Candida albicans impairs macrophage function and facilitates Pseudomonas aeruginosa pneumonia in rat*:

Therapy of traditional Chinese medicine in Candida spp. and Candida associated infections: A comprehensive review

Candida spp. are commonly a group of opportunistic dimorphic fungi, frequently causing diverse fungal infections in immunocompromised or immunosuppressant patients from mucosal disturbs (oropharyngeal candidiasis and vulvovaginal candidiasis) to disseminated infections (systemic candidiasis) with high morbidity and mortality. Importantly, several Candida species can be isolated from diseased individuals with digestive, neuropathic, respiratory, metabolic and autoimmune diseases. Due to increased resistance to conventional antifungal agents, the arsenal for antifungal purpose is in urgent need. Traditional Chinese Medicines (TCMs) are a huge treasury that can be used as promising candidates for antimycotic applications. In this review, we make a short survey of microbiological (morphology and virulence) and pathological (candidiasis and Candida related infections) features of and host immune response (innate and adaptive immunity) to Candida spp.. Based on the chemical structures and well-studied antifungal mechanisms, the monomers, extracts, decoctions, essential oils and other preparations of TCMs that are reported to have fair antifungal activities or immunomodulatory effects for anticandidal purpose are comprehensively reviewed. We also emphasize the importance of combination and drug pair of TCMs as useful anticandidal strategies, as well as network pharmacology and molecular docking as beneficial complements to current experimental approaches. This review construct a therapeutic module that can be helpful to guide in-future experimental and preclinical studies in the combat against fungal threats aroused by C. albicans and non-albicans Candida species.

Molecular Analysis of Volatile Metabolites Synthesized by Candida albicans and Staphylococcus aureus in In Vitro Cultures and Bronchoalveolar Lavage Specimens Reflecting Single- or Duo-Factor Pneumonia

Current microbiological methods for pneumonia diagnosis require invasive specimen collection and time-consuming analytical procedures. There is a need for less invasive and faster methods to detect lower respiratory tract infections. The analysis of volatile metabolites excreted by pathogenic microorganisms provides the basis for developing such a method. Given the synergistic role of Candida albicans in increasing the virulence of pathogenic bacteria causing pneumonia and the cross-kingdom metabolic interactions between microorganisms, we compare the emission of volatiles from Candida albicans yeasts and the bacteria Staphylococcus aureus using single and mixed co-cultures and apply that knowledge to human in vivo investigations. Gas chromatography-mass spectrometry (GC-MS) analysis resulted in the identification of sixty-eight volatiles that were found to have significantly different levels in cultures compared to reference medium samples. Certain volatiles were found in co-cultures that mainly originated from C. albicans metabolism (e.g., isobutyl acetate), whereas other volatiles primarily came from S. aureus (e.g., ethyl 2-methylbutyrate). Isopentyl valerate reflects synergic interactions of both microbes, as its level in co-cultures was found to be approximately three times higher than the sum of its amounts in monocultures. Hydrophilic-lipophilic-balanced (HLB) coated meshes for thin-film microextraction (TFME) were used to preconcentrate volatiles directly from bronchoalveolar lavage (BAL) specimens collected from patients suffering from ventilation-associated pneumonia (VAP), which was caused explicitly by C. albicans and S. aureus. GC-MS analyses confirmed the existence of in vitro-elucidated microbial VOCs in human specimens. Significant differences in BAL-extracted amounts respective to the pathogen-causing pneumonia were found. The model in vitro experiments provided evidence that cross-kingdom interactions between pathogenic microorganisms affect the synthesis of volatile compounds. The TFME meshes coated with HLB particles proved to be suitable for extracting VOCs from human material, enabling the translation of in vitro experiments on the microbial volatilome to the in vivo situation involving infected patients. This indicates the direction that should be taken for further clinical studies on VAP diagnosis based on volatile analysis.

Interkingdom interactions between Pseudomonas aeruginosa and Candida albicans affect clinical outcomes and antimicrobial responses

Infections that involve interkingdom microbial communities, such as those between bacteria and yeast pathogens, are difficult to treat, associated with worse patient outcomes, and may be a source of antimicrobial resistance. In this review, we address co-occurrence and co-infections of Candida albicans and Pseudomonas aeruginosa, two pathogens that occupy multiple infection niches in the human body, especially in immunocompromised patients. The interaction between the pathogen species influences microbe-host interactions, the effectiveness of antimicrobials and even infection outcomes, and may thus require adapted treatment strategies. However, the molecular details of bacteria-fungal interactions both inside and outside the infection sites, are insufficiently characterised. We argue that comprehensively understanding the P. aeruginosa-C. albicans interaction network through integrated systems biology approaches will capture the highly dynamic and complex nature of these polymicrobial infections and lead to a more comprehensive understanding of clinical observations such as reshaped immune defences and low antimicrobial treatment efficacy.

The interactions of Candida albicans with gut bacteria: a new strategy to prevent and treat invasive intestinal candidiasis

BACKGROUND

The gut microbiota plays an important role in human health, as it can affect host immunity and susceptibility to infectious diseases. Invasive intestinal candidiasis is strongly associated with gut microbiota homeostasis. However, the nature of the interaction between Candida albicans and gut bacteria remains unclear.

OBJECTIVE

This review aimed to determine the nature of interaction and the effects of gut bacteria on C. albicans so as to comprehend an approach to reducing intestinal invasive infection by C. albicans.

METHODS

This review examined 11 common gut bacteria's interactions with C. albicans, including Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, Enterococcus faecalis, Staphylococcus aureus, Salmonella spp., Helicobacter pylori, Lactobacillus spp., Bacteroides spp., Clostridium difficile, and Streptococcus spp.

RESULTS

Most of the studied bacteria demonstrated both synergistic and antagonistic effects with C. albicans, and just a few bacteria such as P. aeruginosa, Salmonella spp., and Lactobacillus spp. demonstrated only antagonism against C. albicans.

CONCLUSIONS

Based on the nature of interactions reported so far by the literature between gut bacteria and C. albicans, it is expected to provide new ideas for the prevention and treatment of invasive intestinal candidiasis.

Is Candida albicans a contributor to cancer? A critical review based on the current evidence

The association between Candida albicans (C. albicans) and cancer has been noticed for decades. Whether C. albicans infection is a complication of cancer status or as a contributor to cancer development remains to be discussed. This review systematically summarized the up-to-date knowledge about associations between C. albicans and various types of cancer, and discussed the role of C. albicans in cancer development. Most of the current clinical and animal evidence support the relationship between C. albicans and oral cancer development. However, there is insufficient evidence to demonstrate the role of C. albicans in other types of cancer. Moreover, this review explored the underlying mechanisms for C. albicans promoting cancer. It was hypothesized that C. albicans may promote cancer progression by producing carcinogenic metabolites, inducing chronic inflammation, remodeling immune microenvironment, activating pro-cancer signals, and synergizing with bacteria.

Lung and gut microbiomes in pulmonary aspergillosis: Exploring adjunctive therapies to combat the disease

Species within the Aspergillus spp. cause a wide range of infections in humans, including invasive pulmonary aspergillosis, chronic pulmonary aspergillosis, and allergic bronchopulmonary aspergillosis, and are associated with high mortality rates. The incidence of pulmonary aspergillosis (PA) is on the rise, and the emergence of triazole-resistant Aspergillus spp. isolates, especially Aspergillus fumigatus, limits the efficacy of mold-active triazoles. Therefore, host-directed and novel adjunctive therapies are required to more effectively combat PA. In this review, we focus on PA from a microbiome perspective. We provide a general overview of the effects of the lung and gut microbiomes on the growth of Aspergillus spp. and host immunity. We highlight the potential of the microbiome as a therapeutic target for PA.

