Mauricio Redondo-Solano

Microbial colonization is a major cause of deterioration in paintings, leading to discoloration, pigment degradation, and loss of structural integrity. While biodeterioration of artworks has been studied in temperate climates, tropical environments remain underexplored despite their high humidity and temperature, which can promote microbial growth. This study assessed the microbiological deterioration of two 18 ^th -century oil paintings, La Muerte de San José and Virgen de Guadalupe, located in Orosi’s Colonial Church and Religious Art Museum, Costa Rica. Microorganisms were isolated and identified using VITEK 2, microscopy, and matrix-assisted laser desorption ionization–time of flight mass spectrometry analysis, and their biofilm-forming capacity was evaluated. Additionally, the antimicrobial activity of six essential oil components was tested using direct and indirect contact assays. Seventeen bacterial taxa and 15 fungal genera were identified, with Bacillus , Staphylococcus , Cladosporium , and Aspergillus among the most common. Based on the fungal isolate-frequency distributions, Virgen de Guadalupe had a higher Shannon–Wiener diversity index than La Muerte de San José. Several isolates displayed strong biofilm formation, particularly Bacillus subtilis / amyloliquefaciens / vallismortis , and Staphylococcus saprophyticus . Linalool exhibited the strongest inhibitory activity, achieving complete bacterial growth inhibition in non-contact assays. Short-term environmental monitoring documented daily variation in temperature, relative humidity, and CO ₂ concentration during the 8-day measurement period. Together, these results characterize the culturable microorganisms recovered from two tropical heritage paintings and identify volatile essential oil components as candidates for further evaluation in preventive conservation. IMPORTANCE: Understanding the microbiological deterioration of cultural heritage in tropical environments is crucial for designing sustainable conservation strategies. While microbial colonization of artworks has been widely studied in temperate regions, data from tropical heritage settings remain limited. This study integrates microbiological, environmental, and physicochemical analyses to characterize culturable microorganisms recovered from 18 ^th -century oil paintings in Orosi, Costa Rica. By combining microbial identification, biofilm quantification, and essential oil biocide testing, it bridges applied microbiology and cultural heritage conservation. The in vitro inhibition of biofilm-forming bacteria by volatile compounds such as linalool in a non-contact assay supports further investigation of their potential in conservation, including their efficacy and compatibility with artwork materials. These findings provide a basis for future studies of microbial deterioration in tropical heritage settings and for evaluating conservation applications of volatile compounds.

Introducción: Las dietas frescas para mascotas son populares por su contenido nutricional y menor uso de aditivos. Sin embargo, se debe prestar atención a la inocuidad de estos alimentos, las bacterias ácido lácticas (BAL) podrían ser una opción para mejorar su conservación y reducir el uso de preservantes sintéticos. Objetivo: Evaluar la sobrevivencia y el crecimiento de Salmonella spp. y E. coli enterohemorrágica en carne de res, analizando el efecto de un bioconservante y el almacenamiento a bajas temperaturas. Materiales y métodos: Se trabajó con muestras de carne molida (10 g cada una). A todas las muestras se les realizó un análisis proximal con el fin de determinar sus características fisicoquímicas. Asimismo, se efectuó el recuento de coliformes totales, coliformes fecales y bacterias ácido lácticas (BAL). Se evaluó la sobrevivencia de Salmonella spp. y Escherichia coli enterohemorrágica en carne molida almacenada a -18 °C durante cuatro semanas. Además, se determinó la sobrevivencia de ambos patógenos a 4 °C y 10 °C durante siete días en presencia de Lactobacillus paracasei subsp. tolerans I-C1 y L. paracasei subsp. tolerans II-C2-C, evaluados como bioconservante. Todos los ensayos se realizaron por triplicado. Resultados: Los análisis fisicoquímicos y microbiológicos de las muestras de carne molida evidenciaron características adecuadas para la evaluación de la sobrevivencia bacteriana. Se encontró que ambos patógenos sobreviven a -18 °C durante cuatro semanas en las muestras inoculadas de carne molida. Cuando se evaluaron en presencia de los bioconservante a 4 °C hay una reducción de Salmonella spp. tanto en el control, como en los tratamientos, lo que sugiere que tanto la temperatura (4°C) como las BAL favorecen la reducción del patógeno, el mismo patrón se observó con E. coli. enterohemorrágica. Sin embargo, a 10 °C los resultados muestran un crecimiento de ambos patógenos de aproximadamente 3 log UFC/g para todos los tratamientos. Conclusiones: La aplicación de antimicrobiano podrían contribuir a mejorar la calidad e inocuidad en alimentos frescos para mascotas. Se señala la importancia de mantener la cadena de frío y realizar una adecuada descongelación del producto.

Acrylamide (AA) is a contaminant with carcinogenic and genotoxic properties that occur in heat-produced food products. This study aimed to evaluate the occurrence of AA in different coffee products commercially sold in retail markets of Costa Rica and to develop a probabilistic exposure assessment model to assess the potential human health risk due to its consumption. The average AA concentration in the coffee samples analyzed (n = 110) was 110.29 ± 151.61 µg kg⁻¹. The mean dietary exposure (DE) values, for the middle-bound (MB) approach, varied from 0.025 to 0.083 µg kg⁻¹ BW per day. The margin of exposure (MOE) was calculated with a BDML₁₀: 430 μg kg⁻¹ BW day⁻¹ for neurotoxicity and 170 μg kg⁻¹ BW day⁻¹ for cancer effect, according to EFSA (2015). No neurotoxicity risk was identified as MOE values ranged from 4291 to 467,984 for the adult male population, from 4566 to 477,203 for the adult females, from 4265 to 506,062 for the male minors and from 2512 to 495,151 for the female minors. On the other hand, MOE values for the carcinogenic risk were below 10,000 for the mean and P95th coffee consumers, denoting a possible health concern. The values ranged from 1696 to 6717 for the adult male population, from 1805 to 7201 for the female adults, from 1686 to 6304 for the male minors and from 993 to 2155 for the female minors. The mean incremental lifetime cancer risk (ILCR) values for male adult, female adult, male minor, and female minor were 1.7 × 10⁻⁵, 1.6 × 10⁻⁵, 1.9 × 10⁻⁵, and 3.9 × 10⁻⁵, respectively, for the MB approach. These results denote a potential or considerable risk in consumption of coffee due to AA intake. Thus, no neurotoxicity risk was identified; however, a potential carcinogenic risk was observed based on MOE and ILCR results.

