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CANDIDA

FADHILAH

PROGRAM STUDI BIOMEDIK UNHAS

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Candida

MOST COMMON invasive fungal infection inimmunocompromised patients

4th most common cause of nosocomial blood streaminfection

Species implicated in human disease most often:

C. albicans

C. tropicalis

C. parapsilosis

C. krusei (fluconazole resistant)

C. glabrata

C. lusitaniae (amphotericin B resistant)

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Candida

Thick cell wall of polysaccharides

Unicellular, budding (asexual)

reproduction (blastospores) Filament formation

Pseudohyphae

Hyphae

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Cell wall Candida albicans

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Candida - Pathogenicity / VirulenceFactors

C. albicans>>> virulent than other Candida

species

Rapid switchingof expressed phenotype

Enhanced ability to reassort and regulate genetic

expression by chromosomal rearrangement and

recombination

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Hyphal formation

Hyphal formation is associated with tissueinvasion ( yeast forms associated with epithelial

colonization) spontaneous C.albicansnon-hyphae-forming mutant

shows decreased pathogenicity in a rat Candidavaginitis model

Experimental renal infection - yeast and hyphae initiaterenal lesions, but hyphae are essential for invasion ofthe renal pelvis.

Hyphae adhere more readily to host epithelial surfaces thando yeast cells (50x more adherent)

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Contact sensing - growth of hyphae on filters or

membranes (thigmotropism)

Surface hydrophobicity Hydrophobic C. albicansat 25 C >>virulent than more

hydrophilic C. albicansat 37 C

Hydrophobic CA show increased adherence and more

rapid hyphal germ tube formation

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Candida -Pathogenicity / Virulence Factors

Surface virulence molecules (receptors, adhesins,pyrogens, and immunomodulators)

Candida adhereto:

epithelial cells (buccal, cervical, corneal, urinary,

gastrointestinal mucosa), vascular endothelial cells,

spermatozoa

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CandidaPathogenicity / Virulence Factors

Lytic enzymes

Hydrolases with broad substrate specificities

(proteinase, phospholipase(s), lipase(s), acidphosphomonoesterase).

Aspartyl proteinase- most potent

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Candida

Human commensal(endogenous)

skin, gastrointestinal, genitourinary tracts

5 - 15% carriage rate in normal people

increased carriage with use of antibiotics

Environmental (exogenous)

much less common

food, animals, soil hospital environment

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Candida - Clinical

Mucous membrane infections

Thrush (oropharyngeal)

Esophagitis

Vaginitis Cutaneous infections

Paronychia (skin around nail bed)

Onychomycosis (nails)

Diaper rash

Balanitis

Chronic mucotaneous candidiasis

children with T-cell abnormality11

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Mucosal candidiasis

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Oral thrush

Vaginal candidiasis

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Cutaneous candidiasis

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Onychomycosis and paronychia Chronic mucocutaneous candidiasis

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Candida - Clinical

Urinary tract infection

Fungemia

Disseminated (systemic, invasive) infection

Immunocompromised patients Cancer/chemotherapy

Neonatal candidiasis

Endophthalmitis (eye)

Liver and spleen Kidneys

Skin

Brain

Lungs 14

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Clinical profile

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Parenteral nutrition

Broad-spectrum

antibiotics

Neutropenia

Very low birth weight

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Disseminated candidiasis

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Endophthalmitis Disseminated skin lesion

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Candida- Laboratory Diagnosis 1

Specimens - Blood, tissue (biopsy or autopsy),

sterile fluid, urine, CSF, skin, respiratory

secretions

Microscopy (direct on specimen - except blood

and urine)

Gram stain, Calcofluor

Histopathology (tissues)

H & E - stain poorly

GMS, PMS - stain well17

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Candidaspecies

Top:Calcofluor White x400: Yeast and

pseudohyphae

Bottom:Gram stain x1000: Yeast and

pseudohyphae

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Pathology of disseminated

candidiasis

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Yeast-like cells and septate hyphae

GMS

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Pathology of disseminated candidiasis

20Esophagus, vascular invasion, blastoconidia and pseudohyphae, PAS

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Pathology of disseminated candidiasis

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Hematogenous renal candidiasis. Disseminated miliary abscesses,

cortex and medulla. Necrotic papillae.

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Candida - Laboratory Diagnosis 2

Culture(all specimens) Colony morphology

White, smooth, creamy, sometimes wrinkled

Laboratory identification

Unique color on chromagar Chlamydospore production (terminal vesicle)

Germ tube production (in horse serum)

beginning of true hypha (no constriction)

C. albicans- Germ tube positive

Other Candida- Germ tube negative

Carbohydrate assimilation and fermentation (API 20C, Vitek2,

RapID and reference)

Urea and nitrate

Microscopic morphology on Cornmeal Tween 80 22

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Yeast Identification

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Candidaspecies

Candida albicans

Sabouraud Agar

Morphology: Creamy white yeast,

may be dull, dry irregular and

heaped up, glabrous and tough

Chromagar

producing green pigmented colonies

on specially designed medium tospeciate certain yeasts based on

color they produce

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Candidaspecies

Germ tube: inoculation of yeast in horse

serum incubated at 370C for 2 to 3 hours

Germ Tube: Positive

Germ tube is a continuous filamentgerminating from the yeast cell without constriction

at the point of attachment.

e.g. C. albicans, C. dubliniensis

Germ Tube: Negative

Shows constriction at the attachment site

e.g. other Candidaspecies, esp. C. tropicalis

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Candidaspecies

Candida albicans

Oxgall Agar

large round and thickwalled chlamydospores

Cornmeal Agar

clusters ofblastospores along

pseudohyphae at regular

intervals

x400 x1000

x400

x1000

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Yeast identification

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C. parapsilosisShort, curved pseudohyphae

C. lusitaniaeSlender, branched, curved pseudohyphae

short chains of blastoconidia

C. guil li ermondii

Few, short pseudohyphaeClusters of blastoconidia at septae

C. lipolytica

Elongated blastoconidia in short chains

arthroconidia

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Yeast identification

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C. dubliniensis

Terminal chlamydospores

C. tropicali sGraceful long pseudohyphae

Single/small groups blastoconidia along pseudohyphae

C. krusei

Elongate blastoconidiaCross-matchsticks, tree-like

C. glabrataNo pseudohyphae, small blastoconidia

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Candida - Laboratory Diagnosis 3

Candida antigen, antibody and

metabolite detection

NOT useful in routine practice

Low sensitivity and specificity

Polymerase chain reaction

No more sensitive than blood culture in

studies to date

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Candida - Treatment

Remove infected intravenous lines

Antifungal therapy for systemic infection

Amphotericin B IV

Azoles (fluconazole, itraconazole, voriconazole,

posaconazole) orally, intravenous

Flucytosine (only with Ampho B because of

resistance) Echinocandins (caspofungin, micafungin)

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Candidaantifungal resistance

Primary (inherent) resistance

C. lusitaniae(amphotericin B)

C. glabrata(fluconazole)

C. krusei(fluconazole)

Secondary (acquired) resistance

Fluconazole, other azoles

Amphotericin B 5-FC

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Candidaantifungal susceptibility

testing

Testing methodology

Reference broth microdilution (CLSI)

Commercial broth microdilution with alamar blue

(Sensititre, YeastOne)

E-test

Disk diffusion (CLSI

Vitek 2

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testing

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testing

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Documents

Candida_3