Effects of Reduced Capsular Polysaccharide on Kanamycin Resistance in Escherichia coli B23 Cells

Capsular polysaccharides found in members of the Enterobacteriaceae family play an important role in mediating the interactions between bacteria and their environment. Studies have shown that Escherichia coli B23 pretreated with sub lethal doses of kanamycin show increased capsular polysaccharide production. In addition, it has been suggested that bacterial capsules prevent uptake of aminoglycosides to confer resistance and protect the cell. This study attempted to investigate the effects of reduced capsular polysaccharide on kanamycin resistance. Kanamycin pretreated E. coli B23 were grown in sodium salicylate to decrease capsule production, then treated with 20 μ g/ml kanamycin, a sub lethal concentration. It was observed that cultures grown in the presence of 60 µg/ml sodium salicylate, which had thinner capsules and lower detectable levels of capsular polysaccharide, were more susceptible to kanamycin relative to cells grown in Luria broth alone.