Evaluation of Virulence Factors In vitro, Resistance to Osmotic Stress and Antifungal Susceptibility of Candida tropicalis Isolated from the Coastal Environment of Northeast Brazil

Carbon substrates promotes stress resistance and drug tolerance in clinical isolates of Candida tropicalis

Candida tropicalis is a human pathogen and one of the most prevalent non-Candida albicans Candida (NCAC) species causing invasive infections. Azole antifungal resistance in C. tropicalis is also gradually increasing with the increasing incidence of infections. The pathogenic success of C. tropicalis depends on its effective response in the host microenvironment. To become a successful pathogen, cellular metabolism, and physiological status determine the ability of the pathogen to counter diverse stresses inside the host. However, to date, limited knowledge is available on the impact of carbon substrate metabolism on stress adaptation and azole resistance in C. tropicalis. In this study, we determined the impact of glucose, fructose, and sucrose as the sole carbon source on the fluconazole resistance and osmotic (NaCl), oxidative (H2O2) stress adaptation in C. tropicalis clinical isolates. We confirmed that the abundance of carbon substrates influences or increases drug resistance and osmotic and oxidative stress tolerance in C. tropicalis. Additionally, both azole-resistant and susceptible isolates showed similar stress adaptation phenotypes, confirming the equal efficiency of becoming successful pathogens irrespective of drug susceptibility profile. To the best of our knowledge, our study is the first on C. tropicalis to demonstrate the direct relation between carbon substrate metabolism and stress tolerance or drug resistance.

Identification of Virulence Factors in Isolates of Candida haemulonii, Candida albicans and Clavispora lusitaniae with Low Susceptibility and Resistance to Fluconazole and Amphotericin B

Emerging life-threatening multidrug-resistant (MDR) species such as the C. haemulonii species complex, Clavispora lusitaniae (sin. C. lusitaniae), and other Candida species are considered as an increasing risk for human health in the near future. (1) Background: Many studies have emphasized that the increase in drug resistance can be associated with several virulence factors in Candida and its knowledge is also essential in developing new antifungal strategies. (2) Methods: Hydrophobicity, adherence, biofilm formation, lipase activity, resistance to osmotic stress, and virulence 'in vivo' on G. mellonella larvae were studied in isolates of C. haemulonii, C. albicans, and C. lusitaniae with low susceptibility and resistance to fluconazole and amphotericin B. (3) Results: Intra- and interspecies variability were observed. C. haemulonii showed high hydrophobicity and the ability to adhere to and form biofilm. C. lusitaniae was less hydrophobic, was biofilm-formation-strain-dependent, and did not show lipase activity. Larvae inoculated with C. albicans isolates displayed significantly higher mortality rates than those infected with C. haemulonii and C. lusitaniae. (4) Conclusions: The ability to adhere to and form biofilms associated with their hydrophobic capacity, to adapt to stress, and to infect within an in vivo model, observed in these non-wild-type Candida and Clavispora isolates, shows their marked virulence features. Since factors that define virulence are related to the development of the resistance of these fungi to the few antifungals available for clinical use, differences in the physiology of these cells must be considered to develop new antifungal therapies.

Fruits are vehicles of drug-resistant pathogenic Candida tropicalis

IMPORTANCE

Of 123 identified isolates from the fruit surface, C. tropicalis was the most frequently found species, followed by Meyerozyma caribbica and Candida krusei. All three fluconazole-resistant C. tropicalis were non-susceptible to voriconazole and belonged to the same predominant genotype of azole-resistant C. tropicalis causing candidemia in patients in Taiwan. Our findings provide evidence that fruit should be washed before eaten not only to remove chemicals but also potential drug-resistant pathogenic microbes, especially for immunocompromised individuals. To keep precious treatment options in patients, we not only continuously implement antimicrobial stewardship in hospitals but also reducing/stopping the use of agricultural fungicide classes used in human medicine.

Genotyping and susceptibility testing uncovers large azole-resistant Candida tropicalis clade in Alexandria, Egypt

OBJECTIVES

Candida tropicalis is an emerging medically relevant Candida species. The yeast primarily causes opportunistic infections in intensive care units and is highly prevalent in tropical countries. The genetic diversity within this species is high, and nosocomial transmission has been reported. C. tropicalis genotyping of isolates from low- and middle-income countries is underrepresented when compared with that from high-income countries. Also, in Egypt, only limited genotyping has been conducted for C. tropicalis isolates, while antifungal resistance seems to increase, especially against azoles.

METHODS

Antifungal susceptibility testing was performed on 64 C. tropicalis isolates from ICU patients collected from multiple hospitals in Alexandria, Egypt. Genotyping by means of short tandem repeat (STR) and whole genome sequencing (WGS) single nucleotide polymorphism (SNP) analysis was performed.

RESULTS

Using antifungal susceptibility testing, fluconazole resistance was observed in 24 isolates (38%), of which 23 harboured an ERG11 G464S substitution, previously shown to cause resistance in Candida albicans. STR genotyping showed that these 23 isolates were related, forming a distinct resistant clade. WGS SNP analysis subsequently confirmed this genetic relationship, although isolates within this clade differed in at least 429 SNPs, suggesting that these were independently introduced.

