Bacteriophages to control Shiga toxin-producing E. coli safety and regulatory challenges

Shiga toxin-producing Escherichia coli (STEC) are usually found on food products due to contamination from the fecal origin, as their main environmental reservoir is considered to be the gut of ruminants. While this pathogen is far from the incidence of other well-known foodborne bacteria, the severity of STEC infections in humans has triggered global concerns as far as its incidence and control are concerned. Major control strategies for foodborne pathogens in food-related settings usually involve traditional sterilization/disinfection techniques. However, there is an increasing need for the development of further strategies to enhance the antimicrobial outcome, either on food-contact surfaces or directly in food matrices. Phages are considered to be a good alternative to control foodborne pathogens, with some phage-based products already cleared by the Food and Drug Administration (FDA) to be used in the food industry. In European countries, phage-based food decontaminants have already been used. Nevertheless, its broad use in the European Union is not yet possible due to the lack of specific guidelines for the approval of these products. Furthermore, some safety concerns remain to be addressed so that the regulatory requirements can be met. In this review, we present an overview of the main virulence factors of STEC and introduce phages as promising biocontrol agents for STEC control. We further present the regulatory constraints on the approval of phages for food applications and discuss safety concerns that are still impairing their use.The authors thank the Portuguese Foundation for Scienceand Technology (FCT) through the strategic funding of UID/BIO/04469/2019 unit, and the project PhageSTEC [PTDC/CVT-CVT/29628/2017], under the scope of COMPETE 2020 [POCI-01-0145-FEDER-029628]. The author GP acknowledges theFCT grant [SFRH/BD/117365/2016].info:eu-repo/semantics/publishedVersio

Single-hole properties in the tt-JJ and strong-coupling models

We report numerical results for the single-hole properties in the $t$-$J$ model and the strong-coupling approximation to the Hubbard model in two dimensions. Using the hopping basis with over $10^6$ states we discuss (for an infinite system) the bandwidth, the leading Fourier coefficients in the dispersion, the band masses, and the spin-spin correlations near the hole. We compare our results with those obtained by other methods. The band minimum is found to be at ($\pi/2,\pi/2$) for the $t$-$J$ model for $0.1 \leq t/J \leq 10$, and for the strong-coupling model for $1 \leq t/J \leq 10$. The bandwidth in both models is approximately $2J$ at large $t/J$, in rough agreement with loop-expansion results but in disagreement with other results. The strong-coupling bandwidth for t/J\agt6 can be obtained from the $t$-$J$ model by treating the three-site terms in first-order perturbation theory. The dispersion along the magnetic zone face is flat, giving a large parallel/perpendicular band mass ratio.Comment: 1 RevTeX file with epsf directives to include 8 .eps figures 8 figure files encoded using uufile

Multiwavelength observations of a VHE gamma-ray flare from PKS 1510-089 in 2015

Context. PKS 1510-089 is one of only a few flat spectrum radio quasars detected in the VHE (very-high-energy, > 100 GeV) gamma-ray band. Aims. We study the broadband spectral and temporal properties of the PKS 1510-089 emission during a high gamma-ray state. Methods. We performed VHE gamma-ray observations of PKS 1510-089 with the MAGIC telescopes during a high gamma-ray state in May 2015. In order to perform broad-band modelling of the source, we have also gathered contemporaneous multiwavelength data in radio, IR, optical photometry and polarization, UV, X-ray and GeV gamma-ray ranges. We construct a broadband spectral energy distribution (SED) in two periods, selected according to VHE gamma-ray state. Results. PKS 1510-089 has been detected in a high optical and gamma-ray state, showing for the first time a significant VHE gamma-ray variability. Similarly to the optical and gamma-ray high state of the source detected in 2012, it was accompanied by a rotation of the optical polarization angle and the emission of a new jet component observed in radio. The spectral shape in the VHE band during the flare is similar to the ones obtained during previous measurements of the source. The observed flux variability sets for the first time constraints on the size of the region from which VHE gamma rays are emitted. The broadband SED can be explained in the External Compton scenario