Candida haemulonii complex, an emerging threat from tropical regions?

Antibacterial and antifungal pyrazoles based on different construction strategies

The growing prevalence of microbial infections, and antimicrobial resistance (AMR) stemming from the overuse and misuse of antibiotics, call for novel therapeutic agents, particularly ones targeting resistant microbial strains. Scientists are striving to develop innovative agents to tackle the rising microbial infections and abate the risk of AMR. Pyrazole, a five-membered heterocyclic compound belonging to the azole family, is a versatile scaffold and serves as a core structure in many drugs with antimicrobial and other therapeutic effects. In this review, we have updated pyrazole-based antibacterial and antifungal agents mainly developed between 2016 and 2024, by combining with diverse pharmacophores such as coumarin, thiazole, oxadiazole, isoxazole, indole, etc. Meanwhile, the various strategies (molecular hybridization, bioisosterism, scaffold hopping, multicomponent reactions, and catalyst-free synthesis) for integrating different functional groups with the pyrazole ring are discussed. Additionally, structure-activity relationships of these pyrazole derivatives, i.e., how structural modifications impact their selectivity and therapeutic potential against bacterial and fungal strains, are highlighted. This review provides insights into designing next-generation antimicrobials to combat AMR, and offers valuable perspectives to the scientists working on heterocyclic compounds with diverse bioactivities.

Molecular Epidemiology and Antifungal Susceptibility Profile of Candidozyma Isolates From Argentina

BACKGROUND

Epidemiological surveillance of Candidozyma sp. has become important because many species of this new genus have been reported to be responsible for nosocomial outbreaks and to exhibit elevated minimal inhibitory concentrations (MIC) to one or more classes of antifungal drugs.

OBJECTIVES

To describe the genetic relationships among Argentinian clinical isolates belonging to the Candidozyma genus and to study the molecular mechanisms associated with antifungal resistance.

METHODS

We performed whole-genome sequencing of 41 isolates. Identification was based on ribosomal DNA sequencing and susceptibility testing was determined according to the EUCAST document. Phylogenetic analysis, non-synonymous mutations in genes associated with antifungal resistance and the presence of copy number variations (CNVs) were investigated.

RESULTS

We identified 12 Candidozyma haemuli, 11 Candidozyma haemuli var. vulneris, 5 Cz. haemuli/ Cz. haemuli var. vulneris ITS hybrids, 8 Candidozyma duobushaemuli and 5 Candidozyma cf. pseudohaemuli. Phylogenetic analysis, together with clinical data, demonstrated nosocomial transmission events. In addition, Cz. haemuli and Cz. haemuli var. vulneris were not separated in the phylogenetic tree; the Cz. cf. pseudohaemuli isolates clustered distantly from the Cz. pseudohaemuli type strain. Most isolates were resistant to amphotericin B, and two Cz. haemuli isolates showed fluconazole resistance and Y132F mutation in ERG11. We did not find CNV in genes associated with antifungal resistance.

CONCLUSIONS

These findings highlight the need for epidemiological surveillance of these species and the study of molecular mechanisms associated with antifungal resistance. Furthermore, we propose a taxonomic revision for Cz. haemuli var. vulneris and Cz. pseudohaemuli based on genomic data.

Clonal outbreak of Candida vulturna in a paediatric oncology ward in Maranhão, Brazil

OBJECTIVE

To describe an outbreak due to Candida vulturna, a newly emerging Candida species belonging to the Candida haemulonii species complex in the Metschnikowiaceae family.

METHODS

In this retrospective cohort study we genotyped 14 C. vulturna bloodstream isolates, occurring in a 4-month-period in paediatric cancer patients in a Brazilian hospital. To prove an outbreak, ITS sequence analysis and whole genome sequencing (WGS) was done. Antifungal susceptibility was performed with the reference CLSI method and the commercial Sensititre YeastOne (SYO) YO10 plates. A control C. vulturna isolate from another region in Brazil was included in all analyses.

RESULTS

MALDI-TOF-MS identified isolates as C. pseudohaemulonii and C. duobushaemulonii albeit with low scores and therefore molecular methods were required for accurate identification. ITS sequence analyses clearly differentiated C. vulturna from other species in the C. haemulonii species complex. WGS proved the presence of a clonal outbreak with C. vulturna involving 14 paediatric patients. Antifungal susceptibility testing (AFST) with two methods showed the isolates had low MICs of commonly available antifungals.

CONCLUSION

This study describes an outbreak due to the rare yeast C. vulturna, related to C. auris, during a four-month period in patients admitted to a paediatric oncology ward in a Brazilian hospital. In contrast to previous studies the yeast was susceptible to all antifungals and patient outcome was good.

