Genome-Based Characterization of Listeria monocytogenes, Costa Rica.

Genomic data on the foodborne pathogen Listeria monocytogenes from Central America are scarce. We analyzed 92 isolates collected during 2009-2019 from different regions in Costa Rica, compared those to publicly available genomes, and identified unrecognized outbreaks. Our findings suggest mandatory reporting of listeriosis in Costa Rica would improve pathogen surveillance.

Calidad microbiológica de embutidos crudos: estudio del caso en Latinoamérica / Microbiology of raw sausages: a case of study in Latin America

Introducción. Los embutidos crudos se componen de carne fragmentada y otros ingredientes no cárnicos (sal, especias, fosfatos, nitritos) pero cuya formulación varía según el país; son productos altamente perecederos y podrían representar un riesgo para el consumidor. Objetivo. Los embutidos frescos son de alto consumo en varios países de Latinoamérica, por ello, el objetivo de esta revisión bibliográfica es compilar la información disponible sobre la calidad microbiológica de este tipo de productos en la región. Materiales y métodos. Se realizó una búsqueda de literatura (desde el 2006 a la fecha) en las principales bases de datos. Resultados. Se determinó que la calidad microbiológica de los embutidos crudos latinoamericanos no es adecuada según la reglamentación. Las bacterias más estudiadas son los microorganismos totales aerobios mesófilos (MTAM), y las bacterias ácido-lácticas (BAL); estos dos grupos son los referentes para determinar la vida útil. Los patógenos más analizados son Salmonella spp. y Listeria monocytogenes y llama la atención que Staphyloccoccus aureus no se utiliza como indicador de malas prácticas de higiene o de inocuidad. Conclusiones. En general se confirma que los embutidos frescos podrían ser un riesgo para la salud pública ya que presentan recuentos microbiológicos altos, en ocasiones no regulados. Algunos agentes antimicrobianos como los compuestos etanólicos de propóleos (EEP), compuestos fenólicos y bacteriófagos han sido estudiados. Sin embargo, no está claro si a nivel artesanal este tipo de ingredientes son utilizados del todo. Finalmente, destaca la necesidad de armonizar las metodologías de estudio y la normativa vigente en los distintos países(AU)

Introduction. Raw sausages are products composed of comminuted meat and other non- meat ingredients (salt, spices, phosphates, nitrites) but the formulation varies in each country. Given this nature, raw sausages are highly perishable and may represent an important risk for consumers. Aim. As raw sausages are highly consumed in many Latin-American countries, the objective of this literature review was to compile the available information about studies of the microbial quality of these products in the region. Materials and methods. For that purpose, a literature search was performed on main data bases to compile studies from 2006 to nowadays. Results. In general, it was found that microbiological quality of Latin-American raw sausages is not adequate according to current regulation. Total aerobic mesophilic microorganisms (TAMM) and Lactic Acid Bacteria (LAB) were the most studied indicators; these two groups are the main reference to establish shelf life. Salmonella spp. and Listeria monocytogenes were the most studied pathogens, and it is noticeable that Staphyloccoccus aureus is not used as an indicator for safety or manipulation. Conclusions. It is perceived that raw sausages in the region could represent a public health risk as they frequently present high microbiological counts, not regulated in many cases. For conservation, antimicrobial agents as propolic ethanoplic extracts (PEE), phenolyc compounds, and bacteriophages have been studied. However, it is not clear if these ingredients are used at the artisanal level, even though it can be assumed that they are not given the high microbial numbers that are reported. Finally, it stands out the need of harmonization of methodologies and current regulation in the countries(AU)

Peptaibol Production and Characterization from Trichoderma asperellum and Their Action as Biofungicide.

Peptaibols (Paib), are a class of biologically active peptides isolated from soil, fungi and molds, which have interesting properties as antimicrobial agents. Paib production was optimized in flasks by adding sucrose as a carbon source, 2-aminoisobutyric acid (Aib) as an additive amino acid, and F. oxysporum cell debris as an elicitor. Paib were purified, sequenced and identified by High-performance liquid chromatography (HPLC)coupled to mass spectrometry. Afterward, a Paib extract was obtained from the optimized fermentations. The biological activity of these extracts was evaluated using in vitro and in vivo methods. The extract inhibited the growth of specific plant pathogens, and it showed inhibition rates similar to those from commercially available fungicides. Growth inhibition rates were 92.2, 74.2, 58.4 and 36.2% against Colletotrichum gloeosporioides, Botrytis cinerea, Alternaria alternata and Fusarium oxysporum, respectively. Furthermore, the antifungal activity was tested in tomatoes inoculated with A. alternata, the incidence of the disease in tomatoes treated with the extract was 0%, while the untreated fruit showed a 92.5% incidence of infection Scanning electron microscopy images showed structural differences between the fungi treated with or without Paib. The most visual alterations were sunk and shriveled morphology in spores, while the hyphae appeared to be fractured, rough and dehydrated.

