High-pressure processing treatment of beef burgers: Effect on Escherichia coli O157 inactivation evaluated by plate count and PMA-qPCR.

Propidium monoazide coupled to real time PCR (PMA-qPCR) is a novel methodology proposed for the quantification of viable bacteria in food after microbial inactivation treatments. The aim of this work was to assess the effectiveness of different pressure levels on the lethality of a pool of Escherichia coli O157 strains in beef burgers by plate count and PMA-qPCR using uidA as target gene. Also, the effect on native microbiota counts, E. coli O157 counts, and physiochemical parameters of beef burgers during storage in refrigeration and frozen conditions were assessed. The treatment at 600 MPa for 5 min was the most lethal and was selected for the evaluation of bacteria behavior under storage conditions. Native microbiota and E. coli O157 were not recovered during refrigerated and frozen storage (4°C for 7 days and -18°C for 35 days). Cooking weight loss, pH, chromatic parameters, and texture were affected by HPP. PRACTICAL APPLICATION: Practical Application: PMA-qPCR can be used as an alternative to assess microbial inactivation by different high pressure processing (HPP) conditions (pressure level, holding time and temperature) more rapidly than conventional plate counts. In addition, it has the benefit of being able to quantify viable but nonculturable bacteria from contaminated beef burgers after HPP. Moreover, this novel technique generates less pathogenic residues, which minimizes workers' exposure to human biohazards.

Anthropogenic Infection of Domestic Cats With SARS-CoV-2 Alpha Variant B.1.1.7 Lineage in Buenos Aires.

SARS-CoV-2 reverse zoonosis, particularly to domestic animals, and the potential role of infected animals in perpetuating the spread of the virus is an issue of increasing concern. In this case report, we identified the natural infection of two cats by SARS-CoV-2, in Argentina, whose owner had been previously infected by SARS-CoV-2. Viral genetic material was detected in feline oropharyngeal (OP) and rectal (R) swab by RT-qPCR, and sequence analysis revealed that the virus infecting the owner and one cat were genetically similar. The alpha variant (B.1.1.7 lineage) was identified with a unique additional mutation, strongly suggesting human-to-cat route of transmission. This study reinforces the One Health concept and the importance of integrating human, animal, and environmental perspectives to promptly address relevant health issues.

High expression level of a foot and mouth disease virus epitope in tobacco transplastomic plants.

Chloroplast transformation has an extraordinary potential for antigen production in plants because of the capacity to accumulate high levels of recombinant proteins and increased biosafety due to maternal plastid inheritance in most crops. In this article, we evaluate tobacco chloroplasts transformation for the production of a highly immunogenic epitope containing amino acid residues 135-160 of the structural protein VP1 of the foot and mouth disease virus (FMDV). To increase the accumulation levels, the peptide was expressed as a fusion protein with the beta-glucuronidase reporter gene (uidA). The recombinant protein represented the 51% of the total soluble proteins in mature leaves, a level higher than those of the Rubisco large subunit, the most abundant protein in the leaf of a wild-type plant. Despite this high accumulation of heterologous protein, the transplastomic plants and wild-type tobacco were phenotypically indistinguishable. The FMDV epitope expressed in transplastomic plants was immunogenic in mice. These results show that transplastomic tobacco express efficiently the recombinant protein, and we conclude that this technology allows the production of large quantities of immunogenic proteins.

Evaluation of a bovine rotavirus VP6 vaccine efficacy in the calf model of infection and disease.

Group A bovine rotavirus (BRV) is the major cause of acute viral gastroenteritis in neonatal calves worldwide. Due to the early susceptibility to the infection prevention strategies are based on the improvement of passive immunity levels through cow vaccination in the last third of gestation. The major capsid antigen (VP6) of BRV is the most immunogenic viral protein and it is highly conserved among group A BRV. In this work, VP6 protein from BRV C-486 strain (P[1]G6) was expressed in insect cells using the baculovirus expression vector system. Recombinant VP6 was used to immunize cows and vaccine's efficacy was assessed in a colostrum-deprived calf model of BRV infection and disease. Immune colostrum pool was generated using first and second milking of the immunized cows. Calves receiving one dose of immune colostrum within the first 6h of life, or colostrum-deprived calves were orally inoculated with virulent BRV at 2 days of age. The animals were monitored for diarrhea, virus shedding and isotype-specific antibodies responses to BRV in both feces and serum. Calves receiving VP6-immune colostrum showed a reduction of both diarrhea and virus shedding (in terms of viral titer and excretion period) in comparison with the colostrum-deprived calves.