Candida tropicalis bloodstream infection: Incidence, risk factors and outcome in a population-based surveillance

Emerging trends of invasive yeast infections and azole resistance in Beijing intensive care units

BACKGROUND

Invasive fungal infections pose a substantial threat to patients in healthcare settings globally. Recent changes in the prevalence of fungal species and challenges in conducting reference antifungal susceptibility testing emphasize the importance of monitoring fungi and their antifungal resistance.

METHODS

A two-phase surveillance project was conducted in Beijing, China, involving 37 centres across 12 districts, from January 2012 to December 2013 and from January 2016 to December 2017.

FINDINGS

We found that the proportion of Candida albicans in intensive care units (ICUs) during 2016-2017 exhibited a significant decline compared with the 2012-2013 period, although it remained the most predominant pathogen. In contrast, the prevalence of Nakaseomyces glabratus (formerly Candida glabrata) and Candida tropicalis notably increased during the two-phase surveillance. The high prevalence of C. tropicalis and its resistance to azole drugs posed a serious threat to patients in ICUs. The pathogens causing invasive fungal infections in Beijing were relatively sensitive to echinocandins. While C. albicans continued to exhibit susceptibility to azoles, the resistance and growth rates of C. tropicalis towards azoles were particularly prominent. Concerns were raised due to the emergence of multiple, short-term isolates of Clavispora lusitaniae and Candida parapsilosis complex in neonatal ICUs, given their similarity in antifungal susceptibilities. Such occurrences point towards the potential for transmission and persisting presence of these pathogens within the ICU environment.

CONCLUSIONS

Our study complements existing data on the epidemiology of invasive fungal infections. It is imperative to exercise cautious medication management for ICU patients in Beijing, paying particular attention to azole resistance in C. tropicalis.

Trends in antifungal resistance in Candida from a multicenter study conducted in Madrid (CANDIMAD study): fluconazole-resistant C. parapsilosis spreading has gained traction in 2022

We previously conducted a multicenter surveillance study on Candida epidemiology and antifungal resistance in Madrid (CANDIMAD study; 2019-2021), detecting an increase in fluconazole-resistant Candida parapsilosis. We here present data on isolates collected in 2022. Furthermore, we report the epidemiology and antifungal resistance trends during the entire period, including an analysis per ward of admission. Candida spp. incident isolates from blood cultures and intra-abdominal samples from patients cared for at 16 hospitals in Madrid, Spain, were tested with the EUCAST E.Def 7.3.2 method against amphotericin B, azoles, micafungin, anidulafungin, and ibrexafungerp and were molecularly characterized. In 2022, we collected 766 Candida sp. isolates (686 patients; blood cultures, 48.8%). Candida albicans was the most common species found, and Candida auris was undetected. No resistance to amphotericin B was found. Overall, resistance to echinocandins was low (0.7%), whereas fluconazole resistance was 12.0%, being higher in blood cultures (16.0%) mainly due to fluconazole-resistant C. parapsilosis clones harboring the Y132F-R398I ERG11p substitutions. Ibrexafungerp showed in vitro activity against the isolates tested. Whereas C. albicans was the dominant species in most hospital wards, we observed increasing C. parapsilosis proportions in blood. During the entire period, echinocandin resistance rates remained steadily low, while fluconazole resistance increased in blood from 6.8% (2019) to 16% (2022), mainly due to fluconazole-resistant C. parapsilosis (2.6% in 2019 to 36.6% in 2022). Up to 7 out of 16 hospitals were affected by fluconazole-resistant C. parapsilosis. In conclusion, rampant clonal spreading of C. parapsilosis fluconazole-resistant genotypes is taking place in Madrid.

Incidence, susceptibility and outcomes of candidemia in adults living in Calgary, Alberta, Canada (2010-2018)

BACKGROUND

Candidemia is increasing in frequency and is associated with high mortality. We sought to determine the burden of illness, the population it affects and its resistance profile in our region.

METHODS

The Calgary Zone (CZ) provides all care for residents of Calgary and surrounding communities (~ 1.69 million) via five tertiary hospitals each served by a common single laboratory for acute care microbiology. All adult patients in the CZ with at least one Candida spp.-positive blood culture between January 1, 2010, and December 31, 2018, were identified using microbiological data from Calgary Lab Services, the laboratory that processes > 95% of all blood culture samples in the CZ, were reviewed for the study.

RESULTS

The overall annual incidence of candidemia among individuals living in the CZ was 3.8 per 100,000 persons (Median age 61 years (IQR 48-72) and 221/455 (47.4%) were female). C. albicans was the most common species (50.6%), followed by C. glabrata, (24.0%). No other species accounted for more than 7% of cases. Overall mortality at 30, 90, and 365 days was 32.2, 40.1, and 48.1% respectively. Mortality rate did not differ by Candida species. Of individuals who developed candidemia, more than 50% died within the next year. No new resistance pattern has emerged in the most common Candida species in Calgary, Alberta.

CONCLUSIONS

In Calgary, Alberta, the incidence of candidemia has not increased in the last decade. C. albicans was the most common species and it remains susceptible to fluconazole.

Multilocus sequence typing (MLST) analysis reveals many novel genotypes and a high level of genetic diversity in Candida tropicalis isolates from Italy and Africa

BACKGROUND

Candida tropicalis is a human pathogenic yeast frequently isolated in Latin America and Asian-Pacific regions, although recent studies showed that it is also becoming increasingly widespread throughout several African and south-European countries. Nevertheless, relatively little is known about its global patterns of genetic variation as most of existing multilocus sequence typing (MLST) data come from Asia and there are no genotyped African isolates.

