How to Cite
Abstract
Previous studies have demonstrated that exposure to sublethal levels of kanamycin antibiotic increased the capsular polysaccharide production by Escherichia coli B23 cells. The capsular polysaccharides were associated with resistance against antibiotics. This study attempted to investigate whether an interaction exists between the antibiotic and either isolated capsular polysaccharide or isolated soluble polysaccharide to assess a direct relationship between antibiotic insensitivity and capsular polysaccharides. Three types of polysaccharides including capsular polysaccharides obtained from Escherichia coli B23 grown with or without kanamycin pre-treatment and soluble capsular polysaccharide secreted by Escherichia coli K1-K12 hybrid EV36 were mixed with kanamycin and these samples were used for the MIC assay, kanamycin sensitivity test and the Kirby-Bauer (KB) assay. It was found that the addition of polysaccharides did not have a significant effect on either the growth of cells or the MIC of kanamycin while all three types of polysaccharides provided protection against low concentrations of kanamycin observed in the kanamycin sensitivity tests. In the KB assay, filter disks containing 20 µg/ml and 10 µg/ml of kanamycin near the filter disks of the capsular polysaccharide from cells with kanamycin pre-treatment showed smaller and inward distorted shaped inhibition zones, while the disks of the same kanamycin concentrations near the disks of the capsular polysaccharide from cells grown without kanamycin pretreatment had normal zones. The difference in the degree of protection observed against exposure to low concentrations of kanamycin between the two types of capsular polysaccharides could not be determined.