Serum sensitivity and cell surface hydrophobicity ofKlebsiella pneumoniae treated with gentamicin, tobramycin and amikacin

A suppression of bacterial growth of Klebsiella pneumoniae after 30 min treatment with gentamicin, tobramycin and amikacin at suprainhibitory concentrations was found (postantibiotic effect, PAE). The antibiotics at a concentration of 2 x MIC induced PAEs in the range of 0.5-1.7 h, PAEs manifested by aminoglycosides at a concentration of 4 x MIC varied between 0.8-3.3 h. Susceptibility of exposed bacteria to serum bactericidal activity was efficiently enhanced compared with controls (without antibiotics). A survival of treated bacteria was between 12.7-36.6% (2 x MIC) or 5.0-8.3% (4 x MIC). The percentage of viable nontreated bacteria moved between 70.2-83.0% at these conditions. Surface hydrophobicity of bacteria exposed to aminoglycosides was only slightly increased. The results indicate that exposure of K. pneumoniae to a suprainhibitory concentrations of aminoglycosides in vitro enhanced the susceptibility of this strain to human serum bactericidal activity. Whether this phenomenon occurs in vivo, remains to be determined.