TDK conference 2019

The antimicrobial resistance (AMR) of pathogenic bacteria is an issue of public- and animal health with an increasing significance. The occurrence of antimicrobial resistance genes in the microorganisms’ genome is natural, but the spreading rate and the overall number of them within a population is highly affected by the usage of antimicrobials. According to few studies the phenotypically expressed characteristics of bacteria do not always rely upon the phenotype. This phenomenon can often be observed by Pasteurella multocida too which is a common pathogen of animals of economic importance.

42 strains of Pasteurella multocida originating from domestic and wild animals were subjected to a disc diffusion test of 17 antibiotics, enabling us to choose six strains seeming to be the most distant phenotypically. New generation sequencing of the six chosen strains’ pure cultures was performed. The sequenced whole genomes were examined with various bioinformatic tools based on antimicrobial resistance gene databases (CARD, ResFinder) and their sequential environment was also identified. Thus, we detected the mobile genetic elements which have mayor importance in the horizontal transfer of antimicrobial resistance genes and the spread of antimicrobial resistance.

We managed to identify 18 AMR-gene types. 17 were CARD-based and 9 were ResFinder-based. We discovered 12 genes with CARD and 10 genes with ResFinder located in mobile genetic elements (often the gene types found on mobile genetic elements were the same in the various strains). In conclusion 4 eventualities were pointed out. Antimicrobial resistance presented with the disc diffusion test could have been based upon the presence of specific AMR-genes, whilst in many cases the occurrence of antimicrobial resistance was not specifically justified by the genotypical background. The observed antibiotic susceptibility could rely either upon the lack or interestingly, the presence of the specific antimicrobial resistance genes.

As presented above, the occurrence of antimicrobial resistance genes does not necessarily lead to the expression of a certain bacteria’s antibiotic resistance characteristics. Research based on modern sequencing tools and bioinformatic methods brings us closer to the understanding of these phenomena what may serve as a core step of the battle against antimicrobial resistance in the future.