## 4 Discussion
The results of other studies show a high variability in _Listeria monocytogenes_ resistance to antibiotics. [PERSON] et al. [40] reported that the _Listeria monocytogenes_ strains were resistant to tetracycline (27.9%), ampicillin (20.9%), cephalothin, penicillin G, and streptomycin (each 16.3%), while all strains were susceptible to cefotaxime, gentamicin, kanamycin, and pefloxacin. Similarly, [PERSON] et al. [44] reported that _Listeria monocytogenes_ strains from fish and environmental samples were highly resistant to penicillin (38.1%), ampicillin (38.5%), tetracycline (18.7%), and vancomycin (20.9%), with all the strains being of serotypes 1/2a and 4b, which are commonly associated with foodborne listeriosis in humans. In contrast, other researchers [53,54] reported that _Listeria monocytogenes_ strains were sensitive to the antibiotics examined. Similarly, [PERSON] and [PERSON] [36] conducted a study in Poland and observed that most of the _Listeria monocytogenes_ strains from fresh and smoked fish samples were sensitive to most of the antibiotics tested, including the trimethoprim/sulfamethoxazole combination,erythromycin, and gentamycin. In the present study, resistant strains to ceftaxone, clindamycin, and oxacillin were also identified. Two of the strains were multidrug-resistant. The reporting of high rates of resistance to vancomycin is a public health concern as this antibiotic is used for the treatment of meningitis and endocarditis due to _Listeria monocytogenes_ infection [55]. However, all _Listeria monocytogenes_ strains were susceptible to the trimethoprim/sulfamethoxazole combination, which is the antibiotic of choice for listeriosis treatment in patients who are allergic to penicillin [55]. Antibiotic-resistant _Listeria monocytogenes_ strains have previously been reported to cause severe life-threatening disease, as in the case of neonatal meningitis in an infant in Greece [56]. Antibiotic resistance profiles of foodborne _Listeria monocytogenes_ strains from the same area have been reported in different food commodities. Specifically, [PERSON] and [PERSON] [57] reported that 92.6% of the strains isolated from cheese showed intermediate resistance to ciprofloxacin and 7.4% showed resistance to erythromycin, ciprofloxacin, or meropenem. Similarly, [PERSON] et al. [29] report that among six strains isolated from bulk milk tanks, all were resistant to penicillin and clindamycin, whereas no strain was characterized as being resistant to vancomycin. The resistance profiles of the present study are distinct from the ones reported by [PERSON] and [PERSON] [57] and [PERSON] et al. [29], which implies that the fish production chain is more susceptible to antibiotic-resistant _Listeria monocytogenes_ strains; still, more research is needed on this topic. Although the rates of multidrug-resistant _Listeria monocytogenes_ foodborne strains are low, there appears to be a significant increase in the emergence of resistant _Listeria monocytogenes_ strains from food and its processing environment, which necessitates vigilance [55]. All _Listeria monocytogenes_ strains were able to produce biofilms. According to the literature, there is a lack of data on the production of biofilms by strains collected from fresh fish and their processing facilities. In the study by [PERSON] et al. [58] concerning _Listeria monocytogenes_ in fresh ready-to-eat seafood samples from Japan, they observed that after multiple sampling they could still isolate identical _Listeria monocytogenes_ serotypes from the same fish-processing plant, therefore suspecting the formation of biofilms; the ability to produce biofilms was observed in all strains examined. Also, [PERSON] et al. [59] evaluated the biofilm production ability of 106 _Listeria monocytogenes_ strains and reported that most of them had moderate or weak biofilm production ability.