Angélica Godínez Oviedo

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.

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).

Green synthesis of gold nanoparticles (AuNPs) provides a significantly eco-friendly and low-impact counterpart to conventional chemical methods. In the present study, we synthesized gold nanoparticles using Schinus molle (P-AuNPs) aqueous extract as a reducing and stabilizing agent. The obtained nanoparticles were then stabilized by another biocompatible agent, the chiral amino acids L-cysteine (L-Cys-AuNPs) and D-cysteine (D-Cys-AuNPs), to estimate the potential of the surface modification for enhancing AuNPs surface chemistry and antimicrobial action. The synthesized gold nanoparticles were confirmed by UV-Vis spectroscopy, FTIR, XRD, and circular dichroism to validate their formation, crystalline structure, surface properties, and chirality. Physicochemical characterization confirmed the formation of crystalline AuNPs with size and morphology modulated by chiral functionalization. TEM and DLS analyses showed that L-cysteine-functionalized AuNPs were smaller and more uniform, while FTIR and circular dichroism spectroscopy confirmed surface binding and the induction of optical activity, respectively. L-Cys-AuNPs exhibited the highest antimicrobial efficacy against a broad spectrum of microorganisms, including Escherichia coli, Salmonella enterica, Listeria monocytogenes, Staphylococcus aureus, Staphylococcus epidermidis, and, notably, Candida albicans. L-Cys-AuNPs showed the lowest MIC and MBC values, highlighting the synergistic effect of chirality on biological performance. These findings suggest that L-cysteine surface engineering significantly enhances the therapeutic potential of AuNPs, particularly in combating drug-resistant fungal pathogens such as C. albicans. This research paves the way for the development of next-generation antimicrobial agents, reinforcing the relevance of green nanotechnology in the field of materials science and nanotechnology.

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%).

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.

Salmonella enterica is one of the most commonly reported foodborne pathogens by public health agencies worldwide. In this study, the multilocus sequence typing (MLST) population structure and frequency of antimicrobial resistance (AMR) genes were evaluated in S. enterica strains from Mexico ( n = 2561). The most common sources of isolation were food (44.28%), environment (27.41%), animal-related (24.83%), and human (3.48%). The most prevalent serovars were Newport (8.51%), Oranienburg (7.03%), Anatum (5.78%), Typhimurium (5.12%), and Infantis (4.57%). As determined by the 7-gene MLST scheme, the most frequent sequence types were ST23, ST64, and ST32. The core genome MLST scheme identified 132 HC2000 and 195 HC900 hierarchical clusters, with the HC2000_2 cluster being the most prevalent in Mexico ( n = 256). A total of 78 different AMR genes belonging to 13 antimicrobial classes were detected in 638 genomic assemblies of S. enterica. The most frequent class was aminoglycosides (31.76%), followed by tetracyclines (12.53%) and sulfonamides (11.91%). These results can help public health agencies in Mexico prioritize their efforts and resources to increase the genomic sequencing of circulating Salmonella strains. Additionally, they provide valuable information for local and global public health efforts to reduce the impact of foodborne diseases and AMR.