Carbapenems are beta-lactam antibiotics used as a last resort to treat infections caused by multidrug-resistant bacteria. The spread of carbapenem-resistant bacteria, which is not limited to hospital settings, is particularly concerning. Carbapenem-resistant bacteria have been confirmed several times in aquatic environments outside Slovenia. Research on the presence of these bacteria in the natural environment in Slovenia is currently very limited. The aim of our study was to determine the presence and prevalence of carbapenem-resistant bacteria in freshwater environments in Slovenia. To this end, we sampled water and sediment at 10 locations in the Koroška and Štajerska statistical regions. From the water and sediment samples, we isolated bacteria on mSCA medium, identified them using MALDI-TOF mass spectrometry, and determined their resistance to meropenem and imipenem. We then used the CIM phenotypic test to assess whether resistance to carbapenems in meropenem/imipenem-resistant isolates was due to the secretion of carbapenemases, and further characterised the carbapenemase genes using PCR. A total of 201 isolates were obtained, of which 33 were resistant to meropenem or imipenem according to the disc diffusion antibiogram. More than half of the resistant isolates belonged to the family Enterobacteriaceae. The CIM test confirmed the secretion of carbapenemases in 24 isolates. Molecular analysis confirmed the presence of the carbapenemase genes blaOXA-48, blaNDM, blaVIM, or blaKPC in 21 isolates. Some isolates of the species Klebsiella pneumoniae had two carbapenemase genes, namely blaNDM and blaOXA-48 or blaVIM and blaOXA-48. We thus confirmed the presence of bacteria that secrete carbapenemases and are resistant to carbapenems in water and sediment, and the that resistance mechanisms are the same as in isolates from the clinical environment.
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