## 4 Discussion  
_P. mirabilis_ causes a wide range of infections and its spread is owed to an inherent translocation capability using peritrichous flagellar. Moreover, _P. mirabilis_ harbors a considered arsenal of exoenzymes as urease, protease and hemolysis and strong biofilm formation capability [6, 40]. In the current study, we aimed to evaluate the effects of metronidazole on bacterial pathogenesis by challenging the virulence of highly resistant _P. mirabilis_ isolated from diabetic foot ulcers. Metronidazole is the most globally used nitroimidazole antimicrobial agent, it is usually prescribed to anaerobic infection and is considered as gold standard which all other anaerobic acting antibiotics should be referenced [28, 29]. Metronidazoleare interacts with bacterial DNA and consequently inhibits the bacterial protein synthesis. Metronidazoleare has activity on wide range of bacteria and its use possess several advantages as good tissue penetration, rapid bacterial killing and low cost [29]. In order to evaluate the effect of metronidazoleare on _P. mirabilis_ virulence, we used metronidazoleare in sub-MICs to avoid any effect on bacterial growth. In a previous work, metronidazoleare and secnidazole which harbor similar chemical moiety were efficiently able to curtail the _Pseudomonas aeruginosa_ pathogenesis [41, 42]. Obviously, metronidazoleare has no influence at all on the bacterial growth. The proteolytic enzyme protease cleaves various essential proteins as casein, secretory components, serum albumin and gelatin. Furthermore, protease is able to breakdown 2 classes of immunoglobulins A and G which facilitate the spread of microbial infection and lowering the defense of the host [43, 44]. Urease enzyme is a significant virulence factor that is used by pathogens of urinary and gastrointestinal tracts as _P. mirabilis_. While the production of urease is constitutive in most strains of _P. mirabilis_, it is inducible in some strains by pH changes [6, 44, 45]. Its capability to recycle the nitrogenous compounds enhances the resistance to several biocides [43, 45]. Importantly, the degraded urea due to urease provides an alkaline optimal condition for protease action and in turn increase the microbial spread and increase the production of both urease and protease in repeated cycles [6, 46]. The cytotoxicity of hemolysin that is encoded by 2-component secretion system _hpm_BA genes greatly enhance _P. mirabilis_ pathogenesis [6, 47]. These three enzymes, protease, hemolysis and urease play crucial roles in the spread of bacterial infection especially in lack of efficient immunity as in diabetic foot ulcers [10, 20]. Significantly, metronidazoleare in sub-MIC reduced the production of _P. mirabilis_ exoenzymes protease, urease and hemolysins. The _P. mirabilis_ invading ability to epithelial cells is fundamentally owed to swarmer cells but not vegetative cells [6, 44]. Flagellum dependent _P. mirabilis_ motilities (swarming and swimming) facilitate the spread of infection and formation of biofilms [7, 48]. Moreover, the formation of hyperflagellated swarmer cells is linked to significant increases in the production of other virulence factors as protease and urease [45, 49]. It was suggested a close correlation between biofilm formation and bacterial motility; as the formation of biofilms is decreased in the non-motile bacteria [8]. As a consequence, the bacterial biofilm formation capability beside its motility result in spreading of infection and enhancing of