PCR Assay for Detection of Staphylococcus aureus in Fresh Lettuce (Lactuca sativa)

Abstract

The growth in food demand and production growth of vegetables have led to the development of intensive production systems with the aim of having regular access to enough high-quality food. The aim is to determine the incidence of Staphylococcus aureus in fresh letuce by PCR in order to enhance the eiciency for detection and identiication process. The Baird-Parker method was used for isolating pathogens from 54 letuce samples. Genomic DNA extraction was performed according the Mericon DNA Bacteria Plus Kit. The detection by PCR was performed using the pair of primers: coa gene (5′-ATAGAGCTGATGGTACAGG-3′ and 5′-GCTTCCGATTGTTCGATGC-3′). The phylogenetic tree was constructed by comparing conserved sequences from the adjacent 16S gene, using the F2C 5′-AGAGTTTGATCATGGCTC-3′ and C 5′-ACGGGCGGTGTGTAC-3′ primers. To test the antimicrobial efect, we used the disk difusion method (Kirby-Bauer) using Mueller-Hinton agar and ive antibiotics with diferent concentrations. The incidence of S. aureus was 1.7%. All the isolates were situated in the ATCC 11632 clade in accordance with other reported sequences belonging to this pathogen in the NCBI database. All the isolates seemed to be resistant to penicillin (10U). The molecular techniques used in this study are suitable for the identiication of S. aureus isolated from letuce, increasing our capability of detecting this pathogen by improving the process and increasing the eiciency contributing to the safety of this vegetable.