Reliability and validity of the track dilution method for Candida species quantification

• Grant number: 13/03863-0
• Support Opportunities: Regular Research Grants
• Start date: October 01, 2013
• End date: September 30, 2015
• Field of knowledge: Health Sciences - Dentistry
• Principal Investigator: Lívia Nordi Dovigo
• Grantee: Lívia Nordi Dovigo
• Host Institution: Faculdade de Odontologia (FOAr). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil
• Associated researchers: Denise Madalena Palomari Spolidorio

Abstract

The spread plating method (SPM) has been widely used to quantify the number of colony-forming units per milliliter (cfu/ml) of Candida species. However, problems of cost and time are factors that often limit the evaluation of large numbers of samples. To overcome such limitations, the track dilution method (TDM) was proposed for the measure of cfu/mL of bacterial species. Despite its widely use, there are no reports that have evaluate the reliability and validity of the TDM for plating and quantification of Candida species. The literature suggests that there are variations in counts of micro-organisms of the same sample when different plating methods are employed or when different researchers apply the same method. When neglected, such variations may adversely affect the conclusions of the study and make it difficult to compare results from different authors, especially those that evaluate the efficacy of antimicrobial therapies. This study will evaluate the validity and reliability of the TDM to quantify the number of cfu/mL of different Candida species. This is an experimental double-blind study. The dependent variables are the number of cfu/mL and duration of the plating procedure in minutes (plating and counting the colonies). The independent variables are the plating method (SPM or TDM), the concentration of the microorganism (102, 103, 104, 105, 106 and 107 cfu/ml) and Candida species (C. albicans, C. glabrata, C. tropicalis, and C. krusei). The intra and inter-examiner reproducibility and the agreement between the plating methods will be estimated using the intraclass correlation coefficient. Measures of time (minutes) will be analyzed using descriptive statistics and a two-way analysis of variance (significance level of 5%). (AU)