Presence of <i>Listeria monocytogenes</i> in Ready-to-Eat Artisanal Chilean Foods

• Main Authors: Fernanda Bustamante, Eduard Maury-Sintjago, Fabiola Cerda Leal, Sergio Acuña, Juan Aguirre, Miriam Troncoso, Guillermo Figueroa, Julio Parra-Flores
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: Microorganisms
• Subjects: <i>Listeria monocytogenes</i>; artisanal ready-to-eat foods; food safety; antibiotic resistance profile; virulence; premature stop codons
• Online Access: https://www.mdpi.com/2076-2607/8/11/1669

Ready-to-eat (RTE) artisanal foods are very popular, but they can be contaminated by <i>Listeria monocytogenes</i>. The aim was to determine the presence of <i>L. monocytogenes</i> in artisanal RTE foods and evaluate its food safety risk. We analyzed 400 RTE artisanal food samples requiring minimal (fresh products manufactured by a primary producer) or moderate processing (culinary products for sale from the home, restaurants such as small cafés, or on the street). <i>Listeria monocytogenes</i> was isolated according to the ISO 11290-1:2017 standard, detected with VIDAS equipment, and identified by real-time polymerase chain reaction (PCR). A small subset (<i>n</i> = 8) of the strains were further characterized for evaluation. The antibiotic resistance profile was determined by the CLSI methodology, and the virulence genes <i>hlyA, prfA,</i> and <i>inlA</i> were detected by PCR. Genotyping was performed by pulsed-field gel electrophoresis (PFGE). <i>Listeria monocytogenes</i> was detected in 7.5% of RTE artisanal foods. On the basis of food type, positivity in minimally processed artisanal foods was 11.6%, significantly different from moderately processed foods with 6.2% positivity (<i>p</i> > 0.05). All the <i>L. monocytogenes</i> strains (<i>n</i> = 8) amplified the three virulence genes, while six strains exhibited premature stop codons (PMSC) in the <i>inlA</i> gene; two strains were resistant to ampicillin and one strain was resistant to sulfamethoxazole-trimethoprim. Seven strains were 1/2a serotype and one was a 4b strain. The sampled RTE artisanal foods did not meet the microbiological criteria for <i>L. monocytogenes</i> according to the Chilean Food Sanitary Regulations. The presence of virulence factors and antibiotic-resistant strains make the consumption of RTE artisanal foods a risk for the hypersensitive population that consumes them.