Effect of the type of packaging on the shelf life of ground rabbit meat.

Rabbit meat consumption has increased worldwide due to its health benefits in humans but few studies addressed the stability of this food matrix. The effect of two types of packaging (vacuum, VP; and polystyrene tray overwrap with PVC/polyvinyl plastic film, PT) was evaluated on the microbial stability (psychrotrophic; PSY, lactic acid bacteria; LAB, initial coliforms counts) and physicochemical (pH, thiobarbituric acid reactive substances (TBARS), total volatile basic Nitrogen (TBV-N), color and drip loss) changes of ground rabbit meat during its storage at 4 ± 1 °C. VP packaging delayed PSY growth, lipid oxidation, protein degradation and undesirable color changes compared to PT samples. Shelf life of ground rabbit meat in vacuum condition could be around 10 days of storage, while PT samples presented a shorter shelf life of around 5 days. However, sensory studies must be performed in order to assure the exact shelf life of the final product.

First characterization of the probiotic potential of lactic acid bacteria isolated from Costa Rican pineapple silages.

BACKGROUND: Agro-industrial waste from tropical environments could be an important source of lactic acid bacteria (LAB) with probiotic potential. METHODS: Twelve LAB isolates were isolated from pineapple silages. The species identification was carried out considering 16S rRNA and pheS genes. Experiments to evaluate the probiotic potential of the isolates included survival under simulated gastrointestinal environment, in vitro antagonistic activity (against Salmonella spp. and Listeria monocytogenes), auto-aggregation assays, antibiotic susceptibility, presence of plasmids, adhesiveness to epithelial cells, and antagonistic activity against Salmonella in HeLa cells. RESULTS: Lacticaseibacillus paracasei, Lentilactobacillus parafarraginis, Limosilactobacillus fermentum, and Weissella ghanensis were identified. Survival of one of the isolates was 90% or higher after exposure to acidic conditions (pH: 2), six isolates showed at least 61% survival after exposure to bile salts. The three most promising isolates, based on survivability tests, showed a strong antagonistic effect against Salmonella. However, only L. paracasei_6714 showed a strong Listeria inhibition pattern; this isolate showed a good auto-aggregation ability, was resistant to some of the tested antibiotics but was not found to harbor plasmids; it also showed a high capacity for adhesion to epithelial cells and prevented the invasion of Salmonella in HeLa cells. After further in vivo evaluations, L. paracasei_6714 may be considered a probiotic candidate for food industry applications and may have promising performance in acidic products due to its origin.

Microbiological Safety and Presence of Major Mycotoxins in Animal Feed for Laboratory Animals in a Developing Country: The Case of Costa Rica.

Safety and quality of compound feed for experimental animals in Costa Rica is unknown. Some contaminants, such as Salmonella spp. and mycotoxins, could elicit confounding effects in laboratory animals used for biomedical research. In this study, different batches of extruded animal feed, intended for laboratory rodents in Costa Rica, were analyzed to determine mycotoxin and microbiological contamination (i.e., Salmonella spp., Escherichia coli, total coliform bacteria, and total yeast and molds enumeration). Two methods for Salmonella decontamination (UV light and thermal treatment) were assessed. Only n = 2 of the samples were negative (representing 12.50%) for the 26 mycotoxins tested. Enniatins and fumonisins were among the most frequent toxins found (with n = 4+ hits), but the level of contamination and the type of mycotoxins depended on the supplier. None of the indicator microorganisms, nor Salmonella, were found in any of the tested batches, and no mold contamination, nor Salmonella growth, occurs during storage (i.e., 2-6 months under laboratory conditions). However, mycotoxins, such as enniatins and fumonisins tend to decrease after the fourth month of storage, and Salmonella exhibited a lifespan of 64 days at 17 °C even in the presence of UV light. The D-values for Salmonella were between 65.58 ± 2.95 (65 °C) and 6.21 ± 0.11 (80 °C) min, and the thermal destruction time (z-value) was calculated at 15.62 °C. Results from this study suggest that laboratory rodents may be at risk of contamination from animal feed that could significantly affect the outcomes of biomedical experiments. Thus, improved quality controls and handling protocols for the product are suggested.

Presence of Listeria monocytogenes in Ready-to-Eat Meat Products Sold at Retail Stores in Costa Rica and Analysis of Contributing Factors.

ABSTRACT: Listeria monocytogenes is a pathogenic bacterium associated with ready-to-eat (RTE) meat products sold at the retail level. The objective of this research was to determine the prevalence of L. monocytogenes in RTE meat products sold at retail in Costa Rica and to study the factors associated with the levels of contamination; analyzed factors include hygienic practices within stores (cutting techniques and microbial contamination of products) and the behavior of the isolates (persistence against antimicrobials and transfer potential). A total of 190 samples of RTE meat products were collected and analyzed for the presence of coliforms and Listeria spp. Isolates of L. monocytogenes were then evaluated in terms of resistance to disinfectants (quaternary ammonium compound [QAC] and chlorine) and their transfer potential from food contact surfaces (knife and cutting boards). Overall Listeria spp. prevalence was 37.4% (71 of 190); Listeria innocua was present in 32.1% (61 of 190) of the products, and L. monocytogenes was found in just 2.6% (5 of 190) of the samples. Most contaminated samples were cut with a knife at the moment of purchase (44.2%). When analyzing practices within the stores, it was observed that L. monocytogenes transfer from inoculated knife to salchichón was higher for samples cut at the beginning of the experiment. In addition, L. monocytogenes transfer from inoculated cutting boards was independent of the number of slices but contamination from plastic was higher than wood. Regarding L. monocytogenes resistance to disinfectants, average reductions of 2.6 ± 1.1 log CFU/mL were detected after 6 min of exposure to 200 ppm of chlorine; however, chlorine resistance varied among the strains. Prevalence of L. monocytogenes in RTE meat products sold at retail could be associated with handling practices within the stores; further studies are necessary to estimate the impact of these practices on the overall risk for consumers.

Short communication: Effect of different kefir grains on the attributes of kefir produced with milk from Costa Rica.

Kefir is an artisanal product that is gaining scientific attention due to its increase in consumption attributed to its potential health benefits. The effect on the quality attributes of kefir grains of different origin (household and commercial) and preserved with different methods (drying and freezing) was evaluated to standardize a domestic and semi-industrial process. Chemical (protein, lactose. lactic acid, ethanol, and acetic acid) as well as microbial properties (total plate count and total yeast count) were monitored during the experiment. Results show a statistical difference between the kefir grains in terms of acetic acid and ethanol percentages, which leads to the conclusion that there is a difference in the microbial populations that produce these products. Lactic acid, protein, and lactose parameters are statistically the same as well as the growth in biomass and the total population of yeast. Our results suggest that both types of kefir grains maintain a similar performance and that their metabolic capabilities are stable throughout time (taking into account that the household grains have been productive for years), meaning that domestic or semi-industrial processes could be easily standardized.

Pet Food Quality Assurance and Safety and Quality Assurance Survey within the Costa Rican Pet Food Industry.

Costa Rican animal feed production is continually growing, with approximately 1,238,243 metric tons produced in 2018. Production-wise, pet cat and dog food are in fifth place (about 41,635 metric tons per year) amongst animal feeds, and it supplies up to 90% of the national market. Pet food production has increased as a response to the increase in the population of dogs and cats in Costa Rica, where 50.5% of households own at least one dog and indicates more responsible ownership in terms of feeding pets. Part of the process of making dry pet food involves a thermal process called extrusion, which is capable of eliminating the microbial load. However, extrusion can compromise nutritional quality to some extent by denaturing proteins, oxidizing lipids, and reducing digestibility. The objective of this study was to evaluate the quality and safety of dry pet food and to assess the effect of the extrusion process on digestibility and the quality of proteins, amino acids, and fatty acids. Pet food samples were collected before and after extrusion and were used to evaluate Good Manufacturing Practices (GMP), based on Central American Technical Regulation (RTCA 65.05.63:11). In general terms, weaknesses in infrastructure, documentary evidence, and post-process practices were observed in two Costa Rican feed manufactories. Feed safety was surveyed through the analysis of Salmonella spp., Escherichia coli, Listeria spp., Staphylococcus aureus, aerobic mesophilic microorganisms, fungi, and yeasts counts. The extrusion process effectively reduced pathogenic microorganisms, and showed no effect on the digestibility of dog food (p = 0.347), however, it could reduce the availability of some nutrients (e.g., amino acids, fatty acids). Furthermore, a retrospective diagnosis was made for puppy food (n = 68), dog food (n = 158), and cat food (n = 25), to evaluate the history of nutritional quality and safety. Finally, it can be confirmed that the correct implementation of GMP allows feed manufacturers to deliver a product of optimum texture, smell, nutritional composition, and safety.

