The increased role of non-albicans species in candidaemia: results from a 3-year surveillance study

Species Distribution and Antifungal Susceptibilities of Candida Species Isolated From Blood Culture

Introduction Candida species (spp.) are among the leading agents of bloodstream infections. Candidemias are a major cause of morbidity and mortality. Having an understanding of Candida epidemiology and antifungal susceptibility patterns in each center is crucial in guiding the management of candidemia. In this study, the species distribution and antifungal susceptibility of Candida spp. isolated from blood culture at the University of Health Sciences, Bursa Yuksek Ihtisas Training & Research Hospital were examined and the first data on the epidemiology of candidemia in our center were presented. Methods A total of 236 Candida strains isolated from blood cultures in our hospital over a four-year period were analyzed and their antifungal susceptibilities were studied retrospectively. Strains were identified at the species complex (SC) level by the germ tube test, morphology in cornmeal-tween 80 medium, and the automated VITEK 2 Compact (bioMérieux, Marcy-l'Étoile, France) system. Antifungal susceptibility tests were performed on VITEK 2 Compact (bioMérieux, Marcy-l'Étoile, France) system. The susceptibilities of the strains to fluconazole, voriconazole, micafungin, and amphotericin B were determined according to Clinical and Laboratory Standards Institute (CLSI) guidelines and epidemiologic cut-off values. Results Of the Candida (C.) strains, 131 were C. albicans (55.5%), 40 were C. parapsilosis SC (16.9%), 21 were C. tropicalis (8.9%), 19 were C. glabrata SC (8.1%), eight were C. lusitaniae (3.4%), seven were C. kefyr (3.0%), six were C. krusei (2.6%), two were C. guilliermondii (0.8%) and two were C. dubliniensis (0.8%). Amphotericin B resistance was not detected in Candida strains. Micafungin susceptibility was 98.3%, and four C. parapsilosis SC strains (10%) were intermediate (I) to micafungin. Fluconazole susceptibility was 87.2%. Apart from C. krusei strains which intrinsically resistant to fluconazole, three C. parapsilosis (7.5%), one C. glabrata SC (5.3%) strain were resistant (R) to fluconazole, and one C. lusitaniae (12.5%) strain was wild-type (WT). Voriconazole susceptibility of Candida strains was 98.6%. Two C. parapsilosis SC strains were I to voriconazole, while one strain was R. Conclusion In this study, the first epidemiological data of candidemia agents in our hospital were presented. It was determined that rare and naturally resistant species did not cause any problem in our center yet. C. parapsilosis SC strains showed decreased susceptibility to fluconazole, whereas Candida strains were highly susceptible to the four antifungals tested. Close monitoring of these data will help guide the treatment of candidemia.

Comparison of Clinical Laboratory Standards Institute (CLSI) Microdilution Method and VITEK 2 Automated Antifungal Susceptibility System for the Determination of Antifungal Susceptibility of Candida Species

Introduction

Changes in the epidemiology of Candida infections, increasing resistance, and advances in treatment have increased the need to perform antifungal susceptibility testing in clinical laboratories. Standardized reference, the microbroth dilution method, and various commercial antifungal susceptibility test systems are used to determine antifungal susceptibility. This study aims to determine and compare the antifungal susceptibility of various Candida species isolated from blood cultures in our laboratory with the CLSI M27 microdilution reference method and VITEK 2 automated system (bioMérieux, Marcy-l'Étoile, France).

Methods

The antifungal susceptibility of a total of 140 Candida strains to fluconazole, voriconazole, and amphotericin B, and a total of 92 strains to anidulafungin was tested with the CLSI M27 method and the VITEK 2 automated system. For fluconazole, voriconazole, and amphotericin B, essential and categorical agreement percentages were calculated between the two methods. Because there is no anidulafungin in the VITEK 2 system, anidulafungin results obtained with CLSI were compared with micafungin only in terms of categorical agreement. In the category comparison, CLSI clinical breakpoints were used; the epidemiological cut-off values were used when they were not available. Very major error, major error, and minor error rates were calculated.

