The Impact of Biofilm Formation on the Persistence of Candidemia

Candidemia in Adult Patients in the ICU: A Reappraisal of Susceptibility Testing and Antifungal Therapy

OBJECTIVE

To provide updates on the epidemiology and recommendations for management of candidemia in patients with critical illness.

DATA SOURCES

A literature search using the PubMed database (inception to March 2023) was conducted using the search terms "invasive candidiasis," "candidemia," "critically ill," "azoles," "echinocandin," "antifungal agents," "rapid diagnostics," "antifungal susceptibility testing," "therapeutic drug monitoring," "antifungal dosing," "persistent candidemia," and "Candida biofilm."

STUDY SELECTION/DATA EXTRACTION

Clinical data were limited to those published in the English language. Ongoing trials were identified through ClinicalTrials.gov.

DATA SYNTHESIS

A total of 109 articles were reviewed including 25 pharmacokinetic/pharmacodynamic studies and 30 studies including patient data, 13 of which were randomized controlled clinical trials. The remaining 54 articles included fungal surveillance data, in vitro studies, review articles, and survey data. The current 2016 Infectious Diseases Society of America (IDSA) Clinical Practice Guideline for the Management of Candidiasis provides recommendations for selecting empiric and definitive antifungal therapies for candidemia, but data are limited regarding optimized dosing strategies in critically ill patients with dynamic pharmacokinetic changes or persistent candidemia complicated.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Outcomes due to candidemia remain poor despite improved diagnostic platforms, antifungal susceptibility testing, and antifungal therapy selection for candidemia in critically ill patients. Earlier detection and identification of the species causing candidemia combined with recognition of patient-specific factors leading to dosing discrepancies are crucial to improving outcomes in critically ill patients with candidemia.

CONCLUSIONS

Treatment of candidemia in critically ill patients must account for the incidence of non-albicans Candida species and trends in antifungal resistance as well as overcome the complex pathophysiologic changes to avoid suboptimal antifungal exposure.

Understanding fluconazole tolerance in Candida albicans: implications for effective treatment of candidiasis and combating invasive fungal infections

OBJECTIVES

Fluconazole (FLC) tolerant phenotypes in Candida species contribute to persistent candidemia and the emergence of FLC resistance. Therefore, making FLC fungicidal and eliminating FLC tolerance are important for treating invasive fungal diseases (IFDs) caused by Candida species. However, the mechanisms of FLC tolerance in Candida species remain to be fully explored.

METHODS

This review discusses the high incidence of FLC tolerance in Candida species and the importance of successfully clearing FLC tolerance in treating candidiasis. We further define and characterize FLC tolerance in C. albicans.

RESULTS

This review identifies global factors affecting FLC tolerance and suggest that FLC tolerance is a strategy of C. albicans response to FLC damage whose mechanism differs from FLC resistance.

CONCLUSIONS

This review highlights the significance of the cell membrane and cell wall integrity in FLC tolerance, guiding approaches to combat IFDs caused by Candida species..

K-aurein: A notable aurein 1.2-derived peptide that modulates Candida albicans filamentation and reduces biofilm biomass

Candida albicans is considered one of the most important opportunistic fungi due to the large arsenal of virulence factors that help throughout the progress of the infection. In this sense, antimicrobial peptides (AMPs) appear as an alternative, with great antifungal action. Among these, aurein 1.2 has been widely explored, becoming the basis for the discovery of new AMPs, such as K-aurein (K-au). Thus, this study evaluated the anti-C. albicans potential of K-au against virulence factors, planktonic growth, and biofilm formation of clinical isolates. Firstly, K-au antifungal activity was determined by the microdilution method and time-kill curve. The inhibition of hydrolytic enzyme secretion (proteinase, phospholipase, and hemolysin) and germ tube formation was tested. Then, the antibiofilm potential of K-au was verified through biomass quantification and scanning electron microscopy (SEM). All tests were compared with the classical antifungal drug, amphotericin B (AmB). The outcomes showed fungicidal action of K-au at 62.50 µg mL-1 for all isolates, with a time of action around 150-180 min, determined by the time-kill curve. K-au-treated cells decreased by around 40% of the germinative tube compared to the control. Additionally, K-au inhibited the biofilm formation by more than 90% compared to AmB and the control group. SEM images show apparent cellular disaggregation without the formation of filamentous structures. Therefore, the findings suggest a promising anti-C. albicans effect of K-au due to its fungicidal activity against planktonic cells, or its ability to inhibit important virulence factors like germ tube and biofilm formation. Thus, this peptide could be explored as a useful compound against C. albicans-related infection.

Antifungal activity of cisatracurium against fluconazole-resistant Candida isolates and its antibiofilm effects

Aim: To evaluate the antifungal activity of cisatracurium against Candida spp. resistant to fluconazole strains in planktonic and biofilm forms, in addition to determining its mechanism of action. Materials & methods: Antifungal activity and pharmacological interactions were determined using broth microdilution methods and the mechanism of action was evaluated by flow cytometry and molecular docking. Results: Cisatracurium presented antifungal activity against Candida spp. planktonic cells due to alterations of mitochondrial transmembrane potential leading to cellular apoptosis in addition to interacting with important targets related to cellular respiration, membrane and cell wall evidenced by molecular docking. Furthermore, the drug both prevented biofilm formation and impaired mature biofilms. Conclusion: Cisatracurium exhibits potential antifungal activity against Candida spp.

Epidemiology, antifungal susceptibility, risk factors, and mortality of persistent candidemia in adult patients in China: a 6-year multicenter retrospective study

BACKGROUND

Data on persistent candidemia (PC), a recognized complication of candidemia, are lacking in China. This study aimed to investigate the clinical characteristics and risk factors for the mortality of PC among adults in China.

METHODS

This 6-year retrospective study analyzed the prevalence, species distribution, antifungal susceptibility, risk factors, and patient mortality of PC among adults in three regional tertiary teaching hospitals in China from 2016 to 2021. We collected electronic laboratory records data of PC and non-PC patients and used the Student test or Mann-Whitney U test for a retrospective study. Logistic regression was used to identify risk factors associated with persistent candidemia.

