# Methicillin Resistance of Food-Borne Biofilm-Forming Staphylococcus-Crocei
## 4 Discussion  
In this study, the ability of 34 _Staphylococcus_ isolates recovered from RTE street foods to form biofilms was evaluated. This set included coagulase positive _Staphylococcus_ (CPS) as well as coagulase negative (CNS). The CNS have emerged as pathogens with risk potential for humans and animals similar to coagulase-positive _Staphylococcus_ (CPS) [12,18]. These isolates were selected from a group of 70 Staphylococcus received previously characterized by antibiotic resistance profile and presence of virulence and antibiotic resistance genes [12]. Some of these isolates (namely, _S. aureus_ isolate 68, _S. sapproplictivis_ isolate 19, and _S. xylosus_ isolate 65) are not only multidrug-resistant but also present more than one of the seven virulence genes investigated most associated with their pathogenicity. Three different surfaces were used, namely stainless steel, polystyrene, and glass surface. The methodology used was based on the removal of aggregated cells and enumeration of CFUs after plating (log CFU/cm\({}^{2}\)). Of the three tested surfaces, polystyrene was the surface on which both CPS and CNS showed the highest biofilm production. However, for each surface tested, no statistical differences were found between CPS and CNS isolates. There was a high and significant correlation between stainless steel and glass counts. This indicates that these two surfaces have similar properties related to biofilm adhesion. On the other hand, there was a low correlation between stainless steel and polystyrene, and between glass and polystyrene. This indicates differences in biofilm adhesion between polystyrene and the other two materials, glass, and stainless steel. Polystyrene is more hydrophobic and has low surface energy, while stainless steel is moderately hydrophilic and has a slight negative charge [7]. Therefore, polystyrene surfaces, which are naturally hydrophobic, promote greater adhesion of microbial cells when compared to other hydrophilic surfaces, such as stainless steel and glass [19]. In  
Figure 4: Logarithmic reductions (Log CFU/cm\({}^{2}\)) obtained after exposure of biofilms to five concentrations of methicillin, for 24 h at 37 \({}^{\circ}\)C. Means followed by the same letter do not differ statistically from each other, according to the Tukey test at a 5% probability level. Yellow horizontal line: Breakpoint of minimum biofilm eradication concentration (MBEC). a study using _S. epidermidis_, [PERSON] et al. (2014) [20] showed a decrease in biofilm formation on the cobalt-chromium molybdenum (Co-Cr-Mo) alloy, which was attributed to the increase in hydrophilicity in this alloy [20; 21]. However, other studies have shown opposite results. For instance, the yeast _C. albicans_ has been shown to have less metabolic activity on polycarbonate and stainless steel (hydrophilic surfaces) compared to Teflon (hydrophobic surface) [22]. Similarly, some studies claim that hydrophilicity has only trace impact on biofilm formation, as shown by the fact that _S. epidermidis_ biofilm formation was not significantly altered by differences in surface wettability [23]. Another determining factor that influences cell adhesion and biofilm production are the electrostatic interactions established between the surface and the cells due to the formation of an electrostatic double layer on each part [24]. The formation of this double layer depends on the ionic strength and the pH value of the surrounding medium. For example, _S. aureus_ has been described as adhering more to positively charged polymeric surfaces than to negatively charged ones [24; 25]. This observation corroborates our results, in which a greater production of biofilm was observed on polystyrene surfaces than on glass and stainless steel.