Results

In general, the minimum inhibitory concentration (MIC) values obtained with VITEK 2 for azole group drugs were found to be one-fold higher than the CLSI MICs read at the 24th hour. While the essential agreement between the two methods was >90% for amphotericin B and voriconazole, it remained at 85% for fluconazole. Overall, the best categorical agreement was obtained with amphotericin B (99.3%), and the least categorical agreement was obtained with voriconazole (85.7%). A very major error was seen with amphotericin B (0.7%) and fluconazole (0.7%) in one C. parapsilosis strain each. No resistance was detected with VITEK 2 in one C. glabrata strain found to be resistant to fluconazole by the reference method. Major and minor error rates were higher for azole drugs than amphotericin B and anidulafungin/micafungin.

Conclusion

The VITEK 2 system is a fast and highly applicable system, and with these features, it is advantageous for routine laboratories. In this study, although the error rate was not very high, one fluconazole-resistant C. parapsilosis and C. glabrata strain could not be detected with VITEK 2. The increase in data on the antifungal performance of the VITEK 2 system, which is available in many routine laboratories due to its ability to be used for bacteria identification and sensitivity, will contribute to the usability of the system for this purpose. In this study, data that will support the literature information in terms of the antifungal performance of the VITEK 2 system are presented.

Virulence Factors and Antifungal Susceptibility Profile of C. tropicalis Isolated from Various Clinical Specimens in Alexandria, Egypt

BACKGROUND

The incidence of candidiasis caused by non-albicans Candida (NAC) species is increasing. Candida tropicalis has emerged as one of the most important NAC species. This study aims to examine the antifungal susceptibility profile and some virulence factors of C. tropicalis isolated from various clinical specimens.

METHODS

A total of 71 C. tropicalis isolates from various clinical specimens (69.01%, 18.31%, 9.86%, and 2.82% of isolates were collected from urine, respiratory samples, blood, and skin and soft tissue infections, respectively) from ICU patients in Alexandria, Egypt. The isolates were identified at species level by CHROMagar Candida and VITEK 2 compact system. Furthermore, the antifungal susceptibility was determined using the VITEK 2 system AST-YS07 card containing different antifungals. Hemolysin, phospholipase, and proteinase activity and biofilm formation were also tested as virulence factors.

RESULTS

Only 30 isolates (42.25%) were non-susceptible (MIC ≥ 4 µg/mL) to fluconazole, of which 28 isolates showed non-susceptibility (MIC ≥ 0.25 µg/mL) to voriconazole. All isolates showed both hemolysin and proteinase activities, while only 9 isolates (12.68%) showed phospholipase production and 70 isolates (98.59%) demonstrated biofilm formation. Strong biofilm production was observed among the blood culture isolates (85.71%), followed by the respiratory and urinary isolates (61.54% and 46.94%, respectively).

CONCLUSIONS

This study sought to provide useful data on the antifungal susceptibility of C. tropicalis isolates from ICU patients suffering from invasive infections with an increased trend towards elevated MICs levels of both fluconazole and voriconazole. Due to the high incidence of systemic candidiasis and antifungal resistance, C. tropicalis is emerging as a serious root of infections. Therefore, early and accurate identification of Candida species along with susceptibility testing is of utmost importance.

Current Aspects in the Biology, Pathogeny, and Treatment of Candida krusei, a Neglected Fungal Pathogen

Fungal infections represent a constant and growing menace to human health, because of the emergence of new species as causative agents of diseases and the increment of antifungal drug resistance. Candidiasis is one of the most common fungal infections in humans and is associated with a high mortality rate when the fungi infect deep-seated organs. Candida krusei belongs to the group of candidiasis etiological agents, and although it is not isolated as frequently as other Candida species, the infections caused by this organism are of special relevance in the clinical setting because of its intrinsic resistance to fluconazole. Here, we offer a thorough revision of the current literature dealing with this organism and the caused disease, focusing on its biological aspects, the host-fungus interaction, the diagnosis, and the infection treatment. Of particular relevance, we provide the most recent genomic information, including the gene prediction of some putative virulence factors, like proteases, adhesins, regulators of biofilm formation and dimorphism. Moreover, C. krusei veterinary aspects and the exploration of natural products with anti-C. krusei activity are also included.

Differential recognition of Candida tropicalis, Candida guilliermondii, Candida krusei, and Candida auris by human innate immune cells

Background

The deep-seated infections caused by the Candida genus are associated with a high mortality rate, and Candida albicans is the most frequent species associated with these diseases. The fungal wall is composed of macromolecules not synthesized by the host, and therefore is a source of ligands recognized by innate immune cells.

