Epidemiology 

The epidemiology of Candida dubliniensis is the study of the distribution and determinants of this yeast infection in human populations. Candida dubliniensis is a closely related species to Candida albicans, the most common cause of candidiasis. However, Candida dubliniensis has some distinctive features that make it an exciting subject of research. 

Some of the main aspects of the epidemiology of Candida dubliniensis are: 

• Candida dubliniensis was first described as a novel species in 1995 from oral samples of HIV-infected patients in Dublin, Ireland1. However, later studies revealed that this species had been isolated earlier from other countries, such as the UK and the Netherlands. 
• Worldwide, Candida dubliniensis is a common infection that is primarily associated with oral carriage and oropharyngeal infections in HIV-infected and AIDS patients. However, it can also cause infections in other immunocompromised individuals, such as chemotherapy and transplant recipients, as well as in healthy individuals. 
• Candida dubliniensis is less virulent and less resistant to antifungal drugs than Candida albicans. However, it can develop resistance to azole drugs, such as fluconazole, by various mechanisms, such as mutations in the ERG11 gene or overexpression of efflux pumps. 
• Candida dubliniensis shares many phenotypic characteristics with Candida albicans, such as the production of chlamydospores and germ tubes. However, it can be differentiated by various methods, such as carbohydrate assimilation profiles, growth at high temperatures, colony morphology on different media, or molecular techniques. 

Classification and Structure 

• Kingdom: Fungi 
• Phylum: Ascomycota 
• Class:      Saccharomycetes 
• Order:     Saccharomycetales 
• Family:   Saccharomycetaceae 
• Genus:    Candida 
• Species:  C. dubliniensis 

 Some possible points about the structure of Candida dubliniensis are: 

• Fungal opportunistic pathogen C. dubliniensis is closely related to Candida albicans but forms a distinct phylogenetic cluster in DNA fingerprinting. 
• C. dubliniensis possesses 9–10 chromosome-sized bands in electrophoretic gels, but its ploidy status has not yet been determined. 
• C. dubliniensis can produce chlamydospores, which are thick-walled, dormant structures that can germinate under favorable conditions. 
• C. dubliniensis has four antigenic types based on the reactivity of its cell wall mannoproteins with monoclonal antibodies. The letters A to D stand for these kinds. 
• C. dubliniensis exhibits more significant karyotype variability than C. albicans, but its population structure is less divergent and comprises only three distinct clades (C1–C3) 

Antigenic Types 

The antigenic types of C. dubliniensis need to be better defined. Still, some studies have suggested that there are differences in the expression and structure of cell wall antigens between C. dubliniensis and C. albicans. For example, one study found that C. dubliniensis has lower levels of β-1,6-glucan and mannoprotein antigens than C. albicans. Another study reported that C. dubliniensis has a unique antigenic determinant on its surface mannoproteins that a monoclonal antibody can recognize. These antigenic differences may have implications for the diagnosis, immune response, and virulence of C. dubliniensis. 

Pathogenesis 

The pathogenesis of Candida dubliniensis is the study of how this yeast causes infections in humans. Candida dubliniensis is very closely related to Candida albicans, the most common cause of candidiasis, but it has some distinctive features that affect its virulence and susceptibility to antifungal drugs. 

Some of the factors that are involved in the pathogenesis of Candida dubliniensis are: 

• Morphological switching: Candida dubliniensis can switch between yeast and hyphal forms, which are associated with different functions and responses to environmental cues. The yeast form is more suitable for colonization and dissemination, while the hyphal form is more invasive and resistant to host defenses. Candida dubliniensis can also produce chlamydospores, which are thick-walled cells that can survive harsh conditions and serve as a source of infection. 
• Biofilm formation: Candida dubliniensis can form biofilms on various surfaces, such as medical devices, mucosal tissues, or dentures. Complex populations of microorganisms known as biofilms are embedded in a matrix of extracellular polysaccharides and proteins. Biofilms protect the host immune system, antifungal drugs, and environmental stresses. Candida dubliniensis biofilms have been shown to be less mature and less resistant than Candida albicans biofilms. 

• Secreted enzymes: Candida dubliniensis can secrete various enzymes that can damage host tissues and facilitate invasion. These include phospholipases, aspartyl proteinases, lipases, and hemolysins. These enzymes can degrade host cell membranes, proteins, lipids, and blood cells. Candida dubliniensis has been reported to produce lower levels of these enzymes than Candida albicans. 
• Adhesion and invasion: Candida dubliniensis can adhere to and invade host cells by using various surface molecules, such as adhesins and invasins. These molecules can bind to specific receptors on host cells, including endothelium and epithelial cells or immune cells. Adhesion and invasion can trigger host cell responses, such as cytokine production, apoptosis, or phagocytosis. Candida dubliniensis has been shown to have similar or lower adhesion and invasion abilities than Candida albicans. 
• Immune evasion: Candida dubliniensis can evade the host immune system by using various strategies, such as antigenic variation, phenotypic switching, masking of cell wall components, modulation of cytokine production, or induction of immunosuppression. These strategies can help Candida dubliniensis to avoid recognition, elimination, or clearance by host immune cells and molecules. Candida dubliniensis has been shown to have similar or lower immune evasion capacities than Candida albicans. 

