Abstract Salmonella is a pathogenic bacterium considered a threat to the food industry, its timely detection being relevant. The objective of the study was to evaluate the real-time polymerase chain reaction coupled to immunomagnetic separation (rtPCR-IMS) as an alternative method to the Official Mexican Standard (NOM-114-SSA1-1994) for the detection of Salmonella in beef. The parameters evaluated were limit of detection, sensitivity, specificity, selectivity (inclusivity and exclusivity) and degree of agreement between both methods for the detection of Salmonella in presumptive and artificially contaminated beef samples. The incidence of Salmonella in presumptive beef samples (n= 60) ranged from 20.0 to 21.6 % by both methods. In the inoculated samples (n= 60), the detection rate of Salmonella by rtPCR-IMS (93.3 %) and NOM-114-SSA1-1994 (98.3 %) showed a match of 56 occasions with a negative deviation. The comparison of rtPCR-IMS and NOM-114-SSA1-1994 in beef reported an accuracy of 98.3 %, sensitivity of 98.2 %, specificity of 100 % and selectivity of 100 %. The limit of detection for both methods was 1-5 CFU·25 g-1 of beef. The statistical analysis indicates that the rtPCR-IMS is equivalent to the reference method for the detection of Salmonella in beef. These results warn of the high incidence of Salmonella in beef and propose rtPCR-IMS as an ideal and fast method for the control of Salmonella in the meat industry.

Resumen Salmonella es una bacteria patógena considerada una amenaza para la industria alimentaria, siendo relevante su detección oportuna. El objetivo del estudio fue evaluar la reacción en cadena de polimerasa en tiempo real acoplado a separación inmunomagnética (rtPCR-IMS) como método alternativo a la Norma Oficial Mexicana (NOM-114-SSA1-1994) para la detección de Salmonella en carne de res. Los parámetros evaluados fueron límite de detección, sensibilidad, especificidad, selectividad (inclusión y exclusividad), y grado de concordancia entre ambos métodos para la detección de Salmonella en muestras de carne de res presuntivas y contaminadas artificialmente. La incidencia de Salmonella en las muestras presuntivas de carne (n= 60) osciló de 20.0 a 21.6 % por ambos métodos. En las muestras inoculadas (n= 60), la tasa de detección de Salmonella por rtPCR-IMS (93.3 %) y NOM-114-SSA1-1994 (98.3 %) mostró una coincidencia de 56 ocasiones con una desviación negativa. La comparación de rtPCR-IMS y NOM-114-SSA1-1994 en carne de res reportó una exactitud de 98.3 %, sensibilidad de 98.2 %, especificidad de 100 % y selectividad de 100 %. El límite de detección para ambos métodos fue 1-5 UFC·25 g-1 de carne. El análisis estadístico indica que el rtPCR-IMS es equivalente al método de referencia para la detección de Salmonella en carne de res. Estos resultados advierten la alta incidencia de Salmonella en carne de res y proponen al rtPCR-IMS como un método idóneo y rápido para el control de Salmonella en la industria cárnica.

Abstract The formulation of diets from vegetable protein enriched with immunostimulants is a suitable feeding strategy for shrimp culture. This study evaluated a feed formulated with wheat (Tritium sativum) and chickpea (Cicer arietinum) enriched with spirulina (Spirulina maxima) for shrimp Litopenaeus vannamei farming. A feed based on wheat and chickpea (2.5:1) containing 3% spirulina was developed and characterized by proximal chemical analysis. The experimental feed was evaluated along with a commercial feed in a five-week field bioassay to determine the growth, survival, and health status of the juvenile shrimp. In addition, water salinity (mg-L-1) was monitored as an environmental stability factor for shrimp cultures. The proximal chemical composition of the experimental feed contained 17.5 ±0.1% protein, 2.2 ±0.3% lipids and 68.0 ±0.3% carbohydrates. The specific growth rate (0.22 ±0.05 g-days-1) of the shrimp under experimental feed did not show statistical differences in comparison with the commercial feed (P> 0.05). Also, it was determined that the shrimp fed with experimental feed presented a biomass production (0.74 ±0.17 g), survival rate (>98%) (P <0.05) and health status better than shrimp fed with commercial feed. The influence of salinity on shrimp survival was rule out (P> 0.05). This study demonstrated that the experimental feed offers a suitable diet in benefit of the performance and health of the shrimp.