Relationship Between Invasive Fungal Infection and Hypostatic Pneumonia: A Prospective Cohort Study

Background

The short-term mortality of hypostatic pneumonia (HP) is very high, and the treatment outcome is poor. The clinical diagnosis and treatment are primarily focused on bacterial and viral infection, ignoring the role of fungal infection at present. This study aims to validate the relationship between Invasive Fungal Infections (IFI) and HP.

Methods

In the cross-sectional study, a total of 11,371 participants have been enrolled. In the prospective cohort study, 4,441 individuals have been included at baseline and followed up from 2015 to 2019 with a total person years of 8,484.65. The standard procedures were used to assess questionnaire investigations, laboratory testing, and anthropometric indicators. For data analysis, logistic regression, restricted cubic spline, log-rank regression, Cox regression, and linear mixed effects model were applied to assess the relationship between IFI and HP risk longitudinally.

Results

In the cross-sectional study, elevated β-D-Glucan (BDG) concentrations are associated with a higher risk of HP prevalence in the total population, men, and women (OR_{T3 vs}._T1 [95% CIs]: 2.12 [1.55, 2.91]; 2.01 [1.35, 2.99]; 2.34 [1.39, 3.94]), which were verified by a dose–effect relationship in the restricted cubic spline model. In the cohort study, Cox and Log-rank regression showed that the elevated BDG concentrations are associated with a significantly higher risk of HP incidence than participants with lower BDG concentrations (HR_{T3 vs}._T1 [95% CIs]: 2.72 [1.36, 5.43], p_Log–rank = 0.0086). During 5 years, the globulin (GLB) and C-reactive protein (CRP) were always on the top in the highest category of BDG concentrations. Between low and high BDG concentration, the total trend of GLB concentration was falling and the total trend of CRP concentration was rising with the increase of years (all the p-values < 0.0001).

Conclusion

In this study, IFI is associated with a higher risk of HP, with time sequence and related mechanisms requiring further investigation in the future.

Intranasal Delivery of Antigen-Coated Polymer Particles Protects against Pseudomonas aeruginosa Infection

Pseudomonas aeruginosa is an opportunistic human pathogen that is intrinsically resistant to multiple antibiotics, causing severe and persistent infections in immunocompromised individuals. This bacterium has been listed as a priority pathogen by the WHO in 2017, and there is no vaccine available for human use. In this study, 10 vaccine candidate antigens were selected for particulate vaccine design. We engineered Escherichia coli to assemble biopolymer particles (BPs) that were either coated with epitopes (Ag) derived from OprF/I-AlgE proteins or PopB or PopB-Ag or coated with single or double copies of epitopes (10Ag and 10Ag(2x)) derived from OprF, OprI, AlgE, OprL, PopB, PilA, PilO, FliC, Hcp1, and CdrA. Antigen-coated BPs showed a diameter of 0.93-1.16 μm with negative surface charge. Antigens attached to BPs were identified by mass spectrometry. Vaccination with BP-Ag, BP-PopB, BP-PopBAg, PB-10Ag, and BP-10Ag(2x) with and without Alhydrogel adjuvant induced significant antigen-specific humoral and cell-mediated immune responses in mice. All particulate vaccines with Alhydrogel induced protection in an acute pneumonia murine model of P. aeruginosa infection, contributing to up to 80% survival when administered intramuscularly, and the addition of Alhydrogel boosted immunity. The BP-10Ag(2x) vaccine candidate showed the best performance and even induced protective immunity in the absence of Alhydrogel. Intramuscular administration of the BP-10Ag(2x) without Alhydrogel vaccine resulted in 60% survival. Intranasal vaccination induced immunity, contributing to about 90% survival. Overall, our data suggest that vaccination with BPs coated with P. aeruginosa antigens induce protective immunity against P. aeruginosa infections. The possibility of intranasal delivery will strongly facilitate administration and use of BP vaccines.

New Insights in the Pathophysiology of Hospital- and Ventilator-Acquired Pneumonia: A Complex Interplay between Dysbiosis and Critical-Illness-Related Immunosuppression

Both hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) have long been considered as diseases resulting from the invasion by pathogens of a previously sterile lung environment. Based on this historical understanding of their pathophysiology, our approaches for the prevention and treatment have significantly improved the outcomes of patients, but treatment failures remain frequent. Recent studies have suggested that the all-antimicrobial therapy-based treatment of pneumonia has reached a glass ceiling. The demonstration that the constant interactions between the respiratory microbiome and mucosal immunity are required to tune homeostasis in a state of symbiosis has changed our comprehension of pneumonia. We proposed that HAP and VAP should be considered as a state of dysbiosis, defined as the emergence of a dominant pathogen thriving at the same time from the catastrophic collapse of the fragile ecosystem of the lower respiratory tract and from the development of critical-illness-related immunosuppression. This multidimensional approach to the pathophysiology of HAP and VAP holds the potential to achieve future successes in research and critical care. Microbiome and mucosal immunity can indeed be manipulated and used as adjunctive therapies or targets to prevent or treat pneumonia.

Vaccination of mice with hybrid protein containing Exotoxin S and PcrV with adjuvants alum and MPL protects Pseudomonas aeruginosa infections

Pseudomonas aeruginosa as a common pathogen causing urinary tract infections (UTIs) has been resistant to different antibiotics and developing an effective vaccine can be an alternative strategy. In the present study, the immunogenicity and protection efficacy of formulations composed of a hybrid protein composed of P. aeruginosa V-antigen (PcrV) and exoenzyme S (ExoS) with alum and MPL were evaluated. The hybrid protein could increase the specific systemic and mucosal immune responses, as well as cellular responses as compared with control groups. Combining of alum or MPL adjuvant with the hybrid protein significantly improved the levels of IgG1, serum IgA, mucosal IgG, and IL-17 as compared to the ExoS.PcrV alone. After bladder challenge with a P. aeruginosa strain, the bacterial loads of bladder and kidneys were significantly decreased in mice received ExoS.PcrV admixed with alum and ExoS.PcrV admixed with MPL than controls. The present study indicated that immunization of mice with a hybrid protein composed of ExoS and PcrV could induce multifactorial immune responses and opsonize the bacteria and decrease the viable bacterial cells. Because P. aeruginosa have caused therapeutic challenges worldwide, our study proposed ExoS.PcrV + alum and ExoS.PcrV + MPL as promising candidates for the prevention of infections caused by P. aeruginosa.

Lung Microbiome in Critically Ill Patients

The historical hypothesis of sterility of the lungs was invalidated over a decade ago when studies demonstrated the existence of sparse but very diverse bacterial populations in the normal lung and the association between pulmonary dysbiosis and chronic respiratory diseases. Under mechanical ventilation, dysbiosis occurs rapidly with a gradual decline in diversity over time and the progressive predominance of a bacterial pathogen (mainly Proteobacteria) when lung infection occurs. During acute respiratory distress syndrome, an enrichment in bacteria of intestinal origin, mainly Enterobacteriaceae, is observed. However, the role of this dysbiosis in the pathogenesis of ventilator-associated pneumonia and acute respiratory distress syndrome is not yet fully understood. The lack of exploration of other microbial populations, viruses (eukaryotes and prokaryotes) and fungi is a key issue. Further analysis of the interaction between these microbial kingdoms and a better understanding of the host−microbiome interaction are necessary to fully elucidate the role of the microbiome in the pathogenicity of acute diseases. The validation of a consensual and robust methodology in order to make the comparison of the different studies relevant is also required. Filling these different gaps should help develop preventive and therapeutic strategies for both acute respiratory distress syndrome and ventilator-associated pneumonia.

Candida spp. isolation from critically ill patients' respiratory tract. Does antifungal treatment affect survival?

INTRODUCTION

Isolation of Candida spp. from bronchial samples of patients on mechanical ventilation is common. Even though it may not always reflect infection, it may induce immunological changes that can facilitate bacterial pneumonia. In this case, antifungal treatment is of uncertain value. This study examined the impact of antifungal treatment on the outcome of intensive care unit (ICU)-acquired respiratory tract infection (RTI) of critically ill, immunocompetent patients, with Candida isolation from their respiratory tract.

METHODS

This is a retrospective cohort study of adult patients hospitalized in the ICU of the University Hospital of Heraklion, Greece, from 2014 through 2016 with ICU-acquired RTI and Candida spp. isolated from their bronchial secretions. Data regarding medical history, demographics (gender, age), reason for ICU admission, previous antimicrobial use or hospitalization, SOFA and APACHE II score, clinical outcomes (primary clinical outcome: overall mortality during hospitalization; secondary clinical outcome: mortality during the ICU stay and duration of ICU and hospital stay) at the end of their ICU stay and at the end of their hospital stay were recorded and consequently evaluated. A logistic regression analysis model evaluated the effect of the recorded parameters in association with ICU mortality and overall mortality during hospitalization.

RESULTS

A total of 90 individuals were enrolled. Of them, 47 (52.2%) were treated with antifungals during their hospitalization around the time of Candida isolation. Patients treated with antifungals had higher SOFA and APACHE II scores, longer duration of stay in the ICU, more days on ventilator and higher total mortality during hospitalization. Multivariate logistic regression analysis identified antifungal use to be independently associated with total mortality during hospitalization.

CONCLUSIONS

Antifungal use in patients with ICU-acquired RTI was associated with higher overall mortality as compared to those not receiving such agents.

Recent Advances in Presentation, Diagnosis and Treatment for Mixed Vaginitis

Mixed vaginitis is the simultaneous presence of at least two types of vaginitis, contributing to an abnormal vaginal milieu and leading to vaginal symptoms and signs. However, associations between symptoms and the type of mixed vaginitis have not been clearly elucidated, and research on mixed vaginitis is still in the preliminary stage. Therefore, the pathogenic mechanism of mixed vaginitis remains understudied. Mixed vaginitis generally involves the formation of mixed biofilms. The study of polymicrobial interactions and mixed biofilms will provide a new idea for the understanding of mixed vaginitis. Moreover, this review summarizes some effective management and laboratory diagnosis of mixed vaginitis to avoid inappropriate therapy, recurrence, and reinfection. It is of high clinical importance to obtain relevant clinical data to improve clinical knowledge about mixed vaginitis.

Candida Spp. in Lower Respiratory Tract Secretions - A Ten Years Retrospective Study

Introduction

Lower respiratory tract secretions (LRTS) like sputum and tracheal aspirates are frequently sent to the microbiology laboratory from patients with various respiratory pathologies. Improper collection techniques can lead to false-positive results, resulting in improper therapy.

Aim of the study

To determine the percentage of contaminated samples sent to the microbiology laboratory, to establish the prevalence of Candida spp. in non-contaminated samples and therefore, the presence of Candida spp. originating in lower respiratory tract infections. Material and

Methods

A 10-year data survey was conducted to assess the differences in Candida prevalence from contaminated versus non-contaminated samples, assessed and categorised by Bartlett grading system, and to emphasise the importance of quality control for potentially contaminated samples. The data were analysed according to gender, age, referring departments, and the species of Candida. For the statistical analysis, Kruskal-Wallis and Fisher tests were used, and the alpha value was set for 0.5.

Results

The prevalence of Candida spp. in all analysed samples was 31.60%. After excluding the contaminated samples, the actual prevalence was 27.66%. Of all sputum samples, 31.6% were contaminated. Patients aged more than 40 years old were more prone to provide contaminated sputum samples. C. albicans is more prevalent in non-contaminated sputum samples. In both sputum and tracheal aspirates, the chances of identifying a single species are higher than the chances of identifying multiple species.

Conclusions

The study emphasises the importance of assessing the quality of sputum samples because of the high number of improperly collected samples sent to the microbiology laboratory.

Effect of Nebulized Amphotericin B in Critically ill Patients With Respiratory Candida spp. De-colonization: A Retrospective Analysis

The potential relationship among airway Candida spp. de-colonization, nebulized amphotericin B (NAB), and occurrence of ventilator-associated pneumonia (VAP) in patients who are critically ill has not been fully investigated, especially concerning effects on survival. In this observational, retrospective, cohort study in a 22-bed central intensive care unit, we included patients aged >18 years who required mechanical ventilation (MV) for >48 h, with at least two consecutive positive Candida spp. test results. Patients were categorized into NAB and no NAB (control) groups. Propensity matching at 1:1 was performed according to strict standards, and multiple Cox proportional hazard model and multivariate analyses were performed to evaluate the effects of NAB treatment. Throughout an 8-year study period, 526 patients had received MV and had positive respiratory tract Candida spp. cultures. Of these, we included 275 patients and excluded 251 patients. In total, we successfully matched 110 patients from the two groups (each group, n = 55; total population median age, 64 years; Acute Physiology and Chronic Health Evaluation II [APACHE II] score, 25.5; sequential organ failure assessment score, 9). The Candida spp. de-colonization rate was 69.1% in patients treated with NAB. VAP incidence did not differ significantly between the NAB (10.91%) and control (16.36%) groups (P = 0.405). Pseudomonas aeruginosa-related VAP rates differed significantly between the NAB (10.91%) and control (25.45%) groups (P = 0.048). Five (9.1%) patients in the NAB group died during hospitalization compared with 17 (30.9%) controls (P = 0.014). At 28 days, 9 (16.4%) and 16 (29.1%) deaths occurred in the NAB and control groups, respectively, (P = 0.088). The cumulative 90-day mortality rate differed significantly between the two groups (23.6 vs. 43.6%, P = 0.015). Multivariate logistic regression analyses indicated a decreased 90-day mortality in the NAB group (adjusted odds ratio 0.413; 95% confidence interval 0.210–0.812; P = 0.01). In subgroup analyses, the NAB-associated decreased risk of death at 90 days was consistent across subgroups of patients with a Candida score of 2, younger age (<64 years), a higher APACHE II score (≥25), fewer Candida sites (<2), or MV at admission. NAB treatment contributed to Candida spp. airway de-colonization, was associated with a reduced risk of P. aeruginosa-related VAP, and improved 90-day mortality in patients critically ill with Candida spp. tracheobronchial colonization who had received MV for >2 days. NAB may be an alternative treatment option for critically ill patients with VAP.

