This document discusses the fungus Candida. It notes that Candida includes approximately 200 species, about 20 of which can cause infections in humans. C. albicans is the most common cause of infection. Candida is normally found in the gastrointestinal tract but can cause superficial or deep infections. Superficial infections include oral and vaginal candidiasis. Deep infections involve organs and can become disseminated. Virulence factors that enable Candida pathogenesis include adhesion, dimorphism, and production of enzymes. Laboratory diagnosis involves direct microscopic examination of samples and culture isolation followed by identification of Candida species.

1. Candida

2. Candida
 Family: Sachharomycetaceae
 Phylum: Ascomycota
 Approx 200 species
 About 20 associated with pathology in
humans and animals

3. Candida
 Candida – anamorph (asexual form)
 Teleomorphs of several genera demonstrated for
different species of Candida
 Teleomorph genera:
 Clavispora
 Debaromyces
 Issatchenkia
 Kluyveromyces
 Pichia
 Yarrowia

4. Habitat
 Ubiquitous yeast
 Found on many plants
 Normal flora of GI tract of mammals and
mucocutaneous membranes of humans
 Present in all areas of human GI tract
 Common species in GI tract
 C. albicans
 C. tropicalis
 C. parapsilosis
 C. glabrata

5. Major pathogenic species
 C. albicans
 C. glabrata
 C. krusei and its teleomorph Issatchenkia
orientalis
 C. kefyr and its teleomorph Kluyveromyces
marxianus
 C. guilliermondii and its teleomorph Pichia
guilliermondii
 C. parapsilosis
 C. tropicalis
 C. lusitaniae and its teleomorph Clavispora
lusitaniae

6. Morphology
 Polymorphic yeast, i.e., yeast cells, hyphae and
pseudohyphae are produced
 Ability to assume various forms may be related to the
pathogenicity
 Yeast form:
 10-12 microns in diameter
 gram positive
 grows overnight on most bacterial and fungal media
 pseudohyphae may be formed from budding
yeast cells that remain attached to each other.
 Spores may be formed on the pseudomycelium,
called chlamydospores and can be used to identify
different species of Candida.

7. Morphology

9. Morphology
 On Glucose Peptone Agar (GPA) after 3 days at
25oC
 Diameter 2-3mm
 White to cream colored
 Smooth or umbonate
 May become wrinkled after further incubation
 Dull to glistening
 On corn meal agar: intraspecies variation

10. Candida albicans
 On corn meal agar
after 3 days of
incubation:
produce true mycelia
and pseudomycelia,
grape like cluster of
blastoconidia at the
septa and
chlamydoconidia at
the ends of hyphae or
their short lateral
branches

11. Candida albicans
 Incubation for 2 hours
in 10% serum at
37oC: forms typical
cell elongations
known as germ tubes

12. Epidemiology of C. albicans
Habitat
 human commensal
 major reservoir- GI tract
 can invade into bloodstream from GI tract afgter
damaging GI mucosa
Source of infection
 Endogeneous:
 primarily
 can spread hematogenously into various organs
 Exogenous:
 introduction into the body through medical devices,
catheters
 important in the development of deep-seated and
systemic infections

13. Epidemiology of C. albicans
Transmission: Person to person transmission
 not predominant
 In case of oral thrush, from mother with
vaginal candidiasis to newborn, during birth
 sexual transmission from females with
vaginitis to their sexual partners
Risk factor
 Prolonged therapy with broad spectrum
antibiotics

14. Clinical significance
 Disease: Candidiasis
 Clinical manifestations may be acute, sub acute,
chronic or episodic
 Can cause various forms of infections, ranging
from superficial manifestations involving skin,
nails and mucosal surfaces, to deep-seated
infections involving various internal organs to
disseminated disease
 Diseases sub-divided into 2 large groups:
 Mucocutaneous candidiasis
 Deep-seated candidiasis

15. Mucocutaneous candidiasis
3 forms
 Cutaneous infections
 Nail infections
 Mucosal infections

16. Cutaneous candidiasis
1. Candidal intertrigo (Intertriginous candidiasis)
 Most common form
 Organisms colonize skin folds, particularly in
moist and macerated sites (axilla, groin, inter and
sub mammary folds, umbilicus)
 Form erythrematous lesions with vesicles
(elevation of skin with clear fluid) and pustules
(elevation of skin with purulent fluid) in
combination with pruritis (severe itching)

