The sphingolipid inhibitor myriocin increases Candida auris susceptibility to amphotericin B

BACKGROUND

The emergence of the pathogenic yeast Candida auris is of global concern due to its ability to cause hospital outbreaks and develop resistance against all antifungal drug classes. Based on published data for baker's yeast Saccharomyces cerevisiae, sphingolipid biosynthesis, which is essential for maintaining membrane fluidity and formation of lipid rafts, could offer a target for additive treatment.

METHODS

We analysed the susceptibility of C. auris to myriocin, which is an inhibitor of the de novo synthesis of sphingolipids in eukaryotic cells in comparison to other Candida species. In addition, we combined sublethal concentrations of myriocin with the antifungal drugs amphotericin B and fluconazole in E-tests. Consequently, the combinatory effects of myriocin and amphotericin B were examined in broth microdilution assays.

RESULTS

Myriocin-mediated inhibition of the sphingolipid biosynthesis affected the growth of C. auris. Sublethal myriocin concentrations increased fungal susceptibility to amphotericin B. Isolates which are phenotypically resistant (≥2 mg/L) to amphotericin B became susceptible in presence of myriocin. However, addition of myriocin had only limited effects onto the susceptibility of C. auris against fluconazole.

CONCLUSIONS

Our results show that inhibition of de novo sphingolipid biosynthesis increases the susceptibility of C. auris to amphotericin B. This may potentially enhance antifungal treatment options fighting this often resistant yeast pathogen.

Diverse mechanisms control amino acid-dependent environmental alkalization by Candida albicans

Candida albicans has the capacity to neutralize acidic growth environments by releasing ammonia derived from the catabolism of amino acids. The molecular components underlying alkalization and its physiological significance remain poorly understood. Here, we present an integrative model with the cytosolic NAD+-dependent glutamate dehydrogenase (Gdh2) as the principal ammonia-generating component. We show that alkalization is dependent on the SPS-sensor-regulated transcription factor STP2 and the proline-responsive activator Put3. These factors function in parallel to derepress GDH2 and the two proline catabolic enzymes PUT1 and PUT2. Consistently, a double mutant lacking STP2 and PUT3 exhibits a severe alkalization defect that nearly phenocopies that of a gdh2-/- strain. Alkalization is dependent on mitochondrial activity and in wild-type cells occurs as long as the conditions permit respiratory growth. Strikingly, Gdh2 levels decrease and cells transiently extrude glutamate as the environment becomes more alkaline. Together, these processes constitute a rudimentary regulatory system that counters and limits the negative effects associated with ammonia generation. These findings align with Gdh2 being dispensable for virulence, and based on a whole human blood virulence assay, the same is true for C. glabrata and C. auris. Using a transwell co-culture system, we observed that the growth and proliferation of Lactobacillus crispatus, a common component of the acidic vaginal microenvironment and a potent antagonist of C. albicans, is unaffected by fungal-induced alkalization. Consequently, although Candida spp. can alkalinize their growth environments, other fungal-associated processes are more critical in promoting dysbiosis and virulent fungal growth.

Evaluation of Eazyplex® LAMP test for fast Candida auris direct detection of colonized patients

Candida auris is a multidrug-resistant pathogen yeast that produces nosocomial outbreaks, due to its ability in colonizing the skin, mucous membranes and surfaces. Rapid diagnosis is essential to control its spread. The aim of this study was to compare the Eazyplex® Candida auris kit (AmplexDiagnostics GmbH) for the rapid identification of patients colonized with C. auris, with the reference method used in our institution (culture and identification by MALDI-TOF). This easy-to-perform test allows obtaining a fast result, in ~30 min. First, we achieved a preliminary study from previously characterized Candida species colonies obtained from 51 clinical samples, with 100% agreement between culture isolation and the Eazyplex® Candida auris LAMP. Second, 152 epidemiological surveillance samples (pharyngeal and axillary-rectal swabs) were tested retrospectively. The sensitivity, specificity, positive and negative predictive values were 91.8%, 98.8%, 98.2% and 94.5%, respectively. Eazyplex® Candida auris showed acceptable results compared with culture in detecting C. auris from surveillance samples with the advantage of single-test and shorter time for handling and result than culture, in addition to its great specificity, positive and negative predictive values.

