# Methicillin Resistance of Food-Borne Biofilm-Forming Staphylococcus-Crocei
## 3 Results
### Evaluation of Biofilm-Forming Ability on Tree Types of Surfaces  
In order to evaluate the ability of biofilm formation in three different materials, 18 isolates of _Staphylococcus_ spp. (8 CPS and 10 CNS) were used. On stainless-steel, the biofilm-forming ability expressed in Log (CFU/cm\({}^{2}\)) ranged between 4.58 \(\pm\) 0.02 and 6.86 \(\pm\) 0.02 in CPS isolates, and between 4.30 \(\pm\) 0.04 to 6.97 \(\pm\) 0.01 in CNS isolates (Table 3). In the glass, the results were between 6.30 \(\pm\) 0.01 and 7.66 \(\pm\) 0.01 log CFU/cm\({}^{2}\) in the CPS isolates, and between 6.10 \(\pm\) 0.01 and 7.67 \(\pm\) 0.03 log CFU/cm\({}^{2}\) in the CNS isolates (Table 3). On polystyrene, the biofilm-forming ability varied between 7.04 \(\pm\) 0.13 and 8.47 \(\pm\) 0.53 log CFU/cm\({}^{2}\) in CPS isolates, and between 6.68 \(\pm\) 0.11 and 8.13 \(\pm\) 0.05 log CFU/cm\({}^{2}\) in SCN isolates (Table 3). The lowest and highest production capacity on polystyrene were verified for the species _S. pasteuri_ where counts ranged from 6.64 log CFU/cm\({}^{2}\) to 9.72 log CFU/cm\({}^{2}\), followed by _S. xylosus_ with counts ranging from 7.53 log CFU/cm\({}^{2}\) to 9.4 log CFU/cm\({}^{2}\)) (Table 3). _S. pasteuri_ and _S. saprophyticus_ were the species with the highest biofilm productivity, with mean counts above 8 log CFU/cm\({}^{2}\) (Table 3). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Strain Code** & **Species** & **MIC (ug/mL)** & **MBC (ug/mL)** & **MBC/MIC** \\ \hline
11 & _S. aureus_ & 8 & 8 & 1 \\
15 & _S. aureus_ & 2 & 4 & 2 \\
32 & _S. aureus_ & 16 & 32 & 2 \\
47 & _S. aureus_ & 2 & 4 & 2 \\
48 & _S. aureus_ & 4 & 4 & 1 \\
49 & _S. aureus_ & 4 & 8 & 2 \\
50 & _S. aureus_ & 32 & \textgreater{}32 & - \\
52 & _S. aureus_ & 4 & 8 & 2 \\
53 & _S. aureus_ & 32 & \textgreater{}32 & - \\
68 & _S. aureus_ & \textgreater{}32 & \textgreater{}32 & - \\ \hline  
textgreater{}32 & - \\
30 & _S. xylosus_ & 4 & 4 & 1 \\
65 & _S. xylosus_ & 32 & \textgreater{}32 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 2: MIC and MBC of methicillin for _Staphylococcus_ isolates and MBC/MIC ratio. The comparison between means for CPS (_S. aureus_) and for CNS (the other species) were not significantly different (\(p>0.05\)) on the three surfaces used. However, when comparing the averages obtained for the biofilm-forming ability of the 18 isolates, the values obtained (log CFU/cm\({}^{2}\)) in polystyrene were significantly higher (\(p<0.05\)) than those obtained with the isolates on stainless steel (Figure 2). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Isolate Code**} & \multirow{2}{*}{**Species**} & \multicolumn{3}{c}{**Biofilm-Forming Ability (log CFU/cm\({}^{-2}\))**} \\ \cline{3-5}  & & **Stainless Steel** & **Glass** & **Polystyrene** \\ \hline  
\hline \hline \end{tabular}
\end{table} 
Table 3: Biofilm-forming ability of the _Staphylococcus_ isolates on three types of surfaces (stainless steel, glass, and polystyrene). Figure 1: Methicillin resistance profile (%) of _Staphylococcus_ isolates (susceptible—MIC \(\leq\) 4 \(\mu\)g/mL: resistant—MIC \(>\) 4 \(\mu\)g/mL). At least two biological replicates were performed, with two technical replicates each. The count values obtained on the three surfaces (log CFU/cm\({}^{2}\)) by the 18 isolates were transformed into rank orders and evaluated by principal component analysis (PCA) (Figure 3). The initial three-dimensional space (three variables-three surfaces) was reduced to a plane (Dim1/Dim2) defined by the two principal components that account for 85.3% of the variability of the data (51.5% in the first component and 33.8% in the second component). When the 18 isolates were projected in this plane (Dim1/Dim2), the biofilm-forming ability was not consistently determined on the three tested surfaces. The capacity for biofilm formation on polystyrene is positively correlated with Dim2, indicating that higher values of Dim2 correspond, in general, to an increase in the biofilm-forming ability of the isolates.