Effect of Growth in Sublethal Levels of Kanamycin and Streptomycin on Capsular Polysaccharide Production and Antibiotic Resistance in Escherichia coli B23.

Aerobic Gram negative bacilli in general demonstrate adaptive resistance to stresses from the environment such as the ability to transiently acquire resistance against antimicrobial killing by certain antibiotics. Previous studies have shown that Escherichia coli B23 pretreated with sublethal doses of kanamycin and streptomycin showed elevated levels of capsular polysaccharide. It has also been reported that bacterial capsules may impede uptake of aminoglycosides and thus protect the cell. This study attempted to investigate the potential development of protection from the antibiotics kanamycin and streptomycin due to the elevated capsular polysaccharide production. E. coli B23 was pretreated with 10 µg/ml of kanamycin or streptomycin. It was observed that both kanamycin and streptomycin pretreated cells developed increased antibiotic resistance relative to untreated cells, which correlated with a significant increase in the production of capsular polysaccharide.