Efficacy of biofilm disrupters against Candida auris and other Candida species in monomicrobial and polymicrobial biofilms

Candida species are now considered global threats by the CDC and WHO. Candida auris specifically is on the critical pathogen threat list along with Candida albicans. In addition, it is not uncommon to find Candida spp. in a mixed culture with bacterial organisms, especially Staphylococcus aureus producing polymicrobial infections. To eradicate these organisms from the environment and from patient surfaces, surface agents such as chlorhexidine (CHD) and Puracyn are used. Biofilm disrupters (BDs) are novel agents with a broad spectrum of antimicrobial activity and have been used in the management of chronic wounds and to sterilise environmental surfaces for the past several years. The goal of this study was to evaluate BDs (BlastX, Torrent, NSSD) and CHD against Candida spp. and S. aureus using zone of inhibition assays, biofilm and time-kill assays. All BDs and CHD inhibited C. auris growth effectively in a concentration-dependent manner. Additionally, CHD and the BDs showed excellent antimicrobial activity within polymicrobial biofilms. A comparative analysis of the BDs and CHD against C. auris and C. albicans using biofilm kill-curves showed at least 99.999% killing. All three BDs and CHD have excellent activity against different Candida species, including C. auris. However, one isolate of C. auris in a polymicrobial biofilm assay showed resistance/tolerance to CHD, but not to the BDs. The fungicidal activity of these novel agents will be valuable in eradicating surface colonisation of Candida spp, especially C. auris from colonised environmental surfaces and from wounds in colonised patients.

Structure-activity relationships of bensulfuron methyl and its derivatives as novel agents against drug-resistant Candida auris

With the emergence of the human pathogen Candida auris as a threat to human health, there is a strong demand to identify effective medicines to prevent the harm caused by such drug-tolerant human fungi. Herein, a series of 33 new derivatives of bensulfuron methyl (BSM) were synthesized and characterized by 1 H NMR, 13 C NMR, and HRMS. Among the target compounds, 8a possessed the best Ki value of 1.015 μM against C. auris acetohydroxyacid synthase (CauAHAS) and an MIC value of 6.25 μM against CBS10913, a clinically isolated strain of C. auris. Taken together the structures of BSM and the synthesized compounds, it was found that methoxy groups at both meta-position of pyrimidine ring are likely to provide desirable antifungal activities. Quantum calculations and molecular dockings were performed to understand the structure-activity relationships. The present study has hence provided some interesting clues for the discovery of novel antibiotics with this distinct mode of action.

Whole genome sequencing analysis demonstrates therapy-induced echinocandin resistance in Candida auris isolates

Candida auris is an emerging, multidrug-resistant yeast, causing outbreaks in healthcare facilities. Echinocandins are the antifungal drugs of choice to treat candidiasis, as they cause few side effects and resistance is rarely found. Previously, immunocompromised patients from Kuwait with C. auris colonisation or infection were treated with echinocandins, and within days to months, resistance was reported in urine isolates. To determine whether the development of echinocandin resistance was due to independent introductions of resistant strains or resulted from intra-patient resistance development, whole genome sequencing (WGS) single-nucleotide polymorphism (SNP) analysis was performed on susceptible (n = 26) and echinocandin-resistant (n = 6) isolates from seven patients. WGS SNP analysis identified three distinct clusters differing 17-127 SNPs from two patients, and the remaining isolates from five patients, respectively. Sequential isolates within patients had a maximum of 11 SNP differences over a time period of 1-10 months. The majority of isolates with reduced susceptibility displayed unique FKS1 substitutions including a novel FKS1M690V substitution, and nearly all were genetically related, ranging from only three to six SNP differences compared to susceptible isolates from the same patient. Resistant isolates from three patients shared the common FKS1S639F substitution; however, WGS analysis did not suggest a common source. These findings strongly indicate that echinocandin resistance is induced during antifungal treatment. Future studies should determine whether such echinocandin-resistant strains are capable of long-term colonisation, cause subsequent breakthrough candidiasis, have a propensity to cross-infect other patients, or remain viable for longer time periods in the hospital environment.

