In vivo assessment of bacteriophages specific to multidrug resistant Escherichia coli on fecal bacterial counts and microbiome in nursery pigs.

Escherichia coli is the most common cause of economic loss in swine industry. Nowadays, bacteriophages have been proven as good candidates for controlling bacterial infections. In this study, 6 phages were isolated and selected based on their high efficacy against 11 stains of E. coli isolated from diarrheal pigs. Six groups of weaned piglets were assigned (control, bacterial control (BC), two phage control (PC) and two phage treatment (PT) groups). Two titers (2 × 109 PFU/animal and 2 × 1010 PFU/animal) of phage cocktails consisting of these phages were tested in the PC and PT groups via oral gavage at 24, 48, and 72 h against an E. coli cocktail (2 × 109 CFU/animal) that was given to the piglets at 0, 12, 24, and 48 h of the trial. A significant reduction of fecal E. coli counts was observed in both PT groups from day 1 to 7 following the final phage dosage when compared to those of the BC group. Microbiomes in feces obtained 24 h after the final phage administration revealed phage therapy with both dosages could restore the gut's bacterial composition. Moreover, the given phage cocktails resulted in a significantly higher average daily gain of piglets during the first few weeks in both PC groups and the PT group receiving a higher phage dosage. These findings suggest that bacteriophages might be a potential alternative to antibiotics in the treatment of pathogens. In addition, they could also be utilized to improve pig growth performance.

PCV3 in Thailand: Molecular epidemiology and relationship with PCV2.

Porcine circovirus type 3 has been circulating throughout the world and since their first report, various clinical signs and disease developments have been documented. The virus is similar to the closely related PCV2 and is associated with several clinical signs called porcine circovirus-associated diseases (PCVAD). PCV2 or PCV3 is occasionally reported with clinical signs such as PDNS, respiratory signs and reproductive failure. Retrospective research conducted in Thailand revealed that both PCV2 and PCV3 have been circulation for decades. However, awareness about PCV3 infection has just arisen in recent years because of the similarities observed in disease circulation and clinical signs that have led to concerns. This study was conducted to find the relationship between the quantity of PCV2 and PCV3 in Thai pigs displaying the clinical signs related to PCVAD. A total of 479 serum samples with different production phases and clinical signs were sent to Kamphaeng Saen Veterinary Diagnostic Center (KVDC) for qPCR to detect the presence of PCV2 or PCV3. There was no relationship between the PCV3 and PCVAD-related clinical signs. Also, the relationship between PCV2 and PCV3 with no clinical signs suggested that both viruses might come from the same reservoir or have been circulating in Thailand for a long time, leading to common incidents in finding. The viral load of PCV2 was significantly different among the pig groups with and without clinical signs. The capsid sequence analysis of PCV3 revealed that 22 capsid sequences obtained from this study were found as clusters within PCV3a with a minor variation. Additional control measures are further needed to reduce the findings of the viruses. A future study with a control experiment may be needed to clarify the pathogenesis of PCV3.

High rate misidentification of biochemically determined Streptococcus isolates from swine clinical specimens.

In this study, 22 bacterial isolates from swine necropsy specimens, which were biochemically identified as Streptococcus suis and other Streptococcus species, were re-examined using species-specific PCR for authentic S. suis and 16S rRNA gene sequencing for the verification of the former judge. Identification of S. suis on the basis of biochemical characteristics showed high false-positive (70.6%) and false-negative (60%) rates. The authentic S. suis showed various capsular polysaccharide synthesis gene types, including type 2 that often isolated from human cases. Five of 22 isolates did not even belong to the genus Streptococcus. These results suggested that the misidentification of the causative pathogen in routine veterinary diagnosis could be a substantial obstacle for the control of emerging infectious diseases.

The retrospective identification and molecular epidemiology of porcine circovirus type 3 (PCV3) in swine in Thailand from 2006 to 2017.

Porcine circovirus type 3 (PCV3) has recently been detected in pigs worldwide, with similar clinical manifestations to porcine circovirus-associated disease (PCVAD) from porcine circovirus type 2 (PCV2) infection. Here, we report the identification and molecular epidemiology of PCV3 in swine in Thailand from clinical samples retrieved from 2006 to 2017. The epidemiological data revealed co-infection with PCV2, PRRSV, and PCV2/PRRSV was common in our samples. Circulating PCV3 from this study shared a high similarity of nucleotide and deduced amino acid sequences of the partial capsid gene (96.7%-100% and 96.7%-100% respectively), indicated the genetic stability of PCV3 in Thailand. Phylogenetic analysis based on the capsid gene revealed scatter clustering with current PCV3 having no relation to the geographical origin of the virus strains. In this retrospective study, results have demonstrated that PCV3 has spread extensively within Thai swine from as early as 2006 and may also be involved in PRDC and PCVAD.