Quantitative Imaging of Bacteriophage Amplification for Rapid Detection of Bacteria in Model Foods

Rapid detection of bacteria in water and food samples is a critical need. The current molecular methods like real-time PCR can provide rapid detection after initial enrichment. However, these methods require significant preparation steps, specialized facilities to reduce contamination, and relatively expensive reagents. This study evaluates a novel approach for detecting bacteria based on imaging of bacteriophage amplification upon infection of the target host bacteria to mitigate some of these constraints and improve the specificity of discriminating live vs. dead bacteria. Thus, this research leverages the natural ability of lytic bacteriophages to rapidly amplify their genetic material and generate progeny phages upon infecting the host bacterium. This study uses a nucleic acid staining dye, a conventional fluorescence microscope, and quantitative image analysis for imaging the amplification of bacteriophages. The sensitivity and assay time for imaging-based quantification of phage amplification for detecting Escherichia coli were compared with RT-PCR and the standard plaque-forming assay for detection phage amplification in model systems, including coconut water and spinach wash water. The results demonstrate that the imaging approach matches both the sensitivity and speed for detecting E. coli using the RT-PCR method without requiring isolation of nucleic acids, expensive reagents, and specialized facilities. The quantitative imaging results demonstrate the detection of 10 CFU/ml of E. coli in coconut water and simulated spinach wash water with a chemical oxygen demand (COD) of 3,000 ppm within 8 h, including initial enrichment of the bacteria. In summary, the results of this study illustrate a novel phage amplification-based approach for detecting target bacteria in complex food and water samples using simple sample preparation methods and low-cost reagents.

Identification of Potentially Hazardous Microorganisms and Assessment of Physicochemical Deterioration of Thermally Processed King Coconut (Cocos nucifera var. aurantiaca) Water under Different Processing Conditions in Sri Lanka

King coconut water (KCW) is a sweet relish product that is more prone to rapid quality deterioration, and several safety concerns are emerging due to its inappropriate thermal processing. Therefore, the objective of this study was to identify the potential spoilage/pathogenic microorganisms associated with the processing of KCW, with the assessment of possible physicochemical changes as providing preliminary information required for the thermal process validation of bottled KCW. Samples (n = 6, 150 ml/sample) were collected from three different KCW processing facilities at five critical processing steps $\left(P_1-P_5\right)$ . A facility survey, physicochemical analyses, and microbial enumeration and isolation, along with their molecular identifications, were conducted. It was found that all tested physicochemical properties were significantly changed $\left(p<0.05\right)$ among sampling points at each processing facility. The colour of thermally processed KCW samples has significantly changed $\left(p<0.05\right)$ compared to the fresh KCW, which causes a distinct effect on the appealing quality of the final product. A pattern of initial lower counts with gradually increased microbial counts at intermediate processing steps (1.0 × 103–5.3 × 106 CFU/ml) and significantly lowered $\left(p<0.05\right)$ counts after thermal treatment was observed. Among the bacterial and fungal isolates identified, several potential pathogenic bacterial species, such as Pantoea dispersa, Bacillus siamensis, Pseudomonas stutzeri, and Acinetobacter lactucae; a few thermal resistant yeasts, Pichia kudriavzevii, Debaryomyces nepalensis, and Candida carpophila; and moulds, Penicillium citrinum, Microdochium fisheri, and Trichosporon asahii, have survived in the thermally processed KCW. Based on the results of the study, it is suggested that the thermal process validation of KCW should be targeted according to the revealed knowledge on the identified hazardous microorganisms, while adhering to Good Manufacturing and Hygienic Practices with minimized handling time to avoid rapid quality deterioration.

Métodos combinados para incrementar la vida en anaquel de agua de coco obtenida de comercios no establecidos de la Ciudad de Puebla, México

Objetivo Evaluar el efecto de la aplicación de métodos combinados para incrementar la vida en anaquel de agua de coco. Métodos Agua de coco fue obtenida de comercios no establecidos en la Ciudad de Puebla, México. El agua de coco fue tratada con luz ultravioleta-C, vainillina o cinamaldehído y almacenada a 5 y 22°C. Se evaluó el efecto de estas tecnologías sobre el crecimiento microbiano de bacterias mesófilas aerobias, mohos y levaduras. Resultados El tratamiento con luz ultravioleta-C redujo la carga microbiana de bacterias mesófilas aerobias y mohos y levaduras en 2.7 ± 0.01 y 3.1 ± 0.03 ciclos logarítmicos, respectivamente. Durante el almacenamiento del agua de coco, la combinación de luz ultravioleta-C, cinamaldehído y baja temperatura mantuvo una carga microbiana en ambos grupos de microorganismos por debajo de 10 UFC/mL durante 30 días. Conclusión La aplicación de métodos combinados puede ser una alternativa a bajo costo para la conservación de agua de coco.

An Overview of Phytoconstituents, Biotechnological Applications, and Nutritive Aspects of Coconut (Cocos nucifera)

Cocos nucifera is one of the highest nutritional and medicinal value plants with various fractions of proteins which play a major role in several biological applications such as anti-microbial, anti-inflammatory, anti-diabetic, anti-neoplastic, anti-parasitic, insecticidal, and leishmanicidal activities. This review is focused on several biotechnological, biomedical aspects of various solvent extracts collected from different parts of coconut and the phytochemical constituents which are present in it. The results obtained from this source will facilitate most of the researchers to focus their work toward the process of diagnosing diseases in future.

Rapid quantification of Escherichia coli in food and media using bacteriophage T7 amplification and liquid chromatography-multiple reaction monitoring tandem mass spectrometry

Conventional microbiological assays have been a valuable tool for specific enumeration of indicative bacteria of relevance to food and public health, but these culture-based methods are time-consuming and require tedious biochemical and morphological identification. In this work, we exploit the ability of bacteriophage T7 to specifically infect Escherichia coli and amplify nearly a 100-fold in 1–2 h. Bacteriophage amplification is integrated with liquid chromatography-multiple reaction monitoring tandem mass spectrometry (LC-MRM–MS/MS) for quantitation of phage-specific peptides. Heavy isotopic 15N labeled T7 is introduced as the inoculum phage and internal standard. Quantification is performed by determining the ratio of phage-specific peptides over the internal standard which value is proportional to E. coli numbers. A broad dynamic range of 6-log orders ranging from 3.0 × 10(3) to 3.0 × 10(9) CFU/ml is attained in LB, while between 4.1 × 10(4)–2.7 × 10(9) CFU/ml and 1.9 × 10(3)–3.0 × 10(7) CFU/ml was enumerated respectively in coconut water and apple juice. With this method, viable E. coli are quantified in 4 h with a detection limit of 3.0 × 10(3) CFU/ml, 4.1 × 10(4) CFU/ml and 1.9 × 10(3) CFU/ml in LB, coconut water and apple juice, respectively. This method has potential as a rapid tool for detection of fecal contamination during food bioprocessing and distribution to safeguard public health.