Candida auris from colonisation to candidemia: A four-year study

BACKGROUND

Candida auris has become a worrisome multi-drug resistant healthcare-associated pathogen due to its capacity to colonise patients and surfaces and to cause outbreaks of invasive infections in critically ill patients.

OBJECTIVES

This study evaluated the outbreak in our setting in a 4-year period, reporting the risk factors for developing candidemia in previously colonised patients, the therapeutic measures for candidemia and the outcome of candidemia and colonisation cases among all C. auris isolates and their susceptibility to antifungals.

METHODS

Data were retrospectively collected from patients admitted to Consorcio Hospital General Universitario de Valencia (Spain) from September 2017 to September 2021. A retrospective case-control study was designed to identify risk factors for developing C. auris candidemia in previously colonised patients.

RESULTS

C. auris affected 550 patients, of which 210 (38.2%) had some clinical sample positive. Isolates were uniformly resistant to fluconazole, 20 isolates were resistant to echinocandins (2.8%) and four isolates were resistant to ampfotericin B (0.6%). There were 86 candidemia cases. APACHE II, digestive disease and catheter isolate were proven to be independent risk factors for developing candidemia in previously colonised patients. Thirty-day mortality rate for C. auris candidemia cases was 32.6%, while for colonisation cases was 33.7%.

CONCLUSIONS

Candidemia was one of the most frequent and severe infections caused by C. auris. The risk factors identified in this study should help to detect patients who are at more risk of developing candidemia, as long as an adequate surveillance of C. auris colonisation is performed.

Drug repurposing against Candida auris: A systematic review

Candida auris is a drug-resistant pathogen with several reported outbreaks. The treatment of C. auris infections is difficult due to a limited number of available antifungal drugs. Thus, finding alternative drugs through repurposing approaches would be clinically beneficial. A systematic search in PubMed, Scopus and Web of Science databases, as well as Google Scholar up to 1 November 2021, was conducted to find all articles with data regarding the antifungal activity of non-antifungal drugs against the planktonic and biofilm forms of C. auris. During database and hand searching, 290 articles were found, of which 13 were eligible for inclusion in the present study. Planktonic and biofilm forms have been studied in 11 and 8 articles (with both forms examined in 6 articles), respectively. In total, 22 and 12 drugs/compounds have been reported as repositionable against planktonic and biofilm forms of C. auris, respectively. Antiparasitic drugs, with the dominance of miltefosine, were the most common repurposed drugs against both forms of C. auris, followed by anticancer drugs (e.g. alexidine dihydrochloride) against the planktonic form and anti-inflammatory drugs (e.g. ebselen) against the biofilm form of the fungus. A collection of other drugs from various classes have also shown promising activity against C. auris. Following drug repurposing approaches, a number of drugs/compounds from various classes have been found to inhibit the planktonic and biofilm forms of C. auris. Accordingly, drug repurposing is an encouraging approach for discovering potential alternatives to conventional antifungal agents to combat drug resistance in fungi, especially C. auris.

Global Prevalence and Subgroup Analyses of Coronavirus Disease (COVID-19) Associated Candida auris infections (CACa): A Systematic Review and Meta-Analysis

Background

Increased hospitalisation rates in the Coronavirus disease 19 (COVID‐19) era lead to a new wave of hospital‐acquired infections such as emerging multidrug‐resistant Candida auris. We aimed to evaluate and estimate the global prevalence of coronavirus‐associated C. auris infection (CACa).

Methods

We searched related databases between December 2019 and April 2022 for studies that reported data about CACa. Meta‐analysis was performed using MedCalc software version 20.104 according to the DerSimonian and Laird method applying the random‐effects model. We evaluated heterogeneity using the χ²‐based Q statistic (significant for p‐value < .1) and the I² statistic (>75% indicative of ‘notable’ heterogeneity). Moreover, if possible, an odds ratio (OR) analysis was performed for eligible data.

Results

Our meta‐analysis includes ten eligible studies, including 1942 patients hospitalised with COVID‐19; 129 were C. auris cases. The overall pooled prevalence of CACa was estimated at 5.7%. The mortality rate of CACa was estimated at 67.849%. Hypertension was the most prevalent comorbidity (59.374%), followed by diabetes mellitus (52.898%) and cardiovascular diseases (31.392%). Men with a prevalence rate of 80.012% were 3.27 (OR) times more prone to getting infected by C. auris.

