zoonoses and communicable diseases common to ... - PAHO/WHO

318 MYCOSESMost infections have an endogenous source. The infection can be spread throughcontact with oral secretions, skin, vagina, and feces of sick individuals or carriers. Amother with vaginal candidiasis can infect her child during childbirth. Balanitis mayin some cases be due to sexual relations with women suffering from vaginitis causedby C. albicans. In nurseries, particularly in units for premature infants, the infectionmay have an environmental source (see the section on occurrence in man). An exogenousinfection probably occurred due to indirect contact between patients in a hospitalbone marrow transplant unit and an intensive care unit (Vázquez et al., 1993).Role of Animals in the Epidemiology of the Disease: It is a disease common toman and animals. There are no known cases of transmission from animal to animal,but human-to-human transmission has occurred, as in the case of mothers who infecttheir children during childbirth.Diagnosis: Given the ubiquitous nature of the yeast, laboratory diagnosis must beconducted with great care. Direct examination of lesions in the nails, skin (in potassiumhydroxide) or the mucous membranes (in lactophenol-cotton blue), or microscopicobservation of gram-stained films, is diagnostically significant if the microorganismis found in great numbers. The examination should be carried out with freshspecimens. The presence in lesions of the budding yeast form together with formswith hyphae or pseudohyphae has diagnostic value. Isolation of the agent fromblood, pleural or peritoneal fluid, cerebrospinal fluid, or biopsy material obtainedaseptically from closed localized foci permits diagnosis of disseminated candidiasis.However, it should be kept in mind that fungemia may be transient and is not alwaysindicative of systemic infection. Hemocultures can detect candidemia in 35% to44% of patients with disseminated candidiasis. C. albicans grows well in a mediumof blood agar and Sabouraud agar at 25°C and 37°C. It can be identified by demonstratingthe presence of chlamydospores upon seeding in depth a plate of corn mealagar and observing it at 24 and 48 hours. Since another characteristic of this speciesis the production of germinating tubes, identification can be performed by adding asmall amount of culture to a small amount of serum and incubating the mixture at37°C for two to four hours (Carter and Chengappa, 1991). The other species ofCandida can be identified by their biochemical properties of carbohydrate fermentationand assimilation. A labeled anti-C. albicans globulin for immunofluorescencetesting of smears of pathologic or cultured materials is available.The most widely used serologic test to diagnose systemic candidiasis is immunodiffusionor double diffusion in ouchterlony agar gel, which cumulative experiencehas shown to be highly sensitive and specific. The immunoelectrophoresis test correlateswell with the immunodiffusion test and results are obtained in only two hours.Nonetheless, serologic diagnosis of systemic candidiasis presents serious difficultiesand an increase in patients’ titers should be confirmed. Immunosuppressed patientshave a poor humoral response, and thus an attempt has been made to use techniquesthat detect antigenemia rather than circulating antibodies. To date the results have notbeen very encouraging. Sensitivity is low (Lemieux et al., 1990; Bougnoux et al.,1990). Tube agglutination, indirect immunofluorescence, and indirect hemagglutinationare also useful tests if the antibody level detected is above that prevalent in thenormal population. The predominant or sole antibodies in healthy individuals areIgM. In contrast, with systemic candidiasis there is an initial rapid increase of IgMand then IgG, with subsequent reduction of IgM and persistence of IgG.