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Home » Archive » 2013

TDK conference 2013

The effects of biofilm production on the susceptibility of Pseudomonas aeruginosa
Albrecht Vivien - year 5
SzIU, Faculty of Veterinary Science, Department of Pharmacology and Toxicology
Supervisor: Jerzsele Ákos DVM

Abstract:

Diseases caused by Pseudomonas aeruginosa, like external otitis and pyoderma are serious challenges in the veterinary medicine. Treatments are even more difficult nowadays, as P. aeruginosa strains are frequently multiresistant. On the other hand the bacteria are able to form biofilms, which decrease the antimicrobial susceptibility of these strains. The aim of this study was to evaluate the in vitro activity of marbofloxacin, gentamicin, colistin and their combinations. We compared the sensitivity of planktonic cells with bacteria in biofilms. The susceptibility of the planktonic cells was determined to marbofloxacin, marbofloxacin-gentamicin and marbofloxacin-colistin combination with the microdilution method by determining MIC values according to CLSI (Clinical Laboratory Standards Institute) guidelines. In the second part of the study the bacterial strains were incubated without antimicrobials in microplate wells for 12 hours to form biofilms. To determine the sensitivity of biofilm-grown cells a photometric method utilizing MTS-formazan formation was performed. Among the examined planktonic P. aeruginosa strains, 91.7% was sensitive to marbofloxacin and all of the strains were susceptible to the 1:1 combination of the antimicrobials. In case of marbofloxacin, MICs ranged from 0.25 to 4 µg/ml, in case of the marbofloxacin: gentamicin and marbofloxacin:colistin combinations these were between 0.0625 and 1 µg/ml. The MIC50 and MIC90 values of marbofloxacin were 1 µg/ml and 2 µg/ml, respectively. These values for the marbofloxacin:gentamicin combination were 0.5 µg/ml and 1 µg/ml, respectively, while the marbofloxacin:colistin combination these proved to be 0.0625 µg/ml and 0,5 µg/ml, respectively. To examine the susceptibility of biofilm-grown strains EC50 (effective concentraion 50%) was used. Concerning marbofloxacin these values ranged from 64 to 4096 µg/ml. In case of marbofoxacin-gentamicin combination the EC50 was found between 8-2048 µg/ml, while the 1:1 combination of marbofloxacin-colistin showed EC50 values between 8-128 µg/ml. Based on our results, the susceptibility of the examined strains was significantly decreased by biofilms compared to planktonic cells, and the antimicrobial combinations increased the sensitivity of these strains.



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