Influence of the Sample Preparation Method in Discriminating Candida spp. Using ATR-FTIR Spectroscopy.

Savithri Pebotuwa,Anton Peleg,Bayden R Wood,Philip Heraud,Kamila Kochan

doi:10.3390/molecules25071551

Abstract

Several studies have investigated the capacity of ATR-FTIR spectroscopy for fungal species discrimination. However, preparation methods vary among studies. This study aims to ascertain the effect of sample preparation on the discriminatory capacity of ATR-FTIR spectroscopy. Candida species were streaked to obtain colonies and spectra were collected from each preparation type, which included: (a) untreated colonies being directly transferred to the ATR crystal, (b) following washing and (c) following 24-h fixation in formalin. Spectra were pre-processed and principal component analysis (PCA) and K-means cluster analysis (KMC) were performed. Results showed that there was a clear discrimination between preparation types. Groups of spectra from untreated and washed isolates clustered separately due to intense protein, DNA and polysaccharide bands, whilst fixed spectra clustered separately due to intense polysaccharide bands. This signified that sample preparation had influenced the chemical composition of samples. Nevertheless, across preparation types, significant species discrimination was observed, and the polysaccharide (1200–900 cm−1) region was a common critical marker for species discrimination. However, different discriminatory marker bands were observed across preparation methods. Thus, sample preparation appears to influence the chemical composition of Candida samples; however, does not seem to significantly impact the species discrimination potential for ATR-FTIR spectroscopy.

Highlights

There has been a significant increase in incidence and prevalence of fungal infections in humans since the 1980s [1]
Recently there has been a mycological shift to non-albicans Candida species (NAC) such as Candida glabrata, Candida parapsilosis and Candida krusei [4,5,6,7]
This study aims to investigate the influence of different preparation methods on the capacity of attenuated total reflectance (ATR)-Fourier transform infrared spectroscopy (FTIR) spectroscopy for discriminating Candida species and whether discriminatory markers vary for each preparation method

Summary

Introduction

There has been a significant increase in incidence and prevalence of fungal infections in humans since the 1980s [1]. Of the fungi infecting humans, those of the genus Candida are most common and present clinically as superficial or systemic infections [2]. Candida species are commonly found as commensals in the gastrointestinal tract, oral cavity, esophageal tract, skin and genitourinary tract [1]. The rise in incidence of Candidiasis can be attributed to the increased number of immunocompromised patients, invasive procedures and inappropriate use of antibiotics [3]. Candida albicans is the most commonly isolated species from all forms of Candidiasis. Recently there has been a mycological shift to non-albicans Candida species (NAC) such as Candida glabrata, Candida parapsilosis and Candida krusei [4,5,6,7]

Objectives

Methods

Results

Discussion

Conclusion