CONCLUSION

Overall, STR and WGS SNP analysis of this collection indicates limited C. tropicalis nosocomial transmission in Alexandria, while the presence of this large azole-resistant C. tropicalis clade within this city hampers the treatment of intensive care unit patients.

High prevalence of fluconazole resistant Candida tropicalis among candiduria samples in China: An ignored matter of concern

Introduction

The rapid rise of azole resistance in Candida tropicalis causing invasive infections has become a public health concern; however, the prevalence of resistant isolates in urine samples was not well studied, because the clinical significance of candiduria was not unambiguous due to possible host colonization.

Methods

We performed a 12-year laboratory-based surveillance study of C. tropicalis causing either invasive infection or candiduria and studied their susceptibility profiles to common antifungal drugs. The complete coding domain sequence of the ERG11 gene was amplified in all fluconazole resistant isolates, and aligned with the wild-type sequence to detect nucleotide mutations.

Results

A total of 519 unique C. tropicalis strains isolates, 69.9% of which were isolated from urine samples and remaining 30.1% were invasive strains. Overall, 16.5% isolates were confirmed to be resistant to fluconazole, of which 91.9% were cross-resistant voriconazole. Of note, at the beginning of surveillance (2010-2011), the fluconazole resistance rates were low in both candiduria and invasive groups (6.8% and 5.9%, respectively). However, the resistant rate in the candiduria group significantly increased to 29.5% since 2012-2013 (p = 0.001) and stayed high since then, whilst the resistance rate in the invasive group only showed a gradually increasing trends till 2021 (p > 0.05). Sequence analysis of ERG11 from fluconazole-resistant strains revealed the prevalence of A395T/W mutations were relatively low (16.7%) in the beginning but reached 87.5-100% after 2014. Moreover, the A395W heterozygous mutation isolates became predominant (>60% of resistant strains) after 2016, and indeed isolates carrying corresponding amino acid substitution (Y132F) was highly resistant to fluconazole with MIC₅₀ exceeded 256 μg/ml.

Conclusion

Our study revealed high azole resistant rate in candiduria with its increasing trends observed much earlier than stains causing invasive infections. Given antimicrobial resistance as a critical "One Health" issue, the emergence of antifungal resistance in Candida species that are common commensal colonizers in the human body should be concerned.

Comparison of the antifungal effect of voriconazole and fluconazole on oral candidiasis before and during radiotherapy

Background

Head-and-neck radiotherapy can change oral Candida species and cause candidiasis resistance to common antifungals by making the changes to the oral cavity environment. Voriconazole is a synthetic azole with extensive antifungal activity. The current study aimed at comparing the antifungal activity of fluconazole and voriconazole on Candida species isolated from the oral cavity of patients undergoing head-and-neck radiotherapy.

Materials and Methods

The present in vitro study was performed on samples isolated from patients undergoing head-and-neck radiotherapy, before and during radiotherapy. After the identification of the species, the antifungal effect of fluconazole and voriconazole was determined by the microdilution method, and the minimum inhibitory concentration (MIC), the minimum fungicidal concentration, and the antifungal susceptibility of the isolated strains were also measured. The data were analyzed by the Chi-squared and then two-sided Fisher's exact tests. P < 0.05 was considered statistically significant.

Results

The study findings showed no significant difference in the susceptibility of Candida albicans to voriconazole and fluconazole before and during radiotherapy. Before radiotherapy, both voriconazole and fluconazole had similar effects on Candida tropicalis, but after radiotherapy, voriconazole was less effective. However, both before and during radiotherapy, fluconazole had a greater antifungal effect than voriconazole on Candida glabrata strains. The MICs of voriconazole and fluconazole for both Candida parapsilosis and Candida krusei isolates were within the susceptible or dose-dependent range.

Conclusion

The current study results showed that voriconazole was not more effective than fluconazole in the treatment of oral candidiasis in patients undergoing head-and-neck radiotherapy.

Similarities and Differences among Species Closely Related to Candida albicans: C. tropicalis, C. dubliniensis, and C. auris

Although Candida species are widespread commensals of the microflora of healthy individuals, they are also among the most important human fungal pathogens that under certain conditions can cause diseases (candidiases) of varying severity ranging from mild superficial infections of the mucous membranes to life-threatening systemic infections. So far, the vast majority of research aimed at understanding the molecular basis of pathogenesis has been focused on the most common species—Candida albicans. Meanwhile, other closely related species belonging to the CTG clade, namely, Candida tropicalis and Candida dubliniensis, are becoming more important in clinical practice, as well as a relatively newly identified species, Candida auris. Despite the close relationship of these microorganisms, it seems that in the course of evolution, they have developed distinct biochemical, metabolic, and physiological adaptations, which they use to fit to commensal niches and achieve full virulence. Therefore, in this review, we describe the current knowledge on C. tropicalis, C. dubliniensis, and C. auris virulence factors, the formation of a mixed species biofilm and mutual communication, the environmental stress response and related changes in fungal cell metabolism, and the effect of pathogens on host defense response and susceptibility to antifungal agents used, highlighting differences with respect to C. albicans. Special attention is paid to common diagnostic problems resulting from similarities between these species and the emergence of drug resistance mechanisms. Understanding the different strategies to achieve virulence, used by important opportunistic pathogens of the genus Candida, is essential for proper diagnosis and treatment.