ABSTRACT Vibrio parahaemolyticus is recognized as a human pathogen as well as the causative agent of vibriosis in shrimp. This study determined the pathogenic, antimicrobial, and biotic potential of V. parahaemolyticus isolated from white shrimp (Penaeus vannamei) and seawater on a northwestern Mexico farm. A total of 140 samples were randomly collected, including juvenile organisms (n = 120) and seawater (n = 20). The pH, salinity, and biota of the ponds were used to correlate with bacterium presence. The strains were characterized by virulence genes presence, biofilm formation capacity, antimicrobial sensitivity, and the kinetics growth using PCR, microplates method, minimum inhibitory concentration (MIC), and spectrophotometry, respectively. V. parahaemolyticus was detected in 7.1% of the samples with a mean concentration of 3.72 1.24 log CFU mL-1; 6.7% (8/120) in shrimp and 10.0% (2/20) in seawater. Cultivation conditions were not predictive of the specie (P > 0.05). V. parahaemolyticus showed an adaptation time of 1.0 h, and a growth rate of 0.375 h−1 in seawater at 30°C. The strains were classified into two pathotypes: tlh+/tdh−/trh−/AP2− (75%) and tlh+/tdh−/trh−/AP2+ (25%) and three resistant profiles to clinical drugs (ampicillin, amikacin, gentamicin, and netilmicin). The MIC values against oxytetracycline (OTC), florfenicol (FFC) and enrofloxacin (ENRO) were >0.50, >0.25 and >0.06 μg mL−1, respectively. Biofilm formation was a property identified in 40% of the strains. The presence of infectious V. parahaemolyticus with high adaptative potential justifies integrating integrated aquaculture practices and management to control pathogen growth and shrimp health.

Abstract The nature, production and consumption of cold cuts and sausages define these foods as vulnerable to contamination by pathogenic microorganisms that cause foodborne diseases. The aim of the study was to evaluate the influence of the bulk sale of cold cuts and sausages, on the hygienic quality and prevalence of L. monocytogenes and Salmonella. Thus, 96 samples of sausages (sausage and ham) from 15 national brands were collected and classified by type of sale: original package (n= 48) and bulk (n= 48). The detection of total coliforms, Escherichia coli, Salmonella, and L. monocytogenes was analyzed by traditional culture method. 42.7 % (41/96) of the samples of cold cuts and sausages failed to comply with the sanitary specifications in terms of total coliforms and E. coli. The statistical analysis showed that the type of sale is an indicator of the microbial risk in cold cuts and sausages (χ2 = 40.0, P= 0.000), since the number of samples with poor hygienic quality was higher for bulk sales (69.0%) compared to those sold in packages (17.0 %). Additionally, the risk analysis showed that bulk sale increases 41.8 and 5.9 times the risk of acquiring ham and frankfurters of poor microbiological quality (P<0.05), respectively, while the type of sales did not influence the presence of L. monocytogenes (6.3 %). Consumers are advised to avoid bulk sale of cold cuts and sausages, and producers and sellers should reinforce good hygienic practices that will ensure food safety, and minimize the risk of infection.