OBJECTIVES

We report detailed genotyping data from a large set of C. tropicalis isolates recovered from different clinical sources in Italy, Egypt and Cameroon in order to expand the allele/genotype library of MLST database (https://pubmlst.org/ctropicalis), and to explore the genetic diversity in this species.

METHODS

A total of 103 C. tropicalis isolates were genotyped using the MLST scheme developed for this species. All isolates were also tested for in vitro susceptibility to various antifungals to assess whether certain genotypes were associated with drug-resistance.

RESULTS AND CONCLUSIONS

A total of 104 different alleles were detected across the MLST-loci investigated. The allelic diversity found at these loci resulted in 51 unique MLST genotypes of which 36 (70.6%) were novel. Global optimal eBURST analysis identified 18 clonal complexes (CCs) and confirm the existence of a specific Italian-cluster (CC36). Three CCs were also statistically associated with fluconazole resistance, which was elevated in Cameroon and Egypt. Our data show high genetic diversity in our isolates suggesting that the global population structure of C. tropicalis is still poorly understood. Moreover, its clinical impact in Italy, Egypt and Cameroon appears to be relevant and should be carefully considered.

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.

Whole Genome Sequencing Shows Genetic Diversity, as Well as Clonal Complex and Gene Polymorphisms Associated with Fluconazole Non-Susceptible Isolates of Candida tropicalis

Resistance to azoles in Candida tropicalis is increasing and may be mediated by genetic characteristics. Using whole genome sequencing (WGS), we examined the genetic diversity of 82 bloodstream C. tropicalis isolates from two countries and one ATCC strain in a global context. Multilocus sequence typing (MLST) and single nucleotide polymorphism (SNP)-based phylogenies were generated. Minimum inhibitory concentrations (MIC) for antifungal agents were determined using Sensititre YeastOne YO10. Eleven (13.2%) isolates were fluconazole-resistant and 17 (20.5%) were classified as fluconazole-non susceptible (FNS). Together with four Canadian isolates, the genomes of 12 fluconazole-resistant (18 FNS) and 69 fluconazole-susceptible strains were examined for gene mutations associated with drug resistance. Fluconazole-resistant isolates contained a mean of 56 non-synonymous SNPs per isolate in contrast to 36 SNPs in fluconazole-susceptible isolates (interquartile range [IQR] 46−59 vs. 31−48 respectively; p < 0.001). Ten of 18 FNS isolates contained missense ERG11 mutations (amino acid substitutions S154F, Y132F, Y257H). Two echinocandin-non susceptible isolates had homozygous FKS1 mutations (S30P). MLST identified high genetic diversity with 61 diploid sequence types (DSTs), including 53 new DSTs. All four isolates in DST 773 were fluconazole-resistant within clonal complex 2. WGS showed high genetic variation in invasive C. tropicalis; azole resistance was distributed across different lineages but with DST 773 associated with in vitro fluconazole resistance.

EQUAL Candida score, an effective tool for predicting the outcomes of Candida tropicalis candidaemia: a retrospective cohort study

BACKGROUND

Candida tropicalis is the most common non-albicans Candida species found in Asia-Pacific countries, including Thailand. The pathogen is known for its great virulence, which causes a high case-fatality rate. Associations between case fatality and patient characteristics, infectious disease unit consultation, and EQUAL Candida score were investigated.

METHODS

This retrospective cohort study was conducted with 160 cases of C. tropicalis bloodstream infection between 2015 and 2019 at a single, large, tertiary centre in Thailand. Clinical characteristics, clinical presentations, patient outcomes (30-day case-fatality rate) and independent predictive factors were analysed.

RESULTS

The 30-day case-fatality rate was 68.1%. The median of the EQUAL Candida score was 8. Independent factors for the prediction of case fatality were septic shock (hazard ratio, 1.84), the use of mechanical ventilation (hazard ratio, 2.03) and the EQUAL Candida score (hazard ratio, 0.75).

CONCLUSIONS

The predictive factors for 30-day case fatality were septic shock, mechanical ventilation use and the EQUAL Candida score. It is recommended that the EQUAL score be considered for patients infected with C. tropicalis candidaemia to reduce the case-fatality rate.

Prognostic factors of Candida spp. bloodstream infection in adults: A nine-year retrospective cohort study across tertiary hospitals in Brazil and Spain

Background

Mortality rates among adults with candidemia vary widely in different geographical settings. Studies directly comparing epidemiology and clinical practices between countries are scarce and could bring insights into improving clinical outcomes.

Methods

Retrospective cohort including adults with candidemia diagnosed in five tertiary hospitals from Brazil and Spain between 2010-2018. Adequate therapeutic management included appropriate antifungal therapy and central-venous-catheter (CVC) removal within 48 h of fungemia. Primary endpoints were mortality rates at 14 and 30 days. Secondary endpoints were prognostic factors associated with 30-day mortality.