RESULTS

The definition of PC was fulfilled by 36 patients (13.7%, 36/263). The mean age of the patients was 59.9 years (60 years for patients with PC; 59.8 years for those with non-PC; P > 0.05) and 131 (60.1%) were men [16 with PC (44.4%), 115 with non-PC (63.2%), P < 0.05]. The mean annual incidence was 0.15/1000 admissions (including PC 0.03/1000 admissions vs. non-PC 0.12/1000 admissions, P < 0.05). Candida parapsilosis (14/36, 38.9%) and Candida albicans (81/182, 44.5%) were the predominant pathogens in patients with PC and non-PC, respectively. Most isolates were susceptible to flucytosine (99.0%) and amphotericin B (99.5%), and the activity of antifungal agents against Candida species was not statistically significantly different between patients with PC and non-PC (P > 0.05). The 30-day mortality rate was 20.2% (16.7% with PC vs. 20.9% with non-PC, P > 0.05). Multivariable regression analysis showed that use of broad-spectrum antibiotics (odds ratio (OR), 5.925; 95% confidence interval (CI), 1.886-18.616, P = 0.002), fluconazole (OR, 3.389; 95% CI, 1.302-8.820, P = 0.012) and C. parapsilosis infection (OR, 6.143; 95% CI, 2.093-18.031, P = 0.001) were independent predictors of PC, sex (male) (OR, 0.199; 95% CI, 0.077-0.518, P = 0.001) was the protective factor for PC. Respiratory dysfunction (OR, 5.763; 95% CI, 1.592-20.864, P = 0.008) and length of hospital stay(OR, 0.925; 95% CI, 0.880-0.973, P = 0.002) were independent predictors of 30-day mortality in patients with non-PC. C. tropicalis bloodstream infection (OR, 12.642; 95% CI, 1.059-150.951; P = 0.045) was an independent predictor of 30-day mortality in patients with PC.

CONCLUSIONS

The epidemiological data of patients with PC and non-PC were different in the distribution of Candida species, the mean annual incidence and independent predictors of 30-day mortality. Flucytosine and amphotericin B could be used as first-choice drugs in the presence of PC infections.

Secreted aspartyl proteases family: a perspective review on the regulation of fungal pathogenesis

Secreted aspartyl proteases (SAPs) are important enzymes for fungal pathogenicity, playing a significant role in infection and survival. This article provides insight into how SAPs facilitate the transformation of yeast cells into hyphae and engage in biofilm formation, invasion and degradation of host cells and proteins. SAPs and their isoenzymes are prevalent during fungal infections, making them a potential target for antifungal and antibiofilm therapies. By targeting SAPs, critical stages of fungal pathogenesis such as adhesion, hyphal development, biofilm formation, host invasion and immune evasion can potentially be disrupted. Developing therapies that target SAPs could provide an effective treatment option for a wide range of fungal infections.

Polymicrobial Infections and Biofilms: Clinical Significance and Eradication Strategies

Biofilms are population of cells growing in a coordinated manner and exhibiting resistance towards hostile environments. The infections associated with biofilms are difficult to control owing to the chronicity of infections and the emergence of antibiotic resistance. Most microbial infections are contributed by polymicrobial or mixed species interactions, such as those observed in chronic wound infections, otitis media, dental caries, and cystic fibrosis. This review focuses on the polymicrobial interactions among bacterial-bacterial, bacterial-fungal, and fungal-fungal aggregations based on in vitro and in vivo models and different therapeutic interventions available for polymicrobial biofilms. Deciphering the mechanisms of polymicrobial interactions and microbial diversity in chronic infections is very helpful in anti-microbial research. Together, we have discussed the role of metagenomic approaches in studying polymicrobial biofilms. The outstanding progress made in polymicrobial research, especially the model systems and application of metagenomics for detecting, preventing, and controlling infections, are reviewed.

Pediatric Candida Bloodstream Infections Complicated with Mixed and Subsequent Bacteremia: The Clinical Characteristics and Impacts on Outcomes

Background: Pediatricians face a therapeutic challenge when patients with Candida bloodstream infections (BSIs) simultaneously have positive bacterial culture. We aim to characterize the clinical characteristics of pediatric Candida BSIs complicated with mixed bacteremia and subsequent bacterial infections, risk factors and impacts on outcomes. Methods: All episodes of pediatric Candida BSIs between 2005 and 2020 from a medical center in Taiwan were reviewed. Mixed Candida/bacterial BSIs were defined as isolation of a bacterial pathogen from blood cultures obtained within 48 h before or after the onset of Candida BSI. The clinical features and impacts of mixed Candida/bacterial BSIs were investigated. Results: During the study period, 320 patients with a total of 365 episodes of Candida BSIs were identified and analyzed. Mixed Candida/bacterial BSIs were 35 episodes (9.6%). No significant difference was found between mixed Candida/bacterial BSIs and monomicrobial Candida BSIs in terms of patient demographics, Candida species distributions, most chronic comorbidities or risk factors. Patients with mixed Candida/bacterial BSIs were associated with a significantly higher risk of subsequent bacteremia (51.4% vs. 21.2%, p < 0.001) and a relatively higher candidemia-attributable mortality rate (37.2% vs. 22.4%, p = 0.061) than those with monomicrobial Candida BSIs. Mixed Candida/bacterial BSIs were not an independent risk factor of treatment failure or final mortality according to multivariate logistic regression analyses. Conclusions: The clinical significance of mixed Candida/bacterial BSIs in children included a longer duration of septic symptoms, significantly higher likelihood to have subsequent bacteremia, and relatively higher risk of candidemia attributable mortality.

Targeting Virulence Factors of Candida albicans with Natural Products

Natural products derived from natural resources, including nutritional functional food, play an important role in human health. In recent years, the study of anti-fungal and other properties of agri-foods and derived functional compounds has been a hot research topic. Candida albicans is a parasitic fungus that thrives on human mucosal surfaces, which are colonized through opportunistic infection. It is the most prevalent cause of invasive fungal infection in immunocompromised individuals, resulting in a wide variety of clinical symptoms. Moreover, the efficacy of classical therapeutic medications such as fluconazole is often limited by the development of resistance. There is an ongoing need for the development of novel and effective antifungal therapy and medications. Infection of C. albicans is influenced by a great quantity of virulence factors, like adhesion, invasion-promoting enzymes, mycelial growth, and phenotypic change, and among others. Furthermore, various natural products especially from food sources that target C. albicans virulence factors have been researched, providing promising prospects for C. albicans prevention and treatment. In this review, we discuss the virulence factors of C. albicans and how functional foods and derived functional compounds affect them. Our hope is that this review will stimulate additional thoughts and suggestions regarding nutritional functional food and therapeutic development for patients afflicted with C. albicans.

