Discuss infections caused by Candida albicans under the following headings:

(a)	types of infection.
(b)	predisposing factors.
(c)	laboratory diagnosis

Suggested Answer:

(a)	Candida albicans is an oval yeast with a single bud. It is part of the normal flora of mucous membranes of the upper respiratory, gastrointestinal, and female genital tracts. In tissues it may appear as budding yeasts or as elongated budding ‘pseudohyphae’.

	The infections caused by Candida albicans are known as candidiasis. Candidiasis may be classified as superficial or deep. Superficial candidiasis may involve the epidermal and mucosal surfaces, including those of the oral cavity, pharynx, esophagus, intestines, urinary bladder, and vagina. The alimentary tract and intravascular catheters are the major portals of entry for deep (or visceral) candidiasis. The kidneys, liver, spleen, brain, eyes, heart, and other tissues are the major organ sites involved in deep or visceral candidiasis. 

Cutaneous candidiasis: These superficial infections of moist epidermal surfaces are associated with moist surfaces subject to regular friction: most commonly the submammary folds in obese women and the groins and buttocks of babies (napkin dermatitis). In both cases, satellite lesions can be observed at a distance from the primary lesion. 

Chronic mucocutaneous candidiasis: A clinical syndrome characterized by development, usually in infancy or childhood, of a chronic, often widespread candidiasis of skin, nails, and mucous membranes. It may be secondary to one of the immunodeficiency syndromes, inherited as an autosomal recessive trait, or associated with defects in cell-mediated immunity, endocrine disorders, dental stomatitis, or malignancy. 

            Oral candidiasis, or thrush is a common clinical feature in immunocompromised patients, consisting of dense white plaques lying the oral mucosa.

	Esophageal candidiasis: The presenting symptoms are dysphagia and retrosternal pain. Diagnosis is by microscopy of a potassium hydroxide or Gram-stained preparation of white plaque scraped from affected mucosa. 

	Candida infections of the gastrointestinal tract include peritonitis and hepatosplenic candidiasis which may spread to the gallbladder. 

	Vaginal discharge. Vaginitis caused by Candida albicans is typically associated with a thick, creamy discharge and a white, curd-like inflammatory exudate. This condition is not necessarily transmitted sexually and is often caused by local factors such as tight underwear, ecological disturbances resulting from antibiotic use or variation in hormonal background during particular phases of the menstrual cycle.

	Urinary tract infections with Candida albicans can lead to cystitis and prostatitis. Haematogenous or ascending infections is a dangerous complication, resulting in formation of fungal balls in renal tissue, perinephric abscess and papillary necrosis.

	In immunocompromised individuals, Candida albicans may disseminate through the blood, causing septicaemia and spread to many organs. Ocular endophthalmitis is inflammation of the uveal tract or posterior chamber, usually caused by an intraocular infection. Candida endophthalmitis is spread by blood-borne infection following intravascular cannulation or parenteral infection. Symptoms are visual blurring, pain and a floating scotomata.Intravenous drug abuse and hyperalimentation can lead to right-sided endocarditis. Spread of infection in other parts of the body can also result in myocarditis, purulent pericarditis and osteomyelitis. Central nervous system involvement affects the brain parenchyma and meninges with formation of abscesses. Clinical manifestations are fever, headache, stiff neck, seizures and focal neurologic deficits.

(b)	Infections by Candida albicans are often the result of impaired local or systemic host defenses. Vulvovaginitis with itching and discharge is favored by high pH, diabetes, or use of antibiotics. Skin invasion occurs in warm, moist areas, which become red and weeping. Fingers and nails become involved when repeatedly immersed in water; persons employed as dishwashers in restaurants and institutions are commonly affected. The predisposing factors for candida endocarditis are underlying heart disease, intravenous drug abuse, cancer chemotherapy, prosthetic valves and prolonged use of intravenous catheters/ Antibiotic use and indwelling catheters also predispose to candida urinary tract infections while hepatosplenic candidiasis is common in recovering neutropenic patients.

The principal risk factors predisposing to deeply invasive candidiasis are protracted courses of broad spectrum antibiotics, cytotoxic chemotherapy, corticosteroids, neutropenia, vascular catheters and intravenous drug abuse.

(c)	Laboratory confirmation of the diagnosis of infections by Candida albicans is by microscopy of a saline-mounted preparation of exudate and fungal culture on Sabouraud’s medium. In exudates or tissues, budding yeast and pseudohyphae are seen microscopically. Such specimens grow typical yeasts when cultured. Germ tubes form in serum at 37C, which serves to distinguish Candida albicans from other candida species.