The emerging threat antifungal-resistant Candida tropicalis in humans, animals, and environment

Antifungal resistance in humans, animals, and the environment is an emerging problem. Among the different fungal species that can develop resistance, Candida tropicalis is ubiquitous and causes infections in animals and humans. In Asia and some Latin American countries, C. tropicalis is among the most common species related to candidemia, and mortality rates are usually above 40%. Fluconazole resistance is especially reported in Asian countries and clonal spread in humans and the environment has been investigated in some studies. In Brazil, high rates of azole resistance have been found in animals and the environment. Multidrug resistance is still rare, but recent reports of clinical multidrug-resistant isolates are worrisome. The molecular apparatus of antifungal resistance has been majorly investigated in clinical C. tropicalis isolates, revealing that this species can develop resistance through the conjunction of different adaptative mechanisms. In this review article, we summarize the main findings regarding antifungal resistance and Candida tropicalis through an "One Health" approach.

Qualitative and Quantitative Beach Cleanliness Assessment to Support Marine Litter Management in Tropical Destinations

In addition to its ecological and recreational relevance, beach cleanliness is also one of the five most important aspects (i.e., the “Big Five”) for beach visitors around the world. Nonetheless, few efforts have been carried out to guide the sound management of this rising issue. This paper presents a quantitative and qualitative method to assess the level of beach cleanliness, in order to allow managers to focus their attention on the environmental management of the most frequent and relevant types of litter in tropical areas. In a first step, a survey on users’ perception was applied to 361 beachgoers in eight beaches in Colombia to identify the most relevant types of beach litter and the weighting factors to obtain quantitative calculations. In a second step, the thirteen categories of litter identified were analyzed in relation to beach cleanliness, origin of litter, and environmental impact, to define its individual weighting importance. Some categories were also selected according to particularities of tropical countries, such as the presence of abundant natural vegetation debris and gross polystyrene items, largely transported by rivers in great quantities. In a third step, the method was then tested at eight beaches in the Caribbean coast of Colombia through a period of four months, during which 192 transect samplings were carried out. The qualitative module of the proposed technique, named Beach Litter Assessment Technique—Qualitative and Quantitative (BLAT-QQ), identified the main types of beach litter and the quantitative module gave an overview on the state of beach cleanliness. The method is demonstrated to be quick and effective in diagnosing beach cleanliness, providing a simple instrument to carry out sound environmental management actions in coastal destinations.

Collateral consequences of agricultural fungicides on pathogenic yeasts: A One Health perspective to tackle azole resistance

Candida and Cryptococcus affect millions of people yearly, being responsible for a wide array of clinical presentations, including life-threatening diseases. Interestingly, most human pathogenic yeasts are not restricted to the clinical setting, as they are also ubiquitous in the environment. Recent studies raise concern regarding the potential impact of agricultural use of azoles on resistance to medical antifungals in yeasts, as previously outlined with Aspergillus fumigatus. Thus, we undertook a narrative review of the literature and provide lines of evidence suggesting that an alternative, environmental route of azole resistance, may develop in pathogenic yeasts, in addition to patient route. However, it warrants sound evidence to support that pathogenic yeasts cross border between plants, animals and humans and that environmental reservoirs may contribute to azole resistance in Candida or other yeasts for humans. As these possibilities could concern public health, we propose a road map for future studies under the One Health perspective.

Efficacy of three lytic bacteriophages for eradicating biofilms of multidrug-resistant Proteus mirabilis

Proteus mirabilis is one of the most frequent causes of catheter-associated urinary tract infections (CAUTIs) owing to its capability to colonize and develop crystalline multidrug-resistant (MDR) biofilms. Here, we report the isolation and partial characterization of three novel bacteriophages, vB_PmiM-ES1a, vB_PmiM-ES1b, and vB_PmiM-ES1c, which were active against the planktonic form and biofilms of the MDR P. mirabilis strain ES01, isolated from CAUTIs in Egypt. The antibiotic susceptibility profile of the P. mirabilis isolates showed resistance to most of the antibiotics tested. The isolated phages were identified morphologically using TEM, and each appeared to have myovirus-like morphology. The three phages displayed strong lytic activity and a narrow host range, and they were stable at different ranges of temperatures and pH values. One-step growth kinetics showed a lysis time of 180 min with a burst size of 99.6, 95, and 86 PFU/cell for phage vB_PmiM-ES1a, vB_PmiM-ES1b, and vB_PmiM-ES1c, respectively. The three phages exhibited different digestion patterns using different restriction enzymes. The genome size was estimated to be 59.39 kb, 62.19 kb, and 52.07 kb for phage vB_PmiM-ES1a, vB_PmiM-ES1b, and vB_PmiM-ES1c, respectively. A phage cocktail including the three phages showed a potential ability to reduce and eradicate a biofilm formed by the MDR Proteus mirabilis EG-ES1. Accordingly, a phage cocktail of vB_PmiM-ES1a, vB_PmiM-ES1b, and vB_PmiM-ES1c is considered a promising candidate for use as a biocontrol agent against MDR Proteus mirabilis bacteria.

