Search

Salmonella Enteritidis (SE) and Salmonella Typhimurium (ST) are the most commonly reported serotypes detected for the occurrence of Salmonellosis through foodborne transmission in recent years. In this study, a phagomagnetic separation in combination with qPCR (PhMS‐qPCR) based on phage T102 as a recognition element was developed for rapid enrichment and detection of Salmonella in dairy products. Phage T102 was coated onto magnetic beads for capturing Salmonella from samples through magnetic separation, with a capture efficiency of ~90% demonstrated. During the subsequent qPCR process, captured Salmonella was identified by detecting the OmpC gene, and specific sdf and STM4495 genes to further distinguish the serotypes of Salmonella Enteritidis (SE) and Salmonella Typhimurium (ST), respectively. The whole procedure can be performed in 2.5 h with a low detection limit of 10 CFU/mL in PBS. Subsequently, this detection strategy was successfully applied for the detection of Salmonella and serotype identification in spiked milk samples. This cell separation and detection system offers a promising alternative for rapid and accurate detection of Salmonella or Salmonella spp. [ABSTRACT FROM AUTHOR]

Application of bacteriophages to eliminate foodborne pathogens in food matrices is an emerging research field. In this study, a promising phage candidate specific for Salmonella strains was screened and its ability to decrease Salmonella counts in some food, such as milk, sausage, and lettuce, was investigated. A total of 58 Salmonella phages were isolated from a wastewater treatment plant, sewage near a river, farm ditch near a lake, and poultry house. Among them, phages LPST10, LPST18, and LPST23 were highly efficient in infecting Salmonella Typhimurium ATCC 14028. In particular, phage LPST10 could infect all the tested Salmonella Typhimurium and Salmonella Enteritidis strains with high efficiency. Bacterial challenge tests revealed that phage LPST10 and its combination with phages LPST18 and LPST23 could consistently inhibit the growth of multiple strains. Phage LPST10 presented a lysis time of about 50 min with a burst size of 101 PFU/CFU, exhibited two distinct phases in the one-step growth curve, and was stable at a pH range of 3–13 that corresponds to the pH of most of the foods (pH 3.5–7.5) and at temperatures between 30 °C and 60 °C. Transmission electron microscopy demonstrated that phage LPST10 belongs to the Siphoviridae family, with an icosahedral head with a diameter of 83.26 nm and tail length and width of approximately 144.89 nm and 10.9 nm, respectively. A significant decrease in the bacterial counts (0.92–5.12 log 10 CFU/sample) and an increase in phage titers (0–2.96 log 10 PFU/sample) were observed in different food matrices tested. These results demonstrated that phage LPST10 is a promising candidate for controlling Salmonella contamination in foods owing to its safety and effectiveness. [ABSTRACT FROM AUTHOR]

Multiplex bacteria detection is essential to monitor various pathogens situations where multiple pathogen species are a concern. Herein, we explored novel dual phage amplification-based strategies (PAA) combined with a multiplex detection technique for simultaneous bacteria detection in one single tube. This assay was normalized on two common foodborne pathogens: Salmonella enterica and Staphylococcus aureus. In the presence of the target bacteria, phages could specifically recognize the viable cells and replicate themselves within the cells to produce more progeny phages. After thermal lysis within 10 min, the products with DNA of the progeny phages were analyzed with multiplex detection strategies. The specificity of the multiplex detection strategies integrated with the high sensitivity of the PAA assay allowed this assay to be rapid, specific, and sensitive for simultaneous quantification of Salmonella and Staphylococcus aureus. Optimized parameters of PAA, single and multiplex qPCR were defined, and the analytical sensitivities, specificities, and stabilities of single and multiplex reactions were validated under defined experimental conditions and in real samples. The results demonstrated wide linear ranges (10–108 CFU/mL), with detection limits of 10 CFU/mL for all bacteria tested. Moreover, the total detection time could be reduced to no more than 4 h. This assay was successfully applied to real food samples consistent with the results comparable to traditional plate counting methods. Due to the rapid and simple operation, low sensitivity and cost, high specificity, and the ability to distinguish live bacteria, the proposed PAA-based multiplex qPCR assay provides an effective and promising strategy for the simultaneous detection of viable bacteria. [Display omitted] • PAA relied on novel phages allows signal amplification to increase sensitivity. • PAA combined with single detection assay can achieve sensitive quantification for either Salmonella or Staphylococcus. • Dual PAA-mediated multiplex detection assay was applied for simultaneous detection. • This assay presented wide linear ranges of 10–108 CFU/mL, with the LODs of 10 CFU/mL for all bacteria tested. [ABSTRACT FROM AUTHOR]

