self-learning slides

Candida albicans: Vaginitis

A 54-year old woman presented to OBG OPD with complaint of thick whitish vaginal discharge along with pruritis. On examination the vaginal walls as well as vulva were found erythematous and with white patches.

What is your diagnosis?
It is a case of vulvo-vaginitis. The common etiological agents of vaginitis are Candida albicans and Trichomonas vaginalis. The differential diagnosis include bacterial vaginosis and trichomoniasis.

What is the specimen collected?
Vaginal discharge is collected using a sterile cotton swab.

Which the necessary investigations to be performed?
A vaginal pH greater than 5.0 suggests the possibility of bacterial vaginosis, trichomoniasis, or a mixed infection whereas in Candida vulvo-vaginitis the pH remains normal (4-4.5).The vaginal discharge is subjected to both unstained and stained preparation. Unstained preparation include a saline wet mount to rule out Trichomonas or a KOH wet mount. Absence of pus cells or their presence in small numbers is notable in Candida infections. Stained preparations include Gram stain and Papanicolaou stain to rule out Trichomonas. Confirmation of the fungal etiological agent is achieved by culture on Sabouraud's dextrose agar.

What is your observation?
Saline wet mount as well as Papanicolaou smears did not reveal any Trichomonas. Plenty of yeast like budding cells, with pseudohyphae were observed in both saline and KOH wet mounts. Wet mount did not reveal significant number of pus cells. Gram positive yeast like budding cells with pseudohyphae were also observed in Gram stained smear.

Describe the culture findings.
White- cream colored, smooth, butyrous, bacteria-like colonies are observed on Sabouraud's Dextrose Agar following overnight incubation at 37oC. Gram stained smear of the colonies confirm Gram positive yeast-like cells.

How do you identify the isolate?
The organism isolated is Candida species. In order to identify the species additional tests such as Germ tube test, Chlamydospore formation on cornmeal agar, sugar fermentation and sugar assimilation tests are performed. The Germ tube test is positive (Raymond-Braude), chalmydopores are formed on the cornmeal agar (Dalmau Plate Culture). On CHROMagar Candida (BBL) C. albicans forms green colonies and are easily identifiable. A 90-min test for N-acetyl-,B-galactosaminase coupled with a test for prolyl aminopeptidase has been shown to be as accurate as the germ tube test. Commercial identification system such as API 20C Yeast Identification System is also helpful.

What is germ tube and pseudophyphae?
A filamentous, tube-like structure arising from the yeast cell is called a germ tube. Some authors consider it as a true hyphae while others believe that it represents the origin of pseudohypahe. When a small inoculum (≤105/ml) of Candida is made in 0.5ml rabbit, fetal calf or human serum and incubated at 37oC for 2-3 hours, Candida albicans produce germ tube. Germ tube-negative strains of C. albicans represent 1 to 2% of the species, and other mycelium like forms, such as pseudohyphae, may be misinterpreted as germ tubes in non-C. albicans species. Candida albicans, in addition to its usual oval budding form, is also able to produces pseudohyphae. The buds elongate forming a tube-like structure and the elongated buds remain attached to one another and eventually produce a filament called a pseudohyphae. It is called so because it resembles the hyphae. The pseudohyphae help the yeast to invade deeper tissues after it colonizes the epithelium. The point of origin helps in distinguishing germ tube from pseudohyphae; while pseudohyphae originates with a constriction, there is none in case of germ tube.

What is the significance of this isolate?
Typically, Candida albicans is present in vagina flora of 20% of asymptomatic healthy young women as commensal. They gain access to vagina from the adjacent perianal area. Candida can cause a variety of opportunistic infections in people who are debilitated, immunosuppressed, or have received prolonged antibacterial therapy.  The hormonal changes in menopause result in decreased glycogen in vagina and the loss of acidic pH favours growth of Candida. Since C. albicans is normally present in the vagina, it must be clinically correlated.

Which are the various predisposing factors for candida vulvo-vaginitis?
The predisposing conditions include menopause, pregnancy, use of high-oestrogen oral contraceptives, Diabetes Mellitus, taking of wide spectrum antibiotics and corticosteroid, use of IUCD, tight-fitting synthetic underwear, premenstrual phase of the menstrual cycle, depressed cell mediated immunity (e.g. AIDS) and obesity.

How do you treat this condition?
Topical treatment include polyene antifungals (Nystatin), Imidazole antifungals (Clotrimazole) or oral medications such as Itraconazole, Fluconazole, Ketoconazole can be given in resistant or frequent relapse cases.

Which are the other infections/diseases caused by this fungus?
Candida can cause mucocutaneous infections (oral thrush, glossitis, cheilits, oesophagitis, pruritis ani, balanitis, chronic mucocutaneous candidiasis, gastrointestinal candidiasis), cutaneous infections (onychomycosis, paronychia,  candidal granuloma, diaper rash, intertrigo) and systemic infections (endocarditis, urinary tract infection, meningitis, endophthalmitis, osteomyelitis, peritonitis/intra-abdominal abscess, arthritis, septicemia).

Which are the other species of Candida?
The various species of Candida include C. tropicalis, C. krusei, C. parapsilosis, C. stellatoidea, C. pseudotropicalis, C. guilliermondii, C. dubliniensis, and C. glabrata.

Which are the other yeast-like fungi?
Trichosporon, Torulopsis, Geotrichum, Rhodotorula etc are the other yeast like fungi while Cryptococcus is a true yeast.