Capture and concentration of viral and bacterial foodborne pathogens using apolipoprotein H

Concentration of SARS-CoV-2-Infected Cell Culture Supernatants for Detection of Virus-like Particles by Scanning Electron Microscopy

There is currently a need for new rapid viral diagnostic electron microscopy methods. Although the gold standard remains the transmission electron microscopy (TEM) negative staining method for electron microscopic examination of samples containing a virus, difficulties can arise when the virus particle content of the sample that has to be examined is poor. Such samples include supernatants of virus-infected cells that can be difficult to examine, as sometimes only a few virus particles are released in the culture medium upon infection. In addition to TEM, scanning electron microscopy (SEM) can also be used for visualizing virus particles. One advantage of SEM over TEM is its ability to rapidly screen several large specimens, such as microscopy slides. In this study, we investigated this possibility and tested different coating molecules as well as the effect of centrifugation for analyzing SARS-CoV-2-virus-infected cell culture supernatants deposited on microscopy glass slides by SEM. We found that centrifugation of 25XConcanavalinA-coated microscopy glass slides in shell vials provided an improved method for concentrating SARS-CoV-2-virus-infected cell supernatants for virus-like particle detection by SEM.

Detection of Enteric Viruses on Strawberries and Raspberries Using Capture by Apolipoprotein H

Human noroviruses (HuNoVs) and the hepatitis A virus (HAV) are the main viral causes of foodborne illness worldwide. These viruses are frequently transmitted via fresh and frozen berries, such as strawberries and raspberries. ISO 15216:1 (2017), currently the preferred method for their detection, involves several steps and is time-consuming. Apolipoprotein H (ApoH) has been shown to have a strong affinity for several microorganisms, including HuNoVs. In this article, we report an ApoH-based method of capturing the HAV and HuNoVs adherent to berries and concentrating them for assay. The limit of detection of both viruses suspended in a buffer was low. On strawberries, the HAV was detected down to 10⁴ genome copies/25 g in 100% of cases and down to 10³ genome copies/25 g on raspberries in 50% of cases. This sensitivity was not significantly different from that of the ISO method 15216:1 (2017). HuNoV GII.4 was more difficult to detect using the ApoH method. The ApoH CaptoVIR kit does, nevertheless, appear to be usable in the near future as a single-test, multiple-detection method for viruses on fresh and frozen berries.

Biofabricating a Silk Scaffold as a Functional Microbial Trap

Silk fibroin produced from silkworms has been intensively utilized as a scaffold material for a variety of biotechnological applications owing to its remarkable mechanical strength, extensibility, biocompatibility, and ease of biofunctionalization. In this research, we engineered silk as a novel trap platform capable of capturing microorganisms. Specifically, we first fabricated the silk material into a silk sponge by lyophilization, yielding a 3D scaffold with porous microstructures. The sponge stability in water was significantly improved by ethanol treatment with elevated β-sheet content and crystallinity of silk. Next, we biofunctionalized the silk sponge with a poly-specific microbial targeting molecule, ApoH (apolipoprotein H), to enable a novel silk-based microbial trap. The recombinant ApoH engineered with an additional penta-tyrosine was assembled onto the silk sponge through the horseradish peroxidase (HRP) mediated dityrosine cross-linking. Last, the ApoH-decorated silk sponge was demonstrated to be functional in capturing our model microorganism targets, E. coli and norovirus-like particles. We envision that this biofabricated silk platform, capable of trapping a variety of microbial entities, could serve as a versatile scaffold for rapid isolation and enrichment of microbial samples toward future diagnostics and therapeutics. This strategy, in turn, can expedite advancing future biodevices with functionality and sustainability.

Pathogen enrichment from human whole blood for the diagnosis of bloodstream infection: Prospects and limitations

Blood culture represents the current reference method for the detection of bacteria or fungi in the circulation. To accelerate pathogen identification, molecular diagnostic methods, mainly based on polymerase chain reaction (PCR), have been introduced to ensure early and targeted antibiotic treatment of patients suffering from bloodstream infection. Still, these approaches suffer from a lack of sensitivity and from inhibition of PCR in a number of clinical samples, leading to false negative results. To overcome these limitations, various approaches aiming at the enrichment of pathogens from larger blood volumes prior to the extraction of pathogen DNA, thereby also depleting factors interfering with PCR, have been developed. Here, we provide an overview of current systems for diagnosing bloodstream infection, with a focus on approaches for pre-analytical pathogen enrichment, and highlight emerging applications of pathogen depletion for therapeutic purposes as a potential adjunctive treatment of sepsis patients.