Species identification and strain typing of candida isolates by PCR-RFLP and RAPD-PCR analysis for determining the probable sources of nosocomial infections

ABSTRACT

Since the incidence of nosocomial Candida infections have been increasing in parallel with the raising in the number of patients involving in predisposing factors, determining the sources and the ways of acquisition of infection is necessary as an efficient strategy for controlling the diseases. The aim of this study is identification and strain typing of Candida strains isolated from hospitals to facilitate tracing the sources of infections in hospitalized patients in addition to assess the discriminatory power of some random primers by using RAPD analysis. Samples were collected from patients who were hospitalized in oncology, intensive care unit [ICU], and organ transplants wards of the Shohadaye-Tajrish Hospital affiliated to Tehran University of Medical Sciences, Tehran, Iran, and their environments. The yeasts were isolated on CHRO Magar Candida. Species identification was performed by PCR-amplification of ITS1-5.8SrDNA-ITS2 region followed by restriction digestion with the enzyme MspI. To determine the probable origin of Candidia infections, in case of each patient whose the clinical and relevant environmental isolates were identified as the same species, a set of eight primers namely number 1 to 8, were applied in RAPD-PCR to find out the possible homogeny or variation within the isolated strains. One hundred and four Candida strains were identified. The most common species was C. albicans [57.5%] followed by C. tropicalis [13.5%], C. glabrata [12.5%], C. parapsilosis [8.65%], C. famata [3.8%], C. krusei [1.9%], C. guilliermondii [0.96%]. and C. lusitaniae [0.96%]. While the source of infection for three patients were not determined by RAPD analysis, interpretable results from RAPD-typing of Candida species isolated from 8/18 of cases implied that the infections might originate from the exogenous sources. Moreover, according to the function of each primer, primer No. 1 was determined as a best primer for typing of Candida albicans strains. The species of yeast isolates were determined by PCR-RFLP. It was found that RAPD assay can point out the genomic variability within the Candida species. Besides, the method could show a probable relationship between acquired infections and their sources