Conclusion

We concluded that the prevalence of C. auris infections decreased during the COVID‐19 pandemic and the prevalence gradient changed from Asia to America. Unfortunately, there are many descriptive studies with duplicate content in the field of epidemiology of C. auris infections which are increasing every day. We suggest further non‐descriptive studies to accurately establish the cause‐and‐effect relationships between C. auris and COVID‐19 infections.

Prevalence, Risk Factors, Treatment and Outcome of multidrug resistance Candida auris Infections in Coronavirus Disease (COVID-19) Patients: A Systematic Review

BACKGROUND

Candida auris is an emerging multidrug-resistant pathogen in intensive care settings (ICU). During the coronavirus disease 19 (COVID-19) pandemic, ICU admissions were overwhelmed, possibly contributing to the C. auris outbreak in COVID-19 patients.

OBJECTIVES

The present systematic review addresses the prevalence, underlying diseases, iatrogenic risk factors, treatment and outcome of C. auris infections in COVID-19 patients.

METHODS

MEDLINE, Scopus, Embase, Web of Science and LitCovid databases were systematically searched with appropriate keywords from 1^st January 2020 to 31^st December 2021.

RESULTS

A total of 97 cases of C. auris were identified in COVID-19 patients. The prevalence of C. auris infections in COVID-19 patients was 14%. The major underlying diseases were diabetes mellitus (42.7%), hypertension (32.9%), and obesity (14.6%), followed by the iatrogenic risk factors such as a central venous catheter (76.8%%) intensive care unit (ICU) stay (75.6%), and broad-spectrum antibiotic usage (74.3%). There were no significant differences in underlying disease and iatrogenic risk factors among C. auris non-candidemia/colonisation and C. auris candidemia cases. The mortality rate of the total cohort is 44.4%, whereas, in C. auris candidemia patients, the mortality was 64.7%.

CONCLUSION

This study shows that the prevalence of C. auris infections remains unchanged in the COVID-19 pandemic. Hospital-acquired risk factors may contribute to the clinical illness. Proper infection control practices and hospital surveillance may stop future hospital outbreaks during the pandemic.

Expert recommendations for prevention and management of Candida auris transmission

Candida auris was first described as a yeast pathogen in 2009. Since then, the new species has emerged worldwide. In contrast to most other Candida spp., C. auris frequently exhibits multi-drug resistance and is readily transmitted in hospital settings. While most isolations so far are from colonized patients, C. auris does cause life-threatening invasive infections. During management of the first documented C. auris transmission in a German hospital, experts from the National Reference Centers for Invasive Fungal Infections (NRZMyk) and the National Reference Center for Surveillance of Nosocomial Infections screened available literature and integrated available knowledge on infection prevention and C. auris epidemiology and biology to enable optimal containment. Relevant recommendations developed during this process are summarized in this guidance document, intended to assist in management of C. auris transmission and potential outbreak situations. Rapid and effective measures to contain C. auris spread require a multidisciplinary approach that includes clinical specialists of the affected unit, nursing staff, hospital hygiene, diagnostic microbiology, cleaning staff, hospital management and experts in diagnostic mycology / fungal infections. Action should be initiated in a step-wise process and relevant interventions differ between management of singular C. auris colonized / infected patients and detection of potential C. auris transmission or nosocomial outbreaks. [word count 205].

Successful control of Candida auris transmission in a German COVID-19 intensive care unit

BACKGROUND

Candida auris is a frequently multi-drug resistant yeast species that poses a global health threat due to its high potential for hospital outbreaks. While C. auris has become endemic in parts of Asia and Africa, transmissions have so far rarely been reported in Western Europe except for Great Britain and Spain. We describe the first documented patient-to-patient transmission of C. auris in Germany in a COVID-19 intensive care unit (ICU) and infection control measures implemented to prevent further spread of the pathogen.

METHODS

Identification of C. auris was performed by MALDI-TOF and confirmed by internal transcribed spacer (ITS) sequencing. Antifungal susceptibility testing was carried out. We conducted repeated cross-sectional examinations for the presence of C. auris in the patients of the affected ICU and investigated possible routes of transmission.

