TDK conference 2024

Nowadays, dog owners are increasingly visiting veterinary practices with suspected ear infections. Inflammation of the external ear canal is a common disease caused by a number of factors including bacteria, with the second most common being potentially multiresistant Pseudomonas aeruginosa. This Gram-negative pigment-producing opportunistic pathogen is one of the most common bacterium associated with nosocomial infections. The management of this disease can be challenging, as the bacterium can have multiple resistance mechanisms and has a significant biofilm-forming capacity. Therefore, the exploration of the genetic basis of resistance mechanisms may be important not only for the use of antibiotics in veterinary medicine, but also for the spread of antimicrobial resistance, which may have serious public health consequences.

Our research is based on an experiment of the Department of Phramacology and Toxicology with a biofilm-producing reference strain of P. aeruginosa ATCC® 27853™. In the experiment, the antibacterial and anti-biofilm effects of marbofloxacin, geraniol, and Tris-EDTA, and combinations of two or three of these were investigated. The minimum inhibitory concentration (MIC) was tested by a series of passages on the strain for 10 days. These were sampled on days 2, 6 and 10 for nucleic acid extraction and then for next-generation sequencing. Synergism was found when the active substances were used in combination, and the combination partners delayed the increase in the MIC value of marbofloxacin. Based on this, our aim was to genotype bacterial isolates passaged with the active substances and explore whether a change at the genomic level could explain this.

Although the sequencing data alone did not provide a clear explanation for the development of resistance to marbofloxacin, it highlighted the need to include transcriptomic analyses in the future, which may provide deeper insights into the phenotypic expression of the resistance mechanisms under investigation.