The aim of this study was to investigate the patterns of antibiotic resistance of Aeromonas spp. bacteria isolated from the sea trout (Salmo trutta) from the state fish hatcheries of the Institute of Food Safety, Animal Health and Environment ‘BIOR’, Latvia. Bacteriological investigations were performed at four state fish hatcheries located in the drainage basins of the main Latvian rivers – Daugava, Venta and Gauja, during the five-year period (2012 – 2016). In fish with visible clinical signs, bacteriological samples were collected from heart, liver, spleen, kidney and ulcer surfaces. Aeromonas hydrophila and Aeromonas salmonicida were isolated from sea trouts. A total of 52 individual sea trouts were examined. Resistance to amoxicillin, ampicillin, cephalexin, colistin, doxycycline, enrofloxacin, erythromycin, florfenicol, gentamycin, kanamycin, lincomycin, neomycin, oxytetracycline, spectinomycin, streptomycin, tetracycline, trimethoprim/sulfamethoxazole was tested. The results of this study suggest a multi-drug resistance pattern among the A. hydrophila isolates. All the isolates were resistant to amoxicillin (100%), ampicillin (100%), cephalexin (100%) and erythromycin (100%). The lowest level of resistance was found against florfenicol (4.55%), gentamycin (4.55%), kanamycin (4.55%), but susceptibility was recorded to enrofloxacin, neomycin and trimethoprim/sulfamethoxazole. A. salmonicida isolates were resistant to oxytetracycline (9.38%) and tetracycline (9.38%). For other antibiotics A. salmonicida isolates were susceptible.

The purpose of this study was to evaluate the effect of probiotics, herbals and buckwheat bran (Fagopyrum esculentum L.) on growth, profile of blood, gut microbiota, profile of fatty acid in meat and shedding of resistant Escherichia coli (E. coli) in piglets. A total of 44 piglets (Sus scrofa domesticus) from age of day 14 to 56 were divided into 4 groups. Control received basal diet (group C), basal diet + probiotics (group P), basal diet + 3% buckwheat bran (group PB) and basal diet + 1.5% herbals (group H). No effect was observed in growth in all groups. The count of Lactobacillus spp. increased (p is less than 0.05) in jejunum in group P. In the faeces, Enterobacteriaceae decreased in the group P (p is less than 0.05) of 35 days old piglets, but Enterobacteriaceae and E. coli decreased in the group H (p is less than 0.05) of 56 days old piglets. The prevalence of resistance to at least one antibiotic class was 66.7% before and 50% after the experiment in all groups. Multidrug resistance of E. coli was not observed in 14 days old piglets, but was observed in 50% and more in all of study groups of 56 days old piglets. The fatty acid composition of Longissimus thoracis muscle had higher levels of α-linolenic acid and palmitoleic acid (p is less than 0.05), but lower level of stearic acid (p is less than 0.05) in group P. In conclusion, probiotics and herbals improved gut microbiota, fatty acid profile and affected shedding of resistant E. coli, but not growth performance.