Clinical and epidemiological aspects of Candidemia in eight medical centers in the state of Parana, Brazil: Parana Candidemia Network

Objectives

Candida spp. has been reported as one of the common agents of nosocomial bloodstream infections and is associated with a high mortality. Therefore, this study evaluated the clinical findings, local epidemiology, and microbiological aspects of candidemia in eight tertiary medical centers in the state of Parana, South of Brazil.

Methods

In this study, we reported 100 episodes of candidemia in patients admitted to eight different hospitals in five cities of the state of Parana, Brazil, using data collected locally (2016 and 2017) and tabulated online.

Results

The incidence was found to be 2.7 / 1000 patients / day and 1.2 / 1000 admissions. C. albicans was responsible for 49% of all candidemia episodes. Cancer and surgery were the two most common underlying conditions associated with candidemia. The mortality rate within 30 days was 48%, and removal of the central venous catheter (p = 0.029) as well as empirical or prophylactic exposure to antifungals were both related to improved survival (p = 0.033).

Conclusions

This study highlights the high burden and mortality rates of candidemia in hospitals from Parana as well as the need to enhance antifungal stewardship program in the enrolled medical centers.

Early Virulence Predictors during the Candida Species-Galleria mellonella Interaction

Fungal infections are a serious and increasing threat for human health, and one of the most frequent etiological agents for systemic mycoses is Candida spp. The gold standard to assess Candida virulence is the mouse model of systemic candidiasis, a restrictive, expensive, and time-consuming approach; therefore, invertebrate models have been proposed as alternatives. Galleria mellonella larvae have several traits that make them good candidates to study the fungal virulence. Here, we showed that a reduction in circulating hemocytes, increased melanin production, phenoloxidase, and lactate dehydrogenase activities were observed at 12 and 24 h postinoculation of highly virulent Candidatropicalis strains, while minimal changes in these parameters were observed in low-virulent strains. Similarly, the most virulent species Candida albicans, Candida tropicalis, Candida auris, Candida parapsilosis, and Candida orthopsilosis have led to significant changes in those parameters; while the low virulent species Candida guilliermondii, Candida krusei, and Candida metapsilosis induced modest variations in these immunological and cytotoxicity parameters. Since changes in circulating hemocytes, melanin production, phenoloxidase and lactate dehydrogenase activities showed a correlation with the larval median survival rates at 12 and 24 h postinoculation, we proposed them as candidates for early virulence predictors in G. mellonella.

Candida tropicalis RON1 is required for hyphal formation, biofilm development, and virulence but is dispensable for N-acetylglucosamine catabolism

NDT80-like family genes are highly conserved across a large group of fungi, but the functions of each Ndt80 protein are diverse and have evolved differently among yeasts and pathogens. The unique NDT80 gene in budding yeast is required for sexual reproduction, whereas three NDT80-like genes, namely, NDT80, REP1, and RON1, found in Candida albicans exhibit distinct functions. Notably, it was suggested that REP1, rather than RON1, is required for N-acetylglucosamine (GlcNAc) catabolism. Although Candida tropicalis, a widely dispersed fungal pathogen in tropical and subtropical areas, is closely related to Candida albicans, its phenotypic, pathogenic and environmental adaptation characteristics are remarkably divergent. In this study, we focused on the Ron1 transcription factor in C. tropicalis. Protein alignment showed that C. tropicalis Ron1 (CtRon1) shares 39.7% identity with C. albicans Ron1 (CaRon1). Compared to the wild-type strain, the C. tropicalis ron1Δ strains exhibited normal growth in different carbon sources and had similar expression levels of several GlcNAc catabolic genes during GlcNAc treatment. In contrast, C. tropicalis REP1 is responsible for GlcNAc catabolism and is involved in GlcNAc catabolic gene expressions, similar to C. albicans Rep1. However, REP1 deletion strains in C. tropicalis promote hyphal development in GlcNAc with low glucose content. Interestingly, CtRON1, but not CaRON1, deletion mutants exhibited significantly impaired hyphal growth and biofilm formation. As expected, CtRON1 was required for full virulence. Together, the results of this study showed divergent functions of CtRon1 compared to CaRon1; CtRon1 plays a key role in yeast-hyphal dimorphism, biofilm formation and virulence.

LAY ABSTRACT

In this study, we identified the role of RON1, an NDT80-like gene, in Candida tropicalis. Unlike the gene in Candida albicans, our studies showed that RON1 is a key regulator of hyphal formation, biofilm development and virulence but is dispensable for N-acetylglucosamine catabolism in C. tropicalis.

