## 4 Discussion  
Approximately 26 centuries ago, the ancient Greek physician [PERSON] (460 B.C.E.-367 B.C.E.) recorded in his book \"_On Airs, Waters and Places_\" his conclusions about the significance of clean water in the preservation of health, and at the same time made what has been considered to be the earliest scientific reference to the One Health concept [24]. Nowadays, the reports that link water quality to public and animal health demonstrate without doubt the significance of the continuous monitoring of the quality of drinking water, particularly in connection with the spread of microbial pathogens [25, 26] and elements of drug resistance [27, 28]. Based on this, the investigation presented herein relied on two commonly used hygiene indicator organisms of drinking water quality, namely _E. coli_ and coliforms, and focused on the characterization of 358 microbial isolates recovered from drinking water samples collected from several urban and rural locations in Greece. All the microbiological analyses for the water samples were conducted in an accredited laboratory in full compliance with the ISO 17025 requirements. Moreover, this investigation implements similar studies conducted in the past in Greece [29, 30, 31, 32, 33], Peru [34], various African countries [35], Mozambique [36], and Bangladesh [37], which constitute a reliable point of reference for the conclusions reported here. In connection with the phylogeny assignment of the _E. coli_ isolates that were studied, our findings conclude that phylogroups B1 (26.4%) and A (18.6%) are the most prevalent, which agrees with other studies on drinking water in Greece [30, 32], Bangladesh [37], Iran [38], and Kenya [39], and probably accounts for the certain phylogroups harboring the highest percentages of AMR and MDR (29.3% and 36.6% for phylogroups B1 and A, respectively). Based on the information available in the relevant literature, certain phylogroups of _E. coli_ demonstrate high adaptability and environmental resilience, which in effect renders them the most detected in fresh water, particularly in sources of fecal contamination both from humans and animals [40, 41, 42, 43]. Regarding the genus assignment of the detected coliforms, the relevant reports indicate that the most detectable genera are mostly _Citrobacter_, _Enterobacter_, and _Klebsiella_, with _Serratia_ being the least commonly detected genus, which is also consistent with our findings [44, 45, 46, 47]. All the coliforms are commonly found in the environment and may colonize water distribution systems, particularly under conditions conducive to biofilm formation [48, 49]. The detection of these bacteria in drinking water raises concern about potential public health risks, particularly in connection with _Klebsiella_, which is often identified as the causal agent of healthcare-associated infections, especially among immunocompromised individuals, and has been strongly implicated in the horizontal transfer of antibiotic resistance genes [46, 50, 51]. The variations in the prevalence of the most common coliform genera in drinking water probably underscore their varying adaptation ability to different ecological niches within water distribution systems. The composition, quantity, and antibiotic resistance profiles of coliform bacteria in drinking water reservoirs are significantly influenced by seasonal, regional, and environmental dynamics, including climate change and water treatment practices [52]. The occurrence of eutrophication, where excessive nutrients stimulate algal growth and oxygen depletion, can further alter microbial community structures, promoting the dominance of resistant bacteria over non-resistant strains [52]. The results recorded with regard to the antibiotic susceptibility of _E. coli_ indicate that the tested isolates were in all the cases sensitive to gentamicin and meropenem, whereas resistance was recorded primarily in connection with ampicillin and tetracycline. These findings are again consistent with those of other reports [32, 34, 43, 45].