Candida albicans is a major pathogenic yeast that commonly causes opportunistic infections in immunocompromised individuals and forms part of the normal flora in various mucosal surfaces. The organism can lead to various clinical manifestations, including oral, genital, and invasive candidiasis, with diagnosis typically achieved through microscopy and culture methods. Treatment options include antifungal medications like amphotericin B, azoles, and echinocandins, though resistance is an emerging concern.

1. Candida albicans
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2. INTRODUCTION
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• Candida genus comprises a group of yeast-like fungi that are
commonly found in various environments, including soil,
water, and the gastrointestinal and genitourinary tracts of
humans and animals.
• Candida albicans: It is the most pathogenic species of
Candida infecting humans.
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• Other Candida species which can also cause infection are C.
tropicalis (most common species), C. glabrata, C. krusei, C.
parapsilosis, C. dubliniensis, C. kefyr, C. guilliermondii, C.
viswanathii and C. auris.

3. Taxonomy:
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• Domain: Eukaryota
• Kingdom: Fungi
• Division: Ascomycota
• Class: Saccharomycetes
• Order: Saccharomycetales
• Family: Saccharomycetaceae
• Genus: Candida

4. MORPHOLOGY
• Candida albicans is a gram positive ovoid or spherical yeast
with a single bud.
• In direct stained smear (of the pathogenic sample), the yeasts
can often be attached to pseudohyphae.
• Candida albicans also produces true hyphae when it invades
tissues.
• Only C. albicans produces chlamydospores on cornmeal agar
culture at 25°C.

5. MORPHOLOGY
C. albicans produces creamy white,
smooth colonies with a yeasty odor
on Sabouraud’s dextrose agar

6. Candida albicans and Candidiasis
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• C. albicans is the most common Candida species, which
causes opportunistic infections in immunocompromised
hosts.
• It forms the part of the normal flora of the mucous
membrane of the gastrointestinal, genitourinary, and
respiratory tract.
• Candidiasis is worldwide in distribution, accounts for the
most common fungal infection in humans, both in HIV
and non-HIV infected people.

7. Pathogenesis
• Predisposing factors that are associated with increased risk of
infection with Candida include: ™
• Physiological state: Extremes of age (infancy, old age),
pregnancy ™
• Low immunity: Patients on steroid or immunosuppressive
drugs, post-transplantation, malignancy,
• HIV-infected people ™
Patients on broad spectrum
antibiotics—suppress the normal flora ™
• Others: Diabetes mellitus, febrile neutropenia and zinc or iron
deficiency

8. Pathogenesis
• Candida spp. are usually present as part of normal flora on
healthy mucosal surface of the oral cavity, gastrointestinal
tract, and vagina.
• Candida shows colonization at these sites in more than 80%
of healthy people.
• The organism, however, is rarely present on the surface of
normal human skin, except occasionally from certain
intertriginous area, such as the groin.
• Under certain conditions, Candida gains access to systemic
circulation from the oropharynx of the gastrointestinal tract.
Colonization of the mucocutaneous surface is the first stage in
the pathogenesis of Candidal infection

9. Pathogenesis
• The fungus causes invasion in human tissue through different
routes. Disruption of the skin or mucosa allows the organism
access to the blood stream. Massive colonization with large
numbers of Candida also permits the organism to pass
directly into the blood stream, causing the infection.
• In immunocompromised hosts, Candida may disseminate to
many organs, such as lung, spleen, liver, heart, and brain.
Candida may induce inflammation of the eye, causing
endophthalmitis and also may involve skin in 10–30% of
patients with disseminated infection.

10. Virulence factor
• C. albicans possesses several virulence factors that contribute
to its ability to colonize, invade host tissues, and cause
infections.
• C. albicans expresses adhesins on its cell surface that
facilitate adherence to host tissues. These adhesins interact
with specific host receptors, allowing the fungus to attach to
various surfaces and cells within the host.
• Candidalysin is capable of directly damaging the epithelial
membrane, by intercalation, permeabilization, and creating
pores, causing the cytoplasmic contents to weaken.

11. Virulence factor
• Biofilm formation by
Candida enhances
resistance to host
immune responses.
• Candida yeast
switches to its hyphae
form that create ridge
and causing the
membrane to stretch
by a process called
Thigmotrophism.

12. Clinical Manifestation
• Oral Candidiasis (Thrush): This is one of the most
common forms of candidiasis, especially in
immunocompromised individuals such as those with
HIV/AIDS, cancer patients undergoing chemotherapy, or
individuals on prolonged antibiotic therapy.
• Oral candidiasis presents as white, curd-like patches on the
tongue, palate, inner cheeks, or oropharynx. These patches can
be easily scraped off, leaving erythematous (red) and
sometimes bleeding mucosa underneath.