A Pseudomonas aeruginosa-Derived Particulate Vaccine Protects against P. aeruginosa Infection

Despite numerous efforts to develop an effective vaccine against Pseudomonas aeruginosa, no vaccine has yet been approved for human use. This study investigates the utility of the P. aeruginosa inherently produced polyhydroxyalkanaote (PHA) inclusions and associated host-cell proteins (HCP) as a particulate vaccine platform. We further engineered PHA inclusions to display epitopes derived from the outer membrane proteins OprF/OprI/AlgE (Ag) or the type III secretion system translocator PopB. PHA and engineered PHA beads induced antigen-specific humoral, cell-mediated immune responses, anti-HCP and anti-polysaccharide Psl responses in mice. Antibodies mediated opsonophagocytic killing and serotype-independent protective immunity as shown by 100% survival upon challenge with P. aeruginosa in an acute pneumonia murine model. Vaccines were stable at 4 °C for at least one year. Overall, our data suggest that vaccination with subcellular empty PHA beads was sufficient to elicit multiple immune effectors that can prevent P. aeruginosa infection.

Candida species in community-acquired pneumonia in patients with chronic aspiration

Background

When Candida species is found in a sputum culture, clinicians generally dismiss it as a contaminant. We sought to identify cases of community-acquired pneumonia (CAP) in which Candida might play a contributory etiologic role.

Methods

In a convenience sample of patients hospitalized for CAP, we screened for “high-quality sputum” by Gram stain (> 20 WBC/epithelial cell) and performed quantitative sputum cultures. Criteria for a potential etiologic role for Candida included the observation of large numbers of yeast forms on Gram stain, intracellular organisms and > 10⁶ CFU/ml Candida in sputum. We gathered clinical information on cases that met these criteria for possible Candida infection.

Results

Sputum from 6 of 154 consecutive CAP patients had large numbers of extra- and intracellular yeast forms on Gram stain, with > 10⁶ CFU/ml Candida albicans, glabrata, or tropicalis on quantitative culture. In all 6 patients, the clinical diagnoses at admission included chronic aspiration. Greater than 10⁵ CFU/ml of a recognized bacterial pathogen (Streptococcus pneumoniae, Staphylococcus aureus, or Pseudomonas) or > 10⁶ CFU/ml of other ‘normal respiratory flora’ (Lactobacillus species) were present together with Candida spp. in every case. Blood cultures yielded Candida in 2 cases, and 1,3-beta-D glucan was > 500 ng/mL in 3 of 3 cases in which it was assayed. Since all patients were treated with anti-bacterial and anti-fungal drugs, no inference about etiology can be derived from therapeutic response.

Conclusions

Candida spp. together with a recognized bacterial pathogen or normal respiratory flora may contribute to the cause of CAP in patients who chronically aspirate.

Analysis of pathogens and risk factors of secondary pulmonary infection in patients with COVID-19

To investigate the distribution and risk factors of pathogens in secondary pulmonary infection in patients with COVID-19.142 patients with confirmed COVID-19 from Shanghai Public Health Clinical Center were collected, and 32 patients with pulmonary infection were taken as the infection group. The distribution of pathogens in the sputum specimens was applied for retrospective analysis. Meanwhile, 110 patients diagnosed with COVID-19, but without pulmonary infection were regarded as the asymptomatic group. The risk factors of pulmonary infection were analyzed with generalized linear models and logistic regression. The pathogens in the lung infection group were mainly gram-negative bacteria (22, 68.8%), especially Klebsiella pneumoniae. Gram-positive bacteria and fungi accounted for 13 (40.6%), mainly Staphylococcus aureus, and 11 (34.4%), mainly Candida albicans. There were 14 cases (43.8%) infected with two or more pathogens. The comparison between the two groups found that, patients with elder age, underlying diseases, more lung lesions and low protein contents, were more likely to develop lung infections. At last, univariate analysis showed that 6 factors, including indwelling gastric catheter, the number of deep vein catheters, tracheal intubation tracheotomy, invasive mechanical ventilation, hormonal application, and the use of more than three antibacterial drugs, are risk factors for COVID-19 secondary pulmonary infection. Generalized linear models and logistic regression analysis showed antimicrobial use as an independent risk factor for COVID-19 secondary lung infection. There are many risk factors for secondary lung infection in severe COVID-19 patients, and it is recommended to use antibiotics reasonably.

Respiratory Candida in Patients with Bronchitis, Mucus Plugging, and Atelectasis

Background

The significance of Candida in pulmonary secretions is unclear, and usually is regarded as colonization, not contributing to symptoms or disease. Yet, in our experience, Candida seemed associated with chronic sputum, mucus plugging, atelectasis, and poor outcome.

Objective

The aim of this study is to describe the clinical findings of patients with Candida in pulmonary (sputum or bronchoscopy) secretions and the significance of Candida.

Methods

Retrospective study of inpatients and outpatients referred for pulmonary consultation with Candida in pulmonary secretions. Clinical parameters and estimates of whether Candida was likely clinically significant, were determined.

Results

82 inpatients and 11 outpatients were identified, of which 61 (66%) had atelectasis and 68 (73%) bronchoscopies. Of patients having bronchoscopies, 56 (82%) had mucus, and 43 (63%) mucus plugging. Of the inpatients death (or probable death) occurred in 43 (63%), 42 (98%) of which were from definite or probable respiratory failure, with 13 (31%) likely related to mucus plugging, 16 (38%) possibly from mucus plugging, 6 (14%) unknown, and 7 (17%) not due to mucus plugging. Candida was felt likely clinically significant in 57 patients (61%), uncertain significance in 23 (25%), and not significant in 13 (14%). All outpatients had exacerbations, including 7 (64%) within a year.

Conclusion

Patients requiring pulmonary consultation with Candida in pulmonary secretions often have chronic sputum production, exacerbations, mucus plugging, atelectasis, and death from respiratory failure. Candida was likely clinically significant in most patients. Recommendations to consider Candida in pulmonary secretions as colonization should be reconsidered.

Respiratory microbiome in mechanically ventilated patients: a narrative review

The respiratory microbiome has been less explored than the gut microbiome. Despite the speculated importance of dysbiosis of the microbiome in ventilator-associated pneumonia (VAP) and acute respiratory distress syndrome (ARDS), only few studies have been performed in invasively ventilated ICU patients. And only the results of small cohorts have been published. An overlap exists between bacterial populations observed in the lower respiratory tract and the oropharyngeal tract. The bacterial microbiota is characterized by relatively abundant bacteria difficult to cultivate by standard methods. Under mechanical ventilation, a dysbiosis occurs with a drop overtime in diversity. During VAP development, lung dysbiosis is characterized by a shift towards a dominant bacterial pathogen (mostly Proteobacteria) whereas enrichment of gut-associated bacteria mainly Enterobacteriaceae is the specific feature discriminating ARDS patients. However, the role of this dysbiosis in VAP and ARDS pathogenesis is not yet fully understood. A more in-depth analysis of the interplay between bacteria, virus and fungi and a better understanding of the host-microbiome interaction could provide a more comprehensive view of the role of the microbiome in VAP and ARDS pathogenesis. Priority should be given to validate a consensual and robust methodology for respiratory microbiome research and to conduct longitudinal studies. A deeper understanding of microbial interplay should be a valuable guide for care of ARDS and VAP preventive/therapeutic strategies. We present a review on the current knowledge and expose perspectives and potential clinical applications of respiratory microbiome research in mechanically ventilated patients.

