Multicellularity and antibiotic resistance in Klebsiella pneumoniae grown under bloodstream-mimicking fluid dynamic conditions.
BACKGROUND
While the importance of fluid dynamical conditions is well recognized in the growth of biofilms, their role during bacteremia is unknown. We examined the impact of physiological fluid shear forces on the development of multicellular aggregates of Klebsiella pneumoniae.


METHODS
Wild-type and O-antigen or capsular mutants of K. pneumoniae were grown as broth culture in a Taylor-Couette flow cell configured to provide continuous shear forces comparable to those encountered in the human arterial circulation (ie, on the order of 1.0 Pa). The size distribution and antibiotic resistance of aggregates formed in this apparatus were determined, as was their ability to persist in the bloodstream of mice following intravenous injection.


RESULTS
Unlike growth in shaking flasks, bacteria grown in the test apparatus readily formed aggregates, a phenotype largely absent in capsular mutants and to a lesser degree in O-antigen mutants. Aggregates were found to persist in the bloodstream of mice. Importantly, organisms grown under physiological shear were found to have an antibiotic resistance phenotype intermediate between that of fully planktonic and biofilm states.


CONCLUSIONS
When grown under intravascular-magnitude fluid dynamic conditions, K. pneumoniae spontaneously develops into multicellular aggregates that are capable of persisting in the circulation and exhibit increased antibiotic resistance.
Michigan Critical Injury and Illness Research Center and Department of Emergency Medicine, University of Michigan, Ann Arbor, MI 48109, USA.
Margaret M
MM
Thornton
Hangyul M
HM
Chung-Esaki
Charlene B
CB
Irvin
David M
DM
Bortz
Michael J
MJ
Solomon
John G
JG
Younger
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016470:Bacteremia / Q000382:microbiology; D001431:Bacteriological Techniques; D018441:Biofilms / Q000254:growth & development*; D003470:Culture Media / Q000737:chemistry; D024881:Drug Resistance, Bacterial; D057446:Hydrodynamics; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology*; D008962:Models, Theoretical
D000900:Anti-Bacterial Agents; D003470:Culture Media