Methods

We performed a comparative study analyzing the cell wall composition and organization of Candida tropicalis, Candida guilliermondii, Candida krusei, and Candida auris, along with their ability to stimulate cytokine production and phagocytosis by human innate immune cells.

Results

We found that the wall of these species had the basic components already described in C. albicans, with most of the chitin and b1,3-glucan located underneath the mannan layer. However, the walls of C. krusei and C. auris were rich in chitin and the former had a lower content of mannans. C. guilliermondii contained changes in the mannan and the b1,3-glucan levels. These species were differentially phagocytosed by human macrophages and stimulated cytokine production in a dectin-1-dependent pathway. C. krusei showed the most significant changes in the tested parameters, whereas C. auris behaved like C. albicans.

Conclusion

Our results suggest that the cell wall and innate immune recognition of C. tropicalis, C. guilliermondii, C. krusei, and Candida auris is different from that reported for C. albicans.

In Vitro Anti-Biofilm Activities of Citral and Thymol Against Candida Tropicalis

Candida tropicalis is an emerging non-albicans Candida species which is pathogenic to the immune-compromised humans, especially in tropical countries, including India. The acquired resistance of Candida species towards antifungal therapies is of major concern. Moreover, limited efficacy and dosage constraint of synthetic drugs have indicated the prerequisite of finding new and natural drugs for treatment. In the present study, we have compared the influence of citral and thymol on C. tropicalis and its biofilm along with expression levels of certain antifungal tolerance genes. The antifungal and anti-biofilm activities of the both were studied using 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide sodium salt (XTT) reduction assay, field emission scanning electron microscope (FE-SEM) and confocal laser scanning microscope (CLSM) and real-time reverse transcription polymerase chain reaction (RT-PCR) analysis. Citral and thymol have damaged the cells with distorted surface and less viability. Quantitative real-time PCR analysis showed augmented expression of the cell membrane biosynthesis genes including ERG11/CYT450 against citral and the cell wall related tolerance genes involving CNB1 against thymol thus, depicting their differential mode of actions.

Echinocandins for management of invasive candidiasis in patients with liver disease and liver transplantation

Candida species remains one of the most important causes of opportunistic infections worldwide. Invasive candidiasis (IC) is associated with considerable morbidity and mortality in liver disease (LD) patients if not treated promptly. Echinocandins are often recommended as a first-line empirical treatment for managing IC and can especially play a critical role in managing IC in LD patients. However, advanced LD patients are often immunocompromised and critically ill. Hence altered pharmacokinetics, drug interactions as well as tolerance issues of antifungal treatments are a concern in these patients. This comprehensive review examines the epidemiology, risk factors and diagnosis of IC in patients with LD and evaluates differences between three available echinocandins for treating this group of patients.

Candidemia in a major regional tertiary referral hospital - epidemiology, practice patterns and outcomes

Background

Candidemia is a common cause of nosocomial bloodstream infections, resulting in high morbidity and mortality. This study was conducted to describe the epidemiology, species distribution, antifungal susceptibility patterns and outcomes of candidemia in a large regional tertiary referral hospital.

Methods

A retrospective surveillance study of patients with candidemia was conducted at Singapore General Hospital between July 2012 and December 2015. In addition, incidence densities and species distribution of candidemia episodes were analysed from 2008 to 2015.

Results

In the period of 2012 to 2015, 261 candidemia episodes were identified. The overall incidence was 0.14/1000 inpatient-days. C. glabrata (31.4%), C. tropicalis (29.9%), and C. albicans (23.8%) were most commonly isolated. The incidence of C. glabrata significantly increased from 2008 to 2015 (Coefficient 0.004, confidence interval 0–0.007, p = 0.04). Fluconazole resistance was detected primarily in C. tropicalis (16.7%) and C. glabrata (7.2%). fks mutations were identified in one C. albicans and one C. tropicalis. Candidemia episodes caused by C. tropicalis were more commonly encountered in patients with haematological malignancies (p = 0.01), neutropenia (p < 0.001) and higher SAPS II scores (p = 0.02), while prior exposure to echinocandins was associated with isolation of C. parapsilosis (p = 0.001). Echinocandins (73.3%) were most commonly prescribed as initial treatment. The median (range) time to initial treatment was 1 (0–9) days. The 30-day in-hospital mortality rate was 49.8%. High SAPS II score (Odds ratio, OR 1.08; 95% confidence interval, CI 1.05–1.11) and renal replacement therapy (OR 5.54; CI 2.80–10.97) were independent predictors of mortality, while drain placement (OR 0.44; CI 0.19–0.99) was protective.

