Review of the speculative role of co-infections in Streptococcus suis-associated diseases in pigs

Immune response induced by a Streptococcus suis multi-serotype autogenous vaccine used in sows to protect post-weaned piglets

Streptococcus suis is a bacterial pathogen that causes important economic losses to the swine industry worldwide. Since there are no current commercial vaccines, the use of autogenous vaccines applied to gilts/sows to enhance transfer of passive immunity is an attractive alternative to protect weaned piglets. However, there is no universal standardization in the production of autogenous vaccines and the vaccine formulation may be highly different among licenced manufacturing laboratories. In the present study, an autogenous vaccine that included S. suis serotypes 2, 1/2, 5, 7 and 14 was prepared by a licensed laboratory and administrated to gilts using a three-dose program prior to farrowing. The antibody response in gilts as well as the passive transfer of antibodies to piglets was then evaluated. In divergence with previously published data with an autogenous vaccine produced by a different company, the increased response seen in gilts was sufficient to improve maternal antibody transfer to piglets up to 5 weeks of age. However, piglets would still remain susceptible to S. suis disease which often appears during the second part of the nursery period. Vaccination did not affect the shedding of S. suis (as well as that of the specific S. suis serotypes included in the vaccine) by either gilts or piglets. Although all antibiotic treatments were absent during the trial, the clinical protective effect of the vaccination program with the autogenous vaccine could not be evaluated, since limited S. suis cases were present during the trial, confirming the need for a complete evaluation of the clinical protection that must include laboratory confirmation of the aetiological agent involved in the presence of S. suis-associated clinical signs. Further studies to evaluate the usefulness of gilt/sow vaccination with autogenous vaccines to protect nursery piglets should be done.

Molecular profile and epidemiological traits of Streptococcus suis isolated from diseased pigs in western Canada reveal multiple-serotype infection: Implications for disease control

Objective

Streptococcus suis is a major agent of disease in modern swine operations, linked to increased mortality, treatment costs, and secondary infections. Although it is ubiquitous in swine, only a fraction of pigs develop clinical disease. The goals of this study were to profile isolates obtained from diseased pigs in western Canada and to investigate potential associations with disease severity.

Procedure

Isolates of S. suis (n = 128) from 75 diagnostic submission and 63 premises were paired with epidemiological surveys completed by submitting practitioners (n = 22). Whole-genome sequencing was used to type isolates.

Results

The most prevalent serotypes identified were 1/2 (7.8%, 10/128), 2 (9.3%, 12/128), 3 (9.3%, 12/128), and 7 (7.8%, 10/128); and sequence types 28 (17%, 23/128) and 839 (14%, 19/128). There was no association between serotype or sequence type and organ source or barn location. Approximately 74% (14/19) of the premises had diseased animals colonized by > 1 S. suis serotype, but only 1 pig was simultaneously infected with multiple serotypes and sequence types. Serotype distribution from diseased pigs in western Canada differed from that of those in other geographic regions.

Conclusion

Infection of diseased pigs by multiple serotypes should be considered when disease control strategies are implemented. No association between S. suis type and isolation organ was identified.

A review of the influence of environmental pollutants (microplastics, pesticides, antibiotics, air pollutants, viruses, bacteria) on animal viruses

Microorganisms, especially viruses, cause disease in both humans and animals. Environmental chemical pollutants including microplastics, pesticides, antibiotics sand air pollutants arisen from human activities affect both animal and human health. This review assesses the impact of chemical and biological contaminants (virus and bacteria) on viruses including its life cycle, survival, mutations, loads and titers, shedding, transmission, infection, re-assortment, interference, abundance, viral transfer between cells, and the susceptibility of the host to viruses. It summarizes the sources of environmental contaminants, interactions between contaminants and viruses, and methods used to mitigate such interactions. Overall, this review provides a perspective of environmentally co-occurring contaminants on animal viruses that would be useful for future research on virus-animal-human-ecosystem harmony studies to safeguard human and animal health.