Findings

Overall, 720 patients were included, being 323 from Spain. Spanish patients received echinocandins more often (52·5% vs. 39·3%, p = 0.001), initiated antifungals earlier [2 (0-7) vs. 2 days (0-16), p<0.001], and had faster CVC-removal [1 (0-42) vs. 2 days (0-38), p = 0.012]. Mortality was higher among Brazilians at 14 days (35·8% vs. 20·1%, p<0.001), and at 30 days (51·9% vs. 31·6%, p < 0.001). Factors associated with mortality included: age [OR 1·02, 95%CI (1·008-1·032), p = 0·001], neutropenia [OR 3·24, 95%CI (1·594-6·585), p = 0·001], chronic pulmonary disease [OR 2·26, 95%CI (1·495-3·436), p < 0·001], corticosteroids [OR 1·45, 95%CI (1·018-2·079), p = 0·039], Pitt-Score>1 [OR 2·56, 95%CI (1·776-3·690), p < 0·001], and inadequate therapeutic management [OR 2·84, 95%CI (1·685-4·800), p < 0·001]. Being from Spain [OR 0·51, 95%CI (0·359-0·726), p < 0·001] and C. parapsilosis [OR 0·36, 95%CI (0·233-0·568), p < 0·001] were protective.

Interpretation

Higher mortality rates were observed in Brazil. Factors associated with 30-day mortality included mainly epidemiological characteristics and inadequate therapeutic management. Thus, effective and prompt antifungals combined with CVC-removal still need to be emphasized in order to improve the prognosis of adults with candidemia.

Funding

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP 2017/02203-7); CAPES Foundation (PDSE 88881.187981/2018-01).

Echinocandins Accelerate Particle Transport Velocity in the Murine Tracheal Epithelium: Dependency on Intracellular Ca2+ Stores

The mucociliary clearance of lower airways is modulated by different physiologic stimuli and also by pathophysiologic agents like polluting substances or pharmaceutical molecules. In the present investigation, we measured the particle transport velocity (PTV) of mouse tracheae as a surrogate for mucociliary clearance. In mouse tracheal preparations, we detected a sustained increase in the PTV under the application of the echinocandins caspofungin, anidulafungin, and micafungin. In further experiments, we observed the effects of echinocandins on the PTV were dependent on intracellular Ca²⁺ homeostasis. In Ca²⁺-free buffer solutions, the amplitude of the echinocandin-evoked rise in the PTV was significantly reduced relative to that in the experiments in Ca²⁺-containing solutions. Depletion of intracellular Ca²⁺ stores of the endoplasmic reticulum (ER) by caffeine completely prevented an increase in the PTV with subsequent caspofungin applications. Mitochondrial Ca²⁺ stores seemed to be unaffected by echinocandin treatment. We also observed no altered generation of reactive oxygen species under the application of echinocandins as probable mediators of the PTV. Consequently, the observed echinocandin effects on the PTV depend upon the Ca²⁺ influx and Ca²⁺ contents of the ER. We assume that all three echinocandins act intracellularly on ER Ca²⁺ stores to activate Ca²⁺-dependent signal transduction cascades, enhancing the PTV.

Continual Decline in Azole Susceptibility Rates in Candida tropicalis Over a 9-Year Period in China

Background

There have been reports of increasing azole resistance in Candida tropicalis, especially in the Asia-Pacific region. Here we report on the epidemiology and antifungal susceptibility of C. tropicalis causing invasive candidiasis in China, from a 9-year surveillance study.

Methods

From August 2009 to July 2018, C. tropicalis isolates (n = 3702) were collected from 87 hospitals across China. Species identification was carried out by mass spectrometry or rDNA sequencing. Antifungal susceptibility was determined by Clinical and Laboratory Standards Institute disk diffusion (CHIF-NET10-14, n = 1510) or Sensititre YeastOne (CHIF-NET15-18, n = 2192) methods.

Results

Overall, 22.2% (823/3702) of the isolates were resistant to fluconazole, with 90.4% (744/823) being cross-resistant to voriconazole. In addition, 16.9 (370/2192) and 71.7% (1572/2192) of the isolates were of non-wild-type phenotype to itraconazole and posaconazole, respectively. Over the 9 years of surveillance, the fluconazole resistance rate continued to increase, rising from 5.7 (7/122) to 31.8% (236/741), while that for voriconazole was almost the same, rising from 5.7 (7/122) to 29.1% (216/741), with no significant statistical differences across the geographic regions. However, significant difference in fluconazole resistance rate was noted between isolates cultured from blood (27.2%, 489/1799) and those from non-blood (17.6%, 334/1903) specimens (P-value < 0.05), and amongst isolates collected from medical wards (28.1%, 312/1110) versus intensive care units (19.6%, 214/1092) and surgical wards (17.9%, 194/1086) (Bonferroni adjusted P-value < 0.05). Although echinocandin resistance remained low (0.8%, 18/2192) during the surveillance period, it was observed in most administrative regions, and one-third (6/18) of these isolates were simultaneously resistant to fluconazole.

Conclusion

The continual decrease in the rate of azole susceptibility among C. tropicalis strains has become a nationwide challenge in China, and the emergence of multi-drug resistance could pose further threats. These phenomena call for effective efforts in future interventions.

