Salmonelloses are among the most common animal-borne infections. The most frequent causes of their occurrence are contaminated chicken eggs. For this reason, the control of bacteria from the Salmonella genus living in the cloaca of laying hens can contribute to the reduction of spreading levels of infections with these bacteria. The most popular methods of rearing laying hens in small agricultural farms comprise run and cage keeping. The aim of the performed studies was to determine the impact of rearing and nutritional systems on the occurrence of egg infections with Salmonella spp. bacteria. Detection by PCR method corroborated presence of bacteria from the Salmonella genus on eggs surface from hens kept in litter system. Latex serotyping test confirmed the presence of Salmonella Enteritidis. Salmonella spp. was not detected on eggs surface from hens kept in cage system. Salmonella spp. isolates from the eggs surface of hens reared on litter were characterized by drug resistance to tetracycline. Addition of EM probiotic failed to show reduction in incidence of Salmonella spp. infection.
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Antibiotic resistance of bacteria was observed in various aquatic environments including seas, rivers, lakes, coastal areas, surface water and sediments. The increased implementation of antibiotics into these environments through medical therapy, agriculture and animal husbandry has resulted in new selective pressures on natural bacterial aquatic populations. Antibiotic resistance of heterotrophic bacteria isolated from the surface microlayer and subsurface water of freshwater coastal polymictic and low-productive lake was studied. Antibiotic resistance was determined by the single disc diffusion method. The resistance level of bacteria to various antibiotics differed considerably. Bacteria were most resistant to ampicillin, ciprofloxacin, clindamycin, erythromycin and penicillin. Majority of bacterial strains showed resistance to 4.6 out of 18 antibiotics tested. As a rule, neustonic bacteria (antibiotic resistance index, ARI 0.44) were more resistant to the studied antibiotics than planktonic bacteria (ARI 0.32). 70-90% of neustonic bacteria were resistant to ampicillin, clindamycin and erythromycin, 60-70% of planktonic bacteria were resistant to ampicillin, ciprofloxacin and penicillin. Differences between pigmented and non-pigmented bacteria in their resistance to the tested antibiotics were observed. Above 40% of achromogenic bacterial strains were resistant to ampicillin, clindamycin and penicillin. Among bacterial strains characterised by their ability to synthesize carotenoids, more than 30% was resistant to ampicillin and ciprofloxacin. Bacterial resistance level to antibiotics depended on their chemical structure. Bacteria isolated from study lake were most resistant to quinolones and lincosamides while they were most susceptible to tetracyclines and aminoglycosides. Results presented in this paper indicate that antibiotics are a significant selection factor and probably play an important role in regulating the composition of bacterial communities in aquatic ecosystems. Adaptive responses of bacterial communities to several antibiotics observed in the present study may have possible implications for the public health.
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