Candida parapsilosis- An Overview

Candida parapsilosis is a type of yeast that belongs to the genus Candida, which includes over 150 species of fungi that can cause infections in humans. Candida parapsilosis is one of the six most common species of Candida that cause invasive candidiasis, a serious infection that can affect the blood, tissues, and organs . Candida parapsilosis was first discovered in 1928 by Ashford from a stool sample of a patient with diarrhea in Puerto Rico. It was initially named Monilia parapsilosis, but later renamed to Candida parapsilosis in 1970.

Candida parapsilosis is normally found on the skin and mucous membranes of healthy people, where it usually does not cause any harm. However, in some situations, such as when the immune system is weakened or the skin is damaged, Candida parapsilosis can overgrow and cause infections. Candida parapsilosis is especially associated with infections in neonates (newborns) and patients in intensive care units (ICUs), who often have indwelling medical devices such as catheters, prosthetic valves, or artificial joints . Candida parapsilosis can also contaminate medical solutions such as parenteral nutrition (intravenous feeding) or blood products, and spread through the hands of health care workers .

Candida parapsilosis infections can range from mild to life-threatening, depending on the site and extent of infection. Some of the common types of infections caused by Candida parapsilosis are:

• Candidemia: infection of the blood
• Endocarditis: infection of the heart valves
• Meningitis: infection of the membranes covering the brain and spinal cord
• Peritonitis: infection of the lining of the abdomen
• Ocular infection: infection of the eye
• Arthritis: infection of the joints
• Vulvovaginitis: infection of the vagina and vulva
• Otomycosis: infection of the ear
• Onychomycosis: infection of the nails
• Urinary tract infection: infection of the bladder or kidneys

The symptoms and signs of Candida parapsilosis infections vary depending on the type and severity of infection. Some common symptoms include fever, chills, pain, swelling, redness, discharge, itching, burning, and reduced vision or hearing. In some cases, Candida parapsilosis infections can cause septic shock, organ failure, or death.

The diagnosis of Candida parapsilosis infections is based on clinical features, laboratory tests, and imaging studies. Laboratory tests include microscopic examination and culture of specimens from infected sites, such as blood, urine, tissue biopsies, or cerebrospinal fluid. Molecular methods such as polymerase chain reaction (PCR) or genomic sequencing can also be used to identify and differentiate Candida parapsilosis from other species of Candida. Imaging studies such as echocardiography or magnetic resonance imaging (MRI) can help to detect complications such as endocarditis or abscesses.

The treatment of Candida parapsilosis infections depends on the type and severity of infection, as well as the patient`s condition and response to therapy. Antifungal drugs are the mainstay of treatment for most types of Candida parapsilosis infections. The most commonly used antifungal drugs are fluconazole, amphotericin B, and echinocandins (caspofungin, micafungin, or anidulafungin). Some strains of Candida parapsilosis may be resistant to certain antifungal drugs, so susceptibility testing is recommended before starting treatment. In some cases, surgical interventions may be needed to remove infected devices or tissues.

The prevention and control of Candida parapsilosis infections involve measures to reduce the risk factors and transmission routes for infection. Some of these measures include:

• Maintaining good hygiene and hand washing practices for health care workers and patients
• Using sterile techniques and disinfecting procedures for medical devices and solutions
• Removing or replacing indwelling devices as soon as possible
• Avoiding unnecessary use or prolonged use of antibiotics or corticosteroids
• Monitoring blood glucose levels and managing diabetes
• Strengthening the immune system by eating a balanced diet and getting enough rest

Candida parapsilosis is an emerging pathogen that can cause serious infections in vulnerable people. By understanding its characteristics, risk factors, transmission routes, clinical features, diagnosis methods, treatment options, and prevention strategies, we can better manage and prevent Candida parapsilosis infections.

Candida parapsilosis is a yeast-like fungus that can be found in various natural and human-made environments. It is typically a commensal of human skin, and its pathogenicity is limited by the intact integument. However, it can also colonize and infect other sites of the human body, such as the mouth, gastrointestinal and respiratory tracts, genitourinary tract, nails, and eyes .