Understanding Human Microbiota Offers Novel and Promising Therapeutic Options against Candida Infections

Human fungal pathogens particularly of Candida species are one of the major causes of hospital acquired infections in immunocompromised patients. The limited arsenal of antifungal drugs to treat Candida infections with concomitant evolution of multidrug resistant strains further complicates the management of these infections. Therefore, deployment of novel strategies to surmount the Candida infections requires immediate attention. The human body is a dynamic ecosystem having microbiota usually involving symbionts that benefit from the host, but in turn may act as commensal organisms or affect positively (mutualism) or negatively (pathogenic) the physiology and nourishment of the host. The composition of human microbiota has garnered a lot of recent attention, and despite the common occurrence of Candida spp. within the microbiota, there is still an incomplete picture of relationships between Candida spp. and other microorganism, as well as how such associations are governed. These relationships could be important to have a more holistic understanding of the human microbiota and its connection to Candida infections. Understanding the mechanisms behind commensalism and pathogenesis is vital for the development of efficient therapeutic strategies for these Candida infections. The concept of host-microbiota crosstalk plays critical roles in human health and microbiota dysbiosis and is responsible for various pathologies. Through this review, we attempted to analyze the types of human microbiota and provide an update on the current understanding in the context of health and Candida infections. The information in this article will help as a resource for development of targeted microbial therapies such as pre-/pro-biotics and microbiota transplant that has gained advantage in recent times over antibiotics and established as novel therapeutic strategy.

Candida in Lower Respiratory Tract Increases the Frequency of Acute Exacerbation of Chronic Obstructive Pulmonary Disease: A Retrospective Case-Control Study

Objective: To explore impact of Candida on the acute exacerbation of chronic obstructive pulmonary disease (AECOPD) outcome. Methods: A retrospective, multi-center, case-control study was performed. Patients hospitalized for AECOPD in 25 centers during Jan 2011-Dec 2016 were enrolled. Data were collected, including demographic information, conditions during the stable phase of COPD, clinical characteristics of AECOPD, and follow-up information within 1 year after discharge. Univariate analysis and binary logistic regression were applied, and p < 0.05 was regarded as significant. Results: Totally 1,103 patients were analyzed, with 644 lower respiratory airway (LTR) Candida positive cases and 459 Candida negative controls. Long-term prognosis was significantly different between Candida positive and negative group, including the recurrent AECOPD within 180 days (75.5 vs. 6.6%, p < 0.001) and mortality within 1 year (6.9 vs. 0.4%, p < 0.001). Univariate logistic analysis showed that LTR Candida isolation was related to higher recurrence rate of AECOPD within 180 days and mortality within 1 year. Binary logistic regression analysis demonstrated that LTR Candida isolation was independently associated with recurrence of AECOPD within 180 days. Conclusions: LTR Candida isolation was associated with worse long-term prognosis of AECOPD and independently related to higher risks of recurrent AECOPD within 180 days.

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.

Microbial Etiology and Prognostic Factors of Ventilator-associated Pneumonia: A Multicenter Retrospective Study in Shanghai

Background

The microbial etiology and mortality risk factors of ventilator-associated pneumonia (VAP) have not been investigated extensively in Shanghai.

Methods

VAP cases were identified from the patients hospitalized during the period from 1 January 2013 to 30 December 2017 in Shanghai. The relevant data were reviewed and analyzed retrospectively.

Results

One hundred ninety-four VAP cases were included in this analysis. The overall mortality rate was 32.47%. The respiratory pathogens isolated from these patients included 212 bacterial strains and 54 fungal strains. The leading pathogens were Acinetobacter baumannii (33.96%), Klebsiella pneumoniae (23.58%), Pseudomonas aeruginosa (19.81%), and Staphylococcus aureus (7.08%). Candida colonization was associated with higher mortality of VAP patients compared to those without Candida colonization (45.45% vs 28.67%, P < .05). The VAP patients with Candida colonization also showed higher prevalence of P. aeruginosa, carbapenem-resistant P. aeruginosa (CRPA), K. pneumoniae, carbapenem-resistant K. pneumoniae (CRKP), A. baumannii, and carbapenem-resistant A. baumannii (CRAB) (P < .05). VAP nonsurvivors had higher prevalence of CRPA, K. pneumoniae, CRAB, and Candida than VAP survivors (P < .05). Multivariate analysis showed that prior antibiotic use was a significant risk factor for Candida colonization, while hypertension and length of hospital stay were significant risk factors of VAP mortality (P < .05).

Conclusions

The top pathogens of VAP patients in Shanghai tertiary teaching hospitals are A. baumannii, K. pneumoniae, and P. aeruginosa, with high prevalence of carbapenem resistance. Carbapenem-resistant bacterial pathogens and Candida may predict poor outcome.

Pathogenetic Impact of Bacterial-Fungal Interactions

Polymicrobial infections are of paramount importance because of the potential severity of clinical manifestations, often associated with increased resistance to antimicrobial treatment. The intricate interplay with the host and the immune system, and the impact on microbiome imbalance, are of importance in this context. The equilibrium of microbiota in the human host is critical for preventing potential dysbiosis and the ensuing development of disease. Bacteria and fungi can communicate via signaling molecules, and produce metabolites and toxins capable of modulating the immune response or altering the efficacy of treatment. Most of the bacterial–fungal interactions described to date focus on the human fungal pathogen Candida albicans and different bacteria. In this review, we discuss more than twenty different bacterial–fungal interactions involving several clinically important human pathogens. The interactions, which can be synergistic or antagonistic, both in vitro and in vivo, are addressed with a focus on the quorum-sensing molecules produced, the response of the immune system, and the impact on clinical outcome.

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.

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.

Klebsiella pneumoniae prevents spore germination and hyphal development of Aspergillus species

Different bacteria and fungi live as commensal organisms as part of the human microbiota, but shifts to a pathogenic state potentially leading to septic infections commonly occur in immunocompromised individuals. Several studies have reported synergistic or antagonistic interactions between individual bacteria and fungi which might be of clinical relevance. Here, we present first evidence for the interaction between Klebsiella pneumoniae and several Aspergillus species including A. fumigatus, A. terreus, A. niger and A. flavus which cohabit in the lungs and the intestines. Microbiological and molecular methods were employed to investigate the interaction in vitro, and the results indicate that Klebsiella pneumoniae is able to prevent Aspergillus spp. spore germination and hyphal development. The inhibitory effect is reversible, as demonstrated by growth recovery of Aspergillus spp. upon inhibition or elimination of the bacteria, and is apparently dependent on the physical interaction with metabolically active bacteria. Molecular analysis of Klebsiella-Aspergillus interaction has shown upregulation of Aspergillus cell wall-related genes and downregulation of hyphae-related genes, suggesting that Klebsiella induces cell wall stress response mechanisms and suppresses filamentous growth. Characterization of polymicrobial interactions may provide the basis for improved clinical management of mixed infections by setting the stage for appropriate diagnostics and ultimately for optimized treatment strategies.

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.