Antifungal and anti-biofilm effects of hydrazone derivatives on Candida spp

Worldwide, invasive candidiasis are a burden for the health system due to difficulties to manage patients, to the increasing of the resistance of the current therapeutics and the emergence of naturally resistant species of Candida. In this context, the development of innovative antifungal drugs is urgently needed. During invasive candidiasis, yeast is submitted to many stresses (oxidative, thermic, osmotic) in the human host. In order to resist in this context, yeast develops different strategy, especially the biosynthesis of trehalose. Starting from the 3D structural data of TPS2, an enzyme implicated in trehalose biosynthesis, we identified hydrazone as an interesting scaffold to design new antifungal drugs. Interestingly, our hydrazone derivatives which demonstrate antifungal and anti-biofilm effects on Candida spp., are non-toxic in in vitro and in vivo models (Galleria mellonella).

Biological and genomic analyses of Clavispora sputum sp. nov., a novel potential fungal pathogen closely related to Clavispora lusitaniae (syn. Candida lusitaniae) and Candida auris

Several human fungal pathogens, including drug-resistant Candida auris and species of the Candida haemulonii complex, have emerged over the past two decades, posing new threats to human health. In this study, we report the isolation and identification of a novel species belonging to the genus Clavispora, herein named as Cl avispora sputum, from a clinical sputum sample of a COVID-19 patient. Cl . sputum is phylogenetically closely related to fungal pathogens Clavispora lusitaniae (syn. Candida lusitaniae) and C. auris. When grown on CHROMagar Candida Plus medium, Cl. sputum exhibited a similar coloration to C. auris strain CBS12372. Cl. sputum was able to develop weak filaments on CM medium. Although Cl. sputum and Cl. lusitaniae are phylogenetically closely related, comparative genomic and synteny analyses indicated significant chromosomal rearrangements between the two species. Although Cl. sputum could not grow at 37 °C under regular culture condition, an increased fungal burden in the lung tissue of a mouse systemic infection model implies that it could be a potential opportunistic pathogenic yeast in humans.

Insight into Virulence and Mechanisms of Amphotericin B Resistance in the Candida haemulonii Complex

The Candida haemulonii complex includes emerging opportunistic human fungal pathogens with documented multidrug-resistance profiles. It comprises Candida haemulonii sensu stricto, Candida haemulonii var. vulnera, Candida duobushaemulonii, Candida pseudohaemulonii, and Candida vulturna. In recent years, rates of clinical isolation of strains from this complex have increased in multiple countries, including China, Malaysia, and Brazil. Biofilm formation, hydrolytic enzymes, surface interaction properties, phenotype switching and cell aggregation abilities, extracellular vesicles production, stress response, and immune evasion help these fungi to infect the host and exert pathological effects. Multidrug resistance profiles also enhance the threat they pose; they exhibit low susceptibility to echinocandins and azoles and an intrinsic resistance to amphotericin B (AMB), the first fungal-specific antibiotic. AMB is commonly employed in antifungal treatments, and it acts via several known mechanisms. Given the propensity of clinical Candida species to initiate bloodstream infections, clarifying how C. haemulonii resists AMB is of critical clinical importance. This review outlines our present understanding of the C. haemulonii complex's virulence factors, the mechanisms of action of AMB, and the mechanisms underlying AMB resistance.

Near-infrared spectroscopy and multivariate analysis as effective, fast, and cost-effective methods to discriminate Candida auris from Candida haemulonii

Candida auris and Candida haemulonii are two emerging opportunistic pathogens that have caused an increase in clinical cases in the recent years worldwide. The differentiation of some Candida species is highly laborious, difficult, costly, and time-consuming depending on the similarity between the species. Thus, this study aimed to develop a new, faster, and less expensive methodology for differentiating between C. auris and C. haemulonii based on near-infrared (NIR) spectroscopy and multivariate analysis. C. auris CBS10913 and C. haemulonii CH02 were separated in 15 plates per species, and three isolated colonies of each plate were selected for Fourier transform near-infrared (FT-NIR) analysis, totaling 90 spectra. Subsequently, principal component analysis (PCA) and variable selection algorithms, including the successive projections algorithm (SPA) and genetic algorithm (GA) coupled with linear discriminant analysis (LDA), were employed to discern distinctive patterns among the samples. The use of PCA, SPA, and GA algorithms associated with LDA achieved 100% sensitivity and specificity for the discriminations. The SPA-LDA and GA-LDA algorithms were essential in selecting the variables (infrared wavelengths) of most importance for the models, which could be attributed to binding of cell wall structures such as polysaccharides, peptides, proteins, or molecules resulting from yeasts' metabolism. These results show the high potential of combined FT-NIR and multivariate analysis techniques for the classification of Candida-like fungi, which can contribute to faster and more effective diagnosis and treatment of patients affected by these microorganisms.

Candida auris from the Egyptian cobra: Role of snakes as potential reservoirs

Candida auris represents one of the most urgent threats to public health, although its ecology remains largely unknown. Because amphibians and reptiles may present favorable conditions for C. auris colonization, cloacal and blood samples (n = 68), from several snake species, were cultured and molecularly screened for C. auris using molecular amplification of glycosylphosphatidylinositol protein-encoding genes and ribosomal internal transcribed spacer sequencing. Candida auris was isolated from the cloacal swab of one Egyptian cobra (Naja haje legionis) and molecularly identified in its cloaca and blood. The isolation of C. auris from wild animals is herein reported for the first time, thus suggesting the role that these animals could play as reservoirs of this emerging pathogen. The occurrence of C. auris in blood requires further investigation, although the presence of cationic antimicrobial peptides in the plasma of reptiles could play a role in reducing the vitality of the fungus.