C. parapsilosis has the ability to grow in total parenteral nutrition (TPN) solutions and form biofilms on catheters and other implanted devices, which facilitate its nosocomial spread by hand carriage and persistence in the hospital environment . It is also associated with hyperalimentation solutions, prosthetic devices, and indwelling devices. Moreover, C. parapsilosis can be isolated from nonhuman sources such as animals, insects, soil, and marine environments .

Candida parapsilosis cells have an oval, round, or cylindrical shape. These cells exist in multiple morphogenetic forms. C. parapsilosis does not form true hyphae and exists in either a yeast phase or a pseudohyphal form . The morphological forms yeast and pseudohyphae formation have been linked to the production of certain amino acids, citrulline, which makes the cellular and colony morphological changes.

On Sabouraud dextrose agar, C. parapsilosis produces white, creamy, shiny, and smooth or wrinkled colonies. On cornmeal agar, it produces blastospores that are located along the pseudohyphae. On CHROMagar Candida medium, it produces pink-colored colonies.

Candida parapsilosis is a yeast that can grow on various media and produce different colony morphologies depending on the culture conditions. Some of the commonly used media and their characteristics are:

• Sabouraud dextrose agar: C. parapsilosis produces white, creamy, shiny, and smooth or wrinkled colonies. It turns rust color with age.
• Cornmeal agar: C. parapsilosis forms pseudohyphae, which are elongated cells that resemble hyphae but are not true hyphae. Pseudohyphae are important for biofilm formation and adherence to surfaces.
• Potato dextrose agar: C. parapsilosis also produces white, creamy, shiny, and smooth or wrinkled colonies with larger blastospores, which are budding yeast cells.
• CHROMagar Candida: C. parapsilosis produces pink-colored colonies on this differential medium that can distinguish between different Candida species based on their color.

Candida parapsilosis can grow at a wide range of temperatures (15°C to 42°C) and pH levels (2 to 10), but it prefers 37°C and neutral pH. It can also tolerate high concentrations of glucose and salt, which makes it able to survive in hyperalimentation solutions and other hospital environments.

Candida parapsilosis is a yeast fungus that can cause invasive fungal infections in humans, especially in immunocompromised and hospitalized patients. The pathogenesis and transmission of C. parapsilosis are influenced by several factors, such as its morphological forms, its ability to grow in high-glucose environments, its secretion of hydrolytic enzymes, its adherence to prosthetic devices, and its formation of biofilms.

C. parapsilosis can exist in either a yeast form or a pseudohyphal form. The yeast form is more common in the environment and on the skin, while the pseudohyphal form is more associated with invasive infections. The pseudohyphae can penetrate the host tissues and evade the immune system. C. parapsilosis can also change its morphology in response to environmental cues, such as amino acids and pH.

C. parapsilosis can also thrive in medium with high glucose levels, such as parenteral nutrition or hyperalimentation solutions that are fed to patients. These solutions can provide a source of nutrients and energy for the fungus, as well as facilitate its growth and spread in the bloodstream. High glucose levels can also induce the expression of virulence genes in C. parapsilosis.

C. parapsilosis can secrete hydrolytic enzymes, such as aspartic proteinases (Saps), phospholipases, and lipases. These enzymes can degrade the host tissues and membranes, facilitate the invasion and dissemination of the fungus, and modulate the host immune response. Saps are especially important for C. parapsilosis virulence, as they can cleave immunoglobulins, complement components, and cytokines.

C. parapsilosis can adhere to prosthetic devices, such as catheters, valves, implants, and artificial joints . This allows the fungus to colonize and persist on these surfaces, as well as to cause device-related infections . The adherence of C. parapsilosis is mediated by adhesins, which are cell surface proteins that bind to specific receptors on the device materials.

C. parapsilosis can also form biofilms on prosthetic devices and host tissues . Biofilms are complex communities of microorganisms that are embedded in a matrix of extracellular polysaccharides . Biofilms can protect C. parapsilosis from the host immune system and antifungal drugs, as well as enhance its resistance and persistence . Biofilms can also serve as reservoirs for disseminating fungal cells into the bloodstream or other organs .

