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Candida Morphology: Presence of Pseudohyphae Used in the Early Identification of Candida glabrata versus Other Candida Species

Abdulhafid, Gwen M (2011)
Master's Thesis (41 pages)
Committee Chair / Thesis Adviser: Sullivan, Kevin M
Committee Members: Lyon III, G Marshall
Research Fields: Biology, Microbiology; Health Sciences, Epidemiology
Partnering Agencies: Does not apply (no collaborating organization)
Keywords: Candida morphology
Program: Rollins School of Public Health, Career Masters of Public Health (Applied Epidemiology)
Permanent url: http://pid.emory.edu/ark:/25593/94853

Abstract

Fungal infections caused by Candida species are the fourth leading cause of nosocomial bloodstream infections in the United States (CDC, 2008). Although Candida albicans is the most commonly isolated species, there has been an increase in the number of non-albicans species isolated. Bloodstream infections caused by Candida glabrata are of particular concern because of high mortality rates and growing resistance to fluconazole, the most commonly prescribed medication for Candida infections. Inappropriate treatment, such as treating a resistant organism with fluconazole, or delay of appropriate treatment of Candida blood stream infections has been associated with increased costs and increased mortality (Ferguson, nd). Due to the increasing resistance to fluconazole shown by C. glabrata and the time required for species to be indentified in standard blood cultures, blood stream infections caused by this species of Candida are especially at risk for inappropriate or delayed treatment. A unique characteristic of C. glabrata is that it does not form pseudohyphae. The primary objective of this research was to analyze the data gathered at the initial identification of a blood culture positive for yeast and compare it to the final culture report to assess the predictive value of the presence or absence of pseudohyphae in identifying Candida species, in particular C. glabrata. Secondary objectives included identifying factors that may influence the primary objective. Data was collected for a year at Emory Healthcare facilities. 348 yeast cultures from 145 patients were assessed. Results: Initial analysis of the data indicated that pseudohyphae were not noted for any culture positive for C. glabrata, a 100% negative predictive value. The risk for C. glabrata in a yeast culture without pseudohyphae that grows in an anaerobic bottle, controlling for hours to positive and facility, was determined to be more than 3 times that of other Candida species (RR=3.00, CI 2.0, 4.6, p < .0001). Alternatively, the risk for C. Glabrata in a yeast culture without pseudohyphae that takes greater than 36 hours to become positive, controlling for aerobic status and facility, is many times that of other Candida species (RR =11.40, CI 1.6, 83.0, p = .016).

Table of Contents



Table of Contents
Introduction.......................................................................................................... 1
Problem Statement................................................................................................... 3
Objectives.............................................................................................................. 5
Figure 1: Candida glabrata………………...…………………………………………...................................….5
Figure 2: Candida with Pseudohyphae.………………………….…………....................…..........…………..5
Methodology.......................................................................................................... 6
Data Collection..........................................................................................................7
Data Analysis……………………...……………………………...............................................................8
Results………………………………………………………………………………………….....................................….9
Figure 3: Hours to Positive Graph…………………………………….………….......................…..........……11
Table 1: Species' Culture and Characteristic Frequencies………............……………………...........…11
Table 2: Facility Specific Species Frequencies……………………..................……………….........…….12
Discussion.............................................................................................................13
References…………………………………………………………………..………..................................…………..17
Appendix A: Microbiology Worksheet………………………………………...............................………....21
Appendix B: 2 x2 Table of Pseudohyphae presence………………………......................………….……22
Appendix C: SAS Output…………………………………………………………………….................................…23

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