Thermal inactivation of MS2 bacteriophage as a surrogate of enteric viruses in cow milk

How to Tackle Bacteriophages: The Review of Approaches with Mechanistic Insight

Bacteriophage-based applications have a renaissance today, increasingly marking their use in industry, medicine, food processing, biotechnology, and more. However, phages are considered resistant to various harsh environmental conditions; besides, they are characterized by high intra-group variability. Phage-related contaminations may therefore pose new challenges in the future due to the wider use of phages in industry and health care. Therefore, in this review, we summarize the current knowledge of bacteriophage disinfection methods, as well as highlight new technologies and approaches. We discuss the need for systematic solutions to improve bacteriophage control, taking into account their structural and environmental diversity.

Efficacy of the PlasmaShield®, a Non-Thermal, Plasma-Based Air Purification Device, in Removing Airborne Microorganisms

Airborne microorganisms play a significant role in the transmission of infectious diseases. As such, improving indoor microbial air quality can enhance infection control in numerous settings. This study examined the efficacy of the PlasmaShield® air purification device to remove airborne microorganisms under laboratory conditions. Pure cultures of model microorganisms at varying concentrations were aerosolized using a 1-jet Collison nebulizer through stainless-steel removable piping prior to reaching the PlasmaShield® device. The surviving microorganisms were captured using the Staplex® MBS-6 Six Stage Microbial Air Sampler and enumerated via culture on agar plates. The positive-hole-corrected colony/plaque-forming units were compared with the negative control (microorganisms aerosolized through an empty PlasmaShield® casing). The PlasmaShield® statistically significantly (p < 0.05) reduced airborne Escherichia coli, Staphylococcus epidermidis, Bacteriophage MS2 and Cladosporium sp. compared with the negative control. The maximum removal achieved was estimated to be 4 × log10E. coli (99.99% removal), 4 × log10S. epidermidis (99.97% removal), 7 × log10 MS2 (99.99998% removal) and 5 × log10Cladosporium sp. (99.999% removal). Scanning electron microscope images of the surviving microorganisms showed that the PlasmaShield® damaged the cell membrane of these model microorganisms. This study provides proof-of-concept evidence to support the use of this technology to improve indoor microbial air quality.

Thermal Inactivation of Hepatitis A Virus, Noroviruses, and Simian Rotavirus in Cows' Milk

Consumption of raw or unpasteurized milk is a risk for the consumers because indirect contaminations such as fecal-cross-contamination could occur and determine the presence of enteric viruses. In this study, milk was treated with several temperature and time combinations chosen by performing a preliminary experiment to evaluate the intervals needed to inactivate Hepatitis A virus (HAV) HM175 strain, noroviruses genogroups I and II (GI and GII), and simian rotavirus SA11 at different temperatures. Results were obtained by measuring the genome copies and infectious units by real-time PCR and plaque assays respectively. At 85 °C, one minute and two minutes were needed to achieve 6.6 log₁₀ ± 0.2 and 8 log₁₀ ± 0 reductions of genome copies of HAV respectively. Similar genome copies reduction was also observed for noroviruses (GI and GII) and simian rotavirus. At higher temperatures, 90 s (s) at 90 °C and 60 s at 95 °C were needed to achieve 8 log₁₀ ± 0 reductions of the genome copies of all studied viruses. Significant higher sensitivity of the infectious units of both HAV and simian rotavirus to heat treatment of milk than their genome copies was observed. At boiling point of milk (100.5 °C), 40 s were needed to achieve 8 log₁₀ ± 0 reductions of genome copies of all the studied viruses, while 10 s were needed to achieve 6 log₁₀ ± 0 reductions of the infectious units of HAV and simian rotavirus. Significant higher reduction of infectious units than genome copies was observed confirming that genome copies reduction does not correspond to infectious virus.