The transmission of C. parapsilosis is mainly nosocomial, meaning that it occurs in health care settings . The most common routes of transmission are:

• Contaminated medical devices, such as catheters, needles, syringes, and infusion sets .
• Contaminated fluids, such as parenteral nutrition solutions, blood products, dialysis fluids, and saline solutions .
• Contaminated hands of health care workers, who can transfer the fungus from patient to patient or from the environment to the patient .
• Prosthetic devices, such as heart valves, artificial joints, pacemakers, and implants .
• Invasive procedures, such as surgery, endoscopy, catheterization, and intubation .

C. parapsilosis can also be transmitted from mother to child during birth or breastfeeding, or from animal to human through contact with pets or livestock.

Candida parapsilosis is a yeast that can cause invasive infections in humans, especially in immunocompromised patients and those with indwelling devices. The virulence of C. parapsilosis is influenced by several factors that enable it to adhere to surfaces, form biofilms, secrete enzymes, and evade host defenses. Some of the main virulence factors of C. parapsilosis are:

• Adherence: This is the ability of C. parapsilosis to attach to various substrates, such as human skin, mucosal membranes, medical devices, and catheters. Adherence is mediated by cell surface proteins, such as adhesins, that recognize specific receptors on the target surfaces. Adherence facilitates colonization and biofilm formation by C. parapsilosis .
• Biofilm formation: This is the ability of C. parapsilosis to form multicellular aggregates on surfaces, embedded in a matrix of extracellular polysaccharides and proteins. Biofilms provide protection from environmental stresses, such as desiccation, pH changes, and antimicrobial agents. Biofilms also enhance resistance to host immune responses, such as phagocytosis and complement activation. Biofilm formation is influenced by environmental factors, such as glucose concentration, pH, temperature, and oxygen availability .
• Secretion of hydrolytic enzymes: This is the ability of C. parapsilosis to produce and secrete enzymes that degrade various substrates, such as proteins, lipids, and phospholipids. These enzymes include aspartyl proteinases (Saps), lipases, and phospholipases. These enzymes contribute to tissue invasion, nutrient acquisition, and immune evasion by C. parapsilosis .
• Immune evasion: This is the ability of C. parapsilosis to avoid or modulate host immune responses, such as inflammation, complement activation, and phagocytosis. C. parapsilosis can evade immune recognition by altering its cell surface antigens, such as mannans and β-glucans. C. parapsilosis can also modulate immune responses by secreting immunomodulatory molecules, such as prostaglandins and cytokines .

These virulence factors enable C. parapsilosis to cause a range of infections in humans, such as fungemia, endocarditis, meningitis, peritonitis, ocular infection, arthritis, vulvovaginitis, otomycosis, onychomycosis, and urinary tract infection. Understanding the molecular mechanisms and regulation of these virulence factors may help to develop novel strategies for prevention and treatment of C. parapsilosis infections.

Candida parapsilosis infections can affect various parts of the body and cause different symptoms depending on the location and severity of the infection. Some of the common clinical features of C. parapsilosis infections are:

