In vitro effect of subinhibitory concentrations of ceftazidime and meropenem on the serum sensitivity of Pseudomonas aeruginosa strains

Drenjančević, Domagoj and Vraneš, Jasmina and Bedenić, Branka and Šakić-Zdravčević, Katarina (2007) In vitro effect of subinhibitory concentrations of ceftazidime and meropenem on the serum sensitivity of Pseudomonas aeruginosa strains. Collegium Antropologicum, 31 (1). pp. 221-225. ISSN 0350-6134

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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.

Abstract in Croatian

Svrha istraživanja bila je odrediti djelovanje subminimalnih inhibicijskih koncentracija (subMIK) ceftazidima, meropenema i gentamicina na in vitro osjetljivost na baktericidnu aktivnost seruma sojeva Pseudomonas aeruginosa izoliranih iz različitih materijala u dva odjela te u jedinici intenzivnog liječenja jedne hrvatske kliničke bolnice. Odabrano je 20 serum-rezistentnih sojeva P. aeruginosa izoliranih iz različitih kliničkih uzoraka. Bakterije su izlagane koncentraciji od 1/2, 1/4, 1/8, 1/16 i 1/32 MIK-a svakog od istraživanih antibiotika. Određena je osjetljivost sojeva P. aeruginosa na baktericidnu aktivnost ljudskog seruma prije i nakon izlaganje bakterija subMIK-ovima. Opažena je značajna razlika u serumskoj osjetljivosti sojeva nakon što su bakterije izložene subMIK-ovima ceftazidima i meropenema, dok izlaganje subMIK-ovima gentamicina nije značajno utjecalo na otpornost istraživanih sojeva na baktericidnu aktivnost seruma. Uspoređujući broj serum-rezistentnih sojeva prije i nakon izlaganja subinhibicijskim koncentracijama antibiotika, uočena je statistički značajna razlika (p<0,01) nakon izlaganja sojeva koncentracijama od 1/2, 1/4, 1/8 i 1/16MIK-a meropenema, te 1/2, 1/4 i 1/8 MIK-a ceftazidima. Subinhibicijske koncentracije ceftazidima i meropenema nisu samo utjecale na rezistenciju bakterija na baktericidnu aktivnost seruma, već i na njihovu morfologiju. Promjene bakterijske morfologije izazvane subMIK-ovima ceftazidima i meropenema mogle bi biti povezane s posljedičnom bakterijskom osjetljivošću na baktericidnu aktivnost seruma.

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