## 4 Discussion
In this regard, it can be stated that the certain profile of antibiotic susceptibility/resistance constitutes a rather common feature of _E. coli_ isolated from drinking water. Regarding the antibiotic resistanceof the studied coliform isolates, the results recorded here were also similar to those of other studies with susceptibility against cefepime, ciprofloxacin, gentamicin, imipenem, meropenem, and trimethoprim/sulfamethoxazole being very common, and resistance recorded in connection primarily with ampicillin and cefoxitin [45; 53; 54]. Ampicillin resistance proved a common feature for most drug-resistant isolates of _E. coli_ (87.7%, 100 of 114) and coliforms (78.3%, 36 of 46) in the present study. The resistance of _E. coli_ and coliform bacteria to penicillin, including ampicillin and other beta-lactam antibiotics, is often mediated by the production of beta-lactamase enzymes such as _TEM_ and _SHV_[55; 56]. These resistant bacteria are frequently detected in drinking water sources contaminated with untreated or partially treated sewage, agricultural runoff, and hospital effluents, which raises concern about the efficiency of currently applicable drinking water management systems [57; 58; 59; 60]. Penicillin-resistant _E. coli_ and coliforms have been shown to survive conventional water treatment processes, including chlorination, particularly through biofilm formation, which, thus, becomes a potent reservoir of drug resistance genes [61; 62; 63], not only because water serves as a very effective medium for their spread, but also because of their high ability to acquire resistance through horizontal gene transfer. In effect, drug-resistant _E. coli_ may spread among bacterial communities in water systems and human microbiota [64; 65]. Comparing antibiotic resistance between the two groups of the tested isolates indicates that AMR percentage was higher for coliforms compared to _E. coli_ (96.5% coliforms vs. 73.9% _E. coli_), with the reverse being recorded in connection with MDR (26.1% _E. coli_ vs. 3.5% coliforms). Notably, none of the coliform isolates exhibited resistance to more than three groups of antibiotics, whereas the relevant percentage of _E. coli_ was 6.5% (MDR4), (Table 3). Regarding the phylogroup and genus allocation of the MDR isolates, the findings that were recorded indicate that most MDR _E. coli_ isolates belonged to phylogeny A, whereas the MDR coliforms were identified in decreasing order as _Klebsiella_, _Enterobacter_, and _Serratia_ (Table 3). The detection of MDR4 _E. coli_ isolates in water does not constitute an uncommon finding, with other research groups reporting the detection of _E. coli_ isolates exhibiting resistance against up to nine groups of antibiotics (MDR9) [41; 65; 66; 67]. To the best of our knowledge, the highest level of drug resistance recorded for _E. coli_ isolates from water has been reported in Greece, with the relevant isolates exhibiting resistance to an impressive 10 groups of antibiotics [32]. It is perhaps worth noting that Greece reports one of the highest consumptions of antibiotics in Europe, both in the community and hospital sector [68]. In more detail, in the year 2019, Greece reported a total of 34.1 defined daily doses (DDD) of antibiotics per 1000 inhabitants per day, with the average in EU/EEA being 19.4 DDD. The relevant percentage recorded in the community the same year in Greece was 32.4 DDD, which indicates broad non-nosocomial antibiotic usage [69]. Certain findings become perhaps more alarming given that the highest antibiotic consumption in Greece refers to broad-spectrum antibiotics, particularly penicillins, third- and fourth-generation cephalospors, and fluoroquinolones [68].