Rapid discrimination of Candida species based on optical diffraction pattern.

Candidiasis occurs mainly in immunocompromised patients. Rapid detection of Candida species can play a major role in the successful management of fungal infections and treatment monitoring. Detection and discrimination of five common strains of Candida species was performed using the optical elastic scattering diffraction pattern of their colonies. Using laser light with 632 nm wavelength and the designed optical system, optical diffraction patterns of C. albicans (ATCC12261), C. tropicalis (ATCC20336), C. glabrata (15545), C. guilliermondii (20216), and C. parapsilosis (22019) were recorded, processed and analyzed. The results of our study show that based on the different structure of Candida species and dissimilar structure of their colonies, the difference between acquired diffraction patterns are recognizable. In addition, through extraction of statistical feature of the diffraction pattern images and using classification techniques, the detection and discrimination could be performed in a semi-automatic way. The analysis of the colonies of five different Candida species by the optical diffraction patterns generated from the interaction of the laser with colonies' structures demonstrated that the technique had the potential to be applied for the detection and discrimination of various species.

Nanoparticles affect bacterial colonies' optical diffraction patterns.

It is increasingly being accepted that bacteria are able to alter their shape/colony pattern in response to adverse environmental conditions. Morphological adaptation of bacteria is known as one of their defence mechanisms against environmental stress/variations. As nanoparticles (NPs) have a unique capacity to induce a wide range of stresses to bacteria, we hypothesized that such NPs can affect the bacterial colony pattern. To test this hypothesis, we incubated a series of superparamagnetic iron oxide nanoparticles (SPIONs) with different physicochemical properties with bacterial colonies and probed the colonies' diffraction patterns by laser. The diffraction patterns of Escherichia coli, Lactobacillus rhamnosus, and Staphylococcus aureus colonies were recorded using a laser. Our results revealed the formation of distinct bacterial diffraction patterns in response to SPIONs with various concentrations and surface chemistries. Our results may pave the way toward the development of new optical approaches for the high-throughput screening of bacterial-NPs/drugs interactions.