Mycology - Opportunistic Infections (Candidiasis) Flashcards
What are the different types of candidiasis infections? [3]
- Oral thrush (oropharyngeal/oesophageal candidiasis)
- Genital/vulvovaginal candidiasis
- Invasive candidiasis
Where can Candida be found normally on the body?
- GI tract
- Mouth
- Vagina
- Skin
Outline the difference between endogenous and exogenous infection. Both can cause candidiasis.
Endogenous (self) infection is most common, where there is an overgrowth of Candida that was already present on the body, the primary site of colonisation being GI tract.
Whereas exogenous infection is infection due to external agents, such as contaminated irrigation fluids, cardiac valves, and instrumentation.
The frequency of hospital acquired infections has _________ steadily in the past 30 years. Approximately __% of health-care associated infections are caused by fungi, and Candida accounts for __-__% of all ________ infections.
Candida species are the _____ most common cause of c______ l___-a_________ b__________ i__________ (CLABSI). They can reach the blood through __ translocation (invasive) and invade deep tissues of target organs (k______, spleen, h____, _____, and brain).
The oral carriages rate is dramatically increased in individuals with AIDs, dentures, and diabetes.
The frequency of hospital acquired infections has increased steadily in the past 30 years. Approximately 15% of health-care associated infections are caused by fungi, and Candida accounts for 70-90% of all invasive infections.
Candida species are the third most common cause of central line-associated bloodstream infections (CLABSI). They can reach the blood through GI translocation (invasive) and invade deep tissues of target organs (kidneys, spleen, heart, liver, and brain).
The oral carriages rate is dramatically increased in individuals with AIDs, dentures, and diabetes.
Name some important pathogenic Candida species.
- C.albicans (90-100% mucosal isolates, causes 40-70% of BSI)
- C.glabrata (intrinsic and acquired resistance to azoles)
- C.tropicalis
- C.krusei
- C.parapsilosis
What are the risk factors for acquiring candidiasis? What are the survival rates of BSI dues to candidiasis in hospitals?
Global view of hospital-acquired candidemia. BSI, Bloodstream infections; GI, gastrointestinal; ICU, intensive care unit.
Describe the morphology of Candida.
Oval, yeast-like form that can produce pseudohyphae and true hyphae.
What are the predisposing factors for different Candida infections?
- Vulvovaginal infection
- Chronic mucocutaneous candidiasis
- UTI
- Pneumonia
- Endocarditis
Describe typical Candidiasis lesions.
White plaques which may ulcerate
Oesophageal candidiasis is an ______________ infection of the oesophagus by Candida ________. The disease occurs in patients in _________________ states, including chemotherapy and AIDs.
Oesophageal candidiasis is an opportunistic infection of the oesophagus by Candida albicans. The disease occurs in patients in immunocompromised states, including chemotherapy and AIDs.
Vulvovaginal candidiasis is characterised by a _______ pain and _____ _________. It is commonplace and may affect up to __% of women at least once in their lifetime. A small subset of women (_-__%) experience chronic recurrent episodes.
Vulvovaginal candidiasis is characterised by a burning pain and white discharge. It is commonplace and may affect up to 75% of women at least once in their lifetime. A small subset of women (5-10%) experience chronic recurrent episodes.
List some forms of deep invasive candidiasis.
- Hepatic
- Splenic
- Bone
- Urinary tract
- CNS
- Endocarditis
- Pericarditis
Outline the virulence factors of Candida species.
- Can adhere to a variety of surfaces and tissues
- Produce proteases: aspartyl proteinases hydrolyse host defense proteins (innate molecules), breach connective tissues, and phospholipases which degrades mucosal cells
- Phenotypic switching: yeast-hyphal transformation in response to pH and temperature
- Immune response: yeast elicits Th1 cytokine response (activates macrophages), hyphae elicit Th2 cytokine response (activates eosinophils)
- Bio film: polysaccharide slime which contains a microcolony with channels to bring in nutrients and carry off waste
- Hyphae may invade, wheras yeast may disseminate
Describe Candida pathogenesis.
- Hyphal tip extension which generates pressure for tip penetration
- Secretion of proteases and lipases from the tip cell
- Yeasts taken up by macrophages produce filaments and pierce the macrophage
- Hyphal growth by contact guidance: locates points of weakened surface integrity and grow along those planes
- Hyphal morphology may impede dissemination
Describe the diagnosis of candidiasis.
- Specimen collection: skin scraping of lesion, mucosal scraping of lesion, vaginal swab, blood, other fluid
- Microscopy: KOH preparation, gram staining, PAS, GMS
- Culture: SAB agar and Corn meal agar
- Serological testing: Latex agglutination for Candida antigen (Cand tec assay), Mannan antigen (ELISA), β Glucan antigen detection.
How can Candida species be distinguished through culture?
Differentiation of Candida species by isolates on CHROMagar Candida. The green colonies are C. albicans, the blue-gray colonies are C. tropicalis, and the large, rough, pale pink colony is C. krusei. The smooth, pink or mauve colonies are another yeast species (only C. albicans, C. tropicalis, and C. krusei can be reliably recognized on this media; other species have colonies ranging from white, to pink, to mauve).
How is candidiasis treated?
- Mucosal and cutaneous infection: topical creams, lotions and ointments containing azoles, oral systemic therapy uses fluconazole or itraconazole
- Bladder colonisation/cystitis: AmB bladder wash, or oral fluconazole, bladder catheters must be removed to be effective
- For severe systemic infections: intravenous fluconazole, resistant strains require AmB, vascular catheters must be removed