13. Clinical Manifestation
• Genital Candidiasis: Also known as vaginal yeast infection
or vulvovaginal candidiasis, this condition primarily affects
women and is characterized by itching, burning sensation,
redness, and swelling of the vulva and vaginal mucosa.
Vaginal discharge may be thick, white, and cottage cheese-
like. Men can also develop genital candidiasis, typically
presenting as balanitis (inflammation of the glans penis) with
redness, itching, and discomfort.

14. Clinical Manifestation
• Cutaneous Candidiasis:
• Candida albicans can infect the skin and adjacent mucous
membranes, particularly in warm and moist areas such as skin
folds (e.g., groin, armpits, under the breasts). Cutaneous
candidiasis presents as erythematous, macerated (softened due
to moisture), and pruritic (itchy) lesions with satellite pustules
or papules.

15. Clinical Manifestation
• Intertrigo: This is a specific type of cutaneous candidiasis
that occurs in skin folds, resulting in red, macerated areas with
a distinct border, often accompanied by itching and
discomfort.
• Nail Candidiasis: Candida albicans can infect the nails,
leading to onychomycosis (fungal nail infection). Infected
nails may become thickened, discolored (yellow or white),
brittle, and may separate from the nail bed. Paronychia and
onychomycosis are seen in occupations that lead to frequent
immersion of the hands in water.

16. Clinical Manifestation
Invasive Candidiasis:
In immunocompromised individuals or those with underlying medical
conditions (e.g., severe burns, indwelling catheters, prolonged ICU
stays), Candida albicans can disseminate from mucosal surfaces to invade
deeper tissues and organs, causing invasive candidiasis.
This can manifest as candidemia (fungemia), where the fungus spreads
through the bloodstream, leading to systemic symptoms such as fever,
chills, hypotension, and organ dysfunction.
Invasive candidiasis can also result in localized infections in various
organs, including the kidneys, liver, spleen, eyes, and central nervous
system, leading to specific clinical syndromes like candida meningitis or
endophthalmitis.

17. Clinical Manifestation
Systemic Candidiasis:
In severely immunocompromised individuals, such as those with
advanced HIV/AIDS or neutropenia, Candida albicans can cause
systemic infections with disseminated candidiasis, involving
multiple organs. This can lead to septic shock and is associated
with high mortality rates if not promptly treated.

18. Laboratory Diagnosis
Direct Microscopy:
Gram staining reveals gram-positive oval budding yeast cells (4–6
µm size) with pseudohyphae .
It has to be differentiated from true hyphae.

19. Laboratory Diagnosis
Culture:
Specimens can be inoculated onto SDA with antibiotic
supplements and then incubated at 37°C.
Candida can also grow in bacteriological culture media such as
blood agar. ™
Colonies appear in 1–2 days and described as creamy white,
smooth, and pasty with typical yeasty odor.
Gram staining of the colonies shows gram-positive budding yeast
cells with pseudohyphae except for C. glabrata which does not
show pseudohyphae.

20. Laboratory Diagnosis
Tests for Species Identification
Germ tube test:
A specific test for C. albicans, Reynolds Braude
phenomenon. Colonies are mixed with human
or sheep serum and incubated for 2 hours.
Wet mount preparation is examined under
microscope.
Germ tubes is long tube like projections
extending from the yeast cells.
It is differentiated from pseudohyphae as there
is no constriction at the origin.

21. Laboratory Diagnosis
Dalmau plate culture:
Culture on cornmeal agar can provide clue for species
identification.
C. albicans produces thick walled chlamydospores
CHROMagar: Different Candida species produce different
colored colonies on CHROMagar.
Growth at 45° C: It differentiates C. albicans (grows)from C.
dubliniensis (does not grow at 45°C)
Molecular methods such as PCR using species specific primers
are useful for species identification

22. Laboratory Diagnosis
Immunodiagnosis ™
Antibody detection: Various formats like ELISA, latex
agglutination tests are available detecting serum antibodies against
cell wall mannan antigen.
Antigen detection: Candida specific antigen such as cell wall
mannan and cytoplasmic antigens can be detected by ELISA

23. Treatment
Amphotericin B, 5-fluorocytosine, imidazoles (miconazole,
ketoconazole), triazoles (itraconazole, fluconazole, voriconazole)
and echinocandins (caspofungin, micafungin) may be used for
disseminated candidosis.
Some clinical isolates of C. albicans are resistant to fluconazole
and C. krusei to amphotericin.