Combined effect of lasioglossin LL-III derivative with azoles against Candida albicans virulence factors: biofilm formation, phospholipases, proteases and hemolytic activity

Candida albicans has several virulence factors at its disposal, including yeast–hyphal transition associated with biofilm formation, phospholipases, proteases and hemolytic activity, all of which contribute to its pathogenesis. We used synthetic derivative LL-III/43 of antimicrobial peptide lasioglossin LL-III to enhance effect of azoles on attenuation of C. albicans virulence factors. LL-III/43 was able to inhibit initial adhesion or biofilm formation of C. albicans strains at 50 µM. Azoles, however, were ineffective at this concentration. Using fluorescently labeled LL-III/43, we observed that peptide covered C. albicans cells, partially penetrated through their membranes and then accumulated inside cells. LL-III/43 (25 µM) in combination with clotrimazole prevented biofilm formation already at 3.1 µM clotrimazole. Neither LL-III/43 nor azoles were able to significantly inhibit phospholipases, proteases, or hemolytic activity of C. albicans. LL-III/43 (25 µM) and clotrimazole (50 µM) in combination decreased production of these virulence factors, and it completely attenuated its hemolytic activity. Scanning electron microscopy showed that LL-III/43 (50 µM) prevented C. albicans biofilm formation on Ti-6Al-4 V alloy used in orthopedic surgeries and combination of LL-III/43 (25 µM) with clotrimazole (3.1 µM) prevented biofilm formation on urinary catheters. Therefore, mixture of LL-III/43 and clotrimazole is suitable candidate for future pharmaceutical research.

A rare clinical entity as large intrarenal abscess in a typeII diabetic patient due to Candida tropicalis: Case report

Background and Purpose:

Fungal renal abscesses are rare entities associated with significant morbidity and mortality. Affected kidneys can have microabscess, pyelonephritis, pyonephrosis, or papillary necrosis.

Case report:

Herein, we reported an unusual case of a large renal abscess cause by Candida tropicalis in a diabetic patient. The entity presented as a lump in the abdomen and later was diagnosed to be an abscess on computed tomography scan. Candida tropicalis was confirmed on the culture of the aspirate. The abscess was successfully treated by percutaneous drainage and administration of amphotericin B deoxycholate.

Conclusion:

Candida tropicalis is now a global concern because of its rising prevalence and high virulence. The growing resistance of this Candida species to azoles, as in our case, calls for a more judicious usage of antifungal agents. Empirical therapy with either amphotericin or echinocandins is an option in case of high azole resistance. This case highlights the importance of timely diagnosis and implementation of aggressive management in cases suffering from fungal abscesses.

Epidemiology and prognostic factors of nosocomial candidemia in Northeast Brazil: A six-year retrospective study

Candidemia has been considered a persistent public health problem with great impact on hospital costs and high mortality. We aimed to evaluate the epidemiology and prognostic factors of candidemia in a tertiary hospital in Northeast Brazil from January 2011 to December 2016. Demographic and clinical data of patients were retrospectively obtained from medical records and antifungal susceptibility profiling was performed using the broth microdilution method. A total of 68 episodes of candidemia were evaluated. We found an average incidence of 2.23 episodes /1000 admissions and a 30-day mortality rate of 55.9%. The most prevalent species were Candida albicans (35.3%), Candida tropicalis (27.4%), Candida parapsilosis (21.6%) and Candida glabrata (11.8%). Higher mortality rates were observed in cases of candidemia due to C. albicans (61.1%) and C. glabrata (100%), especially when compared to C. parapsilosis (27.3%). Univariate analysis revealed some variables which significantly increased the probability of death: older age (P = 0.022; odds ratio [OR] = 1.041), severe sepsis (P < 0.001; OR = 8.571), septic shock (P = 0.035; OR = 3.792), hypotension (P = 0.003; OR = 9.120), neutrophilia (P = 0.046; OR = 3.080), thrombocytopenia (P = 0.002; OR = 6.800), mechanical ventilation (P = 0.009; OR = 8.167) and greater number of surgeries (P = 0.037; OR = 1.920). Multivariate analysis showed that older age (P = 0.040; OR = 1.055), severe sepsis (P = 0.009; OR = 9.872) and hypotension (P = 0.031; OR = 21.042) were independently associated with worse prognosis. There was no resistance to amphotericin B, micafungin or itraconazole and a low rate of resistance to fluconazole (5.1%). However, 20.5% of the Candida isolates were susceptible dose-dependent (SDD) to fluconazole and 7.7% to itraconazole. In conclusion, our results could assist in the adoption of strategies to stratify patients at higher risk for developing candidemia and worse prognosis, in addition to improve antifungal management.

Occurrence, antifungal susceptibility, and virulence factors of opportunistic yeasts isolated from Brazilian beaches

BACKGROUND

Opportunistic pathogenic yeast species are frequently associated with water habitats that have pollution sources of human or animal origin. Candida albicans has already been suggested as a faecal indicator microorganism for aquatic environments.

OBJECTIVES

The goal of this study was to investigate the occurrence of C. albicans and other opportunistic yeasts in sand and seawater samples from beaches in Brazil to assess their correlation with Escherichia coli, and to characterise the pathogenic potential of the yeast isolates.

METHODS

Opportunistic species (yeasts that grow at 37ºC) were isolated from sand and seawater samples from eight beaches in Brazil during the summer and the winter. Opportunistic yeast species were evaluated for their susceptibility to antifungal drugs, virulence factors, and the in vitro and in vivo biofilm formation. Strains were selected to carry out virulence tests using BALB/c mice.

