| Abstract | This dissertation determined the presence of Enterobacterales resistant to third-generation cephalosporins (3GCs) and carbapenems from seven Croatian wastewater treatment plants (WWTPs). Culture-based and qPCR methods revealed that conventional wastewater treatment, while reducing the load of 3GCs-, carbapenem-resistant Enterobacterales (CRE), extended-spectrum β-lactamase (ESBL), and carbapenemase genes, they were inadequate for their complete elimination from treated wastewater, discharging them in significant amount into the environment. For a better understanding the role of wastewater, as a reservoir for resistance to 3GCs and carbapenems, extended-spectrum β-lactamase Enterobacterales (ESBL-E) and CRE were isolated from treated wastewater from Zagreb WWTP and wastewater from two hospitals in Zagreb. Phenotypic analysis confirmed their ESBLs and carbapenemases production and revealed their multidrug-resistant phenotype. Molecular analysis of isolates confirmed presence of ESBL, carbapenemase genes, and resistance genes to other antibiotic classes, including genes conferring resistance to colistin. Molecular epidemiology revealed that most isolates were human-associated clones, where E. coli and K. pneumoniae were recognized as high-risk and emerging-risk clones. These findings highlight the need for implementation of advanced municipal wastewater treatment technologies and hospital wastewater pre-treatment to mitigate the spread of these very pathogens with resistance to important antibiotics, into the environment.This dissertation determined the presence of Enterobacterales resistant to third-generation cephalosporins (3GCs) and carbapenems from seven Croatian wastewater treatment plants (WWTPs). Culture-based and qPCR methods revealed that conventional wastewater treatment, while reducing the load of 3GCs-, carbapenem-resistant Enterobacterales (CRE), extended-spectrum β-lactamase (ESBL), and carbapenemase genes, they were inadequate for their complete elimination from treated wastewater, discharging them in significant amount into the environment. For a better understanding the role of wastewater, as a reservoir for resistance to 3GCs and carbapenems, extended-spectrum β-lactamase Enterobacterales (ESBL-E) and CRE were isolated from treated wastewater from Zagreb WWTP and wastewater from two hospitals in Zagreb. Phenotypic analysis confirmed their ESBLs and carbapenemases production and revealed their multidrug-resistant phenotype. Molecular analysis of isolates confirmed presence of ESBL, carbapenemase genes, and resistance genes to other antibiotic classes, including genes conferring resistance to colistin. Molecular epidemiology revealed that most isolates were human-associated clones, where E. coli and K. pneumoniae were recognized as high-risk and emerging-risk clones. These findings highlight the need for implementation of advanced municipal wastewater treatment technologies and hospital wastewater pre-treatment to mitigate the spread of these very pathogens with resistance to important antibiotics, into the environment. |
| Abstract (croatian) | Ovom je disertacijom utvrđena prisutnost vrsta iz reda Enterobacterales otpornih na cefalosporine treće generacije (CTG-ove) i karbapeneme iz sedam hrvatskih uređaja za pročišćavanje otpadnih voda (UPOV-a). Metodama kultiviranja bakterija i qPCR-om nađeno je da iako konvencionalno pročišćavanje otpadnih voda smanjuje brojnost enterobakterija otpornih na CTG-ove i karbapeneme te gena za β-laktamaze proširenog spektra (ESBL) i karbapenemaze, neadekvatno je za njihovo potpuno uklanjanje, ispuštajući ih u značajnim količinama u okoliš. Za bolje razumijevanje uloge otpadnih voda kao rezervoara otpornosti na CTG-ove i karbapeneme, enterobakterije s β-laktamazama proširenog spektra i karbapenem-otporne enterobakterije, izolirane su iz pročišćene otpadne vode zagrebačkog UPOV-a i otpadnih voda dviju bolnica u Zagrebu. Fenotipska analiza potvrdila je njihovu proizvodnju ESBL-a i karbapenemaza te otkrila njihov višestruko otporan fenotip. Molekularna analiza izolata potvrdila je prisutnost ESBL i karbapenemaznih gene te gena za otpornost na druge klase antibiotika, uključujući gene za otpornost na kolistin. Molekularnom epidemiologijom nađeno je da su većina izolata bili klonski tipovi povezani s ljudima, gdje su E. coli i K. pneumoniae prepoznati kao visokorizični klonovi i visokorizični klonovi u nastajanju. Ovi rezultati naglašavaju potrebu za implementacijom naprednih tehnologija za pročišćavanje komunalnih otpadnih voda i predtretmana bolničkih otpadnih voda radi smanjenja širenja ovih patogena otpornih na vrlo važne antibiotike u okoliš. |