Antiviral Drug Candidate Repositioning for Streptococcus suis Infection in Non-Tumorigenic Cell Models

The increasing prevalence of antimicrobial resistance against zoonotic bacteria, including Streptococcus (S.) suis, highlights the need for new therapeutical strategies, including the repositioning of drugs. In this study, susceptibilities of bacterial isolates were tested toward ten different 3-amidinophenyalanine (Phe(3-Am)) derivatives via determination of minimum inhibitory concentration (MIC) values. Some of these protease inhibitors, like compounds MI-432, MI-471, and MI-476, showed excellent antibacterial effects against S. suis. Their drug interaction potential was investigated using human liver microsomal cytochrome P450 (CYP450) measurements. In our work, non-tumorigenic IPEC-J2 cells and primary porcine hepatocytes were infected with S. suis, and the putative beneficial impact of these inhibitors was investigated on cell viability (Neutral red assay), on interleukin (IL)-6 levels (ELISA technique), and on redox balance (Amplex red method). The antibacterial inhibitors prevented S. suis-induced cell death (except MI-432) and decreased proinflammatory IL-6 levels. It was also found that MI-432 and MI-476 had antioxidant effects in an intestinal cell model upon S. suis infection. Concentration-dependent suppression of CYP3A4 function was found via application of all three inhibitors. In conclusion, our study suggests that the potential antiviral Phe(3-Am) derivatives with 2',4' dichloro-biphenyl moieties can be considered as effective drug candidates against S. suis infection due to their antibacterial effects.

Rethinking the control of Streptococcus suis infection: Biofilm formation

Streptococcus suis is an emerging zoonotic pathogen that is widespread in swine populations. The control of S. suis infection and its associated diseases is a daunting challenge worldwide. Biofilm formation appears to be the main reason for the persistence of S. suis. In this review we gather existing knowledge on S. suis biofilm, describing the role of biofilm formation in S. suis virulence and drug resistance, the regulatory factors of S. suis biofilm formation, and the research progress of inhibiting S. suis biofilm formation, with the aim of providing guidance for future studies related to the field of S. suis biofilms.

Prevalence of Streptococcus suis serotype 2 isolated from pigs: A systematic review and meta-analysis

Background and Aim

Among Streptococcus suis serotypes, S. suis serotype 2 is the most significant serotype that causes serious diseases in pigs and humans worldwide. The present study aimed to estimate the global prevalence of S. suis serotype 2 isolated from pigs, determine its trend, and explore the factors associated with this serotype.

Materials and Methods

We retrieved relevant published studies from PubMed, Scopus, and the Web of Science. The retrieved citations were screened for possible inclusion. Relevant data were then extracted from the included studies. The random-effects model was used for all meta-analyses. A subgroup meta-analysis was used to assess the heterogeneity of the prevalence for four characteristics (continents, sampling organs, reporting unit, and pig's health status). A cumulative meta-analysis was performed to determine the cumulative prevalence over time. Meta-regression analysis was used to determine the trend of pooled prevalence of S. suis serotype 2 over time.

Results

Of 600 articles retrieved, 36 studies comprising a total sample size of 6939 isolates or samples from 16 countries of four continents were included for meta-analysis. The pooled prevalence of S. suis serotype 2 isolated from pigs was 13.6% (95% confidence interval [CI], 10.7%-17.1%), with high heterogeneity among the included studies (Cochran's Q, 431.6; p < 0.001; I2 = 91.9%; Table-1). No statistical significance was observed among subgroups of the four characteristics examined. However, the pooled prevalence of S. suis serotype 2 was as high as 16.0% (95% CI, 12.5%-20.3%; n = 16) in diseased pigs compared with 9.9% (95% CI, 5.6%-17.0%; n = 15) in healthy pigs. The pooled prevalence of S. suis serotype 2 isolated from pigs did not significantly decrease over time [regression coefficient = -0.020 (95% CI, 0.046-0.006, p = 0.139)]. The pooled prevalence of S. suis serotype 2 isolated from pigs fluctuated slightly between 13.2% and 17.8% from 2007 to 2023, although the pooled prevalence gradually decreased from 30.6% in 1987 to over 20% in 2003.

Conclusion

The global prevalence of S. suis serotype 2 isolated from pigs was estimated to be 13.6% (approximately 10% in healthy pigs and around 16% in diseased pigs). S. suis serotype 2 isolated from pigs did not change significantly over time. These results indicate that S. suis serotype 2 remains a problem for the pig industry and poses a threat to human health.