FINDINGS

Several water samples could be classified as inappropriate for primary contact recreation in relation to E. coli densities. C. albicans was isolated in low densities. Of the 144 opportunistic yeasts evaluated, 61% displayed resistance or dose-dependent sensitivity to at least one tested drug, and 40% produced proteinase. Strains of C. albicans and Kodamaea ohmeri exhibited the highest rates of adhesion to buccal epithelial cells. All the C. albicans strains that were tested were able to undergo morphogenesis and form a biofilm on catheter fragments in both in vitro and in vivo experiments. It was possible to confirm the pathogenic potential of three of these strains during the disseminated infection test.

MAIN CONCLUSIONS

The identification of opportunistic yeast species in seawater and sand samples from Brazilian beaches suggest a potential risk to the health of people who use these environments for recreational purposes.

Virulence factors of Candida spp. obtained from blood cultures of patients with candidemia attended at tertiary hospitals in Northeast Brazil

BACKGROUND

Yeasts of the Candida genus are one of the most common causes of bloodstream infections associated with high rates of morbidity and mortality, mainly affecting immunocompromised patients. We aimed to identify yeasts obtained from blood cultures of patients interned at tertiary hospitals in Brazil.

METHODS

We evaluated some of the major virulence factors of Candida spp., including the ability to adhere to human buccal epithelial cells, biofilm formation, hemolytic and phospholipase activity.

RESULTS

We analyzed 70 isolates of Candida spp. obtained from March 2011 and March 2015. Candida spp. showed different peculiarities in terms of expression of virulence factors evaluated in vitro. C. albicans strains were more adherent to HBEC than all the other Candida species. C. tropicalis strains were considered strong biofilm producers. Strains belonging to the C. parapsilosis species complex were able to produce hemolysins, while C. glabrata was also able to lyse erythrocytes and to produce phospholipase.

CONCLUSION

These results suggest that Non-Candida albicans Candida species are also able to express virulence factors which play an important role in bloodstream infectious caused by these yeasts.

To clean or not to clean? A critical review of beach cleaning methods and impacts

Cleaning is a fundamental concern of beach managers in many destinations as well as an important requirement in beach quality awards. However, it has been largely neglected in the literature. This paper provides an overview of empirical studies on beach cleaning and analyzes cleaning-related requirements of 11 beach awards that generate controversy in the literature. This study comments on key aspects of beach cleaning, resolves various misconceptions, and provides new perspectives by integrating related topics drawn from a wide range of literature. The arguments based on both the ecological and tourism managerial perspectives are presented, indicating the gaps and proposing research solutions. The paper calls for empirical studies with regard to the efficiency of different cleaning approaches on beaches with varying levels of use intensity and for methodological designs that separate the impacts of mechanical grooming from those of trampling, dune destruction, shore armoring, artificial lighting, among others.

Candida tropicalis geographic population structure maintenance and dispersion in the coastal environment may be influenced by the climatic season and anthropogenic action

Candida tropicalis is a pathogenic yeast with worldwide recognition as the second or third more frequently isolated species in Latin America, for both superficial and systemic infections. Because of its high prevalence, and growing clinical interest, it is essential to understand genetic variability patterns of this important Candida species in the tropics. Besides belonging to the human normal microbiota, C. tropicalis may be found in other warm blood animals and in the environment, including water and sand of beaches. The aims of the present study were to evaluate genotypic and phenotypic variability of 62 isolates of C. tropicalis obtained from the coastal environment in Northeast Brazil using microsatellite and MALDI-TOF/MS comparisons. There was a relatively low correspondence between these typing techniques employed. Therefore, further studies are needed to consolidate the use of MALDI-TOF/MS as a yeast typing tool. Nevertheless, the two methods employed demonstrated the heterogeneity of C. tropicalis in a coastal environment. We also found relative maintenance of the population structure within the same season, which may reinforce the idea that this species presents the potential to remain in the environment for a long period of time. In addition, highly related strains were found within different geographic points of collection, demonstrating that this strain may be dispersed at long distances, probably influenced by anthropogenic actions and driven by the sea tides and wind.

Trichosporon inkin meningitis in Northeast Brazil: first case report and review of the literature

Background

Trichosporon species may colonize the skin, respiratory tract and gastrointestinal tract of human beings. The yeast is recognized as etiological agent of white piedra, a superficial mycosis. Nevertheless, immunocompromised hosts may develop invasive Trichosporonosis. Central nervous system trichosporonosis is a very rare clinical manifestation. In fact, only a few cases have been published in the literature and none of them was caused by Trichosporon inkin.

Case presentation

Here we report the first clinical case of meningoencephalitis due to this species in a female previously healthy patient under corticosteroids and antibiotics therapy for several months. She was submitted to an invasive procedure to remove a left sided acoustic neuroma and further developed a cerebrospinal fistula. After some days of the procedure, she presented a predominantly and intensive occipital holocranial headache, followed by vomiting, hyporexia, weight loss, asthenia, irritability, difficulty to concentrate and rotator vertigo. The patient further developed a cerebrospinal fistula in the occipital region and was submitted to a surgical correction. After several months of clinical interventions, she was diagnosed with CNS Trichosporonosis, after Magnetic Resonance Imaging and positive microbiological cultures obtained within two different occasions (2 weeks apart). Despite the antifungal therapy with Amphotericin B and Voriconazole, the patient did not survive.