Antimicrobial activity of different sodium and potassium salts of carboxylic acid against some common foodborne pathogens and spoilage-associated bacteria / Actividad antimicrobiana de diferentes sales de ácidos carboxílicos de sodio y potasio contra algunos microorganismos patógenos y de deterioro asociados a alimentos

Cleaning and disinfection represent the most important activities associated with the elimination of dirt and microorganisms at food processing plants. Improper procedures may lead to cross contamination of food leading to its spoilage or even the transmission of foodborne pathogens. Several strategies have been used in order to achieve a good disinfection of sursalts; faces and products; nevertheless, microbial resistance to common-use-products has developed Potassium lately. Due to this fact, the development of new non-toxic-food compatible chemical agents that reduce the impact of foodborne pathogens and spoilage causing microorganisms is desirable for the food industry. The objective of the present study was to evaluate the antimicrobial activity of different sodium and potassium salts of aliphatic and aromatic carboxylic acid on the growth of common food spoilage and pathogenic microorganisms. Growth curves were determined for Leuconostoc mesenteroides, Lactobacillus plantarum, Enterococcus faecalis, Candida albicans, Pseudomonas aeruginosa, Salmonella Enteritidis, and Listeria monocytogenes in contact with different concentrations of carboxylic acid salts. The inhibitory effect of both aliphatic and aromatic carboxylic acid salts, in accordance with concentration levels, was 100 > 50 > 25 mg/ml. The inhibitory effect of aliphatic salts was butanoic > hexanoic> octanoic > decanoic and, benzoic > gallic > caffeic acid salts for aromatic salts. In general, sodium salts were more inhibitory than potassium salts (p < 0.05).

La limpieza y la desinfección representan las actividades más importantes asociadas a la eliminación de suciedad y microorganismos de las plantas procesadoras de alimentos. El uso de procedimientos incorrectos puede llevar a la contaminación cruzada de los alimentos y, por ende, al deterioro de estos o a la transmisión de patógenos de origen alimentario. Se han desarrollado varias estrategias con el fin de obtener una buena desinfección de superficies y productos; no obstante, ha aparecido resistencia microbiana frente a productos de uso común. Debido a esto, el desarrollo de agentes químicos no tóxicos capaces de reducir el impacto de patógenos de origen alimentario y microorganismos causantes de deterioro es deseable para la industria alimentaria. El objetivo de este estudio fue evaluar la actividad antimicrobiana de diferentes sales de sodio y potasio de ácidos carboxílicos alifáticos y aromáticos sobre algunos microorganismos patógenos y asociados a deterioro alimentario, analizando su impacto sobre el crecimiento. Se determinaron las curvas de crecimiento de Leuconostoc mesenteroides, Lactobacillus plantarum, Enterococcus faecalis, Candida albicans, Pseudomonas aeruginosa, Salmonella enteritidis y Listeria monocytogenes en presencia de diferentes concentraciones de las sales de ácidos carboxilicos. El efecto inhibitorio de las sales de ácidos carboxilicos alifáticos y aromáticos, según su nivel de concentración, se ordenó del siguiente modo: 100mg/ml > 50mg/ml > 25 mg/ml. El efecto de las sales de ácidos alifáticos siguió el orden butanoico > hexanoico > octanoico > decanoico, en tanto que las de ácidos aromáticos se ordenó del siguiente modo: benzoico > gálico >cafeico. En general, las sales de sodio fueron más inhibitorias que las de potasio (p < 0,05).

Antimicrobial activity of different sodium and potassium salts of carboxylic acid against some common foodborne pathogens and spoilage-associated bacteria.