Risk Factors and Outcomes of Non-albicans Candida Bloodstream Infection in Patients with Candidemia at Siriraj Hospital-Thailand's Largest National Tertiary Referral Hospital

This study aimed to investigate the risk factors for and the outcomes of patients with candidemia caused by non-albicans Candida. Candidemia patients treated at Siriraj Hospital (Bangkok, Thailand) during January 2016 to December 2017 were enrolled. A total of 156 patients (mean age: 65 years, 56.4% male) were included. The most prevalent underlying conditions were diabetes (32.1%), chronic cardiac disease (28.2%), chronic kidney disease (26.9%), and hematologic malignancies (21.2%). Candida species isolated from patient blood were C. tropicalis (49.4%), C. albicans (28.8%), C. glabrata (16.7%), and C. parapsilosis (5.1%). Fluconazole resistance was significantly increased in C. tropicalis (37.8%). No independent risk factors were associated with patients with non-albicans Candida candidemia compared to those with C. albicans candidemia. There was no significant difference in mortality between patients with non-albicans Candida candidemia and patients with C. albicans candidemia (OR: 1.35, 95% CI: 0.64-2.85). When compared with C. albicans candidemia, multivariate analysis revealed chronic liver disease (OR: 11.39, 95% CI: 1.38-94.02), neutropenia (OR: 4.31, 95% CI: 1.34-13.87), and male gender (OR: 2.34, 95% CI: 1.04-5.29) to be independent risk factors for C. tropicalis candidemia. The observed high resistance of C. tropicalis to fluconazole indicates that fluconazole should not be used for empirical antifungal treatment in these patients.

Trends towards lower azole susceptibility among 200 Candida tropicalis bloodstream isolates from Brazilian medical centres

OBJECTIVES

Candida tropicalis is one of the three most frequent species causing candidaemia in Latin America. Despite the high prevalence of C. tropicalis in candidaemia cases in Brazil, little is known about the trends in fluconazole susceptibility over time. The objective of this study was to evaluate temporal trends in azole resistance rates among C. tropicalis bloodstream isolates from patients treated in six Brazilian medical centres over a 12-year period.

METHODS

We selected 200 C. tropicalis bloodstream isolates from six medical centres in Brazil collected between 2007 and 2018. Species identification was confirmed by MALDI-TOF/MS. Antifungal susceptibility testing for four antifungal agents was performed by the Clinical and Laboratory Standards Institute (CLSI) microbroth method.

RESULTS

Overall, rates of non-susceptibility were 4% and 3.5% to fluconazole and voriconazole, respectively. All isolates were susceptible to amphotericin B and only one isolate was resistant to echinocandins.

CONCLUSION

Although we failed to demonstrate statistical differences in the rates of azole resistance documented during the period of analysis, trends towards lower susceptibility to fluconazole and voriconazole were shown.

Multilocus Sequence Typing Reveals Clonality of Fluconazole-Nonsusceptible Candida tropicalis: A Study From Wuhan to the Global

Candida tropicalis is a globally distributed human pathogenic yeast, and its increasing resistance to azoles makes clinical treatment difficult. In this study, we investigated the clinical features, azole resistance and genetic relatedness of 87 C. tropicalis isolates from central China and combined with the global database to explore the relationship between genetic information and fluconazole susceptibility. Of the 55 diploid sequence types (DSTs) identified by multilocus sequence typing (MLST), 27 DSTs were new to the C. tropicalis MLST database. Fluconazole-nonsusceptible (FNS) isolates were genetically closely related. goeBURST analysis showed that DST225, DST376, DST506, and DST546 formed a distinct and unique FNS clonal complex (CC) in Wuhan. The local FNS CC belongs to the large FNS CC (CC2) in China, in which the putative founder DST225 has been reported from the environment. The three most prevalent types (DST506, DST525, and DST546) in Wuhan had high minimum inhibitory concentrations (MICs) for antifungal azoles, and the six possible nosocomial transmissions we captured were all FNS strains, most of which were from CC2. Unique FNS CCs have been found in Singapore (CC8) and India (CC17) and are close to China's CC2 in the minimum spanning tree. There were no FNS CCs outside Asia. This study is the first to reveal a significant correlation between genetic information and fluconazole susceptibility worldwide and to trace geographical locations, which is of great value for molecular epidemiological surveillance and azole-resistance study of C. tropicalis globally.

Molecular epidemiology of Candida tropicalis isolated from urogenital tract infections

Candida tropicalis is a common human pathogenic yeast, and its molecular typing is important for studying the population structure and epidemiology of this opportunistic yeast, such as epidemic genotype, population dynamics, nosocomial infection, and drug resistance surveillance. In this study, the antifungal susceptibility test and multilocus sequence typing (MLST) analysis were carried out on C. tropicalis from central China. Among 64 urogenital isolates, 45 diploid sequence types (DST) were found, of which 20 DSTs (44.4%) were new to the central database. The goeBURST analysis showed that CC1 (clonal complex) was the only azole‐resistant (100%, 10/10) cluster in Wuhan, which was composed of DST546, DST225, DST376, and DST506, and most of the strains (90%, 9/10) were isolated from the urinary tract. Potential nosocomial infections were mainly caused by CC1 strains. The azole resistance rate of urinary isolates (50.0%, 21/42) was higher than that of vaginal isolates (27.3%, 6/22). The genotype diversity and novelty of vaginal isolates were higher than those of urinary isolates. C. tropicalis population in Wuhan was genetically diverse and divergent from that seen in other countries. In this study, there were significant differences in genotype and azole susceptibility between urine and vaginal strains. The azole‐resistant cluster (CC1) found in urine is of great significance for the clinical treatment and prevention of nosocomial infection. The newly discovered DSTs will contribute to further study the similarity, genetic relationship, and molecular epidemiology of C. tropicalis worldwide.

