20.500.12556/RUL-187874 Breme odpornosti proti protimikrobnim učinkovinam Blejskega jezera in njegovih pritokov The burden of antimicrobial resistance in Lake Bled and its tributaries Odpornost proti antibiotikom je pomemben javnozdravstveni izziv, pri čemer vodni ekosistemi lahko delujejo kot rezervoarji odpornih bakterij in genov za odpornost proti protimikrobnim učinkovinam (ARG). V magistrskem delu smo preučevali fenotipsko in genotipsko breme odpornosti proti antibiotikom v Blejskem jezeru in njegovih pritokih ter ocenili vpliv prostorskih in sezonskih dejavnikov na razširjenost odpornih bakterij in ARG. Za odpornost proti 16 antibiotikom smo z metodo disk-difuzijskih antibiogramov analizirali 745 izolatov bakterije Escherichia coli, ki so bili osamljeni iz vzorcev vode. V 140 vzorcih metagenomske DNA pa smo z metodo PCR določali prisotnost 69 tarčnih ARG. Fenotipska analiza je pokazala razmeroma nizko prevalenco odpornosti; 73,56 % izolatov ni bilo odpornih proti nobenemu antibiotiku, 14,6 % pa je bilo večkratno odpornih (VOB). Osamili smo tudi 32 izolatov, ki tvorijo ESBL, od katerih je bilo 87,50 % VOB. Genotipska analiza je pokazala prisotnost ARG v vseh vzorcih skozi vse leto, najpogosteje genov blaTEM, blaOXA, tetA, tetC, sul2, dfrB, aadA, ermF, intI1 ter genov za nespecifične izlivne črpalke. Gen mcr-4, povezan z odpornostjo proti kolistinu, je bil prisoten v več kot četrtini vzorcev. Največje breme ARG smo zaznali v pritokih, zunaj kopalne sezone, medtem ko se je v jezeru med kopalno sezono breme ARG tudi rahlo povečalo. Rezultati kažejo, da so pritoki, ki tečejo mimo kmetijskih površin in urbanih območij, glavni vir vnosa odpornih bakterij in ARG v Blejsko jezero ter da spremljanje števila fekalnih indikatorskih bakterij samo po sebi ne zadostuje za celovito oceno mikrobiološkega tveganja v rekreacijskih vodah. Raziskava poudarja pomen vključevanja molekularnih analiz odpornosti v prihodnje programe spremljanja kakovosti rekreacijskih voda. Antibiotic resistance represents a major public health challenge, while aquatic ecosystems can act as reservoirs of resistant bacteria and antimicrobial resistance genes (ARGs). In this master's thesis, we investigated the phenotypic and genotypic burden of antibiotic resistance in Lake Bled and its tributaries and evaluated the influence of spatial and seasonal factors on the distribution of resistant bacteria and ARGs. The susceptibility of 745 Escherichia coli isolates, obtained from water samples, to 16 antibiotics was analysed using the disk diffusion method. In addition, the presence of 69 target ARGs was determined by PCR in 140 metagenomic DNA samples. The phenotypic analysis showed a relatively low prevalence of resistance; 73,56 % of the isolates were susceptible to all tested antibiotics, whereas 14,6 % were multidrug-resistant (MDR). We also isolated 32 extended-spectrum betalactamase producing isolates, of which 87,50 % were MDR. The genotypic analysis revealed the presence of ARGs in all samples throughout the year, with the most frequently detected genes being blaTEM, blaOXA, tetA, tetC, sul2, dfrB, aadA, ermF, intI1, and genes encoding non-specific efflux pumps. The mcr-4 gene, associated with colistin resistance, was detected in more than one quarter of the samples. The highest ARG burden was detected in the tributaries outside the bathing season, whereas a slight increase in ARG burden was also observed in the lake during the bathing season. The results indicate that tributaries flowing through agricultural and urban areas are the main source of resistant bacteria and ARGs entering Lake Bled and that monitoring faecal indicator bacteria alone is insufficient for a comprehensive assessment of microbiological risk in recreational waters. The study highlights the importance of incorporating molecular analyses of antimicrobial resistance into future recreational water quality monitoring programmes. mikrobiologija vode Blejsko jezero E. coli metagenomska DNA geni za odpornost proti protimikrobnim učinkovinam antibiotiki občutljivost bakterij za antibiotike water microbiology lake Bled E. coli metagenomic DNA antimicrobial resistance genes antibiotics antimicrobial susceptibility testing true false false [M. Gavez] Slovenski jezik Angleški jezik Magistrsko delo/naloga 2026-09-16 07:17:04 2026-09-16 07:17:13 2026-09-17 04:29:43 0000-00-00 00:00:00 2026 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 579.68:615.33:575.111 289321 291231491 61176.pdf 61176.pdf 1 02673886E2A8C78769158EEAE39CAD87 4123bb0b52ed9a8a264935c041e42d7b7e789241eaa18768ef6fe588fd486b4a d71a1faa-b18d-11f1-8bc5-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=247698 Biotehniška fakulteta 0 0 0