Isolation and application of bacteriophages alone or in combination with nisin against planktonic and biofilm cells of Staphylococcus aureus.

Staphylococcus aureus is a notorious foodborne pathogen since it has ability to produce variety of toxins including heat-stable enterotoxin, form biofilm, and acquire resistance to antibiotics. Biocontrol of foodborne pathogens by lytic bacteriophages garners increasing interest from both researchers and food industry. In the present study, 29 phages against S. aureus were successfully isolated from chicken, pork, and fish. Characterization of the isolates revealed that phage SA46-CTH2 belonging to Podoviridae family had a number of features suitable for food industry applications such as wide host range, short latent period, large burst size, high stress tolerance, and a genome free of virulence genes. Furthermore, phage SA46-CTH2 alone or in combination with nisin exhibited great efficacy in reducing planktonic and biofilm cells of S. aureus at various conditions tested. The combination of phage SA46-CTH2 and nisin was also found to be able to inhibit the regrowth of S. aureus at both 37 and 24 °C.Key points• A total of 29 S. aureus phages were successfully isolated from fish, pork, and chicken products. • Phage SA46-CTH2 was characterized by host range, morphology, and genome sequencing. • SA46-CTH2 significantly reduced both planktonic and biofilm cells of S. aureus. • Combination of SA46-CTH2 and nisin inhibited the regrowth of S. aureus.

Static Aerated Composting of African Swine Fever Virus-Infected Swine Carcasses with Rice Hulls and Sawdust.

Identifying and ensuring the inactivation of the African Swine Fever virus in deadstock is a gap in the swine industry's knowledge and response capabilities. The results of our study demonstrate that ASFv in deadstock was inactivated using static aerated composting as the carcass disposal method. Replicated compost piles with whole market hogs and two different carbon sources were constructed. In-situ bags containing ASFv-infected spleen tissue were placed alongside each of the carcasses and throughout the pile. The bags were extracted at days 0, 1, 3, 7, 14, 28, 56, and 144 for ASFv detection and isolation. Real-time PCR results showed that DNA of ASFv was detected in all samples tested on day 28. The virus concentration identified through virus isolation was found to be below the detection limit by day 3 in rice hulls and by day 7 in sawdust. Given the slope of the decay, near-zero concentration with 99.9% confidence occurred at 5.0 days in rice hulls and at 6.4 days in sawdust. Additionally, the result of virus isolation also showed that the virus in bone marrow samples collected at 28 days was inactivated.

Viability of African Swine Fever Virus with the Shallow Burial with Carbon Carcass Disposal Method.

African swine fever (ASF) is a highly contagious swine disease with high mortality. In many countries, culling pigs infected and exposed to the ASF virus is mandatory to control the disease, which poses a real challenge in the disposal of large numbers of carcasses during ASF outbreaks. Shallow burial with carbon (SBC) Thanks ew mortality disposal method developed from deep burial and composting. The present study investigates the effectiveness of SBC in disposing of ASF virus-infected pigs. The real-time PCR results showed that DNA of the ASF virus was still detected in bone marrow samples on day 56, while the virus isolation test revealed that the infectious ASF virus was destroyed in both spleen and bone marrow samples on day 5. Interestingly, decomposition was found to occur rapidly in these shallow burial pits. On day 144, only large bones were found in the burial pit. In general, the results of this study indicated that SBC is a potential method for the disposal of ASF-infected carcasses; however, further studies are needed to provide more scientific evidence for the efficacy of SBC in different environment conditions.

The use of composting for the disposal of African swine fever virus-infected swine carcasses.

African swine fever (ASF) has been considered as one of the most important and devastating swine diseases with high mortality rates. Since effective vaccines and treatment are not available, mass euthanasia of infected and exposed pigs has been known to be the best measure to control ASF. Although composting has been proved to be a safe method for the rapid disposal of animal carcasses during outbreaks, there is no information about the effect of composting on the viability of ASF virus in swine carcasses. This study investigates the survival of the ASF virus in swine carcasses during composting. The findings suggested that the DNA of the ASF virus was detected in all samples tested. On the contrary, infectious ASF virus particles were rapidly destroyed at day 3.

Isolation, characterization and application of a polyvalent phage capable of controlling Salmonella and Escherichia coli O157:H7 in different food matrices.

Salmonella Enteritidis, Salmonella Typhimurium, and Escherichia coli O157:H7 are the most important foodborne pathogens, causing serious food poisoning outbreaks worldwide. Bacteriophages are increasingly considered as novel antibacterial agents to control foodborne pathogens. In this study, 8 Salmonella phages and 10 E. coli O157:H7 phages were isolated from chicken products. A polyvalent phage PS5 capable of infecting S. Enteritidis, S. Typhimurium, and E. coli O157:H7 was further characterized and its efficacy in reducing these foodborne pathogens was evaluated in in vitro and in foods. Morphology, one-step growth, and stability assay showed that phage PS5 was a myovirus, with relatively short latent periods, large burst sizes, and high stability. Genome sequencing analysis revealed that the genome of PS5 does not contain any genes associated to antibiotic resistance, toxins, lysogeny, and virulence factors. In broth, phage PS5 significantly decreased the viable counts of all the three bacterial hosts by more than 1.3 log CFU/mL compared to controls after 2 h of incubation at 4 °C and 24 °C. In foods, treatment with PS5 also resulted in significant reductions of viable counts of all the three bacterial hosts compared to controls at temperatures tested. This is the first report on single phage capable of simultaneously controlling S. Enteritidis, S. Typhimurium and E. coli O157:H7 in both in vitro and in foods.

Enhanced detection of Porcine reproductive and respiratory syndrome virus in fixed tissues by in situ hybridization following tyramide signal amplification.

This study evaluated the sensitivity of biotinyl-tyramide-based in situ hybridization (TISH) method by comparison with chromogenic in situ hybridization (CISH) and immunohistochemical staining (IHC) methods. This study also determined the effect of fixative and fixation time on the detection of Porcine reproductive and respiratory syndrome virus (PRRSV) in paraffin-embedded tissues. Lung samples were fixed in 4% paraformaldehyde (PFA) or 10% neutral buffered formalin (NBF) for various times before paraffin embedding. Of 30 paraffin-embedded lung samples, fixed for 1 day in 4% PFA or 10% NBF, 18 (60%) were positive for PRRSV by nested reverse transcription polymerase chain reaction (nRT-PCR). All 18 lung samples (100%) also were positive for PRRSV by TISH, but only 10 of these 18 specimens (56%) were positive for PRRSV by IHC and CISH. We demonstrated that TISH can detect PRRSV RNA in paraffin-embedded tissues after up to 90 days of fixation. PRRSV nucleic acids and antigens were better preserved in 4% PFA than in 10% NBF. Compared with CISH and IHC testing methods, TISH appeared to be more sensitive for the detection of PRRSV in paraffin-embedded tissues.