Rezistentā Escherichia coli izplatība cūkām, tā samazināšanas iespējas: promocijas darbs zinātniskā doktora grāda (Ph.D) iegūšanai veterinārmedicīnas zinātnē

The doctoral thesis was carried out during the period from 2014 to 2022 at the Institute of Food and Environmental Hygiene of the Latvia University of Life Sciences and Technologies (LLU) and at the Division of Molecular Biology and Microbiology of the Research Laboratory of Biotechnology of LLU. The study was carried out into three activities — one of them was dedicated to find out the prevalence of resistant E. coli in pigs in Latvia, while the other two were to reduction possibilities of resistance. In the first activity, 615 samples of pig faeces were collected from seven pig breeding farms in the Republic of Latvia. Subsequently, a bacteriological examination of the samples was carried out — 615 commensal Escherichia coli were isolated and their antibiotic resistance was determined. All of the obtained faecal samples of pigs were tested for the presence of extended spectrum beta-lactamase (ESBL) producing E. coli. Presumptive ESBL-producing E. coli were phenotypically and genotypically confirmed subsequently determining their resistance to antibiotics. In the second activity, in one of the pig farms (No. L3), we randomly selected 4 litters containing sows with 14-day-old Landrace-Duroc crossbred piglets (n=44). The piglets of each litter were assigned to their own treatment groups: control group (C), probiotics group (P), probiotics and buckwheat bran group (PB) and herbal group (H). During the study, control group piglets received basal diet, P and PB groups received probiotics that were added to the drinking water; but buckwheat bran and herbal supplement were added to the basal diet for the groups PB and H, respectively. The research period was 6 weeks. During this activity, the potential of probiotics and feed components of plant origin as an alternative solution to antimicrobial agents was evaluated, determining the effect of them on the general health of piglets, intestinal health, and the prevalence of resistant E. coli. In the third activity, the in vitro antibacterial activity of the commercial and Latvian (the author of this doctoral thesis have obtained from medicinal plants during the hydrodistillation process) essential oils was compared against phenotypical and genotypic confirmed faecal ESBL producing E. coli isolated from pigs in the first activity of this study. The hypothesis put forward in the thesis: bacteria Escherichia coli resistance to antibiotics is highly widespread in pig farming farms in Latvia and the use of probiotics, as well as herbal products, could limit the spread of E. coli and ESBL-producing E. coli. The purpose of the thesis: to study the prevalence of resistant Escherichia coli in pigs in Latvia, to evaluate the possibilities of its reduction by using feed components and means of natural origin. Tasks of the doctoral thesis: (1) find out the prevalence of the resistant to antibiotics Escherichia coli in pig farms in Latvia. To identify extended-spectrum beta-lactamase (ESBL)-producing E. coli occurrence in pigs; (2) evaluate the effect of supplementary feed containing probiotics and feed components of plant origin on the health of piglets and their intestines — prevalence of resistant E. coli, intestinal microbiological, histomorphological and immunological condition, meat quality; (3) to compare the antibacterial activity of Latvian and commercial essential oils in vitro against porcine faecal extended-spectrum beta-lactamase (ESBL)-producing E. coli, as well as to evaluate the use of essential oils enriched with caprylic acid and sodium chloride in the control of this resistant E. coli. The personal contributions: (1) bacteriological examination of faecal samples (commensal indicator bacteria E. coli isolation and biochemical confirmation; testing samples for the presence of ESBL-producing E. coli, their phenotypic confirmation; E. coli and ESBL-producing E. coli determination of antimicrobial sensitivity (antibiotic resistance) against 12 and 18 antibiotics, respectively, preparation of isolated cultures for long-term storage); (2) collection of medicinal plants, preparation of a herbal supplement containing them for the implementation of the piglet feeding study; (3) bacteriological examination of the faeces and intestinal contents of obtained piglets (Enterobacteriaceae, E. coli and Lactobacillus spp. determination of the number, isolation of E. coli and determination of its antimicrobial sensitivity (antibiotic resistance); (4) wild and cultivated medicinal plants in Latvia (T. vulgaris, T. serpyllum and S. montana) collection, extraction of essential oils using the hydrodistillation method; (5) examination of the antibacterial activity of Latvian and commercial essential oils, as well as commercial enriched (with caprylic acid and NaCl ) essential oils in vitro.