This document discusses Candida, a fungal pathogen that can cause various infections in humans. It notes that Candida albicans is the most common Candida species causing infection. It identifies several risk factors that increase the risk of Candida infection, including extremes of age, pregnancy, HIV infection, steroid/cytotoxic drug therapy, malignancy, and broad spectrum antibiotic use. The document outlines several types of Candida infections, including mucosal and cutaneous candidiasis. It also describes methods for laboratory diagnosis of Candida infections through microscopy, culture, and other tests. Treatment generally involves the use of antifungal azole drugs or amphotericin B.

1. Candida
Pathology

2. Introduction
• 4th Century BC – ‘Epidemics’ (by Hippocrates) mentioned oral aphtha
(Thrush)
• 200 species  20 A/W human or animal diseases
• Major pathogen – Candida albicans
• Others: C. dubliniensis, C. glabrata, C. guilliermondii, C.kefyr, C.kruesi,
C. lusitaniae, C. parapsilosis, C.tropicalis etc.
• Budding cells, psudohyphae and true hyphae – all simultaneously
possible

3. Pathogenesis
• Most common fungal infection in human
• Increased risk of infection –
• Extremes of age,
• Pregnancy,
• HIV infected,
• Steroid, cytotoxic drug (or similar) therapy,
• Malignancy,
• post transplantation,
• Broad spectrum antibiotics,
• Diabetes,
• neutropenia etc.

4. • Virulence factors
• Adhesins
• Enzymes: proteinases, phospholipase
• Toxins: GP extracts pyrogenic properties
• Pseudohyphae : Active infection marker

5. • Candida albicans transforms frequently between 3 phenotypic forms
in tissues  Phenotypic switching (evasion of host defence)

7. • Mostly endogenous source:
• GI,
• Vagina,
• Urethra,
• Skin,
• subungual
• Exogenous source: Catheters and lines, indwelling device  usually
deep seated systemic infection.
• Person to person transmission: Rare
• oral thrush in new-borns
• Sexual transmission

10. Mucosal candidiasis
Oral thrush Chronic mucocutaneous candidiasis

14. Cutaneous candidiasis
Onychomycosis and paronychia Intertrigo

19. Lab diagnosis
• Specimen: Depending on site – swabs (mucosal patches, skin lesion),
nail scrapings, sputum, blood, urine

20. • Direct Microscopy:
• Gram positive, oval budding yeast (4-6um) or KOH mount
• Pseudohyphae

21. • Pseudohyphae V/S true hyphae
Feature Pseudohyphae True Hyphae
Septa Constricted No Constriction
Origin of branches Constricted and septate No Constriction & No
septum present
Grows by Budding Apical elongation

23. • Culture: SDA with antibiotic, Blood agar, Blood culture bottle, CHROM
agaretc (@ 370C)
• Creamy white colony with yeasty odour after 24-48 hrs (SDA)
• Gram + budding yeast with pseudo-hyphae

25. Species identification
• Germ tube test: Reynold Braude phenomenon
• Colonies mixed with serum & incubated for 2 hours
• Wet mount under microscope
• Long tube like projections extending from yeast cells no constriction at
origin
• Specific for C. albicans (C. dubliniensis)

27. • Cornmeal agar:
• Chlamydiospore is specific for Candida albicans

28. • CHROME Agar
• Growth at 450C : C. albicans & C. dublinensis
• Sugar assimilation tests
• PCR

29. • Serology
• Antibody : ELISA, Latex agglutination
• ANTIGEN DETECTION: Cell wall mannan & Cytoplasmic antigen by ELISA
• Enzyme assay : Enolase, Proteinase
• Metabolites – alpha1-3 glucan (G test)

30. Treatment
• Depending on type of candidiasis
• Azoles
• Amphotericin B