In-situ measurements of bacteria resistance to antimicrobial agents employing retractometric method based on sub-wavelength diffraction grating

Abstract

Testing of drug efefctiveness is one of the most important subjects in pharmacy. The purpose of this study was to investigate the possibility to observe Gram-positive bacteria Staphyloccocus aureus wall changes using different amounts of antimicrobial agent benzylpenicillin (500,000 v.v/ml) in real time. Optical method based on total internal reflection in a sub-wavelength diffraction grating was employed. The proposed optical method is sensitive for the eefective refractive index changes in vicinity of a diffraction grating. The results obtained employing optical method were verified compraring results obtained employing standard microbiology tests and bacteria visualization employing Scanning electron microscopy (SEM). Bacterial solution (8.8 billion/ml S. aureus in 0.9% saline solution) was placed in the temperature controlled measurement cell. Different amounts of benzylpenicillin where injected in the measurement cell and changes of the optical signature where monitored in-vitro for the same durations of time. Samples for microbiology tests and SEM analysis were taken from liquid cell after injection of antimicrobial agent. [...].