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The aim of this study was to determine the spatial distribution of enterococci as indicators of fecal pollution in river water in forest reserves and urban areas. The biodiversity, multidrug resistance, and virulence of enterococci were monitored using conventional and molecular methods, including fluorescence in situ hybridization (FISH). Enterococcal (ENT) counts determined via the FISH method were several thousand times higher than those determined by the culture-based method. This observation points to the abundance of viable but non-culturable (VBNC) bacteria that are often more toxic. Water from the river source was characterized by the lowest number of multidrug-resistant and virulent enterococcal strains. The abundance of the analyzed bacteria was highest (more than 50% of the strains) in the area where treated wastewater was evacuated to the river. Statistical analysis confirmed the presence of relationships between these environments. Pathogenic enterococci, which are not effectively eliminated during wastewater treatment, spread in the river continuum, thus posing a health threat to humans and animals. A combination of conventional and molecular techniques for the identification of bacteria supports a rapid and reliable assessment of pollution sources in the examined environment and the implementation of protective measures.

The aim of this study was to determine the effect of commercial feed (CF) supplemented with 0.1% of the Carnobacterium maltaromaticum environmental probiotic strain on the rearing parameters, apparent nutrient digestibility, and microbial safety of juvenile rainbow trout (Oncorhynchus mykiss). The fish were fed CF (control group, CG) and experimental feed (EF) supplemented with 0.1% of C. maltaromaticum (experimental group, EG) for 56 days. The final body weight and total body length of the fish were measured. The growth rate, condition factor, feed conversion ratio, viscerosomatic and hepatosomatic indices, and apparent digestibility coefficients of protein (PAD), lipids (LAD), ash (AAD), and nitrogen-free extract (NFEAD) were calculated. The total viable counts of C. maltaromaticum bacteria, mesophilic bacteria, hemolytic mesophilic bacteria, Pseudomonas fluorescens, Aeromonas hydrophila, Staphylococcus sp., and sulfite-reducing anaerobic spore-forming Clostridium sp. were determined in digestive tract contents and the skin of fish. Feed supplementation with C. maltaromaticum significantly affected most rearing parameters, as well as the PAD, LAD, AAD and NFE values, and bacterial counts. The principal component analysis (PCA) revealed significant positive correlations (p < 0.05) between fish growth rates, PAD and LAD values vs. C. maltaromaticum counts in the EF and in the digestive tract contents of the fish.

Fish feed should be characterized by microbiological stability to guarantee the optimal health of farmed fish. The aim of this study was to determine the efficacy of amaranth meal (Amaranthus cruentus) and a highly active environmental strain of probiotic bacteria, Carnobacterium maltaromaticum, as novel supplements that stabilize the quantitative and qualitative composition of microbiota in compound fish feeds for aquaculture, regardless of storage temperature. The total viable counts of mesophilic bacteria at 28 °C (TVC 28 °C), hemolytic mesophilic bacteria (Hem 37 °C), Staphylococcus sp. bacteria, aerobic spore-forming bacteria (ASFB), sulfite-reducing anaerobic spore-forming Clostridium sp. bacteria, yeasts, and molds were analyzed in control feed (CF), in feed supplemented with amaranth meal (AF), and in feed supplemented with amaranth meal and C. maltaromaticum (ACF), stored at a temperature of 4 °C and 20 °C for 98 days. Amaranthus cruentus and C. maltaromaticum significantly reduced bacterial counts in fish feeds, regardless of the temperature and duration of storage. The antibacterial and antifungal effects of the tested additives were statistically significant (p ≤ 0.05). The studied novel supplements contribute to the microbiological safety of compound fish feeds. The tested additives could be recognized as the key ingredients of organic, environmentally friendly fish feeds, which guarantee the high quality of fish intended for human consumption.