• A novel phage-based MRS sensor was proposed for Salmonella detection. • Bioorthogonal reaction TCO/Tz improves the sensitivity of this sensor. • This sensor has a LOD of 5 CFU per mL with a linear range of 102-108 CFU per mL. • The detection limit was below 10 CFU/25 mL with 4-h pre-enrichment. Phages are uniquely suited for bacterial detection due to their low cost and ability to recognize live bacteria. Herein, our work establishes the proof-of-concept detection of Salmonella in orange juice based on a phage-mediated portable magnetic relaxation switching (MRS) biosensor. The limit of quantification (LOQ) could reach 5 CFU/mL (95 % confidence interval [CI]: 4–7, N = 4) with a linear range of 102-108 CFU/mL, which has improved 10-fold than that without bioorthogonal signal amplification. The recovery rate of the phage-based MRS biosensor was 95.0 % (95 % confidence interval [CI]: 89.0 %-100.9 %, N = 6). The specificity of the phage-based MRS biosensor was 100 % without false-positive results. In addition, this sensor was able to detect <10 CFU per 25 mL of Salmonella in orange juice with 4-h pre-enrichment. The result from the phage-based MRS biosensor is consistent with that from the standard plate count method. This sensor provides a reliable and ultrasensitive detection platform for pathogens. [ABSTRACT FROM AUTHOR]

[Display omitted] • RBP 41-based magnetic separation may effectively separate and concentrate Salmonella. • RBP 41-mediated MELISA was developed and reached the detection limit of 10 CFU/mL. • MELISA offered a rapid detection of Salmonella within 1.5 h in complex food matrices. Rapid and sensitive quantitative detection methods are required to monitor and detect Salmonella throughout the food supply chain and early prevention of foodborne disease outbreaks. In this study, a magnetic microbead enzyme-linked immunoassay (MELISA) based on phage receptor binding protein was developed for rapid enrichment and detection of Salmonella in complex food matrices. RBP 41 from phage T102 acted as a species-specific recognition element for Salmonella by exploiting its strong binding capacity to Salmonella surface receptors. RBP 41-MBs were prepared by coupling recombinant RBP 41 with MBs and used to separate and enrich Salmonella cells from spiked food samples. The captured complexes were further integrated with ELISA procedures by HRP-labeled anti- Salmonella antibody for rapid and accurate detection of Salmonella. The whole method took <1.5 h and the detection limit was 10 CFU/mL. Therefore, MELISA was successfully developed for the detection of Salmonella in various spiked food samples (skim milk, lettuce, and chicken breast). The ELISA reaction process of this method was carried out on magnetic beads. It simplified the process of the traditional ELISA method and reduces the reaction time. This study expanded the use of phage-associated proteins and demonstrated the promising prospects for practical applications in the detection of foodborne pathogens. [ABSTRACT FROM AUTHOR]

Bacterial detection in foods have to overcome the hindrance of complex matrices, resulting in more sophisticated pre-treatment steps and low sensitivity and reproductivity. Therefore, it remains a challenge to develop simple, rapid, accurate, and low-cost pathogen detection methods which were applicable for detection in turbid or complex food matrices. In this study, a novel bioorthogonal reaction-amplified microparticle counting sensing based on phages has been developed for the rapid detection of viable Salmonella in different foods. Phage not only acted as a bioreceptor to recognize viable Salmonella , but also used as an effective carrier for signal amplifiers due to its large specific surface area. The bioorthogonal reaction was introduced to further amplify the signal, the presence of Salmonella can specifically induce a quantitative change in the functionalized polystyrene microspheres, and thus can be monitored by the microporous resistance particle counter. Under the optimized conditions, this sensor could achieve a limit of detection of 33.58 CFU/mL and a linear range from 102 CFU/mL to 106 CFU/mL. This phage-mediated microporous resistance particle sensor can specifically recognize viable Salmonella in 1 h, providing a powerful platform for rapid and low-cost Salmonella quantification. Graphic abstract of Salmonella detection by pMRP sensor. [Display omitted] • A phage-mediated microporous resistance particle sensor for detection of Salmonella. • Bioorthogonal reaction was used for signal amplification in phage-mediated sensor. • Phages as bioreceptor to capture Salmonella and as a carrier for signal amplifiers. • The sensor achieve rapid detection of Salmonella within 1 h in food matrices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Phage T156-mediated PAA was developed for the quantification of live Salmonella. • Phage T156-mediated PAA reach the detection limit of 1 CFU per mL. • PAA-qPCR offered a rapid analysis in 3.5 h without complicated DNA purification. • This assay also provides an effective tool to assess potential drug resistance. Salmonella , especially drug-resistant Salmonella poses a serious threat to food safety and human health. Herein, we proposed a rapid, accurate and sensitive phage amplification-based analysis (PAA) based on an isolated Salmonella phage T156 with broad host range and potent lysis ability for the quantification of viable Salmonella , as well as rapid antibiotic susceptibility testing. This assay has been successful applied to quantify viable Salmonella in food matrices such as milk and lettuce, with a detection limit of 1 colony forming units (CFU) /mL and high specificity for only detect live bacteria not dead bacteria. When combined with real-time PCR (qPCR), PAA-qPCR further reduced the detection time from 6.5 h to 3.5 h, with a detection limit of 10 CFU/mL and without complicate DNA extraction or purification process. Moreover, this assay could also specifically detect drug-resistant Salmonella , shortening the detection time from 24 h to 6.5 h. The results were consistent with that of the conventional paper disc diffusion method (DDM). These PAA methods were evaluated and applied for Salmonella quantification, as well as the detection of drug-resistant Salmonella , providing a promising platform to trace the foodborne pathogen in the complex food matrix, as well as the detection of drug-resistant Salmonella. [ABSTRACT FROM AUTHOR]

In this study, we used the lytic Siphovirus phage LPST10 to develop a rapid and accurate detection method for Salmonella. Salmonella cells were separated from complex food matrices through magnetic separation, then subjected to SYBR green-based real-time quantitative PCR detection. Bacterial concentrations of 102–106 (Colony forming unit per milliliter, CFU/mL), with 200 of μg LPST10 phage-MBs, and 15 min reactions at 37 °C were found to be optimal to allow the phage-magnetic beads to capture the Salmonella cells. The phage-magnetic beads specifically recognized Salmonella cells of different serotypes. Under optimal conditions, DNA was extracted from the resulting bacteria phage-magnetic bead complexes through either alkaline lysis with sodium dodecyl sulfate (SDS) or boiling. The detection assay was subsequently assessed in food matrices (Tryptic soy broth medium, milk, and lettuce). The detection limit reached <30 CFU/mL in the food matrices. The entire assay, including bacterial capture, DNA extraction, and real-time polymerase chain reaction (RT-PCR) detection, could be completed within 1.5 h. This approach using a lytic Siphovirus phage has potential for rapid, specific, and accurate detection of Salmonella enterica subsp.enterica in different food matrices. • Salmonella can be biodetected by a lytic Siphovirus immobilized on magnetic beads. • Phagomagnetic separation and qPCR were optimized under various conditions. • The limit of detection for Salmonella was 30 CFU/mL within 1.5 h. [ABSTRACT FROM AUTHOR]

Salmonellosis caused by Salmonella contaminated food poses a serious threat to human health. The rapid and accurate detection of Salmonella is critical for preventing foodborne illness outbreaks. In this study, an electrochemical biosensor was developed using a newly identified biorecognition element, RBP 41, which is capable of specifically recognizing and binding to Salmonella. The biosensor was constructed through a layer-by-layer assembly of graphene oxide (GO), gold nanoparticles (GNPs), and RBP 41 on a glassy carbon electrode (GCE), with the GNPs amplifying the detection signal. The established biosensor was able to detect Salmonella in concentrations ranging from 3 to 106 CFU/mL within approximately 30 min by using differential pulse voltammetry (DPV) signal, and the estimated detection limit was to be 0.2984 Log 10 CFU/mL. The biosensor demonstrated excellent specificity and was effective in detecting Salmonella in food matrices, such as skim milk and lettuce. Overall, this study highlights the potential of phage tail receptor binding proteins in biosensing and the proposed biosensor as a promising alternative for rapid and sensitive Salmonella detection in various samples. [Display omitted] • An electrode based on phage RBP 41 was developed to detect Salmonella. • GNPs was used as nanotag for DPV signal amplification from the biosensor. • The biosensor developed can detect Salmonella with LOD of 2 CFU/mL within about 30 min by DPV. • The biosensor was successfully applied to detect Salmonella in food matrices. [ABSTRACT FROM AUTHOR]

[Display omitted] • An identified phage receptor binding protein (RBP 55) was coupled with quantum dots. • A rapid and sensitive Salmonella -detecting method was developed based on RBP 55-QDs. • The method exhibited wide linearity (1.0×101 to 1.0×107 CFU/mL) and LOD of 2 CFU/mL. • Practical potential of phage RBP for detection of Salmonella in food matrices. As a commonly pathogenic bacterium, the rapid detection of Salmonella outbreaks and assurance of food safety require a highly efficient detection method. Herein, a novel approach to Salmonella detection using quantum dot-labeled phage-encoded RBP 55 as a fluorescent nanoprobe is reported. RBP 55, a novel phage receptor binding protein (RBP), was identified and characterized from phage STP55. RBP 55 was functionalized onto quantum dots (QDs) to form fluorescent nanoprobes. The assay was based on the combination of immunomagnetic separation and RBP 55-QDs, which formed a sandwich composite structure. The results showed a good linear correlation between the fluorescence values and the concentration of Salmonella (101–107 CFU/mL) with a low detection limit of 2 CFU/mL within 2 h. The method was used to successfully detect Salmonella in spiked food samples. This approach can be used for the simultaneous detection of multiple pathogens by labeling different phage-encoded RBPs using polychromatic QDs in the future. [ABSTRACT FROM AUTHOR]