Prevalence of biofilms in Candida spp. bloodstream infections: A meta-analysis

CONTEXT

Candida-related infections are nowadays a serious Public Health Problem emerging multidrug-resistant strains. Candida biofilm also leads bloodstream infections to invasive systemic infections.

OBJECTIVE

The present meta-analysis aimed to analyze Candida biofilm rate, type, and antifungal resistance among hospitalized patients between 1995 and 2020.

DATA SOURCES

Web of Science, Scopus, PubMed, and Google Scholar databases were searched for English papers using the following medical subject heading terms (MESH): "invasive candidiasis"; "bloodstream infections"; "biofilm formation"; "biofilm-related infections"; "mortality"; and "prevalence".

STUDY SELECTION

The major inclusion criteria included reporting the rate of biofilm formation and the prevalence of biofilm-related to Candida species, including observational studies (more exactly, cohort, retrospective, and case-control studies). Furthermore, data regarding the mortality rate, the geographical location of the study set, and the use of anti-fungal agents in clinical isolates were also extracted from the studies.

DATA EXTRACTION

Independent extraction of articles by 2 authors using predefined data fields, including study quality indicators.

DATA SYNTHESIS

A total of 31 studies from publicly available databases met our inclusion criteria. The biofilm formation in the data set varied greatly from 16 to 100% in blood samples. Most of the studies belonged to Europe (17/31) and Asia (9/31). Forest plot showed a pooled rate of biofilm formation of 80.0% (CI: 67-90), with high heterogeneity (Q = 2567.45, I2 = 98.83, τ2 = 0.150) in random effects model (p < 0.001). The funnel plot and Egger's linear regression test failed to find publication bias (p = 0.896). The mortality rate in Candida-related bloodstream infections was 37.9% of which 70.0% were from biofilm-associated infections. Furthermore, Candida isolates were also characterized in low, intermediate, or high biofilm formers through their level of biofilm mass (crystal violet staining or XTT assays) after a 24h growth. When comparing between countries, statistical differences were obtained (p = 0.0074), showing the lower and higher biofilm prevalence values in Italy and Spain, respectively. The prevalence of low, intermediate, and high biofilms were 36.2, 18.9, and 35.0% (p < 0.0001), respectively. C. tropicalis was the prevalent species in high biofilm formation (67.5%) showing statistically significant differences when compared to other Candida species, except for C. krusei and C. glabrata. Finally, the rates of antifungal resistance to fluconazole, voriconazole, and caspofungin related to biofilm were 70.5, 67.9 and 72.8% (p < 0.001), respectively.

CONCLUSIONS

Early detection of biofilms and a better characterization of Candida spp. bloodstream infections should be considered, which eventually will help preserve public health resources and ultimately diminish mortality among patients.

Genetic diversity assessed using PFGE, MLP and MLST in Candida spp. candidemia isolates obtained from a Brazilian hospital

Candida spp. are the main causative agents of invasive fungal infections in immunocompromised patients. Candidemia has attributable mortality rates of 15 to 35% and increases hospitalisation time and costs, thus making this disease a public health concern. This study aimed to use pulsed-field gel electrophoresis (PFGE), microsatellite length polymorphism (MLP) and multilocus sequence typing (MLST) to analyse the genetic relationships among 65 Candida spp. bloodstream isolates, including 35 Candida albicans, 15 Candida glabrata and 15 Candida tropicalis isolates, all of which were obtained from patients in a Brazilian hospital. Moreover, patient clinical data were assessed. All techniques resulted in high discriminatory indexes. C. albicans and C. tropicalis isolates showed high genetic variability, while C. glabrata isolates had relatively low genetic variability. Moreover, a cluster of C. glabrata isolates was identified in a hospital unit. New MLST sequence types, diploid sequence types and alleles are described. Relationships were not observed between the molecular typing results and clinical characteristics. The molecular typing of clinical strains increases our understanding of candidemia epidemiology and promotes the development of strategies that can reduce the incidence of this disease. Moreover, this study is the first to combine these techniques to genotype these three species in Brazil.

