Application of immunomagnetic separation for accelerated detection of <i>F. tularensis</i> cells in soil samples using an immunochromatographic test

Abstract

Introduction. Epizootological monitoring of the area contamination with the causative agent of tularemia implies the collection and analysis of a variety of field specimens. The analysis of such objects is time- and labour-consuming. In this context, simple and fast diagnostic techniques are needed to analyze specimens under resource-limited conditions.
 Aim. To study the possibility of using immunomagnetic separation for accelerated detection of Francisella tularensis cells in soil samples using immunochromatography.
 Materials and methods. Immunomagnetic particles (IMPs) were produced by using monoclonal antibodies to lipopolysaccharide (LPS) of the tularemia causative agent. Soil specimens weighing 1 g with preliminary introduced inactivated F. tularensis 15/10 cells were used in the study. The samples were suspended in an extraction buffer (EB) and filtered. Tularemia cells were separated by IMP suspension. The particles were washed, resuspended in EB and heated at 100C for 5 minutes. The supernatant was analyzed with test strips based on F. tularensis IC-test kit.
 Results. A combination of the immunomagnetic separation method and the IC test to detect F. tularensis cells identified up to 1 106 cells of the tularemia pathogen in analyzed soil samples, while 1 107 cells were detected in soil washouts in the absence of immunomagnetic separation.
 Conclusion. The developed technique combining immunomagnetic separation and IC tests opens up prospects for express diagnostics of soil sample contamination in tularemia foci. The analysis takes about 3 hours, and its sensitivity is 1 106 cells/g of soil. The technique is simple, not requiring sophisticated expensive equipment. It can be easily adapted for testing other specimen types (water, grain, etc.). In addition, separated bacterial cells can be used for F. tularensis detection by other methods.