a b s t r a c t
The aim of this study was to assess the impact of a fish farm on the structure of antibiotic resistant bacteria
and antibiotic resistance genes in water of Drwe˛ca River. Samples of upstream river waters; postproduction
waters and treated post-production waters from fish farm; as well as downstream river
waters were monitored for tetracycline resistant bacteria, tetracycline resistant genes, basic physicochemical
parameters and tetracyclines concentration. The river waters was characterized by low levels
of pollution, which was determined based on water temperature, pH and concentrations of dissolved
oxygen and tetracycline antibiotics. Culture-dependent (heterotrophic plate counts, counts of bacteria
resistant to oxytetracycline (OTCR) and doxycycline (DOXR), minimum inhibitory concentrations for oxytetracycline
and doxycycline, multidrug resistance of OTCR and DOXR, qualitative composition of OTCR
and DOXR, prevalence of tet genes in resistant isolates) and culture-independent surveys (quantity of
tet gene copies) revealed no significant differences in the abundance of antibiotic-resistant bacteria
and antibiotic resistance genes between the studied samples. The only way in which the fish farm influenced
water quality in the Drwe˛ca River was by increasing the diversity of tetracycline-resistance genes.
However, it should also be noted that the bacteria of the genera Aeromonas sp. and Acinetobacter sp. were
able to transfer 6 out of 13 tested tet genes into Escherichia coli, which can promote the spread of antibiotic
resistance in the environment.