• Fungemia: This is the infection of C. parapsilosis into the bloodstream, a condition commonly known as candidemia. It affects hospitalized patients, who have had surgeries especially gastrointestinal surgery patients, making abrasions that allow entry of the commensal Candida into the bloodstream. It also affects patients with underlying diseases such as cancer, transplantation, diabetes. It is also a common causative agent of candidemia in neonates, patients with intravenous lines or vascular catheters with a previous history of antifungal treatment, patients under parenteral nutrition. C. parapsilosis accounts for 19% of all candidemia infections. The infection is characterized by fever, septic shock, and renal failure.
• Fungal endocarditis: C. parapsilosis accounts for 17% of fungal endocarditis infection in heart surgery patients. The general predisposing factors for Candida spp being the use of transesophageal ultrasound, and increased use of medical therapies. The specific predisposing factors for C. parapsilosis include prosthetic valves, intravenous drug use, intravenous parenteral nutrition, abdominal surgery, immunosuppression, treatment with broad-spectrum antibiotics, and previous valvular disease. Endocarditis occurs majorly as a result of fungemia, due to tissue infection. It affects the aortic valves, mitral valves, tricuspid valves, ventricular wall, and pulmonary valves.
• Meningitis: Common candidal meningitis is associated with symptoms such as headache, photophobia, nuchal rigidity, fever, and delirium. C. parapsilosis causes acute neutropenic meningitis. It is transmitted with hospital settings and mostly affects neonates using hyperalimentation solutions and prolonged hospital stay patients, such as transplantation patients. It is a progressive infection that occurs due to invasive candidiasis. However, the cases are few and rare.
• Peritonitis: It is common in patients with the end-stage renal disease treated with continuous ambulatory peritoneal dialysis. The major predisposing factor being long administration on bacterial antibiotics, which facilities the growth and overgrowth of fungi. Peritonitis caused by C. parapsilosis is associated with increasing numbers of polymorphonuclear cells in the blood, abdominal pain, fever, formation of abscesses, and bowel obstruction. Evidence from research indicates that C. parapsilosis is the most common cause of fungal peritonitis.
• Ocular infection: C. parapsilosis causes invasive ocular diseases such as endophthalmitis after surgical operation, and keratitis. Endogenous fungal endophthalmitis is rare but not uncommon. C. parapsilosis causes keratitis, associated with redness, photophobia, pain, decreased vision, and a yellow-white infiltrate with dry raised slough and feathery edges; severe disease results in wet necrotic stromal inflammation similar to another microbial keratitis.
• Arthritis: Fungal arthritis caused by C. parapsilosis is rare but not uncommon. It affects immune-compromised persons (HIV/AIDS), the elderly after arthrocentesis, those receiving joint injections, and patients with implantation of prostheses. It can also affect transplant patients. It is associated with swelling, tenderness, and decreased movement of the knees.
• Vulvovaginitis: C. parapsilosis is an uncommon causative agent of vulvovaginitis owing to the fact that Candida albicans causes 99% of these infections in women. The 1% is attributed to other candidal agents including C. parapsilosis which is a commensal in the genitourinary tract. It is common in pregnant women, diabetic patients, long- administration of antibacterial drugs. It is associated with redness, itching, painful urination, burning dyspareunia (painful intercourse), white discharge with an odor.
• Otomycosis: This is a C. parapsilosis infection of otitis and inflammation of the middle ear or outer ear. It is associated with persistent white or colorless otorrhea (ear discharge) with tympanum perforation; edema and erythema (redness) of tympanic membrane residuum; ear pain; increasing hearing loss; and whitish cotton-like or greasy debris in the external auditory canal tympanic membrane or residual space due to excision of cholesteatoma (abnormal skin growth in middle ear). It commonly affects immunocompetent patients with chronic hyperplastic inflammation predisposing them to pathogenic fungi such as C. parapsilosis. The infection causes an increase in the production of mucus and buildup which allows fungal colonization. Otomycosis has also been linked to the aggressive use of antifungal and antibacterial therapies predisposing individuals to pathogenic C. parapsilosis.
• Onychomycosis: This is a common nail infection caused by fungi but majorly by C. parapsilosis. It is common in elderly persons above the age of 50 years with a thickened nail plate and reduced nail growth predisposing them to fungal infections. It can also affect neonates. The predisposing factors include previous traumatic dystrophy (degeneration)of the nail and exposure to soil during gardening. The infection is associated with total dystrophic onychomycosis (nail destruction)in chronic mucocutaneous candidiasis nail dystrophy hyperkeratosis (thickening)of nail plates grooving of the nail ridges discolorization of nail margins onycholysis (separation)of nail from nail bed).

• Urinary Tract Infection: C. parapsilosis is uncommon in causing UTIs unlike Candida albicans which causes most of the fungal UTIs. However the 1% is attributed to UTIs of C. parapsilosis and other Candida spp. It is associated with asymptomatic infections in women.