Experimental Intraperitoneal Infection of Piglets

Streptococcus suis is a swine bacterial pathogen that predominantly causes disease in weaned piglets characterized by swelling of joints, arthritis, septicemia, meningitis, and sudden death. Intravenous, intramuscular, intraperitoneal, and intranasal infection models were developed to study the bacterial pathogenicity and efficacy of vaccines and various therapeutics. The selection of the appropriate infection model is a critical step in any study, as it may impact the outcomes of the study. Here we describe a method for infecting weaned piglets with S. suis using intraperitoneal route as a reliable, consistent, and reproducible animal model to evaluate vaccine protection against systemic bacterial infection.

Evaluation of the Economic Impact of Streptococcus suis-Associated Disease

The economic impact of Streptococcus suis-associated disease at farm level is well known by the producers, but the cost in a region or a country is more difficult to evaluate due to the lack of a centralized data system, the different incidences, and the control measures applied by each producer. In this chapter, we describe a method based on the information gathered through interviews with veterinary practitioners. A comprehensive questionnaire created specifically for the disease can help to conduct the interviews. The questions include information about the proportions of farms, batches and animals clinically affected, mortality, metaphylactic and therapeutic treatments, use of vaccines, and proportion of cases that are diagnosed at the laboratory. As the questionnaire is quite complex, the best option to obtain the data is send the questionnaire to the selected veterinarians to allow them to collect some data and make an interview with them some days later. The information allows to estimate the costs due to mortality, antimicrobial treatments, the use of autogenous vaccines, and analyses performed. Initially they are calculated per animal in each affected production phase, and later it can be extrapolated to estimate the annual cost per affected production unit and per country. The model does not consider indirect costs such as the cost as a zoonosis, the revenues forgone, or an increase of labor.

In Silico Typing and Identification Confirmation of Isolates

Streptococcus suis is an important zoonotic pathogen causing severe infections in pigs and humans. Serotyping of S. suis strains is crucial for epidemiological surveillance, outbreak investigations, and understanding the pathogenesis of this bacterium. Here, we describe a step-by-step approach that enhances a previously developed pipeline by utilizing a computational script for efficient and accurate typing of S. suis strains. The pipeline is implemented in Perl programming language and leverages the Short Read Sequence Typing for Bacterial Pathogens (SRST2) tool. It integrates various bioinformatics techniques and utilizes multiple databases, including a serotype database, cpsH confirmation database, multi-locus sequence typing (MLST) database, recN species-specific gene database, and virulence gene database. These databases contain comprehensive information on S. suis serotypes, genetic markers, and virulence factors. The script can utilize paired-end or single-end fastq files as input and first confirms the species by sequence read data aligning to the recN gene, ensuring the accurate identification of S. suis strains. The pipeline next performs MLST typing and virulence factor identification using SRST2 while in a parallel processes it performs in silico serotyping of the strains. The pipeline offers a streamlined and semiautomated approach to serotyping S. suis strains, facilitating large-scale studies and reducing the manual effort required for data analysis.

An investigation into fecal shedding of Streptococcus suis serotypes in nursery pigs

Objective

The objective of this study was to monitor Streptococcus suis fecal shedding in nursery pigs on a farm with a history of S. suis disease involving serotypes 2 and 9.

Animal and procedure

Four cohorts of pigs (n = 480) were monitored from weaning to end of nursery. Rectal swabs from 297 pigs were tested and S. suis serotypes 15 (n = 7), 31 (n = 3), or untypeable (n = 6) isolates were recovered from 16 (5.4%) pigs.

Results

There was no significant association between S. suis fecal shedding and diarrhea. Streptococcus suis isolates recovered from pigs euthanized due to neurological signs or severe lameness were serotypes 9 (meninges) and 31 (tonsil) or untypeable (meninges, tonsil). Serotypes 9 (meninges, tonsil), 15 (spleen, tonsil), 16 (tonsil), 29 and 33 (nasal swabs), and untypeable (meninges, tonsil, and lung) isolates were identified in lame pigs.

Conclusion and clinical relevance

These results suggest that feces may not be a source of infection for the S. suis serotypes producing disease in pigs; however, the association between S. suis fecal shedding and diarrhea needs further investigation. The coincidence of untypeable isolates in feces from healthy pigs and their isolation from meninges of pigs with neurological signs warrants further investigation to determine the molecular characteristics of those isolates.

Detection and disease diagnosis trends (2017-2022) for Streptococcus suis, Glaesserella parasuis, Mycoplasma hyorhinis, Actinobacillus suis and Mycoplasma hyosynoviae at Iowa State University Veterinary Diagnostic Laboratory

BACKGROUