Biofilm formation by blood isolates of Candida parapsilosis sensu stricto in the presence of a hyperglycidic solution at comparable concentrations of total parenteral nutrition

Culture media influences Candida parapsilosis growth, susceptibility, and virulence

Introduction

Candida parapsilosis, a pathogenic yeast associated with systemic infections, exhibits metabolic adaptability in response to nutrient availability.

Methods

We investigated the impact of RPMI glucose supplemented (RPMId), TSB, BHI and YPD media on C. parapsilosis growth, morphology, susceptibility (caspofungin and amphotericin B), and in vivo virulence (Galleria mellonella) in planktonic and biofilm states.

Results

High-glucose media favors growth but hinders metabolic activity and filamentation. Media promoting carbohydrate production reduces biofilm susceptibility. Virulence differences between planktonic cells and biofilm suspensions from the same media shows that biofilm-related factors influence infection outcome depending on nutrient availability. Pseudohyphal growth occurred in biofilms under low oxygen and shear stress, but its presence is not exclusively correlated with virulence.

Discussion

This study provides valuable insights into the intricate interplay between nutrient availability and C. parapsilosis pathogenicity. It emphasizes the importance of considering pathogen behavior in diverse conditions when designing research protocols and therapeutic strategies.

Systematic Characterization of Epidemiology, Antifungal Susceptibility, Risk Factors and Outcomes of Candidaemia: A Six-Year Chinese Study

Background

Candida bloodstream infection (BSI), the fourth most common nosocomial BSI, is an urgent global health challenge with the tremendous growth in antifungal resistance rate and mortality rate.

Purpose

To establish the epidemiology, species distribution, risk factors, and 30-day mortality of candidaemia among 115 patients in this 6-year surveillance study.

Materials and Methods

We retrospectively analyzed the clinical characteristics, epidemiology, antifungal susceptibility patterns, and risk factors for morbidity and mortality of 115 candidaemia cases diagnosed in one tertiary care hospital from January 2016 through December 2021.

Results

Of the 115 candidaemia cases, the most prevalent species were Candida tropicalis (33.0%), followed by Candida albicans (27.8%), Candida parapsilosis complex (19.1%), and others. The overall incidence was 0.21 cases/1000 admissions. The overall crude resistance rate of Candida spp. against azoles was 20.0% (23/115), while Candida tropicalis showed a significant increase in the resistance rate to azoles (from 1/6, 16.7% in 2017 to 6/10, 60.0% in 2021). Multivariate analyses demonstrated that hematological malignancy and neutropenia were significantly associated with Candida tropicalis BSI than Candida non-tropicalis BSI. Candida albicans BSI had a significantly higher rate of previous surgery than Candida non-albicans BSI. Candida parapsilosis BSI had a significantly higher rate of receiving total parenteral nutrition (TPN). The overall 30-day mortality rate was 27.0% (31/115). The presence of high age-adjusted Charlson comorbidity index (aCCI), neutropenia, and septic shock were factors independently associated with increased 30-day mortality.

Conclusion

Candida tropicalis are emerging as the predominant isolate in candidaemia. Of note, the unexpectedly increased resistance rate to azoles in Candida tropicalis BSI was observed. The aCCI scores, neutropenia, and septic shock were independently associated with 30-day mortality. Prompt, adequate antifungal treatment among high-risk patients may lead to a reduction in mortality.

Risk factors and clinical analysis of peripherally inserted central catheter-related fungal colonization in premature infants

We aimed to analyze the risk factors of positive peripherally inserted central catheter (PICC)-related fungal colonization in preterm infants. This retrospective study collected data from 2018 to 2020. The enrolled infants who underwent PICC insertion were born at < 32 weeks’ gestation or birth weight < 1500 g. The demographics, PICC-related characteristics, and treatment information were collected. Univariate and multivariate analyses were performed to investigate risk factors for PICC-related fungal colonization. The receiver operating characteristic (ROC) curve was used to determine the optimal cut-off values for the duration of antibiotics and parenteral nutrition. In total, 124 premature infants underwent PICC insertion. Among them, 19 patients had positive results of fungi on the PICC tips. The duration of antibiotics (odds ratio [OR] 1.16, 95% confidence interval [CI] 1.02–1.31), parenteral nutrition infusion (OR 1.27, 95% CI 1.05–1.54), and postnatal glucocorticoid exposure (OR 9.48, 95% CI 1.06–84.98) were independent risk factors for fungal colonization in PICCs. The ROC curves showed that the risk increased after 15 days of antibiotic use and 28 days of parenteral nutrition infusion. Appropriate clinical management should be used to prevent fungal colonization and fungemia.

Candidemia by Candida parapsilosis in a neonatal intensive care unit: human and environmental reservoirs, virulence factors, and antifungal susceptibility

The Candida parapsilosis complex has emerged as one of the main causes of candidemia worldwide. This study aims to evaluate possible C. parapsilosis sensu stricto reservoirs in a NICU, the expression of virulence factors, and antifungal susceptibility, and to analyze their genetic and phenotypic similarity. The study included 17 isolates of C. parapsilosis: seven environmental, one from a newborn's mother, and nine samples from six newborns. We used molecular and phenotypic tests to characterize the isolates and to trace possible routes of infection. The genetic similarity was determined by random amplified polymorphic DNA. The hemolytic and DNAse activity was determined using sheep's blood and DNAse agar, biofilm production by XTT method, and the susceptibility to antifungals through microdilution methodology. Two environmental strains isolated in the same month had high similarity. The 17 isolates expressed at least one of the three virulence factors studied, and one environmental isolate was resistant to fluconazole. This study shows that environmental contamination can be an important reservoir of potentially pathogenic microorganisms, since isolates of C. parapsilosis sensu stricto collected from the hospital environment were able to express virulence factors. Therefore, we emphasized the importance of determining the transmission routes in NICU in order to detect pathogen sources and reservoirs, as well as to establish prevention measures, such as adequate disinfection of the environment.

Disparate Candida albicans Biofilm Formation in Clinical Lipid Emulsions Due to Capric Acid-Mediated Inhibition

Receipt of parenteral nutrition (PN) remains an independent risk factor for developing catheter-related bloodstream infections (CR-BSI) caused by fungi, including by the polymorphic fungus Candida albicans, which is notoriously adept at forming drug-resistant biofilm structures. Among a variety of macronutrients, PN solutions contain lipid emulsions to supply daily essential fats and are often delivered via central venous catheters (CVCs). Therefore, using an in vitro biofilm model system, we sought to determine whether various clinical lipid emulsions differentially impacted biofilm growth in C. albicans We observed that the lipid emulsions Intralipid and Omegaven both stimulated C. albicans biofilm formation during growth in minimal medium or a macronutrient PN solution. Conversely, Smoflipid inhibited C. albicans biofilm formation by approximately 50%. Follow-up studies revealed that while Smoflipid did not impair C. albicans growth, it did significantly inhibit hypha formation and hyphal elongation. Moreover, growth inhibition could be recapitulated in Intralipid when supplemented with capric acid-a fatty acid present in Smoflipid but absent in Intralipid. Capric acid was also found to dose dependently inhibit C. albicans biofilm formation in PN solutions. This is the first study to directly compare different clinical lipid emulsions for their capacity to affect C. albicans biofilm growth. Results derived from this study necessitate further research regarding different lipid emulsions and rates of fungus-associated CR-BSIs.