Biofilm formation of Candida isolates from xerostomic post-radiotherapy head and neck cancer patients

Oral candidiasis is a common problem in post-radiation head and neck cancer (HNC) patients. While biofilm formation is a crucial virulence factor for Candida colonization, existing information on biofilm formation capability of Candida in cancer patients is scarce.

OBJECTIVE

To evaluate biofilm formation capability of Candida spp. colonized in xerostomic post-radiotherapy HNC patients.

DESIGN

Candida albicans and non-albicans Candida species were previously isolated from xerostomic post-radiation cancer patients and healthy individuals. Biofilm mass and biofilm metabolic activity were investigated by crystal violet and MTT assays, respectively. Their relationship with clinical parameters was analyzed using Mann-Whitney U and Chi-square tests.

RESULTS

A total of 109 and 45 Candida isolates from 64 cancer patients and 34 controls, respectively, were evaluated. Both biofilm mass and metabolic activity of Candida isolates from cancer patients were higher than those from controls. The between-group differences were statistically significant in C. albicans (p < 0.001) for biofilm mass, and in C. tropicalis (p = 0.01) for biofilm metabolic activity. Overall, C. tropicalis was the best biofilm producers in both groups. Additionally, we found that higher biofilm formation among C. albicans was associated with low saliva buffering capacity.

CONCLUSIONS

C. albicans and C. tropicalis isolated from xerostomic post-radiation cancer patients had higher biofilm formation capability than those from healthy individuals. Our findings suggest that, in addition to compromised host factors, higher biofilm formation capability may also contribute to the pathogenesis of oral candidiasis in HNC patients. This novel information potentially adds to proper management for these patients.

Clinical and Microbiological Characteristics of Neonates with Candidemia and Impacts of Therapeutic Strategies on the Outcomes

Neonatal candidemia is associated with significant morbidities and a high mortality rate. We aimed to investigate the clinical characteristics of Candida bloodstream infections in neonates and the impact of therapeutic strategies on the outcomes. We identified all the neonates with candidemia from a medical center in Taiwan over an 18-year period (2003−2021) and analyzed them. Clinical isolates were confirmed by DNA sequencing, and antifungal susceptibility testing was performed. The prognostic factors associated with clinical treatment failure (30-day, all-cause mortality and persistent candidemia > 72 h after antifungal agents) and in-hospital mortality were analyzed using logistic regression modeling. A total of 123 neonates with 139 episodes of candidemia were included in the study. The median (IQR) gestational age and birth weight of the neonates with candidemia were 29.0 (26.0−35.0) weeks and 1104.0 (762.0−2055) g, respectively. The most common Candida spp. was Candida albicans (n = 57, 41.0%), followed by C. parapsilosis (n = 44, 31.7%), Candida guilliermondii (n = 12, 8.6%), and C. glabrata (n = 11, 7.9%). The overall susceptibility to fluconazole was 81.3%, and the resistant rates against other antifungal agents were less than 3%. The cumulative mortality rate at 7 and 30 days after the first episode of candidemia was 11.3% and 32.3%, respectively. The overall in-hospital mortality rate was 42.3%. The treatment outcomes did not change over the study period and were not affected by delayed initiation of antifungal agents. Multivariate analysis showed that delayed catheter removal (odds ratio [OR], 5.54; 95% confidence interval [CI]: 1.93−15.86, p = 0.001), septic shock (OR, 7.88; 95% CI: 2.83−21.93, p < 0.001), and multiple chronic comorbidities (OR, 8.71; 95% CI: 1.82−41.81, p = 0.007) were independently associated with the final in-hospital mortality. We concluded that the overall mortality of neonatal candidemia has remained consistently high over the past decade. Prompt early catheter removal and an aggressive treatment strategy for neonatal candidemia with septic shock would be critical to improving patient outcomes.

Exebacase: A Novel Approach to the Treatment of Staphylococcal Infections

Lysins are bacteriophage-derived enzymes that degrade essential components of bacteria. Exebacase (Lysin CF-301) is an attractive antimicrobial agent because it demonstrates rapid bacteriolytic activity against staphylococcal species, including Staphylococcus aureus, has a low resistance profile, eradicates biofilms, and acts synergistically with other antibiotics. Combinations including exebacase and standard of care antibiotics represent an alternative to antibiotic monotherapies currently used to treat invasive staphylococcal infections. This manuscript reviews what is known about exebacase and explores how this novel agent may be used in the future to treat human bacterial pathogens.

Recent Developments on Using Nanomaterials to Combat Candida albicans

Vaginal candidiasis (VC) is a common disease of women and the main pathogen is Candida albicans (C. albicans). C. albicans infection incidence especially its drug resistance have become a global health threat due to the existence of C. albicans biofilms and the low bioavailability of traditional antifungal drugs. In recent years, nanomaterials have made great progresses in the field of antifungal applications. Some researchers have treated fungal infections with inorganic nanoparticles, represented by silver nanoparticles (AgNPs) with antifungal properties. Liposomes, polymeric nanoparticles, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs) were also used to improve the bioavailability of antifungal drugs. Herein, we briefly introduced the recent developments on using above nanomaterials to combat C. albicans in antifungal applications.

The Glucocorticoid PYED-1 Disrupts Mature Biofilms of Candida spp. and Inhibits Hyphal Development in Candida albicans

Invasive Candida infections have become a global public health problem due to the increase of Candida species resistant against antifungal therapeutics. The glucocorticoid PYED-1 (pregnadiene-11-hydroxy-16α,17α-epoxy-3,20-dione-1) has antimicrobial activity against various bacterial taxa. Consequently, it might be considered for the treatment of Candida infections. The antifungal activity of PYED-1 was evaluated against several fungal strains that were representative of the five species that causes the majority of Candida infections-namely, Candida albicans, Candida glabrata, Candida tropicalis, Candida parapsilosis and Candida krusei. PYED-1 exhibited a weak antifungal activity and a fungistatic effect on all five Candida species. On the other hand, PYED-1 exhibited a good anti-biofilm activity, and was able to eradicate the preformed biofilms of all Candida species analyzed. Moreover, PYED-1 inhibited germ tube and hyphae formation of C. albicans and reduced adhesion of C. albicans to abiotic surfaces by up to 30%.

