Sessions

Pseudomonas aeruginosa is a widely prevalent Gram-negative bacterium, that can cause chronic otitis externa (inflammation of the external ear canal) in dogs. This pathogen, which often falls into the category of multidrug-resistant bacteria, is capable of infecting humans and can even have zoonotic potential. Due to its ability to form biofilms, its virulence factors, and various antimicrobial resistance mechanisms, infections caused by this bacterium are challenging to treat in both human and animal health contexts. Compared to other prokaryotes, P. aeruginosa has a relatively large genome, which enables the development of several resistance mechanisms. Mapping of antimicrobial resistance genes can help in understanding the genetic background of phenotypic study results and assessing the risk of horizontal spread of resistance genes.

Our research was conducted at the Department of Pharmacology and Toxicology. The P. aeruginosa strains used in the studies were isolated from cases of chronic otitis externa in dogs between 2010 and 2017. The genetic repertoire of a total of 59 isolates was evaluated. The DNA extracted from the bacteria was examined using Nanopore technology, which belongs to the new generation sequencing (NGS) methods. The resistance genes in the genome were identified using ABRicate (CARD database).

We identified 44 different resistance genes in the 59 isolates, which could lead to resistance against drug groups commonly used in the treatment of otitis externa in companion animal practice or those of particular importance in human healthcare (aminoglycosides, cephalosporins, fluoroquinolones, carbapenems, peptides). Furthermore, we determined which mobile genetic elements (MGEs) are present in the bacterial genome and how far they are located from the resistance genes. Resistance genes were found to be associated with MGEs in 188 cases. Resistance gene was located within 1000 base pairs (bp) of the nearest MGE in only one isolate. The distance was within 10,000 bp in 21 cases, and within 50,000 bp in 166 cases. Additionally, we found a plasmid-borne CrpP gene in six isolates, that is responsible for fluoroquinolone resistance.

The plasmid-borne and MGE-associated resistance genes discovered in this study are particularly concerning regarding the spread of antimicrobial resistance.