17. Cutaneous candidiasis (contd.)
2. Erosio interdigitalis
 Skin folds between the fingers become
macerated and itchy
 Associated with excessive exposure to moisture
 Common in dishwashers, barlenders, fruit
cannery workers
3. Perianal rash (Diaper candidiasis)
 Involves infants wearing nappies
 Rashes seen in perianal area and on the buttocks
 Infection may be secondary to pre-existing
inflammatory condition

18. Cutaneous candidiasis (contd.)
4. Chronic mucocutaneous candidiasis
 Relatively rare condition
 Most severe clinical form of superficial candidiasis
 Cause: C. albicans
 Characterised by the presence of persistent
lesions, with high rate of recurrence, starting in
early childhood and persisting throughout the
individual’s lifetime
 Lesions at various skin site, not limited to skin
folds
 Warty lesions termed as candida granuloma

19. Nail infections
(Paronychia and Onychia)
 Agent: C. albicans (major), C.
parapsilosis, C.
guilliermondii
 Characterised by prominent
swelling, redness, pain
 Paronychia: infection of nail
folds (fold of skin supporting nail
at its base)
 Onychia: infection of nails
 Affected nails become
discolored, eroded,
brittle,detached from nail bed
and painful

20. Mucosal infections
 Oral candidiasis
 Vaginal candidiasis

21. Oral candidiasis
 Most frequent
 Major agent: C. albicans
 Others: C. glabrata, C. guilliermondii, C.
parapsilosis, C. tropicalis
 Several different clinical forms
 Acute pseudomembranous candidiasis (oral thrush)
 Acute atrophic candidiasis
 Chronic atrophic candidiasis
 Chronic hyperplastic candidiasis
 Angular chelitis

22. Oral candidiasis
1. Oral thrush
 Characterised by white-grey lesions on the gums,
tongue,or oral mucosa, can appear as single
lesion or as confluent large plaques
 Lesions covering large area may be painful and
disturb food intake
 May spread to the oesophageal mucosa, and
cause dysphagia
 Generally occurs in AIDS patient, cancer patient,
debilitated individuals, elderly people and in
infants of the mothers with vaginal candidiasis

23. Oral candidiasis
2. Acute atrophic candidiasis
 Characterised by painful, erythematous mucosa,
particularly on the tongue
 May cause loss of tongue paillae, affecting food
intake.
3. Chronic atrophic candidiasis
 Known as denture stomatitis
 Occur in elder individuals wearing dentures
 Characterised by erythema and/or oedema of the
mucosa under the dentures
 Not painful

24. Oral candidiasis
4. Chronic hyperplastic candidiasis
 Also known as candida leucoplakia
 Rarer condition
 Characterised by white plaques, can appear on
various sites of oral mucosa
 Can’t be removed like pseudomembranous form
 May transform into a malignant state
5. Angular cheilitis
 Characterised by erythema and fissures at the folds of
the corners of the mouth
 May be associated with denture stomatitis or oral
thrush

25. Vaginal candidiasis
 Common infection in females of reproductive age
group, primarily during the fecund period
 Prevalence : 5-20%
 Prevalence increases in particular groups like
pregnant or diabetic women, using oral
contraceptives (hormonal effect) and after
antibiotic treatment
 Cause: C. albicans, C. glabrata, C. tropicalis
 Imporatant feature: recurrence of infection
 Transmission: sexual transmission to male
partners

26. Vaginal candidiasis (Contd.)
Syndrome:
 Complaints of vulvovaginal pruritis and discharge
(thick curd like or thin)
 Erythema of the vulvovaginal mucosa and also of
perianal area
 Lesions on the mucosal surface are basically
adherent plaques
 May cause pain and discomfort during sexual
intercourse

27. Deep-seated candidiasis
 Infection of visceral organs and possibly to
multiple organs or disseminated disease
 Includes
 Candidiasis of GI tract
 Candidiasis of respiratory system
 Candidiasis of CNS
 Candidiasis of renal and urinary system
 Candidiasis of cardiovascular system
 Hematogenous disseminated disease
 Ocular infection and a variety of other specific
manifestations

