Original scientific paper
In vitro Effect of Subinhibitory Concentrations of Ceftazidime and Meropenem on the Serum Sensitivity of Pseudomonas aeruginosa Strains
Domagoj Drenjančević
Jasmina Vraneš
Branka Bedenić
Katarina Šakić-Zdravčević
Abstract
The aim of this study was to determine the effect of subminimal inhibitory concentrations (subMICs) of ceftazidime,
meropenem and gentamicin on the in vitro serum sensitivity of Pseudomonas aeruginosa strains isolated from a variety
of isolation sites at two medical wards and an intensive care unit in a government university hospital in Croatia. A total
of 20 serum-resistant P. aeruginosa strains isolated from different clinical specimens were selected. Bacteria were exposed
to 1/2, 1/4, 1/8, 1/16, and 1/32 x MIC of each antibiotic tested. Sensitivity of P. aeruginosa strains to bactericidal activity
of normal human serum before and after bacterial exposure to subMICs was determined. Significant difference in
serum sensitivity of the strains was observed after the bacteria were exposed to subMICs of ceftazidime and meropenem
(p<0.01), while the exposure to subMICs of gentamicin did not affect significantly the resistance of tested strains to the
serum bactericidal activity. Comparing the number of serum-resistant strains before and after exposure to subMICs of
antibiotics, statistically significant differences were determined (p<0.01) after exposure of the strains to 1/2, 1/4, 1/8 and
1/16 x MIC of meropenem, and after exposure to 1/2, 1/4 and 1/8 x MIC of ceftazidime. SubMICs of ceftazidime and
meropenem affected not only the resistance to serum bactericidal activity of bacteria, but also their morphology. The alterations
in bacterial morphology caused by subMICs of ceftazidime and meropenem could be connected with consecutive
bacterial serum sensitivity.
Keywords
Pseudomonas aeruginosa; antibiotics; subminimal inhibitory concentrations; serum bactericidal activity
Hrčak ID:
27289
URI
Publication date:
4.1.2007.
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