Conclusions

Despite CNS Fungal infections are mostly due to Cryptococcus spp., other emergent yeasts, such as T. inkin may be considered as a likely etiological agent. This is the first case report of CNS Trichosporonosis, where species identification was performed with rDNA sequencing.

Polymicrobial antibiofilm activity of the membranotropic peptide gH625 and its analogue

This work illustrates a new role for the membranotropic peptide gH625 and its derivative gH625-GCGKKK in impairing formation of polymicrobial biofilms. Mixed biofilms composed of Candida and bacterial species cause frequently infections and failure of medical silicone devices and also show a major drug resistance than single-species biofilms. Inhibition and eradication of biofilms were evaluated by complementary methods: XTT-reduction, and crystal violet staining (CV). Our results indicate that gH625-GCGKKKK, better than the native peptide, strongly inhibited formation of mixed biofilms of clinical isolates of C. tropicalis/S. marcescens and C. tropicalis/S. aureus and reduced the biofilm architecture, interfering with cell adhesion and polymeric matrix, as well as eradicated the long-term polymicrobial biofilms on silicone surface.

Conserved and Divergent Functions of the cAMP/PKA Signaling Pathway in Candida albicans and Candida tropicalis

Fungal species undergo many morphological transitions to adapt to changing environments, an important quality especially in fungal pathogens. For decades, Candida albicans has been one of the most prevalent human fungal pathogens, and recently, the prevalence of Candida tropicalis as a causative agent of candidiasis has increased. In C. albicans, the ability to switch between yeast and hyphal forms is thought to be a key virulence factor and is regulated by multiple signaling cascades—including the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA), calcineurin, high-osmolarity glycerol (HOG), and mitogen-activated protein kinases (MAPK) signaling pathways—upon receiving environmental cues. The cAMP/PKA signaling pathway also triggers white-opaque switching in C. albicans. However, studies on C. tropicalis morphogenesis are limited. In this minireview, we discuss the regulation of the yeast-hypha transition, virulence, and white-opaque switching through the cAMP/PKA pathway in the closely related species C. albicans and C. tropicalis.

A coupled process of same- and opposite-sex mating generates polyploidy and genetic diversity in Candida tropicalis

Sexual reproduction is a universal mechanism for generating genetic diversity in eukaryotes. Fungi exhibit diverse strategies for sexual reproduction both in nature and in the laboratory. In this study, we report the discovery of same-sex (homothallic) mating in the human fungal pathogen Candida tropicalis. We show that same-sex mating occurs between two cells carrying the same mating type (MTLa/a or α/α) and requires the presence of pheromone from the opposite mating type as well as the receptor for this pheromone. In ménage à trois mating mixes (i.e., “a x a + α helper” or “α x α + a helper” mixes), pheromone secreted by helper strains promotes diploid C. tropicalis cells to undergo same-sex mating and form tetraploid products. Surprisingly, however, the tetraploid mating products can then efficiently mate with cells of the opposite mating type to generate hexaploid products. The unstable hexaploid progeny generated from this coupled process of same- and opposite-sex mating undergo rapid chromosome loss and generate extensive genetic variation. Phenotypic analysis demonstrated that the mating progeny-derived strains exhibit diverse morphologies and phenotypes, including differences in secreted aspartic proteinase (Sap) activity and susceptibility to the antifungal drugs. Thus, the coupling of same- and opposite-sex mating represents a novel mode to generate polyploidy and genetic diversity, which may facilitate the evolution of new traits in C. tropicalis and adaptation to changing environments.

The fungal pathogen Candida tropicalis not only lives as a commensal in humans but is also widely distributed in diverse environments. Until recently, C. tropicalis was thought to be an asexual diploid organism. In this study, we report the discovery of same-sex mating and reveal an unusual process in which same- and opposite-sex mating are coupled in this fungus. The coupling process represents a novel mode of mating which produces unstable polyploid products and results in a high level of genetic and phenotypic diversity. This biological process may benefit the adaptation of C. tropicalis to a variety of ecological niches and promotes survival under stressful conditions. Our study expands the repertoire of mating strategies in fungi and sheds new lights on the generation of polyploidy and genomic flexibility.

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.

Evaluation of biofilm formation ability in different Candida strains and anti-biofilm effects of Fe3O4-NPs compared with Fluconazole: an in vitro study

OBJECTIVE

Biofilm formation ability is one of the major virulence factors contributing to the pathogenesis of Candida species. Biofilms produced by Candida spp. cause complicated treatments and contribute to increasing unpleasant mortality rates. Nanoparticles of Fe₃O₄ (Fe₃O₄-NPs) are considered due to their magnetic and biochemical properties, as well as their low costs. The purpose of present study was to determine biofilm formation ability in different Candida strains and evaluation of anti-biofilm effect of Fe₃O₄-NPs compared with FLC.

MATERIALS AND METHODS

In this study, the biofilm-forming ability of Candida strains and the inhibitory effects of Fe₃O₄-NPs on Candida strains biofilms compared with FLC were measured by MTT assay.

