Antimicrobial resistance (AMR) in bacteria and associated human morbidity and mortality is increasing. The use of antimicrobials in livestock selects for AMR that can subsequently be transferred to humans. This flow of AMR between reservoirs demands surveillance in livestock and in humans. We quantified and characterized the acquired resistance gene pools (resistomes) of 181 pig and 178 poultry farms from nine European countries, sequencing more than 5,000 Gb of DNA using shotgun metagenomics. We quantified acquired AMR using the ResFinder database and a second database constructed for this study, consisting of AMR genes identified through screening environmental DNA. The pig and poultry resistomes were very different in abundance and composition. There was a significant country effect on the resistomes, more so in pigs than in poultry. We found higher AMR loads in pigs, whereas poultry resistomes were more diverse. We detected several recently described, critical AMR genes, including mcr-1 and optrA, the abundance of which differed both between host species and between countries. We found that the total acquired AMR level was associated with the overall country-specific antimicrobial usage in livestock and that countries with comparable usage patterns had similar resistomes. However, functionally determined AMR genes were not associated with total drug use.

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-Histopathological, biochemical and toxicological investigations of tissues and blood of normally slaughtered chickens exhibiting different frequencies (1-2%, 40-50% and above 80%) of nephropathy changes (congested or pale and enlarged kidneys) at the slaughtering meat inspection were carried out to elucidate the aetiology of nephropathies of chickens encountered in Bulgaria. A close relationship was observed between the frequency of this nephropathy and the rate of nephrotoxic mycotoxin ochratoxin A in muscles, kidneys and livers of chickens, but the levels of ochratoxin A in corresponding feed samples (0.1-0.3 ppm) were significantly lower than the levels (2-4 ppm) required to reproduce such nephropathy. Clinicomorphological changes such as nervous symptoms, vascular and oedematous changes in various internal organs and the brain, and subcutaneous or liver and kidney haemorrhages in addition to known degenerative changes in the kidneys, liver and lymphoid organs differed from the classical description of the nephropathy made in Scandinavia. The conclusion is that the Bulgarian chicken nephropathy may have a multitoxic aetiology because it cannot be explained by the concentration of ochratoxin A alone. mycotoxic nephropathy / ochratoxicosis / mycotoxin / ochratoxin A / pathology Résumé -Néphropathie mycotoxique spontanée sans étiologie mycotoxique déterminée chez des poulets bulgares. Des études histopathologiques, biochimiques et toxicologiques des tissus et du sang de poulets montrant des fréquences variées (1-2 %, 40-50 % et supérieures à 80 %) de changements néphropathiques (reins congestionnés ou pâles et hypertrophiés) lors de l'inspection des viandes à l'abattoir, ont été entreprises afin de déterminer l'étiologie des néphropathies du poulet en Bulgarie. Une relation étroite a été observée entre la fréquence de cette néphropathie et le taux de la

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Abstract:The main clinical and pathomorphological changes in Aeromonas hydrophila infection in carp provoked by different field strains of this bacterium were studied. The strongest histopathological damages were seen in the functional epithelium of liver and kidneys, followed by intestine and hearth damages in addition to various haemorrhages in interstitial tissues of visceral organs and some skin haemorrhages on the ventral surface of the body and the anal region. As a whole, pathological damages consisted of degenerative changes as cloudy swelling, granular and/or hyaline droplet degeneration or vacuolation in functional epithelium in the respective internal organs in addition to some target vascular disturbances, which appeared to be good biomarkers for field assessment of that disease. Pathological damages in internal organs and haemorrhages were stronger in experimental fishes exposed to higher levels of the respective pathogens, especially those isolated from dead anaconda or the referent strain, and less pronounced damages were seen in fishes infected with of Aeromonas hydrophila isolated from a silver carp with marked signs of septicaemia. Keywords

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