Electro-Optical Analysis of Cell Viability of Tularemia Microbe Vaccine Strain

Abstract

Objective: to study the possibility of applying electro-optical analysis for the assessment of cell viability of tularemia microbe vaccine strain at different stages of experimental live tularemia vaccine production.Materials and methods. The research object was a cell culture of Francisella tularensis 15 NIIEG. Investigations were carried out at all stages of experimental live tularemia vaccine (ELTV) manufacturing according to an advanced technology: cultivation, concentrating, diafiltration, mixing with drying media, stabilization, and storage (two-year period of observation). Electro-optical analysis by the parameter “polarizability anisotropy” of bacterial cell was conducted with the help of EloTrace (EloSystems, Germany). Total concentration of cells was evaluated using density metering at 590 nm and spectrometry – at 650 nm. Viability was assessed through inoculation of plates with FT-agar.Results and discussion. The experiment has demonstrated that the change in polarizability anisotropy of the cell at the frequencies of 900 kHz and 2100 kHz, reflecting the state of cytoplasm and cytoplasmic membrane, respectively, is the earliest response to changes in vital indicators of bacterial culture in the process of cultivation. Thereby, the decrease in viability of F. tularensis cells occurrs well before the decrease in cell concentration. We have shown the preservation of viability of F. tularensis 15 NIIEG cells at all stages of experimental live tularemia vaccine production. Electro-optical analysis allows for registering the changes in vital parameters of microorganism cells in real-time mode, while the assessment of viability applying bacteriological method takes up to 5 days. Different stages of tularemia vaccine manufacturing have impact on the vital indicators of F. tularensis cells, and electro-optical analysis is a prospect method of control of such parameter as “Specific activity (the number of live microbial cells)”.