Host Defenses 

The host defenses of Candida dubliniensis are the mechanisms that the human body uses to protect itself from this yeast infection. Candida dubliniensis is a fungal opportunistic pathogen that can cause oral, genital, skin, and bloodstream infections, especially in immunocompromised patients. Some of the host defenses of Candida dubliniensis are: 

• Innate immunity: This is the first line of defense against Candida dubliniensis and other microorganisms. It consists of physical barriers, such as the skin and mucous membranes, and cellular and molecular components, such as phagocytic cells, complement systems, cytokines, and antimicrobial peptides. These components can recognize and eliminate Candida dubliniensis by various mechanisms, such as opsonization, phagocytosis, oxidative burst, nitric oxide production, and killing. 
• Adaptive immunity: This is the second line of defense against Candida dubliniensis and other microorganisms. It consists of humoral and cellular responses that are specific and memory based. B cells produce antibodies as part of humoral immunity, which might bind to Candida dubliniensis antigens and neutralize them or facilitate their clearance by other immune cells. The process of cellular immunity includes T-cell activation that can produce cytokines or cytotoxic molecules that can modulate the immune response or directly kill Candida dubliniensis-infected cells. 
• Mucosal immunity: This is a specialized type of immunity that protects the mucosal surfaces, such as the oral cavity, from Candida dubliniensis and other microorganisms. It involves both innate and adaptive components, such as epithelial cells, dendritic cells, macrophages, neutrophils, natural killer cells, T cells, B cells, IgA antibodies, and secretory leukocyte protease inhibitors. These components can interact with each other and with Candida dubliniensis to maintain mucosal homeostasis and prevent infection or inflammation. 

Clinical manifestations 

Candida dubliniensis is a yeast closely related to Candida albicans that can infect humans, particularly those with weakened immune systems. It can lead to various clinical problems: 

• Bloodstream Infections: Candida dubliniensis can cause candidemia, which may result in severe complications like heart valve infection, abdominal cavity infection, brain and spinal cord infection, bone infection, joint infection, and eye infection. Symptoms include fever and chills. 

• Oral Infections: It can cause oral candidiasis, leading to white patches, soreness, and discomfort in the mouth and throat. Common in people with HIV/AIDS, diabetes, or dentures. 
• Genital Infections: Candida dubliniensis can cause genital candidiasis, resulting in itching, burning, irritation, and abnormal discharge. It is more common in pregnant women and diabetics. 
• Skin Infections: It can lead to skin and nail infections, causing rash, blisters, and pain. It is more likely in people with diabetes, obesity, or those who wear tight clothing and sweat excessively. 

Diagnosis 

Diagnosing Candida dubliniensis infections is challenging due to its similarity to Candida albicans. Methods include: 

• Blood Culture: The primary method for invasive candidiasis involves blood sample incubation and yeast identification. 
• Endoscopy: Used to diagnose esophageal candidiasis by examining and sampling infected tissue. 
• Culture-Independent Methods: Detect Candida DNA or antigens directly in patient samples, e.g., PCR, FISH, MALDI-TOF MS, ELISA. 
• Beta-D-Glucan Assay: Measures fungal cell wall component (beta-D-glucan) levels in the blood, indicating fungal infection (not very specific for Candida). 

Control 

To prevent Candida dubliniensis infections: 

• Maintain good oral hygiene: Brush teeth regularly, use warm saline mouthwash, and rinse your mouth after using a steroid inhaler. 
• Avoid unnecessary or prolonged use of immune-suppressing drugs. Consult your doctor for appropriate dosages. 
• Follow a healthy diet and lifestyle: Eat balanced, low-sugar foods, stay hydrated, limit alcohol and caffeine, exercise, and manage stress. 
• Keep skin clean and dry: Use mild soap, wear breathable clothing, change underwear daily, and use cotton fabrics. 
• Practice safe sex: Use condoms or dental dams and avoid sexual activity during genital candidiasis symptoms. Consult a doctor if your symptoms continue or get worse. 

References 

• Frontiers | Case Report: Candida dubliniensis as a Cause of Chronic Meningitis (frontiersin.org) 
• Candida dubliniensis: An Appraisal of Its Clinical Significance as a Bloodstream Pathogen | PLOS ONE