Candida isolates causing candidemia show different degrees of virulence in Galleria mellonella

We aim to assess intra- and interspecies differences in the virulence of Candida spp. strains causing candidemia using the invertebrate Galleria mellonella model. We studied 739 Candida spp. isolates (C. albicans [n = 373], C. parapsilosis [n = 203], C. glabrata [n = 92], C. tropicalis [n = 53], and C. krusei [n = 18]) collected from patients with candidemia admitted to Gregorio Marañon Hospital (Madrid, Spain). Species-specific infecting inocula (yeast cells/larva) were adjusted (5 × 105 [C. albicans, and C. tropicalis], 2 × 106-5 × 106 [C. parapsilosis, C. glabrata, and C. krusei]) and used to infect 10 larvae per isolate; percentage of survival and median survival per isolate were calculated. According to the interquartile range of the median survival, isolates with a median survival under P25 were classified as of high-virulence and isolates with a median survival over P75 as of low virulence. The median survival of larvae infected with different species was variable: C. albicans (n = 2 days, IQR <1-3 days), C. tropicalis (n = 2 days, IQR 1.5-4 days), C. parapsilosis (n = 2 days, IQR 2-3.5 days), C. glabrata (n = 3 days, IQR 2-3 days), and C. krusei (n = 7 days, 6.5->8 days) (P < .001). Differences in virulence among species were validated by histological examination (day +1 post-infection) in the larvae infected by the isolates of each virulence category and species. Virulence-related gene expression in C. albicans isolates did not reach statistical significance. We report species-specific virulence patterns of Candida spp. and show that isolates within a given species have different degrees of virulence in the animal model.

Modulation of ERG Genes Expression in Clinical Isolates of Candida tropicalis Susceptible and Resistant to Fluconazole and Itraconazole

Candida tropicalis is a non-albicans Candida specie that causes candidosis in several countries, including Brazil. However, little is known about the mechanisms of drug resistance in C. tropicalis infections. In this study, we used clinical isolates of C. tropicalis susceptible as well as resistant to either Fluconazole or Itraconazole to assess the relationship between drug resistance and the expression of ERG and efflux pump genes. Our results showed that the main mechanism of resistance against both Fluconazole and Itraconazole in this specie is through the up-regulation of ERG rather than that of the efflux pump genes. We demonstrated that, although pre-treatment with azole drugs increases the expression of both ERG6 and ERG11 genes, the resistant or susceptible dose-dependent (SDD) samples are able to maintain high expression levels of these genes for longer periods of time than the susceptible samples.

The yeast, the antifungal, and the wardrobe: a journey into antifungal resistance mechanisms of Candida tropicalis

Candida tropicalis is a prominent non-Candida albicans Candida species involved in cases of candidemia, mainly causing infections in patients in intensive care units and (or) those presenting neutropenia. In recent years, several studies have reported an increase in the recovery rates of azole-resistant C. tropicalis isolates. Understanding C. tropicalis resistance is of great importance, since resistant strains are implicated in persistent or recurrent and breakthrough infections. In this review, we address the main mechanisms underlying C. tropicalis resistance to the major antifungal classes used to treat candidiasis. The main genetic basis involved in C. tropicalis antifungal resistance is discussed. A better understanding of the epidemiology of resistant strains and the mechanisms involved in C. tropicalis resistance can help improve diagnosis and assessment of the antifungal susceptibility of this Candida species to improve clinical management.

Investigation of a healthcare-associated Candida tropicalis candidiasis cluster in a haematology unit and a systematic review of nosocomial outbreaks

BACKGROUND

Non-albicans Candida spp. are an emerging cause of hospital-acquired bloodstream infections, associated with high mortality due to the challenges in diagnosis and delayed treatment.

OBJECTIVES

We aimed to investigate a cluster of healthcare-associated invasive candidiasis caused by C tropicalis and review the literature of healthcare-associated outbreaks or clusters caused by C tropicalis.

METHODS

An investigation was performed to determine clinical presentation, treatment outcomes and the factors contributing to C tropicalis candidemia occurrence. We searched the Medline database via PubMed and Ovid using the keywords of "Candida tropicalis" combined with "outbreak" or "clustering" or "clusters," and we limited the search to studies conducted from January 1989 to January 2019.

RESULTS

We report two related cases of C tropicalis candidemia among patients with AML following a period of neutropenia, who had erythematous skin rash as a first manifesting sign of candidiasis. C tropicalis was isolated from blood and skin cultures of both patients, which were identical by pulsed-field gel electrophoresis typing. Our systematic review of outbreaks caused by C tropicalis suggests that (a) most reported outbreaks have occurred in neonatal and adult ICUs; (b) patients who receive total parenteral therapy, antibiotics and those who have indwelling catheters and recent surgery are at high risk of infection; and (c) environmental and healthcare personnel surveillance suggest that cross-contamination is a major risk factor.

CONCLUSION

Control of nosocomial outbreaks caused by C tropicalis should include better infection control measures, education of healthcare professionals especially working in adult and neonatal intensive care and haematology units.

Clonality of Fluconazole-Nonsusceptible Candida tropicalis in Bloodstream Infections, Taiwan, 2011-2017

Candida tropicalis is the leading cause of non-C. albicans candidemia in tropical Asia and Latin America. We evaluated isolates from 344 patients with an initial episode of C. tropicalis candidemia. We found that 58 (16.9%) patients were infected by fluconazole-nonsusceptible (FNS) C. tropicalis with cross resistance to itraconazole, voriconazole, and posaconazole; 55.2% (32/58) of patients were azole-naive. Multilocus sequence typing analysis revealed FNS isolates were genetically closely related, but we did not see time- or place-clustering. Among the diploid sequence types (DSTs), we noted DST225, which has been reported from fruit in Taiwan and hospitals in Beijing, China, as well as DST376 and DST505-7, which also were reported from hospitals in Shanghai, China. Our findings suggest cross-boundary expansion of FNS C. tropicalis and highlight the importance of active surveillance of clinical isolates to detect dissemination of this pathogen and explore potential sources in the community.