Cleaning and disinfection represent the most important activities associated with the elimination of dirt and microorganisms at food processing plants. Improper procedures may lead to cross contamination of food leading to its spoilage or even the transmission of foodborne pathogens. Several strategies have been used in order to achieve a good disinfection of surfaces and products; nevertheless, microbial resistance to common-use-products has developed lately. Due to this fact, the development of new non-toxic-food compatible chemical agents that reduce the impact of foodborne pathogens and spoilage causing microorganisms is desirable for the food industry. The objective of the present study was to evaluate the antimicrobial activity of different sodium and potassium salts of aliphatic and aromatic carboxylic acid on the growth of common food spoilage and pathogenic microorganisms. Growth curves were determined for Leuconostoc mesenteroides, Lactobacillus plantarum, Enterococcus faecalis, Candida albicans, Pseudomonas aeruginosa, Salmonella Enteritidis, and Listeria monocytogenes in contact with different concentrations of carboxylic acid salts. The inhibitory effect of both aliphatic and aromatic carboxylic acid salts, in accordance with concentration levels, was 100>50>25mg/ml. The inhibitory effect of aliphatic salts was butanoic>hexanoic> octanoic>decanoic and, benzoic>gallic>caffeic acid salts for aromatic salts. In general, sodium salts were more inhibitory than potassium salts (p≤0.05).

First isolation report of Arcobacter cryaerophilus from a human diarrhea sample in Costa Rica.

Arcobacter cryaerophilus is an emerging enteropathogen and potential zoonotic agent transmitted by food and water. In Costa Rica, this bacterium has not been associated with cases of human gastroenteritis, even though it has been isolated from farm animals, especially poultry. This paper reports the first isolation of A. cryaerophilus from a human case of bloody watery diarrhea and the virulence genes associated with this isolate.

Arcobacter Isolation from Minced Beef Samples in Costa Rica.

The presence of Arcobacter spp. in minced meat (including beef) samples has been well documented in different countries, with varying frequencies. Nevertheless, the only Latin American country reporting this bacterium in minced beef samples is Mexico, with a 28.8% frequency in 2003. Previous studies in Costa Rica have demonstrated the presence of Arcobacter species in samples taken from the poultry production chain, but still there are no studies performed in bovine meat. The aim of this study was to determine the frequency of this bacterium in 120 samples of minced beef acquired from the Central Valley region of Costa Rica and to describe the antibiotic sensitivity pattern of the isolates obtained. A total of 75 different Arcobacter strains were isolated from minced beef samples, for a final frequency of 48.3%. After species PCR identification, the strains were classified as A. butzleri (37.3%), A. cibarius (14.7%), A. thereius (12%), and Arcobacter spp. (36%). All samples were sensitive to gentamicin but were resistant to ampicillin, levofloxacin, nalidixic acid, and ciprofloxacin. The results obtained in this study show that the frequency of isolation of Arcobacter in minced beef samples is high and that there is a high resistance rate for antibiotics in common use. This suggests that Arcobacter represents a health risk for Costa Rica and that control measures should be developed to decrease its potential impact.

Isolation and Identification of Arcobacter Species from Costa Rican Poultry Production and Retail Sources.

Arcobacter is a gram-negative rod recognized as a potential food- and waterborne pathogen; nevertheless, little is known about the effects of this pathogen on human and animal health. Although Arcobacter species are commonly found in nature, poultry is suspected to be the main vehicle for the transmission of this pathogen. The aims of this work were to determine the prevalence of Arcobacter spp. in broilers produced in Costa Rica for human consumption and to analyze the pathogenic capacity of the isolates through the detection of virulence genes. One hundred fifty-two samples of cecal content (87 farms), 104 samples of carcass rinse after chiller (six processing plants), and 96 carcass rinses from as many retail stores were analyzed. The suspicious isolates were identified using genus-specific PCR, and species-level identification was achieved with a multiplex PCR. Virulence genes were identified using the protocol described by L. Douidah, L. de Zutter, J. Baré, P. De Vos, P. Vandamme, O. Vandenberg, A.-M. Van den Abeele, and K. Houf (J. Clin. Microbiol. 50:735-741, 2012), which includes nine different virulence genes. The overall isolation frequency of Arcobacter was 6.5% (n = 23). Eight (34.8%) of the isolates came from cecal content, 2 (8.7%) were isolated from samples taken after chiller, and 13 (56.5%) were from retail stores. The species isolated included A. thereius (30.4%), A. butzleri (21.7%), A. skirrowii (4.3%), and A. cibarius (4.3%). The remaining samples were classified as Arcobacter sp. Gene tlyA was the most prevalent virulence gene, present in 9 of 23 samples analyzed; genes hecA and pldA were present in one only strain each. A strain of A. butzleri isolated from a retail store presented the highest number of virulence genes (five), and 11 samples did not present any of the genes analyzed. The results obtained suggest that the presence of virulent Arcobacter isolates in the poultry production chain from Costa Rica could be a risk for individuals who consume the contaminated product.