Comparison of blood cultures versus T2 Candida Panel in management of candidemia at a large community hospital

The T2 Candida Panel (T2CP) has high sensitivity and specificity to detect candidemia. Its role in the diagnosis and management of candidemia compared to blood cultures (BC) remains unclear. The purpose of this study was to evaluate the T2CP versus BC in detecting and treating candidemia. A retrospective, observational cohort study was conducted to compare clinical outcomes in patients with candidemia identified by BC versus T2CP. Patients with a positive BC or T2CP for Candida spp. from January 2012 to August 2020 were grouped by initial method of detection (BC vs T2CP). Co-primary endpoints assessed included time to detection of candidemia and time to antifungal therapy. Key secondary endpoints included length of stay (LOS), ICU LOS, and mortality. One hundred sixty-three patients with a positive BC and 89 patients with a positive T2CP were included in the evaluation. The average time to detection of candidemia was significantly shorter in the T2CP group compared to BC group (9 vs 41 h, p < 0.001). The time to antifungal was also significantly shorter in the T2CP group compared to the BC group (4 vs 37 h, p < 0.001). However, LOS was significantly shorter in the BC positive group than the T2CP group with no difference in ICU LOS. There was no difference in in-hospital or 30-day mortality between the two groups. Of patients diagnosed with candidemia at our large community hospital, identification by T2CP led to faster detection and initiation of antifungal compared to blood cultures without improvement in LOS or mortality.

Epidemiological features of nosocomial candidaemia in neonates, infants and children: A multicentre study in Iran

Nosocomial bloodstream candidaemia is a life-threatening fungal infection with high morbidity and mortality, especially among paediatric patients undergoing intensive immunosuppressive therapy. Limited data on the epidemiology of candidaemia and susceptibility profiles are available for Iran. To characterise candidaemia epidemiology, comorbidity risk factors, species distribution, and antifungal susceptibility profiles among paediatric patients in Iran. This observational cross-sectional study enrolled 26 189 patients <18 years old at three reference paediatric hospitals in Mazandaran and Tehran over 2 years. Blood samples from patients with suspected fungal bloodstream infection were analysed using the BACTEC culture system. Fungal isolates were identified using matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF) and DNA sequencing. Antifungal susceptibility testing was performed using the Clinical and Laboratory Standards Institute broth microdilution guideline. We observed 109 episodes of nosocomial candidaemia in paediatric patients with or without immunosuppressive therapy. The most common healthcare-associated factor was central vascular catheter use (97%). The all-cause mortality rate was 40%, of which 48% was attributable to candidaemia. While Candida albicans was the most frequent causative agent (49%), emerging and uncommon Candida species were also isolated. Candidaemia mortality by non-albicans Candida species was significantly higher than that by C. albicans (P < .05). All fluconazole-resistant species were non-albicans Candida species. Uncommon Candida species with reduced susceptibility to antifungals are emerging as major agents of nosocomial candidaemia in high-risk paediatric patients in Iran. Appropriate source control, antifungal regimens and improved antifungal stewardship are warranted for managing and decreasing the burden of nosocomial candidaemia.

Direct Detection of Candida albicans with a Membrane Based Electrochemical Impedance Spectroscopy Sensor

Candidemia and invasive candidiasis is a cause of high mortality and morbidity rates among hospitalized patients worldwide. The occurrence of the infections increases due to the complexity of the patients and overuse of the antifungal therapy. The current Candida detection method includes blood culturing which is a lengthy procedure and thus delays the administration of the antifungal therapy. Even though the results are available after 48 h it is still the gold standard in pathogen detection in a hospital setting. In this work we present an electrochemical impedance sensor that is capable of detecting Candida albicans yeast. The yeast cells are captured on electrodes specifically functionalized with anti-Candida antibodies and detection is achieved by electrochemical impedance spectroscopy. The sensor allows for detection of the yeast cells at clinically relevant concentrations in less than 1 h.