Candidemia in solid organ transplant recipients in Spain: Epidemiological trends and determinants of outcome

BACKGROUND

Despite being considered a high-risk population for invasive fungal disease, specific features of candidemia among solid organ transplant (SOT) recipients remain poorly characterized.

METHODS

We compiled prospective data from two multicenter studies on candidemia performed over two consecutive periods in Spain: the CANDIPOP Study (2010-2011) and the CANDI-Bundle Study (2016-2018). Episodes diagnosed in adult SOT recipients in 10 participating centers were included. Risk factors for clinical failure (all-cause 7-day mortality and/or persistent candidemia for ≥72 hours) and 30-day mortality were investigated by univariate analysis.

RESULTS

We included 55 episodes of post-transplant candidemia (32 and 23 of which occurred during the first and second periods). Kidney (38.2%) and liver recipients (30.9%) were the most common populations. Candida albicans accounted for 27.3% of episodes. The proportion of C glabrata increased over time (18.8% vs 30.4% for the first and second periods). There were no differences in the rate of fluconazole non-susceptible isolates (50.0% vs 60.0%, respectively). Clinical failure and 30-day mortality occurred in 25.5% and 27.3% of episodes and were associated with the severity of candidemia (Pitt score and severe sepsis/septic shock). Kidney transplantation (unadjusted odds ratio [uOR]: 0.17; 95% confidence interval [CI]: 0.03-0.85; P-value = .020), early catheter removal (uOR: 0.15; 95% CI: 0.03-0.76; P-value = .013), and appropriate early antifungal therapy (uOR: 0.14; 95% CI: 0.02-0.89; P-value = .041) were protective for 30-day mortality.

CONCLUSIONS

High rates of non-albicans species and fluconazole non-susceptibility must be taken into account to optimize therapeutic management and outcomes in SOT recipients with candidemia.

Poor prognosis of Candida tropicalis among non-albicans candidemia: a retrospective multicenter cohort study, Korea

To evaluate clinical features and prognostic factors of non-albicans candidemia, we conducted a retrospective multicenter cohort study at 7 university hospitals in Korea from January 2010 to February 2016. A total of 721 patients with non-albicans candidemia were included in the analysis. C. tropicalis was most commonly identified (36.5%), followed by C. glabrata (27.2%), C. parapsilosis (25.7%), and C. krusei (2.4%). Clinical presentation of C. tropicalis candidemia was most severe with highest median C-reactive protein level (10.1 mg/dL) and Acute Physiology and Chronic Health Evaluation II score (14, both P ≪ 0.05). C. tropicalis showed the highest 14- and 30-day mortality (28.9% and 44.1%). In multivariate analysis, C. tropicalis infection was significantly related with 14- (P = 0.005) and 30-day mortality (P = 0.033). In conclusion, C. tropicalis infection presented most severely and showed worst clinical outcome among non-albicans candidemia.

Implications of the EUCAST Trailing Phenomenon in Candida tropicalis for the In Vivo Susceptibility in Invertebrate and Murine Models

Candida tropicalis isolates often display reduced but persistent growth (trailing) over a broad fluconazole concentration range during EUCAST susceptibility testing. Whereas weak trailing (<25% of the positive growth control) is common and found not to impair fluconazole efficacy, we investigated if more pronounced trailing impacted treatment efficacy. Fluconazole efficacy against two weakly (≤25% growth), two moderately (26% to 50% growth), and one heavily (>70% growth) trailing resistant isolate and one resistant (100% growth) isolate were investigated in vitro and in vivo (in a Galleria mellonella survival model and two nonlethal murine models). CDR1 expression levels and ERG11 sequences were characterized. The survival in fluconazole-treated G. mellonella was inversely correlated with the degree of trailing (71% to 9% survival in treatment groups). In mice, resistant and heavily trailing isolates responded poorly to fluconazole treatment. CDR1 expression was significantly higher in trailing and resistant isolates than in wild-type isolates (1.4-fold to 10-fold higher). All isolates exhibited ERG11 wild-type alleles. Heavily trailing isolates were less responsive to fluconazole in all in vivo models, indicating an impact on fluconazole efficacy. CDR1 upregulation may have contributed to the observed differences. Moderately trailing isolates responded less well to fluconazole in larvae only. This confirms clinical data suggesting fluconazole is effective against infections with such isolates in less severely ill patients and supports the current 50% growth endpoint for susceptibility testing. However, it is still unclear if the gradual loss of efficacy observed for moderately trailing isolates in the larva model may be a reason for concern in selected vulnerable patient populations.

