Candidiasis: Fungal Infections

• Saprobes and saprophytes are free-living microorganisms, typically not a concern in human disease
• Increasing numbers of people with immune system defects are susceptible to opportunistic mycoses.

Candidiasis

• Normal biota of the mucus, skin, and digestive tract are affected
• The most notorious agents of yeast infections

Candida Albicans

• This currently causes the most yeast infections

Candida Glabrata

• This is the second most common to cause disease, and causes 21% of urinary yeast isolates

• Candida multiplies by blastospore formation, creating pseudohyphae or septate hyphae.

• Candida are identified and speciated by their carbohydrate assimilation and fermentation, as well as physiologic and morphologic responses under controlled nutritional conditions.

Factors affecting Candida

• Poor oral hygiene
• Antibiotic consumption
• Dietary factors
• Absence of antagonistic inhibitory bacteria

Factors Predisposing Candidiasis

• Extreme youth
• Pregnancy
• Steroid use
• Diabetes
• Prolonged use of antibiotics
• Debility
• Avitaminosis
• Diseased heart valves
• Pulmonary or systematic candidiasis
• Genetic deficiencies
• Immune defects
• Abnormal leukocytic function
• AIDS
• Catheters
• Hyperalimentation
• Dialysis
• Surgery
• Injection
• Drug abuse
• Trauma
• Burns
• Open wounds

Types of Candidiasis

• Mucocutaneous, affecting mucous membranes and skin
• Cutaneous, affecting the skin
• Penile
• Systemic encompassing various organ systems
• Allergic

Mucocutaneous Candidiasis

• Oral, causing thrush, glossitis, stomatitis, cheilitis, and perleche
• Vaginitis and balanitis
• Bronchial and pulmonary infections
• Alimentary infections like esophagitis, gastritis, peritonitis, enteric, and perianal diseases
• Chronic mucocutaneous candidiasis (CMCC)

Cutaneous Candidiasis

• Intertriginous and generalized
• Paronychia and onychomycosis nail infections
• Diaper rash
• Candidal granuloma

Systemic Candidiasis

• Affects the urinary tract
• Endocarditis
• Meningitis
• Specticemia
• Presents as Latrogenic candidaemia
• Disseminates to other organ systems

Allergic Candidiasis

• Causes candidids
• Eczema
• Asthma
• Gastritis

Laboratory Diagnosis of Candidiasis

• Sputum

• Skin scraping

• Vaginal swabs

• Biopsy material

• Blood

• Examination reveals encapsulated budding yeast cells (blastoconidia) 2 to 4 μm in diameter and/or pseudohyphae

• Culture for 2-3 days at 37°C

• SDA shows smooth, creamy white colonies

• Uses Automated BACTEC and BacT/ALERT systems

• Cornmeal agar w/ 1% Tween 80 and trypan blue

Germ Tube Test

• C. albicans produces hyphal growth when blastospores are suspended in serum at 37°C for 2-3 hours

Candidiasis Treatments

• Antifungal agents (eg. clotrimazole, econazole, ciclopirox, miconazole, ketonazole, nystatin)
• Oral itraconazole (Sporanox)
• Topical antifungals or single-dose oral fluconazole.
• Caspofungin acetate (Cancidas) requires a 70-mg loading dose IV, followed by 50 mg/day IV for at least 2 weeks after improvement or cleared blood cultures

Other Opportunistic Yeast

• Includes Rhodotorula and Aspergillus species

Rhodotorula spp.

• Exhibits a bright salmon-pink color
• Creates a capsule and tests urease-positive
• Some species also test nitrate positive

Aspergillus spp.

• One of the largest fungal genera and second most isolated behind Candida
• Aspergilli are widespread

Aspergillosis Types

• Pulmonary or sinus fungus ball
• Allergic bronchopulmonary aspergillosis
• External otomycosis
• Mycotic keratits
• Onychomycosis
• Sinusitis, endocarditis
• Central nervous system (CNS) infection

Allergic Aspergillosis

• Allergic aspergillosis can be minor early on but severe as the patient ages.
• In secondary colonization, limited distress occurs barring hemoptysis bouts and lung damage that could lead to fungus ball

Systemic Aspergillosis

• Systemic aspergillosis is extreme, serious, often rapidly fatal unless diagnosed early and treated quickly
• Host immune system health affects prognosis

Aspergillosis Laboratory Diagnosis

• The specimen should be a thick, gelatinous sputum sample
• Testing shows hyaline, dichotomously branched, septate hyphae
• Presence of small, rough-walled spores (3-4 μm)

Aspergillus Culture

• Uses SDA
• A rapidly growing mold (2-6 days)
• Creates a fluffy or granular, white to blue-green colony

Aspergillosis Treatment

• Amphotericin B previously used, but had disappointing results
• Itraconazole was introduced as a broad-spectrum anti-fungal in 190

Zygomycosis

• Rhizopus, Absidiam, and Mucor genera have been implicated in it

• These are in the class of fungi known as Phycomycetes, the disease should be called phycomycosis

• They form coenocytic hyphae and reproduce asexually by producing sporangiosphores

Zygomycosis Diagnosis

• Rapid diagnosis is critical.
• Fungal elements are usually not numerous.
• KOH-mounted scrapings from upper turbinates, sinus aspirates, sputum from lungs, and biopsy samples contain thick-walled, refractile hyphae, 6-15 μm in diameter and swollen/distorted hyphae
• Inoculate clinical material onto Sabouraud dextrose agar and incubate at 30°C

Zygomycosis Treatments

• Control diabetes
• Surgical debridement
• High-dose amphotericin B

Cryptococcus Neoformans

• Exists monomorphically and only in yeast form at 25°C or 37°C
• Appears as a spherical, single/multiple budding, thick-walled yeast, 2-15 μm, features an acidic mucopolysaccharide capsule

Cryptococcus serotypes

• A (C. neoformans var grubii)
• B
• C
• D (C. neoformans var. neoformans)

Cryptococcosis disease

• Cryptococcosis is commonly associated in HIV patients
• Primary pulmonary version is usually inapparent, but may be chronic, subacute or acute
• The most common presentation os cryptococcal meningitis
• Osseous and cutaneous disease can occur w/o neurological involvement
• Historically known as Busse-Buschke’s Disease/Torulosis/European Blastomycosis
• It's globally distributed

Sources of Cryptococcus

• Has repeatedly appeared in sites inhabited by pigeons, primarily roosts and droppings
• Pigeons are not naturally infected

Cryptococcus Laboratory testing

• India Ink in CSF: a rapid detection method, the background is black, w/clear unstained halos around individual yeast cells
• KOH for testing respiratory secretions
• Culture for 1-5 days at 20-30°C
• SDA w/o cycloheximide
• Uses CSF- (0.455-mm membrane filter)
• Smooth, white to tan colonies are observed
• Latex Agglutination
• A cryptococcal Antigen Detection is recommended for for routine use in most clinical microbiology laboratories

Cryptococcus Treatment & Prevention

• Amphotericin B w/ 5-fluorocytosine is often successful
• Flucanazole is also effective
• Avoid visiting caves sans protection