Capacidad de formación de biopelículas de cepas de Listeria monocytogenes aisladas a partir de queso tierno de origen costarricense / Biofilm formation capacity of Listeria monocytogens strains isolated from soft cheese from Costa Rica

Listeria monocytogenes, además de ser un género capaz de producir una enfermedad infecciosa grave en el hombre, puede formar biopelículas en distintas superficies relacionadas con el ambiente de producción alimentario. Éstas constituyen un serio problema debido a que son una fuente importante y constante de contaminación para los alimentos y el ambiente de producción, además de que las bacterias presentes en ellas poseen una aumentada resistencia hacia agentes físicos y químicos de uso frecuente. En el presente trabajo se estudió la capacidad de formación de biopelícula de cepas de L. monocytogenes previamente aisladas a partir de queso tierno bajo diferentes condiciones de temperatura y cultivo. Se utilizó una técnica de microplaca con diferentes medios de cultivo (CICC, CTS 1:20 y suero de queso) a diferentes temperaturas de incubación (refrigeración, ambiente y 35ºC). La capacidad de formación de biopelícula fue clasificada según la densidad óptica obtenida a 620 nm. Ninguna de las cepas evaluadas fue clasificada como formadora fuerte de biopelicula bajo ninguna de las variables estudiadas, sí se detectaron formadoras débiles y moderadas. Los resultados obtenidos ponen de manifiesto la influencia del contenido de nutrientes en el medio de cultivo sobre la formación de biopelícula, no obstante, el CICC fue el único medio que permitió la expresión de formadores moderados. Por el contrario, el suero de queso resultó poco favorecedor. La formación de biopelícula es un proceso multifactorial, donde el nivel de adsorción depende de gran cantidad de variables y cuyo estudio debe fomentarse, de manera que se desarrollen metodologías que permitan su reducción o eliminación, de manera que las industrias alimentarias aseguren productos inocuos y de buena calidad microbiológica.

Listeria monocytogenes is a bacteria associated with the production of severe infectious disease in human being, but also with the formation of biofilms in different surfaces related to the food production environment. Biofilm represents a serious problem in food industry, since it is a constant and important contamination source and also, bacteria present in it have an increased resistance towards physical and chemical agents of common use. The capacity of biofilm formation of L. monocytogenes strains previously isolated from soft cheese samples from Costa Rica was studied under different temperature and culture conditions. The microplate technique was performed using different culture media (BHIB, TSB 1:20 and cheese serum) and at different incubation temperatures (refrigeration, environmental and 35ºC). Biofilm formation capacity was classified according to the optical density obtained at 620nm. None of the strains evaluated was classified as strong biofilm former under any of the variables studied, nevertheless, weak and moderate formers were detected. The results obtained show the influence of the nutrient content of the culture media used over biofilm formation; BHIB was the only culture media that allowed the expression of moderate biofilm forms, contrary to cheese serum that did not promote biofilm production. Biofilm formation is a multifactorial process, where adsorption level depends on several variables and its study must be promoted in order to develop methodologies that allow its reduction or elimination, so food industries may offer safe food products to consumers.

[Biofilm formation capacity of Listeria monocytogens strains isolated from soft cheese from Costa Rica]. / Capacidad de formación de biopelículas de cepas de Listeria monocytogenes aisladas a partir de queso tierno de origen costarricense.

Listeria monocytogenes is a bacteria associated with the production of severe infectious disease in human being, but also with the formation of biofilms in different surfaces related to the food production environment. Biofilm represents a serious problem in food industry, since it is a constant and important contamination source and also, bacteria present in it have an increased resistance towards physical and chemical agents of common use. The capacity of biofilm formation of L. monocytogenes strains previously isolated from soft cheese samples from Costa Rica was studied under different temperature and culture conditions. The microplate technique was performed using different culture media (BHIB, TSB 1:20 and cheese serum) and at different incubation temperatures (refrigeration, environmental and 35 degrees C). Biofilm formation capacity was classified according to the optical density obtained at 620 nm. None of the strains evaluated was classified as strong biofilm former under any of the variables studied, nevertheless, weak and moderate formers were detected. The results obtained show the influence of the nutrient content of the culture media used over biofilm formation; BHIB was the only culture media that allowed the expression of moderate biofilm forms, contrary to cheese serum that did not promote biofilm production. Biofilm formation is a multifactorial process, where adsorption level depends on several variables and its study must be promoted in order to develop methodologies that allow its reduction or elimination, so food industries may offer safe food products to consumers.