RESULTS

The index patient had been transferred to Germany from a hospital in Northern Africa and was found to be colonised with C. auris. The contact patient developed C. auris sepsis. Infection prevention and control (IPC) measures included strict isolation of the two C. auris patients and regular screening of non-affected patients. No further case occurred during the subsequent weeks. Reusable blades used in video laryngoscope-guided intubation were considered as the most likely vehicle of transmission.

CONCLUSIONS

In view of its high risk of transmission, vigilance regarding C. auris colonisation in patients referred from endemic countries is crucial. Strict and immediate IPC measures may have the potential to prevent C. auris outbreaks.

Evaluation of CHROMagarTM Candida Plus chromogenic agar for the presumptive identification of Candida auris

Skin colonization by the emerging pathogen Candida auris is common in outbreaks within medical settings. Culture-based screening of patients is an effective management strategy to control the pathogen, and the newly developed CHROMagar^TM Candida Plus medium is claimed to enable the presumptive identification of C. auris. Here, we evaluated the use of this medium with 63 C. auris strains comprising its four well-established clades, as well as genetically related comparators, including species from the Metschnikowia clade. The colors and halos of both confluent growth and discrete colonies of all tested strains were compared. We found that on CHROMagar^TM Candida Plus, C. auris formed characteristic white colonies with blue-green halos that were more evident after 72 h of incubation at 35 ℃ than after 48 h. However, distinguishing between closely related species such as Candida haemulonii, Candida pseudohaemulonii, and Candida duobushaemulonii required the consideration of parameters other than color, including colony size and growth ability at 35 ℃. In conclusion, the novel chromogenic medium CHROMagar^TM Candida Plus constitutes an easy screening tool for C. auris. This article is protected by copyright. All rights reserved.

Antifungal lock therapy: an eternal promise or an effective alternative therapeutic approach?

Each year, millions of central venous catheter insertions are performed in intensive care units worldwide. The usage of these indwelling devices is associated with a high risk of bacterial and fungal colonization, leading to the development of microbial consortia, namely biofilms. These sessile structures provide fungal cells with resistance to the majority of antifungals, environmental stress and host immune responses. Based on different guidelines, colonized/infected catheters should be removed and changed immediately in the case of Candida‐related central line infections. However, catheter replacement is not feasible for all patient populations. An alternative therapeutic approach may be antifungal lock therapy, which has received high interest, especially in the last decade. This review summarizes the published Candida‐related in vitro, in vivo data and case studies in terms of antifungal lock therapy. The number of clinical studies remains limited and further studies are needed for safe implementation of the antifungal lock therapy into clinical practice.

Laboratory-based surveillance of Candida auris in Colombia, 2016-2020

BACKGROUND

Since the first report of Candida auris in 2016, the Colombian Instituto Nacional de Salud (INS) has implemented a national surveillance of the emerging multidrug-resistant fungus.

OBJECTIVES

This report summarises the findings of this laboratory-based surveillance from March 2016 to December 2020.

RESULTS

A total of 1720 C. auris cases were identified, including 393 (23%) colonisation cases and 1327 (77%) clinical cases. Cases were reported in 20 of 32 (62%) departments of Colombia and involved hospitals from 33 cities. The median age of patients was 34 years; 317 (18%) cases were children under 16 years, 54% were male. The peak number of cases was observed in 2019 (n = 541). In 2020, 379 (94%) of 404 cases reported were clinical cases, including 225 bloodstream infections (BSI) and 154 non-BSI. Among the 404 cases reported in 2020, severe COVID-19 was reported in 122 (30%). Antifungal susceptibility was tested in 379 isolates. Using CDC tentative breakpoints for resistance, 35% of isolates were fluconazole resistant, 33% were amphotericin B resistant, and 0.3% isolates were anidulafungin resistant, 12% were multidrug resistant, and no pan-resistant isolates were identified.

CONCLUSION

For five years of surveillance, we observed an increase in the number and geographic spread of clinical cases and an increase in fluconazole resistance. These observations emphasise the need for improved measures to mitigate spread.