The activity of bacterial peptidylarginine deiminase is important during formation of dual-species biofilm by periodontal pathogen Porphyromonas gingivalis and opportunistic fungus Candida albicans

Porphyromonas gingivalis, an anaerobic Gram-negative bacterium critically involved in the development of human periodontitis, belongs to the late colonizers of the oral cavity. The success of this pathogen in the host colonization and infection results from the presence of several virulence factors, including extracellular peptidylarginine deiminase (PPAD), an enzyme that converts protein arginine residues to citrullines. A common opportunistic fungal pathogen of humans, Candida albicans, is also frequently identified among microorganisms that reside at subgingival sites. The aim of the current work was to verify if protein citrullination can influence the formation of mixed biofilms by both microorganisms under hypoxic and normoxic conditions. Quantitative estimations of the bacterial adhesion to fungal cells demonstrated the importance of PPAD activity in this process, since the level of binding of P. gingivalis mutant strain deprived of PPAD was significantly lower than that observed for the wild-type strain. These results were consistent with mass spectrometric detection of the citrullination of selected surface-exposed C. albicans proteins. Furthermore, a viability of P. gingivalis cells under normoxia increased in the presence of fungal biofilm compared with the bacteria that formed single-species biofilm. These findings suggest a possible protection of these strict anaerobes under unfavorable aerobic conditions by C. albicans during mixed biofilm formation.

Immunization with Pseudomonas aeruginosa outer membrane vesicles stimulates protective immunity in mice

Pseudomonas aeruginosa is an opportunistic pathogen responsible for a wide range of severe nosocomial and community acquired infections, these infections are major health problems for cystic fibrosis patients and immune-compromised individuals. The emergence of multidrug-resistant isolates highlights the need to develop alternative strategies for treatment of P. aeruginosa infections. Outer membrane vesicles (OMVs) are spherical nanometer-sized proteolipids that are secreted from numerous of pathogenic Gram-negative bacteria, and a number of studies have confirmed the protective efficacy for use of OMVs as candidate vaccines. In this study, OMVs from P. aeruginosa (PA_OMVs) were isolated, formulated with aluminum phosphate adjuvant and used as a vaccine in a mouse model of acute lung infection. The results confirmed that active immunization with PA_OMVs was able to reduce bacterial colonization, cytokine secretion and tissue damage in the lung tissue, thus protecting mice from lethal challenge of P. aeruginosa. Cytokines assay validated that immunization with PA_OMVs was efficient to induce a mixed cellular immune response in mice. Further, high level of specific antibodies was detected in mice immunized with PA_OMVs, and results from opsonophagocytic killing assay and passive immunization suggested that humoral immune response may be critical for PA_OMVs mediated protection. These findings demonstrated that PA_OMVs may be served as a novel candidate vaccine for the prevention of P. aeruginosa infection.

Pathophysiology of Escherichia coli pneumonia: Respective contribution of pathogenicity islands to virulence

Ventilator-associated pneumonia (VAP) remains the most frequent life-threatening nosocomial infection. Enterobacteriaceae including Escherichia coli are increasingly involved. If a cumulative effect of pathogenicity islands (PAIs) has been shown for E. coli virulence in urinary tract or systemic infections, very little is known regarding pathophysiology of E. coli pneumonia. This study aimed to determine the role of each of the 7 PAIs present in pathogenic E. coli strain 536 in pneumonia pathophysiology. We used mutant strains to screen pathophysiological role of PAI in a rat pneumonia model. We also test individual gene mutants within PAI identified to be involved in pneumonia pathogenesis. Finally, we determined the prevalence of these genes of interest in E. coli isolates from feces and airways of ventilated patients. Only PAIs I and III were significantly associated with rat pneumonia pathogenicity. Only the antigen-43 (Ag43) gene in PAI III was significantly associated with bacterial pathogenicity. The prevalence of tested genes in fecal and airway isolates of ventilated patients did not differ between isolates. In contrast, genes encoding Ag43, the F17-fimbriae subunits, HmuR and SepA were more prevalent in VAP isolates with statistical significance for hmuR when compared to airway colonizing isolates. The E. coli PAIs involved in lung pathogenicity differed from those involved in urinary tract and bloodstream infections. Overall, extraintestinal E. coli virulence seems to rely on a combination of numerous virulence genes that have a cumulative effect depending on the infection site.

The nasopharyngeal microbiome

Human microbiomes have received increasing attention over the last 10 years, leading to a pervasiveness of hypotheses relating dysbiosis to health and disease. The respiratory tract has received much less attention in this respect than that of, for example, the human gut. Nevertheless, progress has been made in elucidating the immunological, ecological and environmental drivers that govern these microbial consortia and the potential consequences of aberrant microbiomes. In this review, we consider the microbiome of the nasopharynx, a specific niche of the upper respiratory tract. The nasopharynx is an important site, anatomically with respect to its gateway position between upper and lower airways, and for pathogenic bacterial colonisation. The dynamics of the latter are important for long-term respiratory morbidity, acute infections of both invasive and non-invasive disease and associations with chronic airway disease exacerbations. Here, we review the development of the nasopharyngeal (NP) microbiome over the life course, examining it from the early establishment of resilient profiles in neonates through to perturbations associated with pneumonia risk in the elderly. We focus specifically on the commensal, opportunistically pathogenic members of the NP microbiome that includes Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae and Moraxella catarrhalis. In addition, we consider the role of relatively harmless genera such as Dolosigranulum and Corynebacterium. Understanding that the NP microbiome plays such a key, beneficial role in maintaining equilibrium of commensal species, prevention of pathogen outgrowth and host immunity enables future research to be directed appropriately.

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.

Protective Efficacy of the Trivalent Pseudomonas aeruginosa Vaccine Candidate PcrV-OprI-Hcp1 in Murine Pneumonia and Burn Models

Pseudomonas aeruginosa is a formidable pathogen that is responsible for a diverse spectrum of human infectious diseases, resulting in considerable annual mortality rates. Because of biofilm formation and its ability of rapidly acquires of resistance to many antibiotics, P. aeruginosa related infections are difficult to treat, and therefore, developing an effective vaccine is the most promising method for combating infection. In the present study, we designed a novel trivalent vaccine, PcrV_28-294-OprI_25-83-Hcp1_1-162 (POH), and evaluated its protective efficacy in murine pneumonia and burn models. POH existed as a dimer in solution, it induced better protection efficacy in P. aeruginosa lethal pneumonia and murine burn models than single components alone when formulated with Al(OH)₃ adjuvant, and it showed broad immune protection against several clinical isolates of P. aeruginosa. Immunization with POH induced strong immune responses and resulted in reduced bacterial loads, decreased pathology, inflammatory cytokine expression and inflammatory cell infiltration. Furthermore, in vitro opsonophagocytic killing assay and passive immunization studies indicated that the protective efficacy mediated by POH vaccination was largely attributed to POH-specific antibodies. Taken together, these data provided evidence that POH is a potentially promising vaccine candidate for combating P. aeruginosa infection in pneumonia and burn infections.

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

Candida is an opportunistic pathogen and the most commonly isolated fungal genus in humans. Though Candida is often detected in respiratory specimens from humans with and without lung disease, its significance remains undetermined. While historically considered a commensal organism with low virulence potential, the status of Candida as an innocent bystander has recently been called into question by both clinical observations and animal experimentation. We here review what is currently known and yet to be determined about the clinical, microbiological and pathophysiological significance of the detection of Candida spp. in the human respiratory tract.

The microbiota of the respiratory tract: gatekeeper to respiratory health

The respiratory tract is a complex organ system that is responsible for the exchange of oxygen and carbon dioxide. The human respiratory tract spans from the nostrils to the lung alveoli and is inhabited by niche-specific communities of bacteria. The microbiota of the respiratory tract probably acts as a gatekeeper that provides resistance to colonization by respiratory pathogens. The respiratory microbiota might also be involved in the maturation and maintenance of homeostasis of respiratory physiology and immunity. The ecological and environmental factors that direct the development of microbial communities in the respiratory tract and how these communities affect respiratory health are the focus of current research. Concurrently, the functions of the microbiome of the upper and lower respiratory tract in the physiology of the human host are being studied in detail. In this Review, we will discuss the epidemiological, biological and functional evidence that support the physiological role of the respiratory microbiota in the maintenance of human health.

Effects of Propidium Monoazide (PMA) Treatment on Mycobiome and Bacteriome Analysis of Cystic Fibrosis Airways during Exacerbation

Introduction and Purpose

Propidium monoazide (PMA)-pretreatment has increasingly been applied to remove the bias from dead or damaged cell artefacts, which could impact the microbiota analysis by high-throughput sequencing. Our study aimed to determine whether a PMA-pretreatment coupled with high-throughput sequencing analysis provides a different picture of the airway mycobiome and bacteriome.

Results and Discussion

We compared deep-sequencing data of mycobiota and microbiota of 15 sputum samples from 5 cystic fibrosis (CF) patients with and without prior PMA-treatment of the DNA-extracts. PMA-pretreatment had no significant effect on the entire and abundant bacterial community (genera expressed as operational taxonomic units (OTUs) with a relative abundance greater than or equal to 1%), but caused a significant difference in the intermediate community (less than 1%) when analyzing the alpha biodiversity Simpson index (p = 0.03). Regarding PMA impact on the airway mycobiota evaluated for the first time here; no significant differences in alpha diversity indexes between PMA-treated and untreated samples were observed. Regarding beta diversity analysis, the intermediate communities also differed more dramatically than the total and abundant ones when studying both mycobiome and bacteriome. Our results showed that only the intermediate (or low abundance) population diversity is impacted by PMA-treatment, and therefore that abundant taxa are mostly viable during acute exacerbation in CF. Given such a cumbersome protocol (PMA-pretreatment coupled with high-throughput sequencing), we discuss its potential interest within the follow-up of CF patients. Further studies using PMA-pretreatment are warranted to improve our “omic” knowledge of the CF airways.

Bacterial-Fungal Interactions Including Quorum Sensing, Between 2 Opportunistic Pathogens, Resulting in Post-Traumatic Sepsis in a Child Presenting With a Closed Femoral Fracture

Pseudomonas aeruginosa and Candida albicans (are opportunistic pathogens that cause systemic infections in immune-suppressed patients. They show important bacterial-fungal interactions including quorum sensing. This involves cell signaling to communicate between the cells of their own colony and the cells of rival microbes or the host. It is thought that this phenomenon is vital in the potential competition and virulence of the organisms. We report a case of a previously healthy 2-year-old boy, where an accidental injury had been sustained resulting in a closed fracture of femur. He subsequently developed sepsis related to co-infection by C. albicans and P. aeruginosa. Trauma may result in a transient immune-suppression and predispose to sepsis caused by opportunistic microorganisms. They can engage in bacterial-fungal interaction. Clinicians should consider invasive co-infection when initial cultures show evidence for only 1 pathogen.

Polymicrobial infections involving clinically relevant Gram-negative bacteria and fungi

Interactions between fungi and bacteria and their relevance to human health and disease have recently attracted increased attention in biomedical fields. Emerging evidence shows that bacteria and fungi can have synergistic or antagonistic interactions, each with important implications for human colonization and disease. It is now appreciated that some of these interactions may be strategic and helps promote the survival of one or both microorganisms within the host. This review will shed light on clinically relevant interactions between fungi and Gram-negative bacteria. Mechanism of interaction, host immune responses, and preventive measures will also be reviewed.

Comparison of foam swabs and toothbrushes as oral hygiene interventions in mechanically ventilated patients: a randomised split mouth study

Introduction

During critical illness, dental plaque may serve as a reservoir of respiratory pathogens. This study compared the effectiveness of toothbrushing with a small-headed toothbrush or a foam-headed swab in mechanically ventilated patients.

Methods

This was a randomised, assessor-blinded, split-mouth trial, performed at a single critical care unit. Adult, orally intubated patients with >20 teeth, where >24 hours of mechanical ventilation was expected were included. Teeth were cleaned 12-hourly using a foam swab or toothbrush (each randomly assigned to one side of the mouth). Cleaning efficacy was based on plaque scores, gingival index and microbial plaque counts.

Results

High initial plaque (mean=2.1 (SD 0.45)) and gingival (mean=2.0 (SD 0.54)) scores were recorded for 21 patients. A significant reduction compared with initial plaque index occurred using both toothbrushes (mean change=−1.26, 95% CI −1.57 to −0.95; p<0.001) and foam swabs (mean change=−1.28, 95% CI −1.54 to −1.01; p<0.001). There was significant reduction in gingival index over time using toothbrushes (mean change=−0.92; 95% CI −1.19 to −0.64; p<0.001) and foam swabs (mean change=−0.85; 95% CI −1.10 to −0.61; p<0.001). Differences between cleaning methods were not statistically significant (p=0.12 for change in gingival index; p=0.24 for change in plaque index). There was no significant change in bacterial dental plaque counts between toothbrushing (mean change 3.7×10⁴ colony-forming units (CFUs); minimum to maximum (−2.5×10¹⁰ CFUs, 8.7×10⁷ CFUs)) and foam swabs (mean change 9×10⁴ CFUs; minimum to maximum (−3.1×10¹⁰ CFUs, 3.0×10⁷ CFUs)).

Conclusions

Patients admitted to adult intensive care had poor oral health, which improved after brushing with a toothbrush or foam swab. Both interventions were equally effective at removing plaque and reducing gingival inflammation.

Trial registration number

NCT01154257; Pre-results.

Candida albicans Airway Colonization Facilitates Subsequent Acinetobacter baumannii Pneumonia in a Rat Model

The objective of the study was to determine the effects of Candida albicans respiratory tract colonization on Acinetobacter baumannii pneumonia in a rat model. Rats were colonized with C. albicans by instillation of 3 × 10(6) CFU into their airways, while sterile saline was instilled in the control group. The colonized rats were further divided into two groups: treated with amphotericin B or not. The rats were subsequently infected with A. baumannii (10(8) CFU by tracheobronchial instillation). A. baumannii lung CFU counts, cytokine lung levels, and rates of A. baumannii pneumonia were compared between groups. In vitro expression of A. baumannii virulence genes was measured by reverse transcription (RT)-PCR after 24-hour incubation with C. albicans or with Mueller-Hinton (MH) broth alone. Rats with Candida colonization developed A. baumannii pneumonia more frequently and had higher A. baumannii CFU burdens and heavier lungs than controls. After A. baumannii infection, lung interleukin 17 (IL-17) concentrations were lower and gamma interferon (IFN-γ) concentrations were higher in Candida-colonized rats than in controls. Candida-colonized rats treated with amphotericin B had a decreased rate of A. baumannii pneumonia and lower IFN-γ levels but higher IL-17 levels than untreated rats. Expression of basC, barB, bauA, ptk, plc2, and pld2 was induced while expression of ompA and abaI was suppressed in A. baumannii cultured in the presence of C. albicans C. albicans colonization facilitated the development of A. baumannii pneumonia in a rat model. Among Candida-colonized rats, antifungal treatment lowered the incidence of A. baumannii pneumonia. These findings could be due to modification of the host immune response and/or expression of A. baumannii virulence genes by Candida spp.