  Laboratory diagnosis of Candida parapsilosis

The laboratory diagnosis of Candida parapsilosis infections involves the following steps:

• Specimen collection: Depending on the site of infection, different types of specimens can be collected, such as blood, urine, tissue biopsies, scrapings (nails), centrifuged spinal fluid, etc. The specimens should be collected aseptically and transported to the laboratory as soon as possible.
• Microscopic examination: The specimens can be examined under a microscope after staining with 10% KOH wet mount and calcofluor stains. These stains can reveal the presence of fungal pseudohyphae, which are characteristic of Candida species. However, microscopic examination cannot differentiate between different Candida species.
• Cultural examination: The specimens can be inoculated on various culture media, such as Sabouraud dextrose agar (SDA), cornmeal agar, potato dextrose agar (PDA), or chromogenic candida agar. SDA is a general medium for the growth of fungi, while cornmeal agar is used to observe the formation of pseudohyphae. PDA and chromogenic candida agar are selective and differential media that can help in the identification of Candida species based on their colony morphology and color. Candida parapsilosis produces white, creamy, shiny, and smooth or wrinkled colonies on SDA and PDA, and pink colored colonies on chromogenic candida agar .
• Biochemical characterization: Some biochemical tests can be performed to further confirm the identity of Candida parapsilosis, such as urease test and secretion of hydrolyzing enzymes (aspartic proteinases, phospholipases, and lipases). Candida parapsilosis is urease positive and produces hydrolyzing enzymes that can degrade various substrates.
• Molecular assays: The most definitive method for the identification of Candida parapsilosis is molecular assays, such as polymerase chain reaction (PCR) and genomic sequencing. These methods can detect and differentiate the fungal genome from the specimens without requiring a culture. PCR can amplify specific regions of DNA that are unique to Candida parapsilosis, while genomic sequencing can reveal the entire genetic makeup of the fungus.

Treatment and prevention of Candida parapsilosis infections

Candida parapsilosis infections can be challenging to treat, especially when they involve medical devices or prosthetic valves. The choice of antifungal drugs depends on the type and severity of the infection, the patient`s condition, and the susceptibility of the fungus. Some of the commonly used antifungal drugs for C. parapsilosis infections are:

• Amphotericin B. This is a broad-spectrum antifungal drug that can be given intravenously or topically. It is effective against most Candida species, including C. parapsilosis. However, it can cause serious side effects such as kidney damage, fever, chills, and anemia. It is usually reserved for severe or life-threatening infections that do not respond to other drugs.
• Fluconazole. This is an oral or intravenous antifungal drug that belongs to the azole class. It inhibits the synthesis of ergosterol, a component of the fungal cell membrane. It is active against C. parapsilosis and has fewer side effects than amphotericin B. However, some strains of C. parapsilosis may be resistant to fluconazole, and it may interact with other drugs.
• Echinocandins. These are a newer class of antifungal drugs that inhibit the synthesis of (1,3)-β-D-glucan, a component of the fungal cell wall. They include caspofungin, micafungin, and anidulafungin. They are given intravenously and have potent activity against C. parapsilosis and other Candida species. They have fewer side effects than amphotericin B and do not interact with other drugs.

The duration of treatment depends on the type and location of the infection, the patient`s response, and the clearance of the fungus from the blood or other sites. In general, treatment should continue for at least two weeks after the resolution of symptoms or signs of infection.

In some cases, treatment may also require the removal or replacement of infected medical devices or prosthetic valves to eliminate the source of infection and prevent relapse. Surgery may also be needed to drain abscesses or repair damaged tissues.