Schiff bases of sulphonamides as a new class of antifungal agent against multidrug-resistant Candida auris

Invasive Candida infections in hospitalized and immunocompromised or critically ill patients have become an important cause of morbidity and mortality. There are increasing reports of multidrug resistance in several Candida species that cause Candidemia, including C. glabrata and C. auris, with limited numbers of antifungal agents available to treat patients with invasive Candida infections. Therefore, there is an urgent need to discover new antifungal agents that work against multidrug-resistant Candida species, particularly C. auris, which has been identified as an emerging global pathogen. In this article, we report a new class of antifungal agents, the Schiff bases of sulphonamides, that show activity against all Candida species tested, with an MIC range of 4-32 µg/ml. Compound 2b showed activity against C. glabrata and a panel of fluconazole-resistant C. auris strains, with MICs of 4-16 µg/ml. The drug-like nature of these Schiff bases offers opportunities to optimize these compounds with medicinal chemistry techniques to obtain more potent analogs that can be progressed toward pre-clinical evaluation.

Characteristics, outcome and risk factors for mortality of paediatric patients with ICU-acquired candidemia in India: A multicentre prospective study

BACKGROUND

The epidemiology, clinical profile and outcome of paediatric candidemia vary considerably by age, healthcare settings and prevalent Candida species. Despite these differences, few comprehensive studies are undertaken. This nationwide study addresses this knowledge gap.

METHODS

487 children who contracted ICU-acquired candidemia at 23 Indian tertiary care centres were assessed for 398 variables spanning demography, clinical characteristics, microbiology, treatment and outcome.

RESULTS

Both neonates (5.0 days; range = 3.0-9.5) and non-neonatal children (7.0 days; range = 3.0-13.0) developed candidemia early after ICU admission. Majority of neonates were premature (63.7%) with low birthweight (57.1%). Perinatal asphyxia (7.3%), pneumonia (8.2%), congenital heart disease (8.4%) and invasive procedures were common comorbidities, and antibiotic use (94.1%) was widespread. C tropicalis (24.7%) and C albicans (20.7%) dominated both age groups. Antifungal treatment (66.5%) and removal of central catheters (44.8%) lagged behind. Overall resistance was low; however, emergence of resistant C krusei and C auris needs attention. The 30-day crude mortality was 27.8% (neonates) and 29.4% (non-neonates). Logistic regression identified admission to public sector ICUs (OR = 5.64), mechanical ventilation (OR = 2.82), corticosteroid therapy (OR = 8.89) and antifungal therapy (OR = 0.22) as independent predictors of 30-day crude mortality in neonates. Similarly, admission to public sector ICUs (OR = 3.62), mechanical ventilation (OR = 3.13), exposure to carbapenems (OR = 2.18) and azole antifungal therapy (OR = 0.48) were independent predictors for non-neonates.

CONCLUSIONS

Our findings reveal a distinct epidemiology, including early infection with a different spectrum of Candida species, calling for appropriate intervention strategies to reduce candidemia morbidity and mortality. Independent factors identified in our regression models can help tackle these challenges.

A high-throughput and rapid method for accurate identification of emerging multidrug-resistant Candida auris

Candida auris is an emerging multidrug-resistant yeast associated with invasive infection in healthcare settings. Recently, C auris cases in the United States have been detected in 11 states with the majority of cases in New York, New Jersey and Illinois. Rapid and accurate identification of C auris is critical for patient care and the implementation of public health measures to control the spread of infection. Our aim was to develop and validate a rapid DNA extraction method using the Roche MagNA Pure 96 instrument and a TaqMan real-time PCR assay for reliable, high-throughput identification of C auris. We evaluated 247 patient dermal swab samples previously analysed by culture/MALDI-TOF. The diagnostic sensitivity and specificity were 93.6% and 97.2%, respectively. The assay was highly reproducible with a detection limit of 1 C auris CFU/10 μL. A receiver operating characteristic curve analysis of the real-time PCR data showed an area of 0.982 under the curve, with a CT cut-off value of ≤37.0. The turnaround time from DNA extraction to real-time PCR results was approximately 200 samples/day. In conclusion, we successfully validated a rapid and high-throughput method for accurate and reproducible identification of C auris with a significantly reduced turnaround time compared to culture/MALDI-TOF based methods.