**5. Conclusion**

**Figure 5.** Phylogenetic tree of *S. aureus* maximum verisimilitude constructed from partial sequences of 16S ribosomal

**Figure 6.** Tests of antibiotic susceptibility; 1: positive control (*Staphylococcus aureus* ATCC11632), 2: isolated 1, 3: isolat‐ ed 2. (a) Oxacillin 1 μg, (b) trimethoprim‐sulfamethoxazole 25 μg, (c) penicillin G 10 U, (d) tetracycline 30 μg, and (e)

For *coa* gene, the temperature gradient showed that 56°C was the optimal annealing temper‐ ature (*T*a) for oligonucleotides, showing an adequate specificity for the detection of *S. aureus*. The *T*a is defined as the highest temperature where the optimal aligning and amplification occur [53]; this parameter is crucial for the standardization of the method because a low *T*<sup>a</sup> can cause nonspecific amplification, giving undesired PCR products; this is when two or more bands are observed in gel electrophoresis. In this study, the primers features and the correct

DNA of 2 prokaryotic clones and 17 reference sequences obtained from NCBI.

clarithromycin 15 μg.

156 Frontiers in Frontiers in Staphylococcus Aureus *Staphylococcus aureus*

**4. Discussion**

The molecular techniques used in this study are suitable for the identification of *S. aureus* isolated from lettuce, increasing our capability of detecting this pathogen by improving the process and increasing the efficiency, contributing to the safety of this vegetable.
