INSTITUTE OF HEALTH TECHNOLOGY, DHAKADepartment of Laboratory Medicine

BSc in Health Technology (Laboratory)- 1st Year

MYCOLOGY Lecture No. 7.1 (Opportunistic Mycoses -Candidiasis)

By

Sk. MIZANUR RAHMANLecturer, Mycology

MS in Biotechnology & Genetic Engineering (UODA)MS in Microbiology (SU)

Candidiasis - an infection caused by a Candida spp.

Candida is a yeast and is is part of the normal flora (commensal) of the skin, mouth, vagina and GI tract.

Antibiotic treatment can alter the normal bacterial flora allowing Candida to flourish.

Thrush - a superficial Candida infection of the mouth or vagina.

Opportunistic Mycoses-Candidiasis

Candida is the most common cause of opportunistic mycoses worldwide.

Candida albicans is the most pathogenic and most commonly encountered species

Systemic candidiasis is common in the immunocompromised (AIDS, chemotherapy, post-surgery)

Disseminated infections arise from hematogenous spread from the primarily infected locus

Candidiasis

Species include:o Candida albicans (the most important)o Candida tropicaliso Candida kruseio Candida parapsilosiso Candida glabratao Candida dubliniensis

Candidiasis

Oral candidiasis (Oral thrush) • Classic thrush is characterised by a white, curd-like coating on the

tongue or elsewhere in the oral cavity. Stomatitis due to Candida is often associated with painful infection of the lips - and corners of the mouth.

Genital or perigenital candidiasis ((vulvo vaginitis) • (vulvo)vaginitis due to Candida .• Contamination of the vagina with Candida stems from the

endogenous endosaprophytic flora of the gastro-intestinal tract.Diagnoses

– in culture, it grows as blastospores, pseudohyphae, and septate hyphae

– Candidiasis the collective term for infection involving Candida• cutaneous• vaginal• systemic

Candidiasis

In normal host, candida albicans may cause:1) Oral thrush or moniliasis (patches of creamy white

exudate that cover the mucous membrane of the mouth).2) Vulvovaginal moniliasis: itching and cheese appearing

vaginal discharge. It occurs in females with:o Prolonged use of broad spectrum antibiotics

(superinfection)o Contraceptive pillso Pregnancy

3) Rash in the skin folds4) Diaper rash.5) Paronychia of the nails (thickening and loss of the nails).

Oral Thrush- the white material consists of budding yeast cells and pseudohyphae.

Mucocutaneous Candidiasis- granulomatous lesions involving the hands.

Candidiasis

Gram positive, oval budding yeast cells. If buds fail to detach, they form pseudohyphae. Pseudohyphae are differentiated from true hyphae

by the presence of constrictions at septations between the cells.

But, Candida glabrata does not form pseudohyphae.

Candidiasis-Characteristics

Candida

Oral thrush

Vulvovaginal moniliasis

Rash in the skin folds

Diaper rash

Paronychia

In immunocompromised individuals such as:

1) Esophageal thrush.2) Chronic mucocutaneous candidiasis.3) Systemic or disseminated candidiasis (even to the eye).

AIDS Diabetes mellitus Malignancy

Defect in cell mediated immunity

Corticosteroids

Catheters

Candidiasis

Specimen: according to the site of the lesion. Direct examination of Gram stained smear: Gram

positive oval budding yeast cells + pseudohyphae.

Candidiasis-Laboratory Diagnosis

Culture: on SDA at 37 degree. Identification of candida on the plate is done by:1. Morphology: soft cream colored colonies with yeasty

odor.

2. Gram film: Gram positive oval budding yeast cells.

Candidiasis-Laboratory Diagnosis

3. Biochemical reactions: to differentiate between Candida albicans and other species.

o Germ tube test: Candida albicans forms germ tube when incubated in serum for 1 – 2 hour at 37 degree.

o Chlamydospore formation: Candida albicans forms chlamydospores on corn meal agar incubated at 30 degree.

o Sugar fermentation: Candida albicans ferment glucose and maltose with acid and gas production.

o Inoculation of the yeast on chromogenic agar: each candida species produces a different color on this medium.

Candidiasis-Laboratory Diagnosis

Germ tube

Chlamydospores CHROMagar