RESULTS

Our finding showed that the biofilm formation ability of C. lusitaniae was significantly higher than other tested Candida strains. However, all the studied Candida strains produced high degree of biofilms. The biofilm formation in different Candida strains was inhibited at concentrations ≥1000μg/mL to ≥4000μg/mL for Fe₃O₄-NPs and ≥512μg/mL to ≥2048μg/mL for FLC. After exposure to various concentrations of Fe₃O₄-NPs, biofilm formation reduction in C. albicans and C. parapsilosis were more than FLC. Although, this reduction was not significant. A significant reduction (P<0.05) was observed in biofilm formation in presence of FLC compared with Fe₃O₄-NPs in C. krusei, C. tropicalis, and C. lusitaniae. The inhibitory effects of Fe₃O₄-NPs and FLC on biofilm formation of C. glabrata were approximately equal.

CONCLUSION

In accordance with the findings, the biofilm reduction effect of FLC for C. krusei, C. tropicalis, and C. lusitaniae were statistically higher than Fe₃O₄-NPs.

Radiation used for head and neck cancer increases virulence in Candida tropicalis isolated from a cancer patient

BACKGROUND

Studies have shown that radiation from radiotherapy increases the yeast colonization of patients. However it is not clear, if such radiation alters the yeast itself. The aim of the present study was therefore to report the direct impact of gamma radiation on Candida tropicalis.

METHODS

C. tropicalis was obtained from a patient with a carcinoma, a suspension of this yeast containing 2.0 × 103 colony forming units per milliliter was prepared. It was submitted to gamma radiation dosage similar to that used in the treatment of head and neck cancer. After a cumulative dose of 7200 cGy some virulence attributes of C. tropicalis, including macro and micromorphological characteristics, adhesion and biofilm abilities, murine experimental infection and phagocytosis resistance were evaluated on irradiated and non-irradiated yeasts.

RESULTS

After irradiation the colony morphology of the yeast was altered from a ring format to a smooth appearance in most colonies. Scanning electron microscopy revealed notable differences in the structures of both these colonies and the yeast cells, with the loss of pseudohyphae following irradiation and an increase in extracellular matrix production. The adherence and biofilm production of the yeast was greater following irradiation, both in terms of the number of yeasts and total biomass production on several abiotic surfaces and TR146 cells. The phagocytic index of the irradiated yeasts was not statistically different; however, the presence of cellular debris was detected in the kidneys of infected animals. Mice infected with irradiated yeasts developed an infection at the site of the yeast inoculation, although systemic infection was unchanged.

CONCLUSIONS

Our findings show for the first time that C. tropicalis, one of the most important yeasts from colonization, which cause fatal candidemia in cancer patients, is affected by gamma irradiation, with changes to its virulence profile.

An Update on Candida tropicalis Based on Basic and Clinical Approaches

Candida tropicalis has emerged as one of the most important Candida species. It has been widely considered the second most virulent Candida species, only preceded by C. albicans. Besides, this species has been recognized as a very strong biofilm producer, surpassing C. albicans in most of the studies. In addition, it produces a wide range of other virulence factors, including: adhesion to buccal epithelial and endothelial cells; the secretion of lytic enzymes, such as proteinases, phospholipases, and hemolysins, bud-to-hyphae transition (also called morphogenesis) and the phenomenon called phenotypic switching. This is a species very closely related to C. albicans and has been easily identified with both phenotypic and molecular methods. In addition, no cryptic sibling species were yet described in the literature, what is contradictory to some other medically important Candida species. C. tropicalis is a clinically relevant species and may be the second or third etiological agent of candidemia, specifically in Latin American countries and Asia. Antifungal resistance to the azoles, polyenes, and echinocandins has already been described. Apart from all these characteristics, C. tropicalis has been considered an osmotolerant microorganism and this ability to survive to high salt concentration may be important for fungal persistence in saline environments. This physiological characteristic makes this species suitable for use in biotechnology processes. Here we describe an update of C. tropicalis, focusing on all these previously mentioned subjects.

Cell wall mannoprotein of Candida albicans induces cell cycle alternation and inhibits apoptosis of HaCaT cells via NF-κB signal pathway

Candida albicans (C. albicans) is a commensal organism in human and a well-known dimorphic opportunistic pathogenic fungus. Though plenty of researches on the pathogenesis of C. albicans have been performed, the mechanism is not fully understood. The cell wall components of C. albicans have been documented to play important roles in its pathogenic processes. To further study the infectious mechanism of C. albicans, we investigated the potential functional role of its cell wall mannoprotein in cell cycle and apoptosis of HaCaT cells. We found that mannoprotein could promote the transition of cell cycle from G1/G0 to S phase, in which Cyclin D1, CDK4 and p-Rb, the major regulators of the cell cycle progression, showed significant upregulation, and CDKN1A (cyclin dependent kinase inhibitor 1A (p21)) showed significant downregulation. Mannoprotein also could inhibit apoptosis of HaCaT cells, which was well associated with increased expression of BCL2 (Bcl-2). Moreover, mannoprotein could increase the phosphorylation levels of RELA (p65) and NFKBIA (IκBα), as the key factors of NF-κB signal pathway in HaCaT cells, suggesting the activation of NF-κB signal pathway. Additionally, a NF-κB specific inhibitor, PDTC, could rescue the effect of mannoprotein on cell cycle and apoptosis of HaCaT cells, which suggested that mannoprotein could activate NF-κB signal pathway to mediate cell cycle alternation and inhibit apoptosis.