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Abstract
Resistance to various antibiotics has been associated with increased capsular polysaccharide production through activation of RelA and SpoT, regulators of the stringent response, through their respective synthesis and hydrolysis of guanosine tetraphosphate in Escherichia coli. In order to further characterize the role of SpoT and RelA in capsular polysaccharide production and in conferring antibiotic resistance, growth patterns and induced capsular polysaccharide levels of various strains were determined following sublethal treatment with kanamycin and further treatment at inhibitory levels of kanamycin. Contrary to previous reports that capsular polysaccharide confers antibiotic resistance, it was found that spoT mutants produced the least capsular polysaccharide but had higher levels of resistance in comparison to relA mutants, which produced the most polysaccharide but exhibited lower resistance. As expected, both these mutants exhibited lower resistance to kanamycin as a result of pre-treatment than the wild-type strain. Thus, we propose that bacterial survival and resistance development upon antibiotic administration is dependent upon a myriad of factors that stem from the regulation of guanosine tetraphosphate which not only include capsular polysaccharide levels, but also other pathways leading to and resulting from the induction of the stringent response.