The aim of this study was to determine the effect of trout aquaculture effluents on the Drwęca River. The count of opportunistic pathogen Pseudomonas fluorescens (OPPF) in the total Pseudomonas fluorescens population (TPFP) were determined by plating on King B medium and fluorescence in situ hybridization. The resistance of OPPF strains to 12 antibiotics and two disinfectants was evaluated. Significant differences (p ≤ 0.05) in OPPF counts were found between seven sampling sites. OPPF counts were highest in samples collected directly downstream from three fish farms. More than 50% of these isolates demonstrated multiple-drug resistance to ampicillin, mezlocillin, cefotaxime, norfloxacin, tetracycline and two disinfectants (Steridial and chloramine T). Of these, 52% were resistant to high doses of cefotaxime and norfloxacin (MIC ≥ 256 µg·mL−1), and 65% were resistant to the maximum doses of Steridial (MIC Ste ≥ 25 mL·m−3) and chloramine T (MIC Chlor ≥ 20 mg·L−1). All OPPF sampled upstream from the farms were sensitive to low concentrations of CTX (cefotaxime) and NOR (norfloxacin) (MIC ≤ 2 µg·mL−1), Steridial (MIC Ste ≤ 5 mL·m−3) and chloramine T (MIC Chlor ≤ 2.5 mg·L−1). Agglomerative clustering revealed two clusters: strains from samples collected upstream and downstream from trout farms. The results indicate that aquaculture effluents significantly affect the prevalence of biocides resistant OPPF along the river continuum.

Pseudomonas fluorescens and Aeromonas hydrophila bacteria are opportunistic pathogens that occur naturally in the aquatic environment and in the gut flora of healthy fish. Both species can pose a serious threat for fish that are highly sensitive to water pollution. The aim of this study was to determine the extent to which the amount of administered fish feed and fish biomass affect the distribution and abundance of Ps. fluorescens and A. hydrophila bacteria in a recirculating aquaculture system (RAS) during farming of European grayling (Thymallus thymallus L.) broodstock. A total of 68 water samples from the inflow, two rearing tanks and the outflow as well as 17 feed samples were collected and analyzed separately. Bacterial populations were analyzed by the culture-dependent method and a molecular method (fluorescence in situ hybridization, FISH) to detect culturable strains and viable but non-culturable strains, respectively. Fish biomass, feed and 16 water quality parameters (temperature, pH, concentration of dissolved oxygen, oxygen saturation, five-day biochemical oxygen demand (BOD5), total phosphorus, total organic phosphorus and nitrogen, orthophosphates, total nitrogen, nitrite and nitrate nitrogen, ammonia nitrogen, ammonium nitrogen, total suspended solids, and total organic carbon) were the explanatory factors. Statistically significant differences (RM-ANOVA, p ≤ 0.05) were stated in bacterial abundance in samples from the inflow, rearing tanks and the outflow. Water samples from the RAS were abundantly colonized by non-culturable Ps. fluorescens and A. hydrophila bacteria. Feed was not a source of bacteria, but a redundancy analysis (RDA) revealed that the amount of feed, fish biomass, BOD5, and total suspended solids and total organic carbon were positively correlated in both Ps. fluorescens and A. hydrophila. These parameters also influenced the distribution of both potentially pathogenic bacterial populations and contributed to the bacterial contamination of water in the RAS. Our results are particularly valuable for aquacultures that help to replenish wild stocks and rebuild populations of threatened species in natural aquatic environments.

The objective of this study was to evaluate the effect of lake restoration by the hypolimnetic withdrawal method on the intensity of ambient odour in the vicinity of the pipeline outlet. The study was carried out in 2012-2013 from the beginning of the summer stagnation period in Lake Kortowskie to complete overturn in fall. Samples of river water and ambient air were collected from two sites: near the pipeline outlet (PO) and behind the academic campus (AC). A total of 44 air samples and 44 water samples were analysed. Odour intensity was measured in samples of ambient air. The following physicochemical parameters of water were determined: flow rate, dissolved oxygen (DO), hydrogen sulphide (H2S), sulphate (SO4), ammonium nitrogen (NH4-N), total nitrogen (TN), dissolved nitrogen (DN), total particulate nitrogen (T-PN), total organic carbon (TOC), dissolved organic carbon (DOC) and total particulate organic carbon (T-POC). Water samples were also analysed to determine total bacterial abundance (TBA) and the counts of bacterial rods, cocci and spiral-shaped bacteria, and sulphate-reducing bacteria (SRB). Significant variations in odour intensity were noted between years and sampling sites. Odour was significantly determined by the proportion of lake water in river water. It was also significantly correlated (P2S, NH4-N, TBA and counts of SRB, rod- and spiral-shaped bacteria only in.