Influence onEnterobacter cloacae metabolism, cell-surface hydrophobicity and motility of suprainhibitory concentrations of carbapenems

The impact of postantibiotic effect (PAE) of carbapenems (imipenem, meropenem) on the metabolism (biosynthesis of macromolecules, respiration), cell-surface hydrophobicity and motility of a clinical isolate ofEnterobacter cloacae was examined. The metabolism was evaluated after 16 h and after 1 d of cultivation using 2× and 4× minimum inhibitory concentrations (MIC) of both antibiotics for the induction of PAE. Imipenem at 4×MIC did not induce PAE. After a 16-h cultivation (in the postantibiotic phase of both carbapenems), inhibition of nucleosynthesis and protein synthesis was found; after a 1-d cultivation, during regrowth stimulation of mainly¹⁴C-leucine incorporation was found. The presence of the exogeneous intermediates of citrate cycle,viz. 2-oxoglutarate, increased the respiratory activity of the cells. The cell-surface hydrophobicity (evaluated by three methods—bacterial adhesion to hydrocarbon, nitrocellulose-filter test and salt-aggregation test) decreased after PAE of both carbapenems; meropenem was more effective. Motility (an important virulence factor) was inhibited in the postantibiotic phase of both carbapenems; the 4×MIC caused a higher inhibition.