Osmotic Stress Induces Kanamycin Resistance in Escherichia coli B23 through Increased Capsule Formation

Abstract

In order to test whether capsule that is induced by non-antibiotic stress can render antibiotic resistance to microbes, this study explored the changes in capsule formation in response to sodium chloride osmotic pressure in Escherichia coli B23 and its protective effects against the bacteriostatic activity of kanamycin. Capsules were induced by incubating cells in four different NaCl concentrations, 0.085 M (control), 0.2 M, 0.4 M and 0.6 M. Capsules were then extracted and size was examined by determining glucose and fucose concentrations using anthrone assay and 6-deoxyhexose assay, respectively. Induced cultures were plated on Luria- Bertani plates supplemented with kanamycin at various concentrations and colony forming units were then counted. Increased NaCl concentration led to greater capsule sizes, and increased survival rate when the cells were exposed to the antibiotic. These results elucidated that capsules induced by NaCl osmotic pressure had a protective effect against kanamycin and allowed for better cell survival.