Resumen La naturaleza, producción y consumo de los embutidos definen al alimento como vulnerable, a la contaminación con microorganismos patógenos que propicien enfermedades transmitidas por los alimentos. El objetivo del estudio fue evaluar la influencia de la venta a granel de embutidos, sobre la calidad higienica y la prevalencia de L. monocytogenes y Salmonella. Para ello, se recolectaron 96 muestras de embutidos (salchicha y jamón) de 15 marcas nacionales, y se clasificaron equitativamente por tipo de venta; paquete original (n= 48) y granel (n= 48). La detección de coliformes totales, Escherichia coli, Salmonella, y L. monocytogenes se analizó mediante cultivo tradicional. El 42.7 % (41/96) de las muestras de embutidos estuvieron fuera de especificación sanitaria en términos de coliformes totales y E. coli. El análisis estadístico mostró que el tipo de venta es un indicador del riesgo microbiano en embutidos (χ2=40.0, P=0.000), ya que el número de muestras con deficiente calidad higiénica fue mayor para la venta a granel (69.0 %) comparada con las que se venden en paquete (17.0 %). Adicionalmente, el análisis de riesgo mostró que la venta a granel incrementa 41.8 y 5.9 veces el riesgo de adquirir jamón y salchichas de mala calidad microbiológica (P<0.05), respectivamente. Mientras que, el tipo de venta no influenció la presencia de L. monocytogenes (6.3 %) en las muestras. Se recomienda a los consumidores evitar la compra a granel de los embutidos; y los productores y vendedores deben reforzar las buenas prácticas higiénicas que permitirán asegurar la inocuidad, y minimizar el riesgo de infecciones.

ABSTRACT Salmonella is one of the main causes of bacterial gastroenteritis and its presence and survival in aquatic ecosystems has been reported. This, coupled with the indiscriminate use of antibiotics in human and agricultural activities, could favor the emergence and dissemination of resistant strains in these environments. Therefore, the objective of this study was to determine antibiotic resistance (AR) in 111 Salmonella strains classified in 28 non-typhoid serotypes, isolated from rivers in northwestern Mexico. The disk diffusion method was used for the evaluation of a panel of 16 antibiotics, as recommended by the Clinical and Laboratory Standards Institute. Of the strains analyzed, 50.5 % (56/111) were resistant to at least one antibiotic and 41.1 % (23/56) presented multiresistance. The majority (87.5%) of the serotypes presented AR, mainly to ampicillin, neomycin, and chloramphenicol. The antibiogram revealed 26 AR patterns among the Salmonella strains. The Salmonella serotypes Oranienburg and Saintpaul, showed a great diversity of AR patterns. These findings improve knowledge about the AR Salmonella serotypes of aquatic origin. In addition, they suggest the potential risk that the rivers in northwestern Mexico serve as reservoirs and sources of propagation of this bacterium between different hosts or environments.

RESUMEN Salmonella es una de las principales causas de gastroenteritis bacteriana y se ha reportado su presencia y sobrevivencia en ecosistemas acuáticos. Esto, aunado al uso indiscriminado de antibióticos en actividades humanas y agropecuarias, podría favorecer la aparición y diseminación de cepas resistentes en estos ambientes. Por ello, el objetivo de este trabajo fue determinar la resistencia a antibióticos (RA) en 111 cepas de Salmonella clasificados en 28 serotipos no tifoideos, aislados de ríos del noroeste de México. Se utilizó el método de difusión en disco para la evaluación de un panel de 16 antibióticos, según lo recomendado por el Instituto de Estándares Clínicos y de Laboratorio. El 50.5 % (56/111) de las cepas fueron resistentes al menos a un antibiótico y el 41.1 % (23/56) de las cepas presentaron multirresistencia. La mayoría (87.5 %) de los serotipos presentaron RA, principalmente a ampicilina, neomicina, y cloranfenicol. El antibiograma reveló 26 patrones de RA entre las cepas de Salmonella. Los serotipos de Salmonella Oranienburg y Saintpaul mostraron gran diversidad de patrones de RA. Estos hallazgos mejoran el conocimiento sobre los serotipos de Salmonella RA de origen acuático. Además, sugieren el riesgo potencial de que los ríos del noroeste de México sirvan como reservorios y fuentes de propagación de esta bacteria entre diferentes hospederos o ambientes.