Diagnosing candidemia with the T2Candida panel: an instructive case of septic shock in which blood cultures were negative

T2Candida that was positive for C. albicans/C. tropicalis supported antifungal treatment of a patient with hematogenously disseminated candidiasis and septic shock in whom blood cultures were negative. T2Candida, used and interpreted as a Bayesian biomarker, can identify patients with candidemia who are missed by blood cultures, including those receiving antifungal treatment.

Three cases of Candida fermentati fungemia following hematopoietic stem cell transplantation

Bloodstream infection with non-Candida albicans Candida species is one of the serious complications among patients with hematological malignancies who receive long-term prophylactic antifungal agents. Here we describe three cases of Candida fermentati (C. fermentati) candidemia after allogeneic stem cell transplantation for hematological malignancies. Case 1 is fluconazole-breakthrough C. fermentati fungemia, which was well controlled with liposomal amphotericin B. Case 2 and 3 were caspofungin-breakthrough C. fermentati fungemia. In case 2, blood culture turned negative for Candida responding to liposomal amphotericin B. Although in vitro susceptibility data for the isolated pathogen suggested the efficacy of both caspofungin and liposomal amphotericin B in all three cases, clinically liposomal amphotericin B seemed to have been more effective for eradication of the pathogen from blood stream. C. fermentati needs to be considered as a possible cause for breakthrough candidemia among post-transplant patients with prolonged antifungal prophylaxis. Discrepancy between in vitro and in vivo susceptibility to antifungals, especially to echinocandins, might provide a clue for the optimal choice of antifungals for C. fermentati infections.

T2 Magnetic Resonance for Fungal Diagnosis

Rapid diagnostic methods for fungal infections are long awaited and are expected to improve outcomes through early initiation of targeted antifungal therapy. T2Candida panel is a novel qualitative diagnostic platform that was recently approved by the US Food and Drug Administration (FDA) for diagnosis of candidemia with a mean time to species identification of less than 5 h. T2Candida panel is performed on the fully automated T2Dx instrument in whole blood K₂EDTA specimens and is able to detect 5 Candida spp., namely Candida albicans, Candida tropicalis, Candida parapsilosis, Candida krusei, and Candida glabrata. By combining magnetic resonance with molecular diagnostics, T2Candida panel amplifies DNA and detects the amplified product by amplicon-induced agglomeration of supermagnetic particles and T2 Magnetic Resonance (T2MR) measurement. Here we describe the materials and methods needed to diagnose candidemia with the T2Candida panel.

Risk factors and predictors of mortality of candidaemia among critically ill patients: role of antifungal prophylaxis in its development and in selection of non-albicans species

PURPOSE

The aim of the present study is to identify risk factors for development and predictors of mortality of candidaemia among critically ill patients.

METHODS

A 1:7 case-control study was conducted during a 4-year period (2012-2015) in a Greek Intensive Care Unit (ICU). Candidaemia was confirmed by positive blood cultures. All yeasts were identified using API 20C AUX System or Vitek 2 Advanced Expert System. Epidemiologic data were collected from the ICU computerized database and patients' chart reviews.

RESULTS

Fifty-three patients developed candidaemia with non-albicans species being the predominant ones (33 patients, 62.3%). Multivariate analysis found that prior emergency surgery, malignancy, hospitalization during summer months, prior septic shock by KPC-producing Klebsiella pneumoniae and number of antibiotics administered were independently associated with candidaemia, while, prior administration of azole was a protective factor. Non-albicans candidaemia was associated with number of antibiotics administered and prior administration of echinocandin. Mortality of 14 days was 28.3% (15 patients) and was associated with SOFA score upon infection onset and septic shock, while, appropriate empirical antifungal treatment was associated with better survival.

CONCLUSIONS

Prophylactic azole administration prevents development of candidaemia, while, echinocandin administration predisposes to non-albicans candidaemia. Empirical administration of an appropriate antifungal agent is associated with better survival.