Modified Pitt bacteremia score for predicting mortality in patients with candidaemia: A multicentre seven-year retrospective study conducted in Japan

BACKGROUND

Several severity indexes have been reported for critically ill patients. The Pitt bacteremia score (PBS) is commonly used to predict the risk of mortality in patients with bacteraemia.

OBJECTIVES

To develop a scoring system for predicting mortality in candidaemia patients.

METHODS

Medical records at five Japanese tertiary hospitals were reviewed. Factors associated with mortality were analysed using logistic regression modelling. The discriminatory power of scoring models was evaluated by assessing the area under the receiver operating characteristic curve (AUC), net reclassification improvement (NRI) and integrated discrimination improvement (IDI).

RESULTS

In total, 422 candidaemia patients were included. Higher PBS, dialysis and retainment of central venous catheter were independent risk factors for all-cause 30-day mortality. However, among the five PBS components, fever was not associated with mortality; therefore, we developed a modified version of the PBS (mPBS) by replacing fever with dialysis. AUC for PBS and mPBS were 0.74 (95% confidence interval [CI]: 0.68-0.80) and 0.76 (95% CI: 0.71-0.82), respectively. The increase in predictive ability of mPBS for 30-day mortality was statistically significant as assessed by NRI (0.24, 95% CI: 0.01-0.46, p = .04) and IRI (0.04, 95% CI: 0.02-0.06, p = .0008). When patients were stratified by mPBS into low (scores 0-3), moderate (4-7) and high risk (≥8), there were significant differences among the survival curves (p < .0001, log-rank test), and 30-day mortality rates were 13.8% (40/290), 36.8% (28/76) and 69.4% (34/49), respectively.

CONCLUSIONS

mPBS can be a useful tool for predicting mortality in candidaemia patients.

Rapid detection of biofilm-producing Candida species via MALDI-TOF mass spectrometry

AIMS

The aim of this study was to evaluate the formation of biofilm by Candida spp. isolated from the bloodstream, using traditional spectrophotometric methodologies. In addition, the goal was to compare the results with those obtained through MALDI-TOF/MS, as well as to verify its use as a potential tool for the detection of biofilm-forming strains.

METHODS AND RESULTS

Hundred and thirteen isolates of Candida spp. were studied: 41 were Candida albicans, 27 C. tropicalis, 18 C. glabrata, 17 C. parapsilosis and 10 C. krusei. Metabolic activity was determined through the tetrazolium salt (XTT) reduction assay and biomass by staining with Crystal Violet. All isolates were able to form biofilm, 94% of which were strong producers, with high biomass quantification (95%; 107/113) and high metabolic activity (99%; 112/113). Mass spectra of the biofilm-producing isolates showed differences in the intensity of mass peaks when compared with the spectra of the nonproducing strains.

CONCLUSIONS

It was demonstrated that MALDI-TOF/MS was able to detect specific biofilm proteins, as the mass spectra of the isolates presented differences when compared with nonproducing strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

MALDI-TOF/MS can become a valuable tool for biofilm detection at the moment of the identification of the microorganism, thus contributing greatly to the management of patients with Candidemia.

Transcription Factors of CAT1, EFG1, and BCR1 Are Effective in Persister Cells of Candida albicans-Associated HIV-Positive and Chemotherapy Patients

Background

Biofilm is an accumulation of cells, which are formed on mucosal surfaces of the host as well as on medical devices. The inherent resistance of Candida strains producing biofilms to antimicrobial agents is an important and key feature for biofilm growth, which can lead to treatment failure. This resistance is due to the regulatory increase of the output pumps, the presence of extracellular matrix, and the existence of persister cells. Persister cells are phenotypic variants that have MICs similar to antibiotic-sensitive populations and are able to tolerate high doses of antibiotics. The current study investigated the possible role of EFG1, BCR1, and CAT1 in the establishment or maintenance of persister cells in Candida albicans strains that produce biofilms.

Methods

After identifying Candida isolates by molecular methods, C. albicans isolates were confirmed by sequencing. Isolation of persister cells and determination of their MIC were performed by microdilution method. Then, RNA extraction and cDNA synthesis were performed from 60 C. albicans isolates under promoting and inducing conditions. Afterward, the mean expression of BCR1, EFG1, and CAT1 genes in both persister and non-persister groups was calculated using real-time qPCR. Phylogeny tree of persister and non-persister group isolates was drawn using ITS fragment.

Results

A total of 77 persister isolates were taken from the oral cavity of HIV patients as well as from patients undergoing chemotherapy. Biofilm intensity in persister isolates separated from HIV-infected patients was different from the non-persister group. The mean fold change of BCR1 (10.73), CAT1 (15.34), and EFG1 (2.41) genes in persister isolates was significantly higher than these genes in isolates without persister.

Conclusion

It can be concluded that the most important factor in the production of persister cells is biofilm binding and production, not biofilm development or mature biofilm production, which was found in the expression of BCR1 gene without change in the expression of EFG1 gene in the persister group. Also, catalase plays an essential role in the production of persister in C. albicans biofilm producers with ROS detoxification.