28. Deep-seated candidiasis
Candidiasis of GI tract
Oesophagitis
 Painful dysphagia and
chest pain
 White patches on
oesophageal mucosa as
in oral candidiasis
 May be associated with
oral candidiasis
 10-30% of AIDS patients
with oral candidiasis may
also have candidal

29. Deep-seated candidiasis
Candidiasis of GI tract
 Gastrointestinal candidiasis
 Though being normal flora of GI tract, clinical
involvement of mucosal surfaces of the stomach
and/or intestine with mucosal white plaques and
ulcerations are found
 Plays an important role in the pathogenesis of
disseminated candidiasis

30. Deep-seated candidiasis
Candidiasis of respiratory system
 Involves lungs
 Bronchopneumonia originates from
hematogenous spread of the fungus as a part of
a disseminated infection or from introduction of
pathogen into the lungs
CNS candidiasis
 C. albicans- cause
 Risk group- AIDS patients and pre-term infants
 Seen as part of disseminated candidiasis,
involving meninges, abscess formation in brain
tissues

31. Deep-seated candidiasis
Candidiasis of cardiovascular system
 Cause: C. albicans, C. parapsilosis, C. tropicalis
 Cause clinical manifestations in various organs of
the cardiovascular system: pericardium,
myocardium and endocardium (common)
 Endocarditis:
 primarily seen in IV drug users and in individuals
with impaired heart valves.
 Also may occur in patients after cardiac surgery
procedures or as a sequelae of anticancer therapy

32. Deep-seated candidiasis
Renal and Urinary tract candidiasis
Lower urinary tract infection:
 Frequently seen in association with indwelling
catheters
 Source: GI and genital biota
 More in women
 Also found in diabetic patients
 Infection may be mild or severe
 No unique symptoms
 Clinical feature: formation of fungal masses,
which may cause obstruction and impair normal
urine flow

33. Deep-seated candidiasis
Deep-seated candidiasis
Renal infection
 Originate from hematogenous dissemination of
Candida spp or as an ascending UTI
 Characterised by microabscess formation,
primarily in the cortex of the kidneys

34. Deep-seated candidiasis
Disseminated candidiasis
 Multi-organ infection and possibly candidemia
 May include CNS, kidneys, heart, eyes or other organs
or systems
 Hepatosplenic candidiasis- a specific clinical
manifestation of disseminated infection
 Seen in cancer patients, particularly those with acute
leukaemia, in patients after surgery (GI and cardiac), in
transplant recepients (bone marrow), in preterm infants,
burn patients and drug addicts
 Ocular infection- common, typical white (cotton-
like)lesions in the retina
 Cutaneous- nodular lesions on the skin

35. Virulence factors
 Adherence: biofilm formation, a significant factor in the
pathogenesis affecting the host’s response to infection and
causing difficulty in therapy
 Dimorphism:
 Specific enzymes that facilitate tissYeast-hyphal morphogenetic
transformation, which facilitate penetration and assist the
microbe to evade the host defense system
 Interference with phagocytosis, immune defenses and
complement
 Production of specific enzymes that could facilitate tissue
penetration and invasion such as secretory aspartyl proteinases
(SAPs) and phospholipases
 Germ tube: adhesin on the surface of tube
 Acidic metabolites
 Growth rate and undemanding nutrient requirement

36. Laboratory diagnosis of Candida
Depends on the nature of infection, whether
mucocutaneous or deep-seated forms
Mucocutaneous candidiasis
 Sample: skin, nail or mucosal surface swabs
 Includes 2 steps:
 Direct examination of the specimen to demonstrate
fungal presence
 Isolation of the fungus and its identification

37. Laboratory diagnosis of Candida
1. Direct examination (wet mount method)
 Treat specimen with keratinolytic substance (10-30%
KOH) to facilitate the microscopic examination of the
specimen
 Demonstration of fungi enhanced by
 the addition of cotton blue or acid Parker’s ink
 the use of calcofluor white, a fluorochrome with an
affinity for chitin and glucan which makes a
demonstration of fungal elements with a
fluorescent microscope relatively simple
 Gram’s staining for nail and skin specimens-not
generally done

38. Laboratory diagnosis of Candida
Mucosal infections
 Vaginal and oral swabs preferably kept in
transport medium before being processed in the
lab
 Oral lesion specimen also obtained by scrappings
 Both wet mount and fixed mount can be done
 Wet mount: unstained slide prepared in saline or
water or stained with lactophenol cotton blue or
calcofluor white
 Fixed mount: stained using Gram’s stain, Geimsa
stain or methylene blue

