammation. The P. aeruginosa quorum-sensing-deficient ΔlasR mutant also enhances C. albicans pathogenicity in coinfection and induces extrusion of the swimbladder. Together, these observations suggest that C. albicans-P. aeruginosa cross talk in vivo can benefit both organisms to the detriment of the host.