Prevalence and Impact of Biofilms on Bloodstream and Urinary Tract Infections: A Systematic Review and Meta-Analysis

This study sought to assess the prevalence and impact of biofilms on two commonly biofilm-related infections, bloodstream and urinary tract infections (BSI and UTI). Separated systematic reviews and meta-analyses of observational studies were carried out in PubMed and Web of Sciences databases from January 2005 to May 2020, following PRISMA protocols. Studies were selected according to specific and defined inclusion/exclusion criteria. The obtained outcomes were grouped into biofilm production (BFP) prevalence, BFP in resistant vs. susceptible strains, persistent vs. non-persistent BSI, survivor vs. non-survivor patients with BSI, and catheter-associated UTI (CAUTI) vs. non-CAUTI. Single-arm and two-arm analyses were conducted for data analysis. In vitro BFP in BSI was highly related to resistant strains (odds ratio-OR: 2.68; 95% confidence intervals-CI: 1.60–4.47; p < 0.01), especially for methicillin-resistant Staphylococci. BFP was also highly linked to BSI persistence (OR: 2.65; 95% CI: 1.28–5.48; p < 0.01) and even to mortality (OR: 2.05; 95% CI: 1.53–2.74; p < 0.01). Candida spp. was the microorganism group where the highest associations were observed. Biofilms seem to impact Candida BSI independently from clinical differences, including treatment interventions. Regarding UTI, multi-drug resistant and extended-spectrum β-lactamase-producing strains of Escherichia coli, were linked to a great BFP prevalence (OR: 2.92; 95% CI: 1.30–6.54; p < 0.01 and OR: 2.80; 95% CI: 1.33–5.86; p < 0.01). More in vitro BFP was shown in CAUTI compared to non-CAUTI, but with less statistical confidence (OR: 2.61; 95% CI: 0.67–10.17; p < 0.17). This study highlights that biofilms must be recognized as a BSI and UTI resistance factor as well as a BSI virulence factor.

"Azole menace"-An underappreciated trigger perpetuating the epidemic of antifungal therapeutic failure in cutaneous mycoses

The South-Asian epidemic of anti-fungal therapeutic failures (AFTF) is on the rise. Although many demographic, environmental, and socioeconomic factors have been implicated in the genesis of this problem, two pharmacological issues warrant attention. While detailed discussions on the role of topical corticosteroid (TCS) in the changing landscape of the superficial mycotic infections in this region have been making headlines, another equally, rather more important pharmacological factor seems to have been undermined by the hype around TCS. The fastidious pharmacokinetic properties and related practical aspects of the triazole group of oral and topical antifungals, especially oral itraconazole seem to contribute significantly to the persistence of AFTF epidemic. In this paper, we shall discuss the broad aspects of the spectral precariousness of oral triazole antifungals with special emphasis to itraconazole, a concept known as the "azole menace" in the overall pathogenesis and tenacity of the AFTF epidemic.

Effect of antifungal agents, lysozyme and human antimicrobial peptide LL-37 on clinical Candida isolates with high biofilm production

Introduction. Candida species can form biofilms on tissues and medical devices, making them less susceptible to antifungal agents.Hypothesis/Gap Statement. Antifungal combination may be an effective strategy to fight against Candida biofilm.Aim. In this study, we investigated the in vitro activity of fluconazole, caspofungin and amphotericin B, alone and in combination, against 17 clinical Candida tropicalis and 6 Candida parapsilosis isolates with high biofilm formation. We also tested LL-37 and lysozyme for anti-biofilm activity against a selected C. tropicalis isolate.Methodology. Candida biofilms were prepared using the 96-well plate-based method. The minimum biofilm eradication concentrations were determined for single and combined antifungal drugs. The activity of LL-37 and lysozyme was determined by visual reading for planktonic cells and using the XTT assay for biofilms.Results. Under biofilm conditions, fluconazole plus caspofungin showed synergistic effects against 60.9% (14 of 23) of the tested isolates, including 70.6% of C. tropicalis [fractional inhibitory concentration index (FICI), 0.26-1.03] and 33.3% of C. parapsilosis (FICI, 0.04-2.03) isolates. Using this combination, no antagonism was observed. Amphotericin B plus caspofungin showed no effects against 78.3% (18 of 23) of the tested isolates. Amphotericin B plus fluconazole showed no effects against 65.2% (15 of 23) of the tested isolates and may have led to antagonism against 2 C. tropicalis and 2 C. parapsilosis isolates. LL-37 and lysozyme had no effect on biofilms of the selected C. tropicalis isolate.Conclusions. We found that fluconazole plus caspofungin led to a synergistic effect against C. tropicalis and C. parapsilosis biofilms. The efficacy of the antifungal combination therapies of the proposed schemes against biofilm-associated Candida infections requires careful and constant evaluation.

Fungicidal Activity of a Safe 1,3,4-Oxadiazole Derivative Against Candida albicans

Candida albicans is the most common species isolated from nosocomial bloodstream infections. Due to limited therapeutic arsenal and increase of drug resistance, there is an urgent need for new antifungals. Therefore, the antifungal activity against C. albicans and in vivo toxicity of a 1,3,4-oxadiazole compound (LMM6) was evaluated. This compound was selected by in silico approach based on chemical similarity. LMM6 was highly effective against several clinical C. albicans isolates, with minimum inhibitory concentration values ranging from 8 to 32 µg/mL. This compound also showed synergic effect with amphotericin B and caspofungin. In addition, quantitative assay showed that LMM6 exhibited a fungicidal profile and a promising anti-biofilm activity, pointing to its therapeutic potential. The evaluation of acute toxicity indicated that LMM6 is safe for preclinical trials. No mortality and no alterations in the investigated parameters were observed. In addition, no substantial alteration was found in Hippocratic screening, biochemical or hematological analyzes. LMM6 (5 mg/kg twice a day) was able to reduce both spleen and kidneys fungal burden and further, promoted the suppresses of inflammatory cytokines, resulting in infection control. These preclinical findings support future application of LMM6 as potential antifungal in the treatment of invasive candidiasis.

Candida albicans biofilms and polymicrobial interactions

Candida albicans is a common fungus of the human microbiota. While generally a harmless commensal in healthy individuals, several factors can lead to its overgrowth and cause a range of complications within the host, from localized superficial infections to systemic life-threatening disseminated candidiasis. A major virulence factor of C. albicans is its ability to form biofilms, a closely packed community of cells that can grow on both abiotic and biotic substrates, including implanted medical devices and mucosal surfaces. These biofilms are extremely hard to eradicate, are resistant to conventional antifungal treatment and are associated with high morbidity and mortality rates, making biofilm-associated infections a major clinical challenge. Here, we review the current knowledge of the processes involved in C. albicans biofilm formation and development, including the central processes of adhesion, extracellular matrix production and the transcriptional network that regulates biofilm development. We also consider the advantages of the biofilm lifestyle and explore polymicrobial interactions within multispecies biofilms that are formed by C. albicans and selected microbial species.

