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.

Subinhibitory Concentrations of Antibiotics Alter the Response of Klebsiella pneumoniae to Components of Innate Host Defense

“…The gene encoding SpoT, an enzyme that contributes to regulation of stress responses (including the stringent response) in K. pneumoniae , was upregulated during culture in NHS, but it was not changed significantly by exposure to mupirocin under our assay conditions ( Fig. 3B ) ( 38 ). It is possible that the stringent response was induced by mupirocin in these ST258 isolates, but our ability to detect changes in gene expression was limited technically.…”

Arcobacter butzleri Biofilms: Insights into the Genes Beneath Their Formation

“…This gene, which encodes the bifunctional (p)ppGpp synthase/hydrolase, has been associated with obtaining maximum protection against stress (nutrient starvation, heat shocks, presence of NaCl and/or ethanol, etc.) and, therefore, facilitating bacterial pathogeny and dissemination [ 124 , 125 ]. Moreover, some authors have related it with the expression of various EPS operons (i.e., vps , pea , peb , bcs ) in diverse bacterial genera, such as Vibrio , Xanthomonas and Pseudomonas ; and, in consequence, with biofilm matrix production [ 26 , 61 , 122 , 123 ].…”

Relationship between biofilm formation and antibiotic resistance of Klebsiella pneumoniae and updates on antibiofilm therapeutic strategies

“…In addition, Li et al reported that low concentrations of antibiotics could induce the formation of persister cells, and K. pneumoniae produces high levels of tolerant persister cells to survive high concentrations of bactericidal antibiotics (Li et al, 2018). Amino acid starvation could increase the biofilm survival percent of K. pneumoniae strains treated with ceftazidime from 22-41% to 70 to 388% (Davis and Brown, 2020). Thus, the bacteria in the persistent state could tolerate the nutrient limitation and stress conditions in the biofilms and increase bacterial antibiotic resistance.…”