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Antibiotic resistance (AR) remains one of the greatest threats to global health, and Aeromonas species have the potential to spread AR in the aquatic environment. The spread of resistance to antibiotics important to human health, such as third-generation cephalosporins (3GCs) and carbapenems, is of great concern. We isolated and identified 15 cefotaxime (3GC)- and 51 carbapenem-resistant Aeromonas spp. from untreated hospital and treated municipal wastewater in January 2020. The most common species were Aeromonas caviae (58%), A. hydrophila (17%), A. media (11%), and A. veronii (11%). Almost all isolates exhibited a multidrug-resistant phenotype and harboured a diverse plasmidome, with the plasmid replicons ColE, IncU, and IncR being the most frequently detected. The most prevalent carbapenemase gene was the plasmid-associated blaKPC-2 and, for the first time, the blaVIM-2, blaOXA-48, and blaIMP-13 genes were identified in Aeromonas spp. Among the 3GC-resistant isolates, the blaGES-5 and blaMOX genes were the most prevalent. Of the 10 isolates examined, three were capable of transferring carbapenem resistance to susceptible recipient E. coli. Our results suggest that conventionally treated municipal and untreated hospital wastewater is a reservoir for 3GC- and carbapenem-resistant, potentially harmful Aeromonas spp. that can be introduced into aquatic systems and pose a threat to both the environment and public health.

Drought is one of the most important factors limiting N fixation, growth and yield of soybean. In this study, fifteen indigenous Bradyrhizobium japonicum strains isolated from different regions of Croatia were subjected to in vitro investigations of different drought conditions (simulated by polyethilene glycol (PEG) 6000) and increased NaCl concentrations. ERIC-PCR method was employed in order to determine genetic variability of strains. At the concentration of 15% PEG 6000 indigenous strain B. japonicum IS1 isolated from east Slavonia region was most tolerant to the lack of water. At the concentraction of 30% PEG 6000, B. japonicum IS2, was distinctively resistant to osmotic pressure and the least tolerant was B. japonicum IS4, both isolated from eastern Slavonia. For all tested strains, good growth was observed at the concentration of 1% NaCl and moderate growth was recorded for the strains from Koprivnica region. Indigenous strans from Baranja, Istria and two from eastern Slavonia were very tolerant to high concentration of 4% NaCl. According to results of ERIC-PCR method genetic similarity was not related to location of the isolation. The greatest genetic similarity was observed for strains isolated from Baranja region, eastern Slavonia, Koprivnica and western Slavonia.

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Summary There is a growing need for new formulations of carriers with better protection for bacterial inoculum. One of the newer techniques in inoculum making is encapsulation method. With this method, the whole bacterial cells are immobilized in defined space – matrix, where the cells are protected from environmental activities before use. Encapsulation of the inoculum was performed with ionic gelation method. The alginate-based microparticles (500-600 µm) containing viable B. japonicum strain were solidified in CaCl2. The initial number of viable bacteria in every sample was 9.0 log CFU/ml. Chitosan coated particles had a higher mortality rate than non-coated particles, with 1.3 log CFU/ml in lyophilized and wet microparticles stored at room temperature. High viability of B. japonicum was registered in wet particles stored at constant −20°C for thirty days with a viability rate of 8.84 log CFU/ml.