39. Laboratory diagnosis of Candida
 Microscopic examination of specimes from
vulvovaginitis or oral candidiasis will reveal the
presence of budding yeast cells, pseudohyphae
and hyphae
 Presence of hyphal elements in direct
microscopic examination important (vagina and
mouth normally colonised by Candida spp)
 Presence of hyphal elements indicates infection

40. Laboratory diagnosis of Candida
Culture
Isolation of Candida spp
 Routine medium: SDA supplemented with
antibiotics (chloramphenicol, gentamycin and /or
tetracyclin) to prevent bacterial overgrowth
 Other medium: SDA with cycloheximide to prevent
the growth of air-borne molds
 Incubation at 28oC or/and at 37oC for 2-3 days
 Growth can also be observed at 24 hours and
some species take more than 3 days

41. Laboratory diagnosis of Candida
Identification
Morphological characteristics
 SDA: appears smooth, but some species (C. krusei)
from dry, creamy colonies
 CHROM agar:
 uses chromogenic substances
 based on the reaction between specific enzymes of
different species and chromogenic substrates, which
results in the formation of differently colored colonies
 rapid presumptive identification of C. albicans, C. krusei
and C. tropicalis
 Wet mount or fixed mount can be done to observe the
cellular morphology of isolates

42. Different species of Candida on Chrome
agar
C. albicans, C. glabrate, C. tropicalis, C. krusei

44. Laboratory diagnosis of Candida
Physiological/ Biochemical characterization
 characterised by patterns of their use of specific
carbohydrate and nitrogen substances
Serologic identification
 Can be identified using specific antisera by slide
agglutination test
 Not used as a routine method

45. Laboratory diagnosis of Candida
Deep-seated candidiasis
 More difficult than in case of mucocutaneous
forms
 Includes
 direct microscopy
 isolation in culture
 immunodiagnosis(presence of antibodies and/or the
presence of microbial antigens in patient’s body
fluid

46. Laboratory diagnosis of Candida
Direct examination
 Demonstration of the presence of candidal cells
and/or hyphal forms in clinical samples from
normally sterile sites such as CSF, bronchial
aspirate, sample from bone marrow and other
tissues
 Sputum and urine specimens may be
contaminated with normal microbiota
 Tissue biopsy can be prepared and stained by
histopathological techniques

47. Laboratory diagnosis of Candida
Culture
Isolation of Candida
 Difficult to isolate if the infection is localized in
internal organ
 Sample: Blood, CSF, tissue biopsies
 Media: SDA with antibiotics
Identification
 Similar as with mucocutaneous candidiasis

48. Laboratory diagnosis of Candida
Immunodiagnosis
 For deep-seated infection, microscopy and culture
methods not sufficient as in case of mucocutaneous
infection
 Based on
 Detection of antibody production
 Detection of fungal antigens in body fluids and in serum
Antibody detection
 Agglutination technique representing anti-mannan
antibodies, can also be found in healthy individuals and
with superficial infections not useful for diagnosis of deep-
seated infection
 Antibody detection for the presence of antibodies to
candidal internal antigens released into patient’s body
during invasion
 Techniques: gel immunodiffusion, CCIE, ELISA, latex

49. Laboratory diagnosis of Candida
Immunodiagnosis
Antigen detection
 Important diagnostic tool, particularly in
immunocompromised patients
 Techniques: LA and ELISA
 Detection in serum, urine and other body fluids
 Antigens: mannan, an undefined glycoprotein, a
47 kDa protein, enolase

50. Treatment
 commonly treated with antimycotics; include
topical clotrimazole, topical nystatin, fluconazole, and
topical ketoconazole
Localized infection
 Oral candidiasis :topical treatments or oral medication
 Candida esophagitis :orally or intravenously; for severe or
azole-resistant esophageal candidiasis, treatment with
amphotericin B may be necessary.
 A one-time dose of fluconazole is 90% effective in treating a
vaginal yeast infection.
 For vaginal yeast infection in pregnancy,
topical imidazole or triazole antifungals.
Blood infection
 intravenous fluconazole or an echinocandin such
as caspofungin may be used.Amphotericin B is another