Association Between Candiduria and Candidemia: A Clinical and Molecular Analysis of Cases

The risk of developing candidemia after candiduria is reportedly very low, but it has not been adequately investigated. The aim of this study was to examine the molecular relatedness between Candida strains isolated from adult patients with candidemia and concomitant candiduria in association with the clinical characteristics of the cases. All episodes of candidemia occurring in a tertiary care academic hospital during a 5-year period were recorded prospectively. Patients with episodes of candiduria occurring two weeks preceding to or one week following a positive for Candida blood culture were included in the study. The genotypic relatedness of Candida strains isolated from blood and urine was investigated by pulsed-field gel electrophoresis after digestion with the BssHII restriction endonuclease. We recorded 141 candidemia episodes, occurring in 134 patients. Twelve episodes of candidemia with concomitant candiduria occurred in 11 patients (8% of all candidemias). In six of these episodes, the strains in the blood-urine pairs belonged to different species. In two episodes, the isolates belonged to the same species but were not genetically related, and only in four (2.8% of all candidemias), the strains were related. All four patients were severely ill and had multiple risk factors for candidemia. These findings indicate that in hospitalized patients with candidemia, concomitant candiduria is rare and usually an independent event, confirming previous reports. In the critically ill, however, the existence of genetically related strains in blood and urine appears to be more frequent, with more probable the hematogenous dissemination.

Candidemia in the elderly: What does it change?

Background

Candidemia is a life-threatening fungal infection and it can affect patients of all ages. Characterization of candidemia in the elderly is lacking.

Methods

We performed a retrospective study of adults (≥ 18 years) with candidemia diagnosed in our center in 2010–2015. Demographics, comorbidities, clinical and microbiologic characteristics, antifungal treatment and outcome were compared between older (≤65 years) and younger (>65 years) patients.

Results

Among 302 patients with candidemia identified during the study period, 188 (62%) belonged to the elderly group. Comorbidities were significantly more frequent in older patients and included chronic pulmonary diseases, cardiovascular diseases, diabetes mellitus, and chronic renal failure (p ranging from <0.0001 to 0.017). A significantly higher proportion of older patients had septic shock (p = 0.040) at the time of candidemia. Candida albicans accounted for 53% of isolates and there were no significant differences between patients’ age and Candida species. Thirty-day mortality was significantly higher in older (45%) than in younger (28%) patients (p = 0.003). Factors associated with a significant higher proportion of death in the elderly included older age (i.e.: old-old), being hospitalized in ICU rather than in other wards, suffering from chronic pulmonary diseases, the presence of septic shock, multiple organ failure, dialysis and being infected with C. glabrata (p ranging from <0.0001 to 0.034). On multivariate analysis septic shock (HR 1.744 [CI95% 1.049–2.898], p = 0.032) and multiple organ failure (HR 2.242 [CI95% 1.070–4.698], p = 0.032) were independently associated with a higher risk of death. The probability of 30-days survival of older patients was significantly reduced when compared to that of younger patients (p = 0.005) who did not receive any treatment. In the elderly, there was a trend toward higher MICs for fluconazole/C. albicans, fluconazole/C. glabrata, amphotericin B/C. albicans, and caspofungin/C. glabrata.

Conclusions

In our study, we found that elderly patients with Candida bloodstream infections are characterized by a high mortality rate. In particular, the lack of any antifungal therapy as well as the occurrence of septic shock increased significantly the overall mortality. Additionally, we found that there was a trend of higher MIC for specific drug/Candida combination.

Epidemiology of Blood Stream Infection due to Candida Species in a Tertiary Care Hospital in Japan over 12 Years: Importance of Peripheral Line-Associated Candidemia

BACKGROUND

Candidemia is an important cause of mortality in healthcare settings. Peripheral lines are a source of candidemia, yet few studies have reported on the clinico-epidemiological features of candidemia due to peripheral-line associated blood stream infection (PLABSI).

