Montserrat Hernández-Iturriaga

La carne de ave es una fuente de enfermedades transmitidas por alimentos causadas por Salmonella. Este estudio tuvo como objetivo determinar el virulotipo, la resistencia antimicrobiana y la formación de biopelículas de Salmonella aislada de pollo crudo comercializado en Jalisco, México. Se analizaron los genes de virulencia por PCR y la susceptibilidad antimicrobiana por el método de Kirby-Bauer para 195 aislamientos de Salmonella enterica; la formación de biopelículas se investigó para tres aislamientos en acero inoxidable a 9, 14 y 25 ºC. Todos los aislamientos portaban un conjunto conservado de genes de virulencia cromosómicos. El gen sspH1 se detectó en 55 % de los aislamientos, sopE en 23 %, pero pefA y spvC estuvieron ausentes, lo que sugiere variabilidad genética en el potencial patogénico. El virulotipo Vb fue más prevalente y se asoció con muestras de supermercados y la temporada cálida (P<0.05). El 79 % de los aislamientos mostraron resistencia a tetraciclina, 78 % a ácido nalidíxico, 76 % a cloranfenicol, 27 % a cefalosporinas de tercera generación y 12 % a ciprofloxacino; 79 % fueron multirresistentes. La multirresistencia se asoció con virulotipos específicos y con el punto de venta. La formación de biopelículas fue dependiente de la cepa y la temperatura (P<0.05), pero no de la microbiota nativa. La carne de pollo comercializada en supermercados y mercados es una fuente de Salmonella con genes de virulencia cromosómicos conservados, alta multirresistencia y resistencia a antimicrobianos críticos. Estos resultados son útiles para modelos de evaluación cuantitativa de riesgo microbiológico que estimen la persistencia y exposición asociadas al patógeno en productos avícolas.

Global dissemination of emergent multidrug-resistant (MDR) Salmonella Infantis (ESI) is of great public health concern. ESI exhibits increased virulence and MDR phenotypes, features conferred by a conjugative megaplasmid (pESI-like). In Mexico, the potential circulation of ESI clones has been overlooked. This study assessed the structure, diversity, genomic features and transmission dynamics of Salmonella Infantis isolates ( n =191) from cattle, pigs, chickens, humans, surface waters and the environment from surveys conducted by research laboratories and government agencies in the 2008–2024 timeframe. Three genomic approaches were implemented: blast analysis, SNP-based phylogenetic analysis and ancestral state reconstruction analysis. The phylogeny divided the population into two divergent sublineages, based on the presence/absence of pESI-like plasmids. The apparently recent and massive acquisition of these plasmids had a profound impact at the population level, changing the proportion of isolates with MDR genotypes from 0 to 68%. Although ESI was mostly associated with chickens, it was also present in surface waters. In fact, our ancestral state reconstruction analysis showed that ESI likely evolved from surface water ancestors within poultry production environments. Most locally circulating ESI clones (73%) harbour resistance factors to 6–8 antibiotic classes, including extended-spectrum cephalosporins ( bla _CTX-M-65 ) and fluoroquinolones ( gyrA D87Y mutation), a feature shared with global ESI variants that we coined as CTX-M-gyrA 6-8. Control measures are urgently needed to prevent further dissemination of ESI, as well as the systematic surveillance of CTX-M-gyrA 6-8 clones, particularly in poultry, to reduce the risk of human exposure to this potentially deadly pathogen.

The objective of this study was to determine the presence of quaternary ammonium compound (QAC) resistance genes in Listeria spp. strains and to evaluate the effect of temperature and substrate on interspecies gene transfer. A total of 23 L. monocytogenes strains, four L. innocua and 37 Listeria spp. isolates (excluding L. grayi, L. ivanovii, L. seeligeri, and L. welshimeri) were recovered from surfaces in a frozen vegetable processing facility. The presence of the bcrABC gene was assessed by endpoint PCR. The bcrABC gene was detected in 73.91% (17/23) of L. monocytogenes isolates, in 50.00% (2/4) of L. innocua strains and was not detected in the other Listeria species (0/37). Two L. innocua strains carrying the bcrABC gene and two L. monocytogenes strains lacking it were selected for mixed culture experiments. Four co-cultures were prepared, inoculated into tryptic soy broth and spinach extract, and incubated at 4, 25, and 36 °C for 10 days. Horizontal transfer of the bcrABC gene was observed in 7.87% (17/216) of reactions in tryptic soy broth and spinach extract, with higher frequencies at 25 °C (10/216, 4.63%) and 36 °C (6/216, 2.78%) and lower frequencies at 4 °C (1/216, 0.46%). Recipient L. monocytogenes strains revealed increased resistance to QACs (500 μg/mL).

El objetivo fue caracterizar el perfil fenotípico y genotípico de resistencia a antimicrobianos (RAM) en Salmonella enterica (SE) aislada de pollo en la Ciudad de México, así como el evaluar la relevancia epidemiológica de los aislamientos obtenidos. Se tomaron muestras de muslo y pierna de pollo en 160 puntos de venta (supermercados y pollerías). Se detectó SE en el pollo que se expende en la mayor parte de las alcaldías de la capital (13/16), con una frecuencia global de contaminación de 22 % (35/160). Se obtuvieron 39 aislamientos de nueve serotipos, siendo Infantis el más frecuente (n = 21). Las muestras positivas a SE se asociaron con el tipo de establecimiento. La frecuencia de contaminación fue más alta en las pollerías (28 %) que en los supermercados (13 %). Este fenómeno se asoció con la presencia de moscas en contacto con el pollo y la falta de refrigeración (P < 0.0001, prueba exacta de Fisher). Se observó resistencia a azitromicina en 39 % de los aislamientos, mientras que 69 % fue multidrogorresistente (MDR) y portó genes de RAM para múltiples clases de antibióticos: blaCMY-2, blaCARB-2, blaTEM, blaCTX-M, qnrAB, gyrA, mph(A), tetA, floR y varios alelos de aac, aadA, aph, sul, dfrA, fosA. Los aislamientos de todos los serotipos, excepto Mbandaka (n = 1), mostraron clonalidad (0–23 SNPs) con cepas clínicas de Estados Unidos de América. En conjunto, los resultados evidencian el papel del pollo como reservorio de cepas de SE de gran relevancia epidemiológica y con fenotipos MDR.

