TDK conference 2014

Pseudomonas aeruginosa – an important pathogen of external otitis and pyoderma – often causes serious problems in veterinary practice mainly in the area of dermatology. The treatment of the diseases caused by this bacterium in veterinary practice poses an ever growing challenge for the vet as it is resistant to most antibiotics. Once the microbe – besides being often multiresistant – reaches a certain population density, it develops the ability to form biofilms, and this makes it more difficult to provide successful treatment for the diseases mentioned above.

The aim of our research was to look for active agents, which are able to prevent the formation of P. aeruginosa biofilms, or can cause damage to mature biofilms. For our examinations we used three active agents. These were N-acetyl-cysteine which is a mucolytic agent, L-tryptophan which is an essential amino acid, and baicalein which belongs to the group of flavonoids. During our examinations we also observed how these active agents affect the vitality of the pathogen in its planktonic forms.

As a result of our examinations we established how effective each active agent is in various concentrations in its ability to prevent the formation of the biofilms, or to what degree is it able to cause damage to already formed, mature biofilms. During our experiment we added N-acetyl-cysteine, L-tryptophan and baicalein in the concentrations of 0,016-8 mg/L, 0,2-100 mg/L 1,625-400 mg/L, respectively, to the forming or already formed biofilms after 4 and 24 hours of incubation, and then evaluated the results after another 24 hours incubation period. To examine the biofilms we used crystal-violet staining, and to examine the vitality of the planktonic forms we applied MTS formazan. Using a photometric method we recorded the absorbance at a wavelength of 590 nm in the first case, and 490 nm the second case. N-acetyl-cysteine proved to be the most effective in both experimental setup. It was able to prevent the formation of the biofilms or substantially damage them at a concentration of 8 mg/L. Baicalein and L-tryptophan were much less effective, however in large concentration L-tryptophan was able to prevent the formation of biofilms.

Based on our results we can conclude that certain active agents, without having anti-bacterial effects, may be able to reduce the formation of biofilms. Therefore these agents could aid the penetration of antibiotics into the biofilms, helping the effectiveness of these antibiotics inside the bacteria.