Microbial colonization is a major cause of deterioration in paintings, leading to discoloration, pigment degradation, and loss of structural integrity. While biodeterioration of artworks has been studied in temperate climates, tropical environments remain underexplored despite their high humidity and temperature, which promote microbial growth. This study assessed the microbiological deterioration of two eighteenth-century oil paintings, La Muerte de San Jose and Virgen de Guadalupe, located in Orosi's Colonial Church and Religious Art Museum, Costa Rica. Microorganisms were isolated and identified using VITEK® 2, microscopy, and MALDI-ToF analysis, and their biofilm-forming capacity was evaluated. Additionally, the antimicrobial activity of six essential oil components was tested using direct and indirect contact assays. Twenty-three bacterial species and fifteen fungal genera were identified, with Bacillus, Staphylococcus, Cladosporium, and Aspergillus among the most common. Notably, La Virgen de Guadalupe displayed the highest microbial diversity, reflected in a high Shannon index, indicative of a more complex microbial community. Several isolates displayed strong biofilm formation, particularly Bacillus subtilis/amyloliquefaciens/vallismortis and Staphylococcus saprophyticus. Linalool exhibited the strongest inhibitory activity, achieving complete bacterial growth inhibition in non-contact assays. Environmental monitoring revealed persistently elevated relative humidity and CO2 levels during the study period. Together, these results reveal the complex microbial ecology of tropical heritage paintings and demonstrate that volatile essential oil components can serve as candidates for low-impact antimicrobial strategies in preventive conservation.

Background/Objectives: Milk and dairy products are among the most relevant foods both nutritionally and commercially. Costa Rica stands out as one of the main producers and consumers of dairy products in Central America. However, in recent years, the use of antibiotics in the livestock industry has increased, with implications for public health and food security, generating a need to monitor residues of these drugs in food. The present research focuses on developing a liquid chromatography method for the simultaneous quantification of penicillin G (PEN) and cloxacillin (CLO) in raw and commercial bovine milk, as well as in various dairy products, including fresh cheese and liquid yogurt. Methods/Results: During the validation of the methodology, average sensitivities of (960 ± 8)·10¹ mg L⁻¹ and (1580 ± 9)·10¹ mg L⁻¹ were achieved for PEN and CLO, respectively. Determination coefficients of 0.9995 and 0.9998 were also achieved, respectively. The limits of detection (LOD) and quantification (LOQ) for PEN and CLO were (0.330 ± 0.025) mg L⁻¹ and (0.65 ± 0.12) mg L⁻¹, (1.10 ± 0.083) mg L⁻¹ and (2.2 ± 0.4) mg L⁻¹, respectively, on both accounts. Recoveries were 68–77%, 92–106%, and 78–112% for PEN and 57–79%, 99–114%, and 95–120% for CLO in milk, cheese, and yogurt, respectively, across all three concentration levels evaluated. The precision of the method, in terms of reproducibility, was assessed for liquid yogurt (3–12% RSD_R for PEN and 4–12% RSD_R for CLO) and in cheese (8–14% RSD_R for PEN and 4–12% RSD_R for CLO). Nineteen bovine milk samples from the Cartago area were evaluated, including commercial and milk samples. Additionally, cheese (n = 17) and yogurt samples (n = 8) were analyzed. Conclusions: None of the samples showed detectable signals of the antibiotics. In addition, antibiotic sensitivity testing was performed on n = 9 Lactic Acid Bacteria (LAB) strains isolated from the raw milk samples, revealing the presence of some resistant traits to several antibiotics, including β-lactams.

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).

Listeria costaricensis was recently isolated from a food-processing facility. However, its pathogenic potential and persistence capacity remain poorly characterized at the phenotypic level, raising concerns about food safety. Therefore, we assessed its pathogenic potential through phenotypic invasion and adhesion assays in HeLa cells, showing that L. costaricensis cannot invade HeLa cells despite displaying a cell adhesion capacity comparable to that of Listeria monocytogenes and Listeria innocua reference strains. Given the industrial origin of the strain, we further evaluated its susceptibility to commonly used disinfectants by broth microdilution, finding susceptibility to a mixture of quaternary ammonium compounds (MIC < 100 µg/mL), and reduced susceptibility to peracetic acid (MIC > 160 µg/mL) and sodium hypochlorite (MIC > 500 µg/mL). Considering its demonstrated adhesion capacity, we assessed its ability to form biofilms on polystyrene surfaces, reporting a weak biofilm-forming phenotype comparable to other L. monocytogenes strains. Finally, using the VFanalyzer platform we identified on the L. costaricensis genome 28 virulence-associated gene sequences related to regulatory and structural functions, adherence, and an incomplete invasion gene group compared to L. monocytogenes strains. Collectively, these findings phenotypically support the previously proposed non-pathogenic nature of L. costaricensis, while also revealing a level of persistence comparable to other L. monocytogenes isolates.