SpoT-mediated stringent response influences environmental and nutritional stress tolerance, biofilm formation and antimicrobial resistance in Klebsiella pneumoniae.

Abstract

Klebsiella pneumoniae is an important opportunistic pathogen with significant potential for virulence and multidrug resistance. Treatment failure often occurs because the pathogen may couple virulence and drug resistance with the stringent response. This study assessed the role of the spoT gene in environmental and nutritional stress tolerance, exopolysaccharide capsule production and biofilm formation. spoT mutants were constructed using the lambda red recombinase technique, and mutant and wild-type (WT) strains were exposed to limiting concentrations of carbon (glucose), phosphate and aminoacid, and environmental stresses of ethanol, salt and heat. Cell viability, capsule production and cell length were assessed as well as the ability to grow biofilm under antibiotic pressure using gentamicin and ceftazidime. spoT mutants were more susceptible to stresses versus WT; the reverse was true for survival during biofilm susceptibility assay (p<0.05), especially when carbon and phosphate were present. spoT mutants were elongated and lacked a capsule versus WT and non-starved strains. The inability to produce capsule in mutants before and after starvation was likely a general effect of spoT mutation. These data suggest that the spoT-mediated stringent response is important for K.pneumoniae in conditions of nutrient limitation, environmental stress and antimicrobial pressure.