Impact of prolonged fructose and fructooligosaccharides stress on the adaptive growth, antimicrobial susceptibility, and genomic mutation of Klebsiella pneumoniae

Klebsiella pneumoniae ( K.pneumoniae ) can make use of various carbohydrates (glucose, fructose, sucrose et al ) as nutrient sources for sustaining its cononization and adaptive growth in human body. Fructose and fructooligosaccharides (FOS) are commonly used as dietary supplements and can be metabolized by gut probiotics, thereby promoting intestinal health and nutrient absorption, whereas the impact of prolonged exposure with fructose or FOS on the adaptive growth and antimicrobial susceptibility of K.pneumoniae remains unclear. Here, fructose- or FOS-induced K.pneumoniae strains were selected from the parental isolates K2044, EKP108 and EKP19. Our data indicated that two FOS-induced strains (K2044-0.5FOS-90G and EKP108-0.5FOS-90G) exhibited the best planktonic growth under different concentrations of fructose or FOS, suggesting the reshaping possibility of the growth adaption of K.pneumonia under fructose or FOS pressure. Interestingly, compared with the media with varying concentrations of fructose of FOS, the planktonic growth of fructose- or FOS-induced K.pneumoniae strains was significantly decreased with the culture media supplemented with low concentration of glucose (1%-2%), whereas high concentrations of glucose (8%,16%) could reactivate their adaptive growth. Moreover, K2044 knockout strain (K2044-Δ envZ mutant) showed the enhanced adaptive growth compared to K2044 WT under different concentrations of fructose, FOS or glucose, whereas a significantly prolonged lag phase was observed for K2044-Δ envZ with sucrose exposure, compared to the control. Notably, EKP108-0.5FOS-90G showed decreased resistance to levofloxacin (LEV), whereas the K2044-Δ envZ mutant displayed increased resistance to gentamicin (GEN) and tigecycline (TGC). Both EKP108-0.5FOS-90G and K2044-Δ envZ demonstrated increased outer membrane permeability and distinct alterations in membrane phospholipid composition. The genetic mutation between the parental strain EKP108 and its FOS-induced derivative (EKP108-0.5FOS-90G) were determined and we identified mutations in genes encoding members of the carbohydrate kinase family, which is primarily associated with carbohydrate metabolism and transport. Collectively, the growth adaptation, antimicrobial susceptibility changes, and membrane remodeling of K. pneumoniae following fructose or FOS exposure might be isolate-specific. Furthermore, isolates exposed to high carbohydrate concentrations do not necessarily exhibit enhanced growth adaptability. Moreover, knockout of the envZ gene may also promote the adaptive growth of K. pneumoniae , and involve membrane remodeling and impact the antimicrobial susceptibility.