Este estudio analizó el cambio en los hábitos de consumo de alimentos en Querétaro durante el primer año de la pandemia de COVID-19 mediante una encuesta en línea. Hubo un aumento en el consumo de alimentos en casa y en pedidos a domicilio. Se registró un incremento notable en la ingesta de comida chatarra (300%), bebidas azucaradas (47.6%) y alcohólicas (60%), consumidas cinco o más veces por semana respecto al periodo previo a la pandemia. Además, incrementó la frecuencia de lavado (43.0%) y desinfección (70.2%) de manos, así como la desinfección de empaques (202.2%). La mitad de los participantes reportaron aumento de peso y alimentación no saludable, atribuidos a aburrimiento (31.3%) y ansiedad (28.6%).

Salmonella enterica is a major foodborne pathogen capable of surviving in low-water-activity (a _W ) foods and retaining the ability to invade intestinal epithelial cells after environmental stress, such as exposure to high salt concentrations. Although multiple serotypes tolerate low a _W , Tennessee strains have been repeatedly linked to outbreaks in dry foods, suggesting specific adaptations. This study evaluated the effects of NaCl (1%, 4%, and 6%) on growth, biofilm formation, post-biofilm recovery, and internalization capacity (Caco-2 cell assays) of six S. enterica strains—four Tennessee and two serogroup B isolates—from peanuts, raisins, chocolate, and dehydrated tomatoes. Growth and biofilm formation were monitored over a 7-day exposure to NaCl; post-biofilm recovery and internalization were assessed afterward. While all strains showed reduced internalization after salt exposure, Tennessee isolates generally maintained higher growth and biofilm formation than the ATCC 14028 reference strain. Phenotypic responses varied by strain and NaCl concentration, indicating differences in osmotic stress adaptation. The persistence of internalization capacity, even at reduced levels, highlights a potential food safety risk in NaCl-preserved products. These findings emphasize the need to consider strain-specific traits when developing control measures for Salmonella in dry food environments.

Bacterial biofilm production is linked to its adaptive capacity to environments throughout its lifecycle. This study aimed to assess the variability in biofilm formation (BF) dynamic by Salmonella enterica and to explore the potential impact of the cell’s prior history, primarily shaped by strain and its isolation source. In vitro BF of 141 S. enterica strains isolated from animal-origin foods, plant-based foods, unspecified food sources, the environment, and clinical cases, was evaluated using the crystal violet assay at 25 °C for up to 72 h. Kruskal–Wallis test was used to assess the effect of time, source, and strain. The Aryani method was used to characterize microbial response variability. The BF capacity of S. enterica strains ranged from 0.07 to 2.3, 0.07 to 2.7, and 0.06 to 2.7OD_595nm at 24, 48, and 72 h, respectively. At 24 h (66.0%; 93/141) and 48 h (56.0%; 79/141), most isolates were classified as nonbiofilm producers, while at 72 h, the majority were weak biofilm producers (39.7%; 56/141). Time, strain, and isolation source significantly influenced BF, with an overall increase in BF occurring over time, and clinical strains being the highest biofilm producers. Strain to strain variability was the highest contributor to the total variance ([ ] = 0.18OD_595nm ², [ ] = 0.23OD_595nm ², [ ] = 0.26OD_595nm ²). Analysis of variability between and within isolation source groups revealed the highest variability among clinical isolates ([ ] = 1.08OD_595nm ², [ ] = 1.36OD_595nm ², [ ] = 1.38OD_595nm ²). Although BF was statistically associated with the strain and its isolation source, the high variability observed within these factors suggests that they alone are insufficient to explain how the cell’s prior history influences BF. A more comprehensive undertanding on BF will require considering additional intrinsic and extrinsic factors.

There is a lack of information about Salmonella enterica strains under acidic conditions and their association with their genome. This study characterized intraspecies variability in the growth of 167 S . enterica isolates under two acid conditions (pH 4 and 5) and linked to the whole genome sequencing (WGS) data. A total of 1002 curves for each condition were obtained using turbidimetry measurements, and Baranyi and Roberts model was used to estimate the maximum rate of change (rc _max ; OD _{600 nm} h ⁻¹ ). Strains were categorized into slow, intermediate, and fast; and associations with their WGS data were performed. Huge variability in was observed at both conditions (pH 5 = 0.016–0.066 OD _600nm h ⁻¹ and pH 4 = 0.003–0.028 OD _600nm h ⁻¹ ). The majority of isolates was classified as intermediate (59.5% at pH 5 and 46.1% at pH 4). Strains classified as fast had a low frequency of allABCD genes at both pHs, and any of them having the presence of pefABCD , spvBCR , aadA2 , dfrA12 , and gyrA_D87G genes were linked to virulence or antimicrobial resistance. This study suggests that strains with fast capacity for growth under acidic conditions could have a fitness cost in their virulence or resistance potential. Practical Application: Data presented in this study could be used to select representative strains to evaluate the exposure assessment in different food items, mainly the growth and survival in acidic foods.