Characterisation of Candida within the Mycobiome/Microbiome of the Lower Respiratory Tract of ICU Patients

Whether the presence of Candida spp. in lower respiratory tract (LRT) secretions is a marker of underlying disease, intensive care unit (ICU) treatment and antibiotic therapy or contributes to poor clinical outcome is unclear. We investigated healthy controls, patients with proposed risk factors for Candida growth in LRT (antibiotic therapy, ICU treatment with and without antibiotic therapy), ICU patients with pneumonia and antibiotic therapy and candidemic patients (for comparison of truly invasive and colonizing Candida spp.). Fungal patterns were determined by conventional culture based microbiology combined with molecular approaches (next generation sequencing, multilocus sequence typing) for description of fungal and concommitant bacterial microbiota in LRT, and host and fungal biomarkes were investigated. Admission to and treatment on ICUs shifted LRT fungal microbiota to Candida spp. dominated fungal profiles but antibiotic therapy did not. Compared to controls, Candida was part of fungal microbiota in LRT of ICU patients without pneumonia with and without antibiotic therapy (63% and 50% of total fungal genera) and of ICU patients with pneumonia with antibiotic therapy (73%) (p<0.05). No case of invasive candidiasis originating from Candida in the LRT was detected. There was no common bacterial microbiota profile associated or dissociated with Candida spp. in LRT. Colonizing and invasive Candida strains (from candidemic patients) did not match to certain clades withdrawing the presence of a particular pathogenic and invasive clade. The presence of Candida spp. in the LRT rather reflected rapidly occurring LRT dysbiosis driven by ICU related factors than was associated with invasive candidiasis.

Evaluation of Virulence Factors and Antifungal Susceptibility in Yeast Isolates from Postmortem Specimens

Invasive fungal infections are a leading cause of morbidity and mortality in immunocompromised patients, especially in cases requiring a prolonged stay in the intensive care unit. A total of 99 yeast strains were isolated from 42 postmortem cases. In this study, virulence factors and antifungal susceptibility of these species were evaluated. The isolates were identified as Candida albicans (54), C. tropicalis (15), C. glabrata (12), C. parapsilosis (6), C. lipolytica (3), C. utilis (3), C. krusei (2), C. kefyr (1), and Cryptococcus neoformans (3). The most commonly isolated species was C. albicans, and no resistant species were determined. Despite the equal number of specimens, no secretion of significant virulence factors was associated with the postmortem specimen in the Candida species. Postmortem fungal investigations in forensic autopsies are useful in explaining cause of death in such cases, also may lead to protocols for the treatment of fungal infections and contribute to fungal pathogenesis and epidemiological data.

Candida albicans and Pseudomonas aeruginosa Interaction, with Focus on the Role of Eicosanoids

Candida albicans is commonly found in mixed infections with Pseudomonas aeruginosa, especially in the lungs of cystic fibrosis (CF) patients. Both of these opportunistic pathogens are able to form resistant biofilms and frequently infect immunocompromised individuals. The interaction between these two pathogens, which includes physical interaction as well as secreted factors, is mainly antagonistic. In addition, research suggests considerable interaction with their host, especially with immunomodulatory lipid mediators, termed eicosanoids. Candida albicans and Pseudomonas aeruginosa are both able to utilize arachidonic acid (AA), liberated from the host cells during infection, to form eicosanoids. The production of these eicosanoids, such as Prostaglandin E₂, by the host and the pathogens may affect the dynamics of polymicrobial infection and the outcome of infections. It is of considerable importance to elucidate the role of host-produced, as well as pathogen-produced eicosanoids in polymicrobial infection. This review will focus on in vitro as well as in vivo interaction between C. albicans and P. aeruginosa, paying special attention to the role of eicosanoids in the cross-talk between host and the pathogens.

Studying Microbial Communities In Vivo: A Model of Host-mediated Interaction Between Candida Albicans and Pseudomonas Aeruginosa in the Airways

Studying host-pathogen interaction enables us to understand the underlying mechanisms of the pathogenicity during microbial infection. The prognosis of the host depends on the involvement of an adapted immune response against the pathogen. Immune response is complex and results from interaction of the pathogens and several immune or non-immune cellular types. In vitro studies cannot characterise these interactions and focus on cell-pathogen interactions. Moreover, in the airway, particularly in patients with suppurative chronic lung disease or in mechanically ventilated patients, polymicrobial communities are present and complicate host-pathogen interaction. Pseudomonas aeruginosa and Candida albicans are both problem pathogens, frequently isolated from tracheobronchial samples, and associated to severe infections, especially in intensive care unit. Microbial interactions have been reported between these pathogens in vitro but the clinical impact of these interactions remains unclear. To study the interactions between C. albicans and P. aeruginosa, a murine model of C. albicans airways colonization, followed by a P. aeruginosa-mediated acute lung infection was performed.

Polymicrobial community-acquired pneumonia: An emerging entity

Polymicrobial aetiology in community-acquired pneumonia (CAP) is more common than previously recognized. This growing new entity can influence inflammation, host immunity and disease outcomes in CAP patients. However, the true incidence is complicated to determine and probably underestimated due mainly to many cases going undetected, particularly in the outpatient setting, as the diagnostic yield is restricted by the sensitivity of currently available microbiologic tests and the ability to get certain types of clinical specimens. The observed rate of polymicrobial cases may also lead to new antibiotic therapy considerations. In this review, we discuss the pathogenesis, microbial interactions in pneumonia, epidemiology, biomarkers and antibiotic therapy for polymicrobial CAP.

Impact of Candida spp. isolation in the respiratory tract in patients with intensive care unit-acquired pneumonia

In immunocompetent patients with nosocomial pneumonia, the relationship between Candida spp. isolation in respiratory samples and outcomes or association with other pathogens is controversial. We therefore compared the characteristics and outcomes of patients with intensive care unit-acquired pneumonia (ICUAP), with or without Candida spp. isolation in the respiratory tract. In this prospective non-interventional study, we assessed 385 consecutive immunocompetent patients with ICUAP, according to the presence or absence of Candida spp. in lower respiratory tract samples. Candida spp. was isolated in at least one sample in 82 (21%) patients. Patients with Candida spp. had higher severity scores and organ dysfunction at admission and at onset of pneumonia. In multivariate analysis, previous surgery, diabetes mellitus and higher Simplified Acute Physiology Score II at ICU admission independently predicted isolation of Candida spp. There were no significant differences in the rate of specific aetiological pathogens, the systemic inflammatory response, and length of stay between patients with and without Candida spp. Mortality was also similar, even adjusted for potential confounders in propensity-adjusted multivariate analyses (adjusted hazard ratio 1.08, 95% CI 0.57-2.05, p 0.80 for 28-day mortality and adjusted hazard ratio 1.38, 95% CI 0.81-2.35, p 0.24 for 90-day mortality). Antifungal therapy was more frequently prescribed in patients with Candida spp. in respiratory samples but did not influence outcomes. Candida spp. airway isolation in patients with ICUAP is associated with more initial disease severity but does not influence outcomes in these patients, regardless of the use or not of antifungal therapy.