Because treating C. parapsilosis infections can be difficult and costly, prevention is important. Some of the preventive measures include:

• Hand hygiene. This is the most effective way to prevent the transmission of C. parapsilosis from person to person or from contaminated surfaces or objects. Healthcare workers should wash their hands with soap and water or use alcohol-based hand rubs before and after contact with patients or their environment. Patients and visitors should also practice good hand hygiene.
• Environmental cleaning. This involves the disinfection of surfaces and equipment that may be contaminated with C. parapsilosis or other fungi. Healthcare facilities should follow standard protocols for cleaning and disinfection of patient rooms, operating rooms, intensive care units, and other areas where C. parapsilosis infections may occur.
• Sterile technique. This involves the use of sterile gloves, gowns, masks, and instruments when performing invasive procedures such as catheter insertion, blood drawing, surgery, or dialysis. Healthcare workers should also follow strict guidelines for the preparation, storage, and administration of parenteral nutrition solutions or other fluids that may be contaminated with C. parapsilosis.
• Antifungal prophylaxis. This involves the use of antifungal drugs to prevent C. parapsilosis infections in high-risk patients such as those who are immunocompromised, have indwelling devices, receive parenteral nutrition, undergo surgery, or have a history of candidemia. The choice and dose of antifungal drugs depend on the patient`s condition and risk factors.

By following these measures, C. parapsilosis infections can be reduced or prevented in medical settings.

Candida parapsilosis infections can be challenging to treat, especially when they involve medical devices or prosthetic valves. The choice of antifungal drugs depends on the type and severity of the infection, the patient`s condition, and the susceptibility of the fungus. Some of the commonly used antifungal drugs for C. parapsilosis infections are:

• Amphotericin B. This is a broad-spectrum antifungal drug that can be given intravenously or topically. It is effective against most Candida species, including C. parapsilosis. However, it can cause serious side effects such as kidney damage, fever, chills, and anemia. It is usually reserved for severe or life-threatening infections that do not respond to other drugs.
• Fluconazole. This is an oral or intravenous antifungal drug that belongs to the azole class. It inhibits the synthesis of ergosterol, a component of the fungal cell membrane. It is active against C. parapsilosis and has fewer side effects than amphotericin B. However, some strains of C. parapsilosis may be resistant to fluconazole, and it may interact with other drugs.
• Echinocandins. These are a newer class of antifungal drugs that inhibit the synthesis of (1,3)-β-D-glucan, a component of the fungal cell wall. They include caspofungin, micafungin, and anidulafungin. They are given intravenously and have potent activity against C. parapsilosis and other Candida species. They have fewer side effects than amphotericin B and do not interact with other drugs.

The duration of treatment depends on the type and location of the infection, the patient`s response, and the clearance of the fungus from the blood or other sites. In general, treatment should continue for at least two weeks after the resolution of symptoms or signs of infection.

In some cases, treatment may also require the removal or replacement of infected medical devices or prosthetic valves to eliminate the source of infection and prevent relapse. Surgery may also be needed to drain abscesses or repair damaged tissues.

Because treating C. parapsilosis infections can be difficult and costly, prevention is important. Some of the preventive measures include:

• Hand hygiene. This is the most effective way to prevent the transmission of C. parapsilosis from person to person or from contaminated surfaces or objects. Healthcare workers should wash their hands with soap and water or use alcohol-based hand rubs before and after contact with patients or their environment. Patients and visitors should also practice good hand hygiene.
• Environmental cleaning. This involves the disinfection of surfaces and equipment that may be contaminated with C. parapsilosis or other fungi. Healthcare facilities should follow standard protocols for cleaning and disinfection of patient rooms, operating rooms, intensive care units, and other areas where C. parapsilosis infections may occur.
• Sterile technique. This involves the use of sterile gloves, gowns, masks, and instruments when performing invasive procedures such as catheter insertion, blood drawing, surgery, or dialysis. Healthcare workers should also follow strict guidelines for the preparation, storage, and administration of parenteral nutrition solutions or other fluids that may be contaminated with C. parapsilosis.
• Antifungal prophylaxis. This involves the use of antifungal drugs to prevent C. parapsilosis infections in high-risk patients such as those who are immunocompromised, have indwelling devices, receive parenteral nutrition, undergo surgery, or have a history of candidemia. The choice and dose of antifungal drugs depend on the patient`s condition and risk factors.

By following these measures, C. parapsilosis infections can be reduced or prevented in medical settings.

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