Conclusions

Decreasing azole susceptibilities to C. tropicalis and the emergence of echinocandin resistance suggest that susceptibility patterns may no longer be sufficiently predicted by speciation in our institution. Candidemia is associated with poor outcomes. Strategies optimising antifungal therapy, especially in the critically-ill population, should be explored.

In Vitro Susceptibility and Trailing Growth Effect of Clinical Isolates of Candida Species to Azole Drugs

Background:

Emergence of resistance to respective antifungal drugs is a primary concern for the treatment of candidiasis. Hence, determining antifungal susceptibility of the isolated yeasts is of special importance for effective therapy. For this purpose, the clinical laboratory standard institute (CLSI) has introduced a broth microdilution method to determine minimum inhibitory concentration (MIC). However, the so-called “Trailing effect” phenomenon might sometimes pose ambiguity in the interpretation of the results.

Objectives:

The present study aimed to determine the in vitro susceptibility of clinical isolates of Candida against azoles and the frequency of the Trailing effect.

Materials and Methods:

A total of 193 Candida isolates were prospectively collected and identified through the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Using a broth microdilution test, according to the guidelines of CLSI M27-A3, antifungal susceptibilities of the isolated yeasts against Fluconazole (FLU), Itraconazole (ITR), Ketoconazole (KET) and Voriconazole (VOR) were assessed. Moreover, trailing growth was determined when a susceptible MIC was incubated for 24 hours, and turned into a resistant one after 48 hours of incubation.

Results:

Among the tested antifungal drugs in this study, the highest rate of resistance was observed against ITR (28.5%) followed by VOR (26.4%), FLU (20.8%) and KET (1.5%). The trailing effect was induced in 27 isolates (14.0%) by VOR, in 26 isolates (13.5%) by ITR, in 24 isolates (12.4%) by FLU, and in 19 isolates (9.8%) by KET.

Conclusions:

The monitoring of antifungal susceptibilities of Candida species isolated from clinical sources is highly recommended for the efficient management of patients. Moreover, the trailing effect should be taken into consideration once the interpretation of the results is intended.

Antifungal susceptibility of invasive Candida bloodstream isolates from the Asia-Pacific region

Bloodstream infections caused by Candida species are of increasing importance and associated with significant mortality. We performed a multi-centre prospective observational study to identify the species and antifungal susceptibilities of invasive bloodstream isolates of Candida species in the Asia-Pacific region. The study was carried out over a two year period, involving 13 centers from Brunei, Philippines, Singapore, South Korea, Taiwan, Thailand, and Vietnam. Identification of Candida species was performed at each study center, and reconfirmed at a central laboratory. Susceptibility testing was performed using a commercial broth dilution panel (Sensititre YeastOne YST-010, Thermofisher, United Kingdom) with susceptibility categorisation (S = susceptible, S-DD = susceptible dose-dependent) applied using breakpoints from the Clinical Laboratory Standards Institute. Eight hundred and sixty-one Candida isolates were included in the study. The most common species were C. albicans (35.9%), C. tropicalis (30.7%), C. parapsilosis (15.7%), and C. glabrata (13.6%). Non-albicans species exceeded C. albicans species in centers from all countries except Taiwan. Fluconazole susceptibility was almost universal for C. albicans (S = 99.7%) but lower for C. tropicalis (S = 75.8%, S-DD = 6.1%), C. glabrata (S-DD = 94.9%), and C. parapsilosis (S = 94.8%). Echinocandins demonstrated high rates of in vitro susceptibility (S>99%) against C. albicans, C. tropicalis, and C. parapsilosis This study demonstrates that non-albicans species are the most common isolates from bloodstream infections in most countries in the Asia-Pacific region, with C. tropicalis as the predominant species. Because of the prevalence of reduced susceptibility to fluconazole in non-albicans species, the study indicates that echinocandins should be the antifungal of choice in clinically unstable or high-risk patients with documented candidemia.

