Candida (Pathmicro)

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Yeast Candida from pathmicro
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  (Sumber : http://pathmicro.med.sc.edu/mycology/mycology-3.htm)  Dr A. Di Salvo  Yeasts are single-celled budding organisms (figure 1). They do not produce mycelia. The colonies areusually visible on the plates in 24 to 48 hours. Their soft, moist colonies resemble bacterial culturesrather than molds. There are many species of yeasts that can be pathogenic for humans. We shalldiscuss only the two most significant species:1.   Candida albicans2.   Cryptococcus neoformansFigure 1. Figure 2. Figure 3. CANDIDIASIS (Candida albicans) There are many species of the genus Candida that cause disease. The infections caused by all speciesof Candida are called candidiasis. Candida albicans (figure 2 and 3) is an endogenous organism. It canbe found in 40 to 80% of normal human beings. It is present in the mouth (figure 4), gut, and vagina.It may be present as a commensal or a pathogenic organism. Infections with Candida usually occurwhen a patient has some alteration in cellular immunity, normal flora or normal physiology. Patientswith decreased cellular immunity have decreased resistance to fungal infections. Prolongedantibiotic or steroid therapy destroys the balance of normal flora in the intestine allowing theendogenous Candida to overcome the host. Invasive procedures, such as cardiac surgery andindwelling catheters, produce alterations in host physiology and some of these patients developCandida infections. Although it most frequently infects the skin and mucosae, Candida can causepneumonia, septicemia or endocarditis in the immuno-compromised patient. The establishment of infection with Candida species appears to be a property of the host - not the organism. The moredebilitated the host, the more invasive the disease. The clinical material to be sent to the labdepends on the presentation of the disease: blood cultures, vaginal discharge, urine, feces, nailclippings or material from cutaneous or mucocutaneous lesions. Candida is a polymorphic yeast, i.e.,yeast cells, hyphae and pseudohyphae are produced. It has been shown that Candida needs atranscription repressor to maintain the yeast form. This ability to assume various forms may berelated to the pathogenicity of this organism. The yeast form is 10 to 12 microns in diameter, grampositive, and it grows overnight on most bacterial and fungal media. It also produces germ tubes(figure 9 and 10), and pseudohyphae (figure 6 and 7) may be formed from budding yeast cells that  remain attached to each other. Spores may be formed on the pseudomycelium. These are calledchlamydospores and they can be used to identify different species of Candida. Some mycologiststhink that the pseudomycelial form represents a more invasive form of the organism. The speciesare identified by biochemical reactions. The organism occurs world-wide. The drugs of choice forsystemic infection are itraconazole and fluconazole. If an artificial heart valve or in-dwelling catheterbecomes infected, it must be replaced. Drug therapy alone will not suppress the organism if theforeign body remains in the host. This resistance is due to biofilms which we will discuss later.CANDIDA SPECIESCandida species (other than albicans) account for an increasing number of nosocomial infections.Speciation is important because there is significant antibiotic resistance among the different species.Figure 4. Figure 5.Figure 6. Figure 7.   Figure 9. Figure 10.Figure 8. Figure 11.Figure 1. Brewer's yeast (also known as Baker's yeast) with bud and bud scars (Saccharomycescerevisiae). © Dennis Kunkel Microscopy, Inc. Used with permissionFigure 2. Candida albicans - yeast and hyphae stages. A yeast-like fungus commonly occuring onhuman skin, in the upper respiratory, alimentary & female genital tracts. This fungus has a dimorphiclife cycle with yeast and hyphal stages. The yeast produces hyphae (strands) and pseudohyphae. Thepseudohyphae can give rise to yeast cells by apical or lateral budding. Causes candidiasis whichincludes thrush (an infection of the mouth and vagina) and vulvo-vaginitis. © Dennis KunkelMicroscopy, Inc. Used with permissionFigure 3. Oval budding yeast cells of Candida albicans. Fluorescent antibody stain. CDC/MaxineJalbert, Dr. Leo Kaufman. lek1@cdc.govFigure 4. Oral thrush. CDCFigure 5. Gross pathology of rabbit kidney lesions due to experimental Candida albicans infection.Rabbit was cortisone-treated. CDCFigure 6. Sputum smear from patient with pulmonary candidiasis. Gram stain. CDC  Figure 7. Histopathology of Candida albicans infection. Methenamine silver stain. Pseudohyphae andtrue hyphae. ASCPFigure 8. Histopathology of Candida esophagitis. Methenamine silver stain (digitally colorized). CDCFigure 9. Candida albicans showing germ tubes. Calcofluor white stain in peptone medium. Germtube production is a diagnostic feature of C. albicans. CDC/Mercy Hospital, Toledo, OH/Dr. BrianHarringtonFigure 10. Candida albicans showing germ tube production in serum. Gram stain. CDC/Dr. Lucille K.GeorgFigure 11. Gram-stain of vaginal smear showing Candida albicans epithelial cells and many gram-negative rods. (1,000X oil) © Danny L. Wiedbrauk, Warde Medical Laboratories, Ann Arbor,Michigan and The MicrobeLibrary
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