Fenotipske i genotipske karakteristike Escherichia coli izolovanih iz fecesa pasa / Phenotypic and genotypic characteristics of Escherichia coli isolated from faeces of dogs

Shiga toxin-producing Escherichia coli (STEC) strains constitute one of six groups of diarrheagenic E. coli. Infection caused by STEC is the most common cause of acute renal failure in young children and elderly people worldwide. As dogs are recognized as a reservoir for STEC, the close contact between humans and dogs poses a risk for zoonotic transmission of these bacteria. Except scarce studies of STEC in humans and domestic animals, there are no available data about this E. coli group in dogs in the Republic of Serbia. Therefore the aim of this doctoral dissertation was to determine the presence and prevalence of STEC in the dog populaton in the area of Novi Sad, to perform typing and molecular characterization of E. coli strains isolated from faeces of dogs, as well to determine the presence of antibiotic resistant E. coli strains. In total 101 dogs from the area of Novi Sad was included in this research. As the material fecal samples of dogs were used. In order to isolate E. coli strains from faeces standard methods of bacterial isolation and biochemical identification were used, and for the confirmation of species identity matrix-assisted laser desorption/ionization time-offlight mass spectrometry (MALDI-TOF MS) was used. In order to determine the presence of STEC in dogs latex agglutination for the serogroup O157, direct agglutination for “big six” serogroups (O26, O45, O103, O111, O121 and O145), Vero cell cytotoxicity assay (VCA), enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) were used. Antibiotic resistance was determined by disc diffusion method according to the EUCAST and CLSI guidelines. In this research, for the first time in the Republic of Serbia, the presence of STEC has been proven in the dog population. By VCA method the prevalence of 1,98% was determined, while by ELISA and PCR the determined prevalence was 5,94% and 4,95% respectively. Two E. coli isolates belonged to some of the STEC “big six” serogroups, while none of the isolates belonged to O157 serogroup. Furthermore, in the dog population included in this research, the presence of strains resistant to one or more of used antibiotics was determined, as well as the presence of one multiresistant strain. Most of the E coli isolates showed resistance to ampicillin (22,5%), while every of the isolates showed susceptibility to gentamicin. In this research significant association between lifestyle of dogs and STEC harbouring. That is to say, significantly higher STEC prevalence was noticed in stray dogs in comparison to pet dogs, what is likely due to unlimited freedom of movement and thereby more frequent contact with contaminated water and food as sources of STEC. Finding of STEC and E. coli strains resistant to antibiotics in dog population is of importance not just in small animal practice, but also in terms of public health in the Republic of Serbia.