Morphometric evaluation of the selimaccide influence on the ultrastructural organization of Escherichia coli and Salmonella enteritidis cells

The purpose of the study is to determine the features of the effect of selimaccid on the ultrastructure of bacterial cells using the analysis of morphometric parameters and to identify relevant quantitative characteristics of the effect of this antimicrobial drug. Tasks: to calculate the morphometric characteristics of both native bacteria and those exposed to selimaccid; to carry out statistical processing of the received data; to draw conclusions about the significance of various variables for assessing the effect of selimaccid on bacterial ultrastructures and about the fact of the presence of such an effect. The object of the study is isolates of enteropathogenic bacteria Salmonella enteritidis and Escherichia coli. To assess the bactericidal efficacy of selimaccid, this drug was used at a concentration of 20 mg/ml. Electron microscopic studies using the method of ultrathin sections were performed on a JEM 100 CX-II transmission electron microscope. Morphometric parameters (area of bacterial cells and their cytoplasm) on electron diffraction patterns were calculated using the FIJI - ImageJ program. Statistical hypotheses were tested using the non-parametric Mann-Whitney test adjusted for multiple comparisons using the Benjamini - Hochberg method; the critical significance level for interpreting the test results was α = 0.05. The bacterial cells of both isolates did not change their size after exposure to selimaccid, the differences between the control and experimental groups were not statistically significant (p = 0.15 for S. enteritidis and p = 0.71 for E. coli). The effect of selimaccid at the submicroscopic level was manifested by an increase in the periplasmic space and thickening of the cytoplasm around the clarified nucleoid, which was accompanied by a decrease in the ratio of the area of the cytoplasm and the whole cell: in S. enteritidis, by 7.5 %, in E. coli, by 6.8 %. The periplasmic space increased: in S. Enteritidis by 67.9 %, in E. coli by 166.7 %. The results indicate the effect of selimaccid on the packaging or even fragmentation of the genetic material, protein synthesis complex, and ion transport system in S. enteritidis and E. coli bacterial cells.