METHODS

We conducted a single-centre retrospective cohort study of all patients with candidemia between 2002 and 2013. PLABSI was defined as the presence of at least one of the following: the presence of phlebitis or the resolution of clinical symptoms after peripheral-line withdrawal, with careful exclusion of an alternative explanation for bacteraemia. We described the epidemiology of candidemia and assessed predictive factors of PLABSI due to Candida spp., peripheral line-associated candidemia (PLAC), compared with non-PLAC.

RESULTS

A total of 301 episodes of candidemia, including 37 of PLAC, were diagnosed during the study period. Central-line associated blood stream infection, intra-abdominal infection, and infection of unknown source accounted for the remaining 233, 14, and 17 cases, respectively. The overall incidence rate of candidemia was 0.11/1000 patient-days. In multivariate analysis, cephalosporin exposure (odds ratio [OR] = 2.22, 95% CI 1.04-4.77), polymicrobial bacteraemia/fungaemia (OR = 2.87, 95% CI 1.02-8.10), and ID specialist consultation (OR = 2.40, 95% CI 1.13-5.13) were identified as independent predictors of PLAC. Although non-PLAC had a higher mortality, the length of hospital stay after candidemia was similar between the two groups and candidemia duration was longer in the PLAC group.

CONCLUSION

PLACs are an important cause of candidemia in hospitalized patients. Appropriate identification and management of PLAC are crucial.

A virtual infection model quantifies innate effector mechanisms and Candida albicans immune escape in human blood

Candida albicans bloodstream infection is increasingly frequent and can result in disseminated candidiasis associated with high mortality rates. To analyze the innate immune response against C. albicans, fungal cells were added to human whole-blood samples. After inoculation, C. albicans started to filament and predominantly associate with neutrophils, whereas only a minority of fungal cells became attached to monocytes. While many parameters of host-pathogen interaction were accessible to direct experimental quantification in the whole-blood infection assay, others were not. To overcome these limitations, we generated a virtual infection model that allowed detailed and quantitative predictions on the dynamics of host-pathogen interaction. Experimental time-resolved data were simulated using a state-based modeling approach combined with the Monte Carlo method of simulated annealing to obtain quantitative predictions on a priori unknown transition rates and to identify the main axis of antifungal immunity. Results clearly demonstrated a predominant role of neutrophils, mediated by phagocytosis and intracellular killing as well as the release of antifungal effector molecules upon activation, resulting in extracellular fungicidal activity. Both mechanisms together account for almost of C. albicans killing, clearly proving that beside being present in larger numbers than other leukocytes, neutrophils functionally dominate the immune response against C. albicans in human blood. A fraction of C. albicans cells escaped phagocytosis and remained extracellular and viable for up to four hours. This immune escape was independent of filamentation and fungal activity and not linked to exhaustion or inactivation of innate immune cells. The occurrence of C. albicans cells being resistant against phagocytosis may account for the high proportion of dissemination in C. albicans bloodstream infection. Taken together, iterative experiment–model–experiment cycles allowed quantitative analyses of the interplay between host and pathogen in a complex environment like human blood.

Candida albicans is the most important fungal pathogen in nosocomial bloodstream infections. So far little is known about the interplay of different cellular and non-cellular immune mechanisms mediating the protective response against C. albicans in blood. The in vivo scenario of C. albicans infection can be mimicked by human whole-blood infection assays to analyze the innate immune response against this pathogen. These experiments reveal the time-evolution of certain mechanisms while leaving the values of other quantities in the dark. To shed light on quantities that are not experimentally accessible, we exploited the descriptive and predictive power of mathematical models to estimate these parameters. The combination of experiment and theory enabled us to identify and quantify the main course of the immune response against C. albicans in human blood. We quantified the central role of neutrophils in the defence against this fungal pathogen, both directly by phagocytosis and indirectly by secreting antimicrobial factors inducing extracellular killing. Other findings include the distribution of C. albicans cells in neutrophils and monocytes as well as the immune escape of C. albicans cells in the course of infection.