Caspofungin and Polymyxin B Reduce the Cell Viability and Total Biomass of Mixed Biofilms of Carbapenem-Resistant Pseudomonas aeruginosa and Candida spp

Pseudomonas aeruginosa and Candida spp. are biofilm-forming pathogens commonly found colonizing medical devices, being mainly associated with pneumonia and bloodstream infections. The coinfection by these pathogens presents higher mortality rates when compared to those caused by a single microbial species. This study aimed to evaluate the antibiofilm activity of echinocandins and polymyxin B (PMB) against polymicrobial biofilms of carbapenem-resistant (CR) Pseudomonas aeruginosa and Candida spp. (C. albicans, C. parapsilosis, C. tropicalis, and C. glabrata). In addition, we tested the antimicrobial effect on their planktonic and monomicrobial biofilm counterparties. Interestingly, beyond inhibition of planktonic [minimum inhibitory concentration (MIC) = 0.5 μg/ml] and biofilm [minimum biofilm inhibitory concentration (MBIC)₅₀ ≤ 2–8 μg/ml] growth of P. aeruginosa, PMB was also effective against planktonic cells of C. tropicalis (MIC = 2 μg/ml), and polymicrobial biofilms of CR P. aeruginosa with C. tropicalis (MBIC₅₀ ≤ 2 μg/ml), C. parapsilosis (MBIC₅₀ = 4–16 μg/ml), C. glabrata (MBIC₅₀ = 8–16 μg/ml), or C. albicans (MBIC₅₀ = 8–64 μg/ml). On the other hand, while micafungin (MFG) showed highest inhibitory activity against planktonic (MIC ≤ 0.008–0.5 μg/ml) and biofilm (MBIC₅₀ ≤ 2–16 μg/ml) growth of Candida spp.; caspofungin (CAS) displays inhibitory activity against planktonic cells (MIC = 0.03–0.25 μg/ml) and monomicrobial biofilms (MBIC₅₀ ≤ 2–64 μg/ml) of Candida spp., and notably on planktonic and monomicrobial biofilms of CR P. aeruginosa (MIC or MBIC₅₀ ≥ 64 μg/ml). Particularly, for mixed biofilms, while CAS reduced significantly viable cell counts of CR P. aeruginosa and Candida spp. at ≥32 and ≥ 2 μg/ml, respectively; PMB was effective in reducing viable cells of CR P. aeruginosa at ≥2 μg/ml and Candida spp. at ≥8 μg/ml. Similar reduction of viable cells was observed for CAS (32–64 μg/ml) combined with PMB (2 μg/ml). These findings highlight the potential of PMB and CAS for the treatment of polymicrobial infections caused by Candida spp. and critical priority CR P. aeruginosa.

Coexistence of Pseudomonas aeruginosa With Candida albicans Enhances Biofilm Thickness Through Alginate-Related Extracellular Matrix but Is Attenuated by N-acetyl-l-cysteine

Bacteria and Candidaalbicans are prominent gut microbiota, and the translocation of these organisms into blood circulation might induce mixed-organism biofilms, which warrants the exploration of mixed- versus single-organism biofilms in vitro and in vivo. In single-organism biofilms, Acinetobacter baumannii and Pseudomonas aeruginosa (PA) produced the least and the most prominent biofilms, respectively. C. albicans with P. aeruginosa (PA+CA) induced the highest biofilms among mixed-organism groups as determined by crystal violet straining. The sessile form of PA+CA induced higher macrophage responses than sessile PA, which supports enhanced immune activation toward mixed-organism biofilms. In addition, Candida incubated in pre-formed Pseudomonas biofilms (PA>CA) produced even higher biofilms than PA+CA (simultaneous incubation of both organisms) as determined by fluorescent staining on biofilm matrix (AF647 color). Despite the initially lower bacteria during preparation, bacterial burdens by culture in mixed-organism biofilms (PA+CA and PA>CA) were not different from biofilms of PA alone, supporting Candida-enhanced Pseudomonas growth. Moreover, proteomic analysis in PA>CA biofilms demonstrated high AlgU and mucA with low mucB when compared with PA alone or PA+CA, implying an alginate-related mucoid phenotype in PA>CA biofilms. Furthermore, mice with PA>CA biofilms demonstrated higher bacteremia with more severe sepsis compared with mice with PA+CA biofilms. This is possibly due to the different structures. Interestingly, l-cysteine, a biofilm matrix inhibitor, attenuated mixed-organism biofilms both in vitro and in mice. In conclusion, Candida enhanced Pseudomonas alginate–related biofilm production, and Candida presentation in pre-formed Pseudomonas biofilms might alter biofilm structures that affect clinical manifestations but was attenuated by l-cysteine.

Advances in Biomaterials for the Prevention and Disruption of Candida Biofilms

Candida species can readily colonize a multitude of indwelling devices, leading to biofilm formation. These three-dimensional, surface-associated Candida communities employ a multitude of sophisticated mechanisms to evade treatment, leading to persistent and recurrent infections with high mortality rates. Further complicating matters, the current arsenal of antifungal therapeutics that are effective against biofilms is extremely limited. Antifungal biomaterials are gaining interest as an effective strategy for combating Candida biofilm infections. In this review, we explore biomaterials developed to prevent Candida biofilm formation and those that treat existing biofilms. Surface functionalization of devices employing clinically utilized antifungals, other antifungal molecules, and antifungal polymers has been extremely effective at preventing fungi attachment, which is the first step of biofilm formation. Several mechanisms can lead to this attachment inhibition, including contact killing and release-based killing of surrounding planktonic cells. Eliminating mature biofilms is arguably much more difficult than prevention. Nanoparticles have shown the most promise in disrupting existing biofilms, with the potential to penetrate the dense fungal biofilm matrix and locally target fungal cells. We will describe recent advances in both surface functionalization and nanoparticle therapeutics for the treatment of Candida biofilms.

Challenges in Antifungal Therapy in Diabetes Mellitus

Diabetic patients have an increased propensity to Candida sp. infections due to disease-related immunosuppression and various other physiological alterations. The incidence of candidiasis has increased in number over the years and is linked to significant morbidity and mortality in critically ill and immunosuppressed patients. Treatment of infection in diabetic patients may be complicated due to the various disease-related changes to the pharmacokinetics and pharmacodynamics (PK/PD) of a drug, including antifungal agents. Application of PK/PD principles may be a sensible option to optimise antifungal dosing regimens in this group of patients. Further studies on PK/PD of antifungals in patients with diabetes mellitus are needed as current data is limited or unavailable.

