Presence of Listeria monocytogenes in Ready-to-Eat Artisanal Chilean Foods

Abstract

Ready-to-eat (RTE) artisanal foods are very popular, but they can be contaminated by Listeria monocytogenes. The aim was to determine the presence of L. monocytogenes 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). Listeria monocytogenes 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 (n = 8) of the strains were further characterized for evaluation. The antibiotic resistance profile was determined by the CLSI methodology, and the virulence genes hlyA, prfA, and inlA were detected by PCR. Genotyping was performed by pulsed-field gel electrophoresis (PFGE). Listeria monocytogenes 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 (p > 0.05). All the L. monocytogenes strains (n = 8) amplified the three virulence genes, while six strains exhibited premature stop codons (PMSC) in the inlA 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 L. monocytogenes 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.

Virulence and Antibiotic Resistance Genes in Listeria monocytogenes Strains Isolated From Ready-to-Eat Foods in Chile

“…In the present study, general positivity for L. monocytogenes in RTE foods was 3.1% (14/436). Positivity for L. monocytogenes in RTE foods in different countries has been reported as 5.5% in China ( Li et al, 2018 ), 7.5% in Chile ( Bustamante et al, 2020 ), 11.9% in Uruguay ( Braga et al, 2017 ), 8.5% in Turkey ( Sanlibaba et al, 2018 ), and 13.5% in Poland ( Szymczak et al, 2020 ). Bustamante et al (2020) reported prevalence values of 17.5, 8.6, and 8.5% in prepared meals and dishes, pre-processed fruits and vegetables, and cooked meats, respectively.…”

“…Positivity for L. monocytogenes in RTE foods in different countries has been reported as 5.5% in China ( Li et al, 2018 ), 7.5% in Chile ( Bustamante et al, 2020 ), 11.9% in Uruguay ( Braga et al, 2017 ), 8.5% in Turkey ( Sanlibaba et al, 2018 ), and 13.5% in Poland ( Szymczak et al, 2020 ). Bustamante et al (2020) reported prevalence values of 17.5, 8.6, and 8.5% in prepared meals and dishes, pre-processed fruits and vegetables, and cooked meats, respectively. Furthermore, positivity for L. monocytogenes was 0% in dairy products and cheeses, which concurs with the present study, and this situation is noteworthy because dairy products and cheeses have been associated in recent years with many outbreaks in Europe and the United States ( Fretz et al, 2010 ; Amato et al, 2017 ; Martínez-Rios and Dalgaard, 2018 ; Churchill et al, 2019 ).…”

“…This is a cause for concern because previous reports in Chile have indicated the susceptibility of L. monocytogenes to ampicillin and also because ampicillin and amoxicillin are currently used to treat this infection ( Seoane, 2013 ; Kumaraswamy et al, 2018 ). Several authors have encountered resistance to ampicillin in L. monocytogenes strains isolated from raw and cooked meats and fish products with a prevalence between 6 and 83% ( Yucel et al, 2005 ; Jamali et al, 2013 ; Arslan and Baytur, 2019 ; Bustamante et al, 2020 ; Maćkiw et al, 2020 ). Emerging resistance to penicillin in clinical strains poses a major public health concern because penicillin is the standard treatment for human listeriosis ( Martínez et al, 2001 ).…”

“…In Europe and North America, invasive listeriosis affects 0.3–0.6 persons per 100,000 inhabitants annually ( Maertens de Noordhout et al, 2017 ; European Centre for Disease Prevention and Control [ECDC], 2018 ). In Chile, L. monocytogenes has been under mandatory laboratory notification and surveillance since 2005 ( Bustamante et al, 2020 ). There were 97 cases in 2018 and 69 in 2019 with lethality of 22% and 26%, respectively ( MINSAL: Ministerio de Salud Chile, Departamento de Estadísticas e Información en Salud [DEIS], 2019 ).…”

Influence of Food Matrices and the Population of Interfering Microorganisms on the Determination of Listeria monocytogenes by Conventional Methods and VIDAS

“…Various works recently compared some of these methods. Bustamante et al (2020) [ 9 ] isolated L. monocytogenes according to the ISO 11290-1:2017 standard, detected with the VIDAS and identified by PCR (polymerase chain reaction), in ready-to-eat artisanal Chilean foods. Additionally, Ríos-Castillo et al (2020) [ 10 ] studied the capacity of real-time PCR (RT-PCR), the VIDAS and conventional methods for detecting L. monocytogenes biofilm cells.…”