Epidemiology of candidemia in Qatar, the Middle East: performance of MALDI-TOF MS for the identification of Candida species, species distribution, outcome, and susceptibility pattern

INTRODUCTION

Bloodstream infections (BSIs) due to Candida spp. constitute the predominant group of hospital-based fungal infections worldwide. A retrospective study evaluated the performance of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the identification of BSI Candida isolates. The epidemiology, risk factors, demographic features, species distribution, and clinical outcome associated with candidemia in patients admitted to a single tertiary-care hospital in Qatar, were analyzed.

METHODS

A single-center, retrospective analysis covering the period from January 1, 2004 to December 31, 2010 was performed. Molecular identification used sequence analysis of the D1/D2 domains of the large subunit ribosomal DNA (LSU rDNA) and the ITS1/2 regions of the rDNA. MALDI-TOF MS-based identification of all yeast isolates was performed with the ethanol/formic acid extraction protocol according to Bruker Daltonics (Bremen, Germany). The susceptibility profiles of 201 isolates to amphotericin B, itraconazole, fluconazole, voriconazole, anidulafungin, caspofungin, posaconazole, and isavuconazole were tested using CLSI standard broth microdilution method (M27-A3 and M27 S4) guidelines. Statistical analyses were performed with the statistical package SPSS 19.0.

RESULTS

A total of 187 patients with 201 episodes of candidemia were identified. Candida albicans was the most common species isolated (33.8 %; n = 68), whereas non-albicans Candida species represented 66.2 % (n = 133) of the episodes. The species distribution and outcome of candidemia showed a difference in the crude mortality between patients infected with C. albicans (n = 30; 45.5 %) and non-albicans Candida species. For example, C. parapsilosis candidemia was associated with the lowest mortality rate (40.6 %), and patients with other non-albicans species had the highest mortality rate (68-71.4 %). High mortality rates were observed among pediatric (<1 year of age) and elderly patients (>60 years of age). All strains showed low minimum inhibitory concentrations (MICs) (MIC90 of 0.063 μg/ml) to isavuconazole. The overall resistance to voriconazole in vitro antifungal activity was 2.5 %. C. glabrata (n = 38) had an MIC90 of 8 μg/ml for fluconazole. Most yeast isolates were susceptible to anidulafungin (>99.5 %) and 81.1 % to caspofungin. Resistance to anidulafungin was detected in 1/8 (12.5 %) isolates of C. orthopsilosis. According to new Clinical and Laboratory Standards Institute (CLSI) breakpoints, C. glabrata (n = 38) showed 100 % resistance, and 37/68 (54.4 %) C. albicans isolates were susceptible dose dependent (SDD) to caspofungin. Identification by MALDI-TOF MS was in 100 % concordance with molecular identification.

CONCLUSION

The Middle East epidemiology of candidemia has a unique species distribution pattern distinct from other parts of the globe. High mortality rates were observed among pediatric (<1 year of age) and elderly patients (>60 years of age). All strains were susceptible to isavuconazole. All isolates of C.glabrata were resistant to caspofungin based on M27 S4. MALDI-TOF MS is a highly useful method for the routine identification of yeast isolates in clinical setting to achieve successful therapeutic treatment.

Diagnostic performance of 1→3-β-d-glucan in neonatal and pediatric patients with Candidemia

Fungal sepsis is one of the major problems in neonatal and pediatric care unit settings. The availability of new diagnostic techniques could allow medical practitioners to rapidly identify septic patients and to improve their outcome. The aim of this study was to evaluate the performance of the 1→3-β-d-glucan (BDG), individually and in comparison with the Candida mannan (CM) antigen, in ten preterm infants and five onco-haematological pediatric patients with Candida bloodstream infections already proven by positive culture. The serum levels of BDG were >80 pg/mL on the same day as a positive blood culture in all examined patients, while CM antigen was negative in the patients with C. parapsilosis fungemia and in one further case due to C. albicans. These results suggest that a regular monitoring of serum circulating antigens (i.e., 1→3-β-d-glucan) combined with other microbiological and clinical information, may allow earlier and accurate diagnosis. However, further studies are necessary to confirm its usefulness in routine clinical practice.