Synergistic Effect of Pseudolaric Acid B with Fluconazole Against Resistant Isolates and Biofilm of Candida tropicalis

Purpose

Candida tropicalis (C. tropicalis) has emerged as an important fungal pathogen due to its increasing resistance to conventional antifungal agents, especially fluconazole (FLC). Pseudolaric acid B (PAB), a herbal-originated diterpene acid from Pseudolarix kaempferi Gordon, has been reported to possess inhibitory activity against fungus. The present study aims to investigate the antifungal effect of PAB alone and in combination with FLC on planktonic and biofilm cells of C. tropicalis.

Methods

The antifungal activity of PAB against planktonic isolates was evaluated alone and in combination with FLC using the chequerboard microdilution method and growth curve assay. The anti-biofilm effects were quantified by tetrazolium (XTT) reduction assay, which were further confirmed by scanning electron microscopy (SEM) and fluorescent microscope to observe morphological changes of biofilm treated with PAB and FLC.

Results

It was revealed that PAB alone exhibited similar inhibitory activity against FLC-resistant and FLC-susceptible strains with median MIC ranging from 8 to 16 µg/mL. When administered in combination, synergism was observed in all (13/13) FLC-resistant and (2/9) FLC-susceptible strains with FICI ranging from 0.070 to 0.375. Moreover, the concomitant use of PAB and FLC exhibited a strong dose-dependent synergistic inhibitory effect on the early and mature biofilm, eliminating more than 80% biofilm formation. SEM found that PAB, different from azoles, could significantly inhibit spore germination and destroy the cell integrity causing cell deformation, swelling, collapse and outer membrane perforation.

Conclusion

PAB was highly active against FLC-resistant isolates and biofilm of C. tropicalis, particularly when combined with FLC. These findings suggest that PAB may have potential as a novel antifungal agent with different targets from azole drugs.

Biofilm-Forming by Carbapenem Resistant Enterobacteriaceae May Contribute to the Blood Stream Infection

Bloodstream infection (BSI) due to carbapenem-resistant Enterobacteriaceae (CRE) has a high mortality rate and is a serious threat worldwide. Ten CRE strains (eight Enterobacter cloacae, one Klebsiella pneumoniae and one Citrobacter freundii) were isolated from the blood of nine patients, a percentage of whom had been treated with indwelling devices. The steps taken to establish cause included minimum inhibitory concentration (MIC) tests, a pulsed-field gel electrophoresis (PFGE), biofilm study, a multiplex PCR for resistant genes of carbapenemases and extended-spectrum beta-lactamases (ESBLs), and plasmid incompatibility typing. All strains showed a tendency toward resistance to multiple antibiotics, including carbapenems. Frequently isolated genes of ESBLs and carbapenemases include bla_TEM-1 (four strains), bla_SHV-12 (four strains) and bla_IMP-1 (six strains). A molecular analysis by PFGE was used to divide the XbaI-digested genomic DNAs of 10 CRE strains into eight patterns, and the analysis showed that three E. cloacae strains detected from two patients were either identical or closely related. The biofilm production of all CRE strains was examined using a microtiter biofilm assay, and biofilm growth in continuous flow chambers was observed via the use of a confocal laser scanning microscope. Our study indicates that biofilm formation on indwelling devices may pose a risk of BSI due to CRE.

Candida blood stream infections observed between 2011 and 2016 in a large Italian University Hospital: A time-based retrospective analysis on epidemiology, biofilm production, antifungal agents consumption and drug-susceptibility

Candida bloodstream infection (BSI) represents a growing infective problem frequently associated to biofilm production due to the utilization of intravascular devices. Candida species distribution (n = 612 strains), their biofilm production and hospital antifungal drug consumption were evaluated in different wards of a tertiary care academic hospital in Italy during the years 2011–2016. In the considered time window, an increasing number of Candida BSI (p = 0.005) and of biofilm producing strains were observed (p<0.0001). Although C. albicans was the species more frequently isolated in BSI with a major biofilm production, an increased involvement of non-albicans species was reported, particularly of C. parapsilosis that displayed a high frequency in catheter infections, and lower biofilm production compared to C. albicans. Although trends of biofilm production were substantially stable in time, a decreasing biofilm production by C. parapsilosis in the Intensive Care Unit (ICU) was observed (p = 0.0041). Principal component analysis displayed a change in antifungal drugs consumption driven by two mutually independent temporal trends, i.e. voriconazole use in the general medicine wards initially, and fluconazole use mainly in the ICU; these factors explain 68.9% and 25.7% of total variance respectively. Moreover, a significant trend (p = 0.003) in fluconazole use during the whole time period considered emerged, particularly in the ICU (p = 0.017), but also in the general medicine wards (p = 0.03). These trends paralleled with significant increase MIC90 of fluconazole (p = 0.05), particularly for C. parapsilosis in the ICU (p = 0.04), with a general and significant decreased trend of the MIC90 values of caspofungin (p = 0.04), and with significant increased MIC50 values for amphotericin B (p = 0.01) over the study period. In conclusion, drug utilization in our hospital turned out to be a putative influencing factor on the ecology of the species, on the increase in time of the biofilm producing strains and on the Candida antifungal susceptibility profile, thus influencing clinical management.

Candida auris: a comparison between planktonic and biofilm susceptibility to antifungal drugs

Introduction. Candida auris is a pathogenic yeast that mainly affects immunosuppressed patients and those with implanted medical devices. This pathogen also displays elevated resistance to common antifungals and high survival and spreading capacities. Since no antifungal breakpoints have yet been defined for this pathogen, the data obtained here can be useful for further research concerning treatment or implementation of a prevention and disinfection protocol. Our aim was to study the antifungal resistance of C. auris to current antifungals in planktonic and sessile states. Using confocal laser scanning microscopy and viable biomass production, we demonstrated the ability of C. auris to develop a mature biofilm. We compared the minimal inhibitory concentration (MIC) and the minimal biofilm eradication concentration (MBEC) for the C. auris DSM 21092 strain plus two clinical isolates, and the results were compared with those obtained for Candida albicans and Candida parapsilosis, two species strongly linked to bloodstream infections and infections associated with biomaterials. We found that the clinical isolates of C. auris were resistant to fluconazole and sensitive to echinocandins and polyenes. The C. auris biofilms did not show susceptibility to any antifungal agent, showing MBECs that were up to 512-fold higher than the MICs. These findings highlight the importance of biofilm formation as a key factor underlying the resistance of this species to antifungals and suggest that the presence of implantable medical devices is one of the major risk factors in immunocompromised patients.