Clinical characteristics of Candida tropicalis fungaemia with reduced triazole susceptibility in Taiwan: a multicentre study

Candida tropicalis is the second most common Candida species causing fungaemia in Taiwan, and decreased susceptibility to fluconazole has been reported. This study analysed the clinical characteristics of adult patients with C. tropicalis fungaemia and the antifungal susceptibilities of isolates at five tertiary hospitals in Taiwan (1 July 2011 to 30 June 2014). A standardised case record form was used retrospectively to collect demographic, clinical and microbiological characteristics, antifungal treatment and outcomes. MICs of non-duplicate isolates were determined using Sensititre^TM YeastOne^TM and were interpreted using cut-off values recommended by the CLSI. A total 248 patients were diagnosed over the study period; 30-day crude mortality was 52.0%. Multivariate analysis showed that high Charlson comorbidity index ≥4 (OR = 2.09, 95% CI 1.22-3.59; P = 0.008), neutropenia (OR = 4.61, 95% CI 1.42-15.00; P = 0.011) and treatment with an azole-based regimen (OR = 0.39, 95% CI 0.17-0.90; P = 0.028) were significantly associated with 30-day mortality. A total of 33.9% of isolates were non-susceptible to fluconazole (MIC₅₀, 2 mg/L; MIC₉₀, 16 mg/L; MIC range, 0.25 to >256 mg/L), whilst 56.9% to voriconazole (MIC₅₀, 0.25 mg/L; MIC₉₀, 1 mg/L; MIC range, 0.015 to >8 mg/L) according to CLSI clinical breakpoints. There was no significant correlation between overall mortality and MICs of fluconazole or voriconazole. This study showed high mortality in patients with C. tropicalis fungaemia, and azole-based antifungal treatment could improve outcomes regardless of fluconazole MICs of infecting isolates compared with patients without any treatment within 48 h.

Multilocus Sequence Typing Reveals a New Cluster of Closely Related Candida tropicalis Genotypes in Italian Patients With Neurological Disorders

Candida tropicalis is a pathogenic yeast that has emerged as an important cause of candidemia especially in elderly patients with hematological malignancies. Infections caused by this species are mainly reported from Latin America and Asian-Pacific countries although recent epidemiological data revealed that C. tropicalis accounts for 6-16.4% of the Candida bloodstream infections (BSIs) in Italy by representing a relevant issue especially for patients receiving long-term hospital care. The aim of this study was to describe the genetic diversity of C. tropicalis isolates contaminating the hands of healthcare workers (HCWs) and hospital environments and/or associated with BSIs occurring in patients with different neurological disorders and without hematological disease. A total of 28 C. tropicalis isolates were genotyped using multilocus sequence typing analysis of six housekeeping (ICL1, MDR1, SAPT2, SAPT4, XYR1, and ZWF1) genes and data revealed the presence of only eight diploid sequence types (DSTs) of which 6 (75%) were completely new. Four eBURST clonal complexes (CC2, CC10, CC11, and CC33) contained all DSTs found in this study and the CC33 resulted in an exclusive, well-defined, clonal cluster from Italy. In conclusion, C. tropicalis could represent an important cause of BSIs in long-term hospitalized patients with no underlying hematological disease. The findings of this study also suggest a potential horizontal transmission of a specific C. tropicalis clone through hands of HCWs and expand our understanding of the molecular epidemiology of this pathogen whose population structure is still far from being fully elucidated as its complexity increases as different categories of patients and geographic areas are examined.

ICU-acquired candidaemia in France: Epidemiology and temporal trends, 2004-2013 - A study from the REA-RAISIN network

OBJECTIVE

Candidaemia is a life-threatening infectious disease, associated with septic shock, multiple organ failure, and a high mortality rate. In France, reported data on the incidence of ICU-acquired candidaemia and the causative Candida species are scarce. The objective of this study was to determine temporal trends in epidemiology and risk factors of intensive care unit-acquired candidaemia (ICU-Cand) and ICU mortality among a very large population of ICU patients.

METHOD

Demographics, patient risk factors, invasive device exposure and nosocomial infection in ICU patient were collected from 2004 to 2013 in a national network of 213 ICUs: REA-RAISIN. Incidence and risk factors for candidaemia and ICU mortality were assessed.

RESULTS

Out of 246,459 ICU patients, 851 developed an ICU-cand, representing 0.3 per 1000 patients-days. The incidence rose sharply over time. Candida albicans was the main species. The overall and ICU mortality was 52.4% in ICU-cand patients. The main risk factors of ICU-cand were length of stay, severity of illness and antimicrobial therapy at ICU admission, immune status and use of invasive procedure. ICU-cand was an independent risk factor of mortality (OR: 1.53; 95%CI [1.40-1.70]); in a sub-group analysis, independent effects on mortality were observed with C. albicans (OR: 1.45 [1.23-1.71]), Candida tropicalis (OR: 2.11 [1.31-3.39]) and "other" Candida species (OR: 1.64 [1.09-2.45]).

CONCLUSION

ICU candidaemia ranked sixth among bloodstream infections, and its average annual incidence was 0.3 per 1000 patients days. Despite of new therapy and international recommendation, the incidence rose sharply during the study period, and ICU mortality remained high.

Central venous catheter (CVC) removal for patients of all ages with candidaemia

BACKGROUND

Candida bloodstream infections most often affect those already suffering serious, potentially life-threatening conditions and often cause significant morbidity and mortality. Most affected persons have a central venous catheter (CVC) in place. The best CVC management in these cases has been widely debated in recent years, while the incidence of candidaemia has markedly increased.

OBJECTIVES

The main purpose of this review is to examine the impact of removing versus retaining a CVC on mortality in adults and children with candidaemia who have a CVC in place.

SEARCH METHODS

We searched the following databases from inception to 3 December 2015: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid SP), EMBASE (Ovid SP), the Commonwealth Agricultural Bureau (CAB), Web of Science and the Cumulative Index to Nursing and Allied Health Literature (CINAHL). We searched for missed, unreported and ongoing trials in trial registries and in reference lists of excluded articles.