Case report and literature review of refractory fungemia caused by Candidavulturna

Candida vulturna is a recently discovered and not widely documented ascomycetous yeast phylogenetically related to the outbreak-causing and multidrug-resistant Candida auris. A middle-aged Japanese man with no discernible immunodeficiency was admitted to hospital with ileal diverticulitis. Following laparoscopic right hemicolectomy against abscess formation on postoperative day (POD) 7, continuous fungemia occurred due to Candida haemulonii, identified using a conventional method by confirming the biochemical phenotype. Micafungin was initiated; however, the fungus was persistently isolated from blood cultures. Eventually, the antifungal agent was changed to a combination of liposomal amphotericin B (L-AMB) and caspofungin (CPFG), which cleared the infection, and no pathogens were detected in the blood cultures on POD 31. Contrast-enhanced computed tomography showed septic emboli in the lungs and spleen; however, no evidence of vasculitis was observed. Moreover, sequential echocardiography did not reveal any signs of infectious endocarditis. Finally, CPFG and L-AMB were administered to the patient for 7 and 9 weeks, respectively, during which the patient's symptoms did not relapse. The strain was later genetically identified as C. vulturna. This case report illustrates a clinical presentation of C. vulturna and provides the diagnostic approach and treatment methods for this pathogen.

Synthesis and evaluation of the antifungal activity of 5-hydroxy-3-phenyl-1H-pyrazole-1-carbothioamide for use in the oral environment

Background and aim

Candida albicans and Candida tropicalis, can cause superficial infections of the oral mucosa as well as disseminated bloodstream and deep-tissue infections. The most frequently employed class of antifungals used for Candida infection treatment are the azole antifungals. Their low price, low toxic qualities, and availability for oral use make fluconazole and similar azole antifungals the preferred treatment for various infections caused by Candida. Nevertheless, developed and intrinsic resistance to antifungals of the azole family has been widely documented in association with various species of Candida. Candida infection management requires synthesizing new compounds to improve azole class antifungals, as Candida isolates resistant to azole are increasingly encountered in the clinical setting. This study aimed to synthesize a new azole compound and investigate its antifungal activity.

Methods

In this experimental study, 5-hydroxy-3-phenyl-1H-pyrazole-1-carbothioamide was synthesized by the reaction between thiosemecarbazide and ethylbezoylacetate. The structure of the synthesized compound was characterized by different techniques such as Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectra and its antifungal activity against Candida albicans and Candida tropicalis was investigated by the Spread Plat method to determine its minimum fungicidal concentration (MFC) and minimum inhibitory concentration (MIC).

Results and discussion

The Spread Plat test demonstrated that with the increase in 5-hydroxy-3-phenyl-1H-pyrazole-1-carbothioamide concentration, colonies of fungi were increasingly eliminated at a significant level(p < 0.001). At a concentration of 1000 ppm, all Candida albicans and Candida tropicalis colonies were destroyed.

Conclusions

The results indicate that the synthesized compound showed a promising antifungal effect. On the other hand, it had a suitable spectrum of effect, because it showed antifungal effects on both Candida albicans and Candida tropicalis strains.

Spectrum and management of rare Candida/yeast infections in Kuwait in the Middle East

Invasive fungal infections (IFIs) are associated with high mortality rates and mostly affect patients with compromised immunity. The incidence of IFIs is increasing worldwide with the expanding population of susceptible patients. Candida and other yeast infections represent a major component of IFIs. Rare Candida/yeast infections have also increased in recent years and pose considerable diagnostic and management challenges as they are not easily recognized by routine phenotypic characteristic-based diagnostic methods and/or by the automated yeast identification systems. Rare Candida/yeasts also exhibit reduced susceptibility to antifungal drugs making proper management of invasive infections challenging. Here, we review the diagnosis and management of 60 cases of rare Candida/yeast IFIs described so far in Kuwait, an Arabian Gulf country in the Middle East. Interestingly, majority (34 of 60, 56.7%) of these rare Candida/yeast invasive infections occurred among neonates or premature, very-low-birth-weight neonates, usually following prior bacteremia episodes. The clinical details, treatment given, and outcome were available for 28 of 34 neonates. The crude mortality rate among these neonates was 32.2% as 19 of 28 (67.8%) survived the infection and were discharged in healthy condition, likely due to accurate diagnosis and frequent use of combination therapy. Physicians treating patients with extended stay under intensive care, on mechanical ventilation, receiving broad spectrum antibiotics and with gastrointestinal surgery/complications should proactively investigate IFIs. Timely diagnosis and early antifungal treatment are essential to decrease mortality. Understanding the epidemiology and spectrum of rare Candida/yeast invasive infections in different geographical regions, their susceptibility profiles and management will help to devise novel diagnostic and treatment approaches and formulate guidelines for improved patient outcome.