DOI: 10.14457/cu.the.2005.1734
title: Evaluation of in vitro bactericidal activity of aminoglycosides, fluoroquinolone and beta-lactam on gram negative pathogen

description: In present, we should have failure on treatment bacteria infection, however, there should have the appropriate treatment. The purposes of this study were to evaluate the bactericidal activity and to study kinetics of killing of aminoglycoside, fluorquinolone and beta-lactam antibiotics against common gram negative bacterial. The minor objectives were to determine the influence factors which altered bactericidal activity such as, inoculum effect. In this investigation, the six species of gram negative bacteria which were selected from the clinical isolates (E.coli, K.pneumoniae, P.mirabilis, Providencia spp., P.aeruginosa and A.buamannii) were randomized to the study. From the randomized, the microorganisms which E.coli, K.pneumoniae, P.mirabilis, Providencia spp., P.aeruginosa were senses to tested antimicrobial agents, but, Abuamannii was multi-resistance to most used antibiotics. There had used through the study. Bactericidal activity was tested bybroth macro dilution which to determine the MIC, MBC and the alter MIC when increse inoculum (inoculum effect). Time killing study in order to determine the bactericidal activity against selected bacteria which should be varied concentrations (sub-MIC, MIC, above MIC, trough, peak). From the study, it has been found that the antibiotics (gentamicin, amikacin, ofloxacin, ciprofloxacin, cefotaxime, amoxicillin/clavulanic acid, piperacillin/tazobactam, ampicillin/sulbactam, cefoperazone/sulbactam and imipenem) which used to against E.coli, should still bactericidal activity (MIC/MBC ranging in 1 to 4) and should have inoculum effect to beta-lactam antibiotics (cefotaxime, ampicillin/sulbactam, and cefoperazone/sulbactam). The 99.9% killing to E.coli without regrowth in the first 2 hr, should be found in aminoglycosides and fluoroquinolone which there could start to kill in the concentration at MIC. But beta-lactam should be found the 99.9% killing to E.coli without regrowth in the 6[superscript th] hr. which could start to kill in the concentration at 4MIC. For K.pneumoniae, the antibiotics (gentamicin, amikacin, ciprofloxacin, cefotaxime, piperacillin/tazobactam, and imipenem) which used to against K.pneumoniae, should still bactericidal activity (MIC/MBC ranging in 1 to 4) and should not have inoculum effect. The 99.9% killing to K.pneumoniae without regrowth in the first 2 hr, should be found in aminoglycosides and imipenem which there could start to kill in the concentration at 4MIC. But beta-lactam and ciprofloxacin should be found the 99.9% killing to K.pneumoniae without regrowth in the 6[superscript th]. which could start to kill in the concentration at 4MIC. In P.mirabilis, the antibiotics (amikacin, netilmicin, ciprofloxacin, cefotaxime, piperacillin/tazobactam, and imipenem) which used to against P.mirabilis should still bactericidal activity (MIC/MBC ranging in 1 to 4) and should have inoculum effect to cefotaxime and imipenem. And the 99.9% killing to P.mirabilis without regrowth in the first 2 hr. should be found in aminoglycosides which there could start to kill in the concentration at 4MIC. But beta-lactam and ciprofloxacin should be found the 99.9% killing to P.mirabilis without regrowth in the 6[superscript th] hr. which could start to kill in the concentration at 4MIC. For Providencia spp., all antibiotics (amikacin, netilmicin, ciprofloxacin, cefotaxime, and imipenem) which used to against Providencia spp. should still bactericidal activity (MIC/MBC ranging in 1 to 4) and should have inoculum effect to imipenem. And the 99.9% killing to Providencia spp. without regrowth in the first 2 hr, should be found in aminoglycosides ciprofloxacin and imipenem which there could start to kill in the concentration at 4MIC. But cefotaxime should be found the 99.9% killing to Providencia spp. without regrowth in the 6[superscript th] hr. which could start to kill in the concentration at 8MIC. For P.aeruginosa all antibiotics (amikacin, netilmicin, ciprofloxacin, ceftazidime, piperacillin/tazobactam and imipenem)which used to against P.aeruginosa should still bactericidal activity (MIC/MBC ranging in 1 to 4) except for imipenem and should have inoculum effect to piperacillin/tazobactam and imipenem. And the 99.9% killing to P.aeruginosa without regrowth in the first 2 hr, should be found in aminoglycosides ciprofloxacin which there could start to kill in the concentration at 8MIC. But beta-lactam should be found the 99.9% killing to P.aeruginosa without regrowth in the 6[superscript th] hr. which could start to kill in the concentration at 8MIC. For A.buamannii should have resist to the antibiotics (amikacin, netilmicin, ciprofloxacin, ceftazidime, ampicillin/sulbactam, cefoperazone/sulbactam and imipenem) which used to against A.buamannii, and no inoculum effect. The 8MIC, the peak, and the peak high dose were the concentration which could kill 99.9% of A.buamannii but there were high concentration to apply in clinical used.