SELECTION CRITERIA

We searched for randomized controlled trials (RCTs) and quasi-RCTs involving adults and children with candidaemia and in which participants were randomized for removal of a CVC (the intervention under study), irrespective of publication status, date of publication, blinding status, outcomes published or language.However, two major factors make the conduct of RCTs in this population a difficult task: the large sample size required to document the impact of catheter removal in terms of overall mortality; and lack of economic interest from the industry in conducting such a trial.

DATA COLLECTION AND ANALYSIS

Our primary outcome measure was mortality. Several secondary outcome measures such as required time for clearance of blood cultures for Candida species, frequency of persistent candidaemia, complications, duration of mechanical ventilation and length of stay in the intensive care unit (ICU) and in the hospital were planned, as were various subgroup and sensitivity analyses, according to our protocol. We assessed papers and abstracts for eligibility and resolved disagreements by discussion. However, we were not able to include any RCTs or quasi-RCTS in this review and, as a result, have carried out no meta-analyses. However, we have chosen to provide a brief overview of excluded observational studies.

MAIN RESULTS

We found no RCT and thus no available data for evaluation of the primary outcome (mortality) nor secondary outcomes or adverse effects. Therefore, we conducted no statistical analysis.A total of 73 observational studies reported on various clinically relevant outcomes following catheter removal or catheter retention. Most of these excluded, observational studies reported a beneficial effect of catheter removal in patients with candidaemia. None of the observational studies reported results in favour of retaining a catheter. However, the observational studies were very heterogeneous with regards to population, pathogens and interventions. Furthermore, they suffered from confounding by indication and an overall high risk of bias. As a consequence, we are not able to provide recommendations or to draw firm conclusions because of the difficulties involved in interpreting the results of these observational studies (very low quality of evidence, GRADE - Grades of Recommendation, Assessment, Development and Evaluation Working Group).

AUTHORS' CONCLUSIONS

Despite indications from observational studies in favour of early catheter removal, we found no eligible RCTs or quasi-RCTs to support these practices and therefore could draw no firm conclusions. At this stage, RCTs have provided no evidence to support the benefit of early or late catheter removal for survival or other important outcomes among patients with candidaemia; no evidence with regards to assessment of harm or benefit with prompt central venous catheter removal and subsequent re-insertion of new catheters to continue treatment; and no evidence on optimal timing of insertion of a new central venous catheter.

Comparison of the antifungal activity of micafungin and amphotericin B against Candida tropicalis biofilms

OBJECTIVES

Candida tropicalis is the fourth most common cause of candidaemia in hospitalized patients and associated mortality is high. C. tropicalis frequently causes biofilm-related infections. Echinocandins and amphotericin B show potent in vitro activity against C. albicans biofilms, but their activity against C. tropicalis biofilms has received little attention.

METHODS

We studied production of biofilm by 54 C. tropicalis isolates from blood and the antifungal susceptibility of these isolates to micafungin, amphotericin B and liposomal amphotericin B. Biofilm production was measured using the crystal violet assay to determine biomass and the XTT reduction assay to determine metabolic activity. The antifungal susceptibility of planktonic and sessile cells was measured using the EUCAST EDef 7.2 procedure and XTT reduction assay, respectively. The sessile MIC endpoint of SMIC80 was defined as an 80% reduction in the metabolic activity of the biofilm treated with the antifungal compared with the control well.

RESULTS

The three drugs were very active against the isolates in planktonic form, with micafungin showing the highest activity (P < 0.001). Micafungin was the most active agent against C. tropicalis biofilms (P < 0.001). In contrast, liposomal amphotericin B showed poor antifungal activity.

CONCLUSIONS

Micafungin was the most active drug against C. tropicalis biofilm. Although the echinocandins and liposomal amphotericin B are considered very active against Candida spp. biofilms, this is not true for C. tropicalis, as liposomal amphotericin B showed poor antifungal activity against biofilms.

Chemical composition and antifungal potential of Brazilian propolis against Candida spp

Propolis is known to have biological properties against numerous microorganisms of clinical interest. This study aimed to determine the chemical composition and antifungal activity of Brazilian propolis (types 3 and 13) against Candida spp. and their effects on the morphology of preformed and mature Candida biofilms. Samples of propolis (3 and 13) collected by Apis mellifera honeybees were obtained from different regions in Brazil. Ethanolic extracts of propolis (EEP) were prepared, fractionated and submitted to chemical analysis by GC/MS. The extracts and their hexane, dichloromethane and ethyl acetate fractions were tested for their ability to inhibit Candida spp. (C. albicans, C. dubliniensis, C. glabrata, C. kruzei, C. tropicalis and C. parapsilosis) by determination of the minimum inhibitory and fungicidal concentrations (MIC/MFC). Additionally, their effects on morphology of preformed and mature biofilms were observed by scanning electron microscopy. The phenolic compounds p-coumaric acid, caffeic acid phenethyl ester (CAPE), kaempferol and quercetin were identified in the EEP-3 and its bioactive dichloromethane fraction; and isoflavonoids such as medicarpin, vestitol and formononetin were found in the EEP-13, and triterpenes in its bioactive hexane fraction. The EEP-3 and EEP-13 and their bioactive fractions showed MIC values ranging from 0.2 to 125μg/mL and MFC values between 125 and 500μg/mL. The EEP and fractions were predominantly fungistatic agents. All extracts and fractions disrupted biofilm structures at 500μg/mL and amorphous areas with cell damage were clearly observed in preformed and mature biofilms. Propolis types 3 and 13 have strong anti-Candida activity and should be considered as promising candidates to treat oral and systemic candidiasis.