Invasive candidiasis: Risk factor for mortality in a pediatric tertiary care hospital in south of Brazil

BACKGROUND

Invasive candidiasis (IC) is a major cause of morbimortality in children. Previous studies described the clinical characteristics and risk factors for this infection; however, limited data are available on the predictors of mortality in these patients. In this context, we evaluated the risk factors associated with death due to IC in a pediatric tertiary care hospital in South of Brazil.

METHODS

This is a retrospective, cross-sectional, observational, and analytical study of a series of pediatric patients with clinical and laboratory diagnosis of IC from March 2014 to September 2017. Univariate and multivariate analysis were performed to estimate the association between the characteristics of the patients and death.

RESULTS

A total of 94 cases of IC were included. The incidence was 1.13 cases per 1000 patients/d, with a mortality rate of 14%. There was a predominance of non-albicans Candida (71.3%) in IC cases and, although there is no species difference in mortality rates, biofilm formation was associated with increased mortality. Clinical characteristics such as male sex, stay in the intensive care unit, and thrombocytopenia; comorbidities such as cardiological disease and renal insufficiency; and risks such as mechanical ventilation and dialysis were associated with increased mortality.

CONCLUSION

Data from this study suggest that biofilm formation by Candida sp. is associated with increased mortality, and this is the first study to correlate the male sex and cardiological disease as risk factors for death in pediatric IC patients.

Activity of base analogues (5-fluorouracil, 5-flucytosine) against planktonic cells and mature biofilm of Candida yeast. Effect of combination with folinic acid

BACKGROUND

The increasing number of Candida infections, especially those caused by non-C. albicans species and resistant strains, is a serious medical problem.

OBJECTIVES

In this study, the antifungal activity of base analogues, 5-flucytosine (5-FC) and 5-fluorouracil (5-FU), was tested against planktonic cells as well as against mature biofilm.

METHODS

Tests were performed according the EUCAST methodology. Antibiofilm effectiveness of tested drugs was determined by the crystal violet staining method. The cytotoxicity assays was performed according to the ISO 10993-5 norm.

RESULTS

5-FC and 5-FU were effective against fifteen fluconazole resistant Candida glabrata strains with an average minimal inhibitory concentration (MIC) of 0.152mg/L and 0.39mg/L, respectively. Folinic acid (folinate- e.g., leucovorin) is a common drug used in oncology simultaneously with 5-FU. In our tests folinate was able to lower MIC for 5-FC from 0.152 to 0.058mg/L (P<0.05). In the biofilm assay 5-FU and 5-FC alone did not induce any changes in the biomass of mature biofilm. Addition of folinate to each base analogue resulted in up to 90% reduction of biomass. Viability tests show that a concentration of 64mg/L of 5-FC and 5-FU supplemented with folinate can be fungicidal against mature biofilms of some Candida isolates. No cytotoxic effect was found for combination of FOL and 5-FC.

CONCLUSION

Therapy of 5-FU+folinate is well known in cancer treatment, in this study we reveal the beneficial effect of folinate on antifungal activity of 5-FC as well as the antifungal potential of 5-FU+folinate.

Persistent Candidemia in adults: underlying causes and clinical significance in the antifungal stewardship era

To investigate the causes and the clinical significance of persistent candidemia (PC) in adults diagnosed in a tertiary hospital with an active antifungal stewardship program. Retrospective cohort including all adults with candidemia from 2010 to 2018. PC was defined as any positive follow-up blood culture (BC) obtained ≥ 5 days from the first BCs yielding the same Candida species. PC was detected in 35/255 (13.7%) patients. There were no differences regarding antifungal adequacy in PC vs. non-PC (94.3% vs. 82.3%, p = 0.084) and primary source control (63.3% vs. 76.4%, p = 0.172) at the time of the follow-up BCs. The average time until source control (2 [0-37] vs. 2 days [0-44], p = 0.311) or adequate antifungal treatment (2 [0-26] vs. 2 days [- 2-10], p = 0.748) was similar. Patients with PC had more non-ocular complications (31.4% vs. 10.5%, p = 0.002). No impact on 30-day mortality was observed (31.4% vs. 22.3%, p = 0.238). The only independent factor associated with PC was to have a previously undetected site of infection [OR 4.28, 95%CI (1.77-10.34), p = 0.001]. Persistent candidemia was not associated with inadequate or delayed therapeutic management, nor higher 30-day mortality rates. Timely screening and control of unexpected infection sources are encouraged to shorten hospitalization and improve patient care.

New N-(oxazolylmethyl)-thiazolidinedione Active against Candida albicans Biofilm: Potential Als Proteins Inhibitors

C. albicans is the most frequently occurring fungal pathogen, and is becoming an increasing public health problem, especially in the context of increased microbial resistance. This opportunistic pathogen is characterized by a versatility explained mainly by its ability to form complex biofilm structures that lead to enhanced virulence and antibiotic resistance. In this context, a review of the known C. albicans biofilm formation inhibitors were performed and a new N-(oxazolylmethyl)-thiazolidinedione scaffold was constructed. 16 new compounds were synthesized and characterized in order to confirm their proposed structures. A general antimicrobial screening against Gram-positive and Gram-negative bacteria, as well as fungi, was performed and revealed that the compounds do not have direct antimicrobial activity. The anti-biofilm activity evaluation confirmed the compounds act as selective inhibitors of C. albicans biofilm formation. In an effort to substantiate this biologic profile, we used in silico investigations which suggest that the compounds could act by binding, and thus obstructing the functions of, the C. albicans Als surface proteins, especially Als1, Als3, Als5 and Als6. Considering the well documented role of Als1 and Als3 in biofilm formation, our new class of compounds that target these proteins could represent a new approach in C. albicans infection prevention and management.