*2.10. Determination of Total Phenolic Content (TPC)*

TPC was determined by the Folin-Ciocalteu method reported previously with some modification [29]. The appropriate dilutions of samples (200 μL) were mixed with 1 mL of 0.5 M Folin–Ciocalteu reagent at room temperature (23 ± 1 ◦C) for 4 min, and then reacted with 800 μL of saturated sodium carbonate solution (75 g/L) in dark for 2 h. Finally, the absorbance of the reaction mixtures was measured at 760 nm with a spectrophotometer (181712007PC, Shanghai Jing Hua Co. Ltd., Shanghai, China) and quantified on the base of the standard curve of gallic acid (0.01–0.1 mM). The results were expressed as milligram gallic acid equivalent (mg GAE)/g DW extract powder. All tests were performed in triplicate.

## *2.11. Statistical Analysis*

All the measurements were performed in triplicate, and the results were expressed as mean ± standard deviation (SD). Statistical analysis was performed using Microsoft Excel 2016 (Microsoft, Seattle, MA, USA) and SPSS 22.0 (IBM SPSS Statistics, IBM Corp, Somers, NY, USA). Pearson linear correlation analysis and principal component analysis (PCA) were performed to analyze relationships among parameters, and *p* value less than 0.01 was defined as statistical significance.

#### **3. Results**

#### *3.1. Verification of Drug-Resistant Bacteria*

The antibiotic-resistant strains of *S. aureus* and *S. enteritidis* were isolated from food samples in our lab previously. In order to confirm their antibiotic resistance, we first tested their resistance to 11 common antibiotics from different categories. The breakpoint concentration of each antibiotic defined by CLSI and corresponding bacterial resistance spectra are shown in Table 2. All tested bacteria were resistant to antibiotics. Except for *S. aureus* SJTUF 20827 and *S. aureus* SJTUF 20973, the remaining bacteria were identified as multi-drug resistant bacteria, resistant to at least three antibiotics. These bacteria showed the highest resistance rate to erythromycin, reaching up to 83.3%, followed by ciprofloxacin (75%), Clindamycin (75%), gentamicin (50%), and streptomycin (50%). However, no strain resistant to oxacillin (methicillin-resistant *Staphylococcus aureus*, MRSA) was detected. Overall, it was confirmed that all selected bacteria were antibiotic-resistant, most of which were multi-drug resistant.