Epidemiology and risk factors for invasive candidiasis

The number of immunosuppressive patients has increased significantly in recent years. These patients are at risk for opportunistic infections, especially fungal infections. Candidiasis is one of the most frequent fungal infections determined in these immunosuppressive patients and its epidemiology has changed over the last two decades. Recently, new antifungal agents and new therapy strategies such as antifungal prophylaxis, secondary prophylaxis, and preemptive therapy have come into use. These changes resulted in the alteration of Candida species causing invasive infections. The incidence of Candida albicans was decreased in many countries, especially among patients with immunosuppressive disorders, while the incidence of species other than C. albicans was increased. In this review, incidence, risk factors, and species distribution of invasive candidiasis are discussed.

Molecular fingerprints to identify Candida species

A wide range of molecular techniques have been developed for genotyping Candida species. Among them, multilocus sequence typing (MLST) and microsatellite length polymorphisms (MLP) analysis have recently emerged. MLST relies on DNA sequences of internal regions of various independent housekeeping genes, while MLP identifies microsatellite instability. Both methods generate unambiguous and highly reproducible data. Here, we review the results achieved by using these two techniques and also provide a brief overview of a new method based on high-resolution DNA melting (HRM). This method identifies sequence differences by subtle deviations in sample melting profiles in the presence of saturating fluorescent DNA binding dyes.

Invasive candidiasis in Pakistan: clinical characteristics, species distribution and antifungal susceptibility

This study reports for the first time, to our knowledge, descriptive epidemiological data for 188 invasive Candida isolates from Pakistan, including species identification and antifungal susceptibility against fluconazole, itraconazole, voriconazole, caspofungin, micafungin, anidulafungin and amphotericin. Risk factors for invasive candidiasis (IC) were determined for 96 patients from Karachi, Pakistan. In adults and neonates, Candida tropicalis (38 and 36 %, respectively) was the most common species, followed in adults by Candida parapsilosis (17.8 %), Candida glabrata (15.9 %) and Candida albicans (12.3 %). C. albicans (21 %) was the second most common in neonates. In children, C. albicans (31.9 %), C. tropicalis (26.4 %) and C. parapsilosis (19.4 %) were the most common. C. albicans IC was significantly associated with paediatric age [crude odds ratio (COR) 3.46, 95 % confidence interval (CI) 1.63-7.32]. Rare species made up 17.5 % of the total isolates studied. Resistance to fluconazole was seen in C. glabrata (15 .0%) and Candida krusei (100 .0%). Only one isolate (C. glabrata) was resistant to all three echinocandins. Low MICs of fluconazole for 98 % (184/188) of isolates tested support its continued use as an empiric therapy for IC. Non-C. albicans IC was associated with the use of β-lactam inhibitor combinations (COR 3.16, 95 % CI 1.05-9.57). Use of healthcare devices was documented in 85.4 % of IC patients, whilst 75 .0% had been admitted to special care units. Surprisingly, 66.7 % of patients with IC were not obviously immunosuppressed. The high frequency of modifiable risk factors in this population indicates that candidaemia can be reduced with stringent antibiotic and infection control measures. These data will be useful for empiric selection of antifungals in Karachi, and contribute to global assessments of antifungal resistance.

Epidemiology and risk factors for non-Candida albicans candidemia in non-neutropenic patients at a Chinese teaching hospital

The purpose of this study was to describe the epidemiology of nosocomial candidemia and identify risk factors involved in infections caused by non-C. albicans Candida species in a Chinese tertiary care center over a 10-year period. A total of 102 cases of nosocomial candidemia in non-neutropenic patients admitted from 1998 through 2007 were included in the study. Candida albicans remained the most common causative agent, accounting for 57.8% of all cases, followed by C. tropicalis (12.8%), C. parapsilosis (10.8%) and C. glabrata (10.8%). Comparison of C. albicans and non-C. albicans candidemia by multivariate logistic regression showed that factors independently associated with non-C. albicans candidemia included head trauma (OR, 5.34; 95% CI, 1.18-24.17; P = 0.029) and bacterial sepsis (OR, 3.58; 95% CI, 1.17-10.98; P = 0.026). Factors independently associated with C. albicans candidemia included tracheal intubation (OR, 0.26; 95% CI, 0.08-0.92; P = 0.037), and increased peripheral WBC count (OR, 0.84; 95% CI, 0.74-0.95; P = 0.006).