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The study aimed to identify the sources involved in the transference of Staphylococcus aureus along the chain production of pasteurized Queso‐Fresco (QF) in one cheese‐processing plant (CPP) in Northwestern Mexico. Eighty‐six samples were collected in the CPP from QF, worker's hands, raw milk, dairy‐products and utensils. The Bacteriological Analytical Manual was used to detect and enumerate S. aureus, and the Pulsed‐Field‐Gel Electrophoresis to genetically relate the strains. S. aureus was found in 18.6% (16/86) of the samples; raw milk (20%), utensils (13.6%) and hands (10.5%) were identified as bacterial sources reflecting its high prevalence (55.6%) and levels in QF samples, which differs from the Mexican legislation (<3.0 Logcfu/g). The genotypic analyses showed nine SmaI‐patterns; one of them represented a predominant clone in QF samples, and the remaining profiles suggested the existence of multiple contamination sources at the CPP. Food handlers were the main carriers of bacterium causing final QF contamination. Practical Applications The number of small‐scale cheese‐processing plants in Northwestern Mexico has increased during the past decade. Combining traditional cheese making and good hygiene practices is a challenge, since several human pathogens pose hazard in the product. S. aureus is an important food poisoning pathogen that can be transmitted via raw milk and/or via hands to cheese. Mexican population regularly consumes handcrafted cheeses, and there is a lack of information on health issues. Surveillance safety programs complemented by the use of molecular tools allow tracing bacterial contamination, and might aid to correct the cheese‐processing plants, also improve the design of adequate hygienic and manufacturing practices to accredit the Queso‐Fresco safety and health regulation.

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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 30ºC. 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.

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Fresh and marine waters are frequently affected by microbiological contamination resulting from anthropogenic activities, including agricultural, industrial, urban (CONAGUA, 2018), and livestock activities (Hathaway et al., 2011). Similarly, the influence of effluent from wastewater treatment plants as a vehicle for the dissemination of microorganisms has been described (Kotlarska et al., 2015). Microbiological contamination can prevail when receiving water bodies compromise the environmental and sanitary quality of these resources (Stone et al., 2008). Exposure to water contaminated with infectious agents increases the risk of contracting gastrointestinal (GI) infections during recreational or irrigation use (World Health Organization, 2016). The World Health Organization (WHO) estimates that 842 000 cases of deaths occur worldwide due to GI diseases associated with inadequate water, which represents 1.5% of the total disease burden and 58% of diarrhoeal diseases (

Palabras clave: bacterias, diseminación, antibiotipos, agua 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.Key words: bacteria, dissemination, antibiotypes, water 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 Rev. Int. Contam. Ambie. 34