Effects of imipenem and meropenem on serum sensitivity and surface hydrophobicity of Klebsiella pneumoniae.

Serum sensitivity and surface hydrophobicity of two Klebsiella pneumoniae strains (internal strain No. 378 and 3259) exposed to imipenem (CAS 64221-86-9) and meropenem (CAS 96036-03-2) at subinhibitory concentrations (sub-MICs; 1/4, 1/8 and 1/16 of the MICs) were evaluated. Carbapenems at all sub-MICs tested (with the exception of 1/16 of the MICs in strain 378) decreased susceptibility of bacteria to serum bactericidal activity. All sub-MICs of the antibiotics tested also reduced the bacterial surface hydrophobicity. The surface hydrophobicity of strain 3259 was most effectively decreased after the exposure to imipenem and meropenem at 1/4 of the MICs (to 3% or 5.2% of the control values). The highest decrease of hydrophobicity in strain 378 was found after exposure to imipenem and meropenem at 1/16 of the MICs (19.2% or 32.3%).