Genetic Diversity of <em>Listeria monocytogenes</em> in Fruits and Vegetables: Environmental Persistence and Antimicrobial Resistance

Background/Objectives: Listeria monocytogenes is a foodborne pathogen that can infect humans and animals, causing non-invasive gastrointestinal listeriosis or invasive listeriosis. The objectives of this study were to determine: the genetic diversity of L. monocytogenes; the genes associated with the resistance to antibiotics, benzalkonium chloride (BC), and CdCl2, and biofilm formation. Methods: Seventeen strains of L. monocytogenes isolated fresh fruits and vegetables were selected for this study. Genetic diversity and the genes associated with antibiotic resistance were determined by PCR amplification. Susceptibility to antibiotics were determined using the agar diffusion method. Resistance to BC and CdCl2 was determined using the minimum inhibitory concentration method. Capacity for biofilm formation was evaluated using the crystal violet staining method. Results: This study demonstrates that the isolates of L. monocytogenes belong to serotypes 1/2a (29.4%) and 1/2b (70.5%). Potential hypervirulent strains containing 70.5% Listeria pathogenicity island 1 (LIPI-1-2), 17.6% (LIPI-1-3), and 11.7% (LIPI-1-4) were also identified. Antibiotic susceptibility tests show that L. monocytogenes exhibit six different multiresistant patterns with a MAR index of &sup3; 0.46 (70.5%); besides, the gen Ide, tetM, and msrA were detected in 52.9%, 29.4%, and 17.6%, respectively, associated with efflux pump Lde, tetracycline and ciprofloxacin resistance. Phenotypic test shows that 58.8% cadmium-resistant L. monocytogenes have a co-resistance to BC of 23.5%. Subsequently, all strains of L. monocytogenes exhibited moderate biofilm. Conclusions: This study contributes to the persistence and genetic diversity of strains L. monocytogenes isolated fresh fruits and vegetables; in addition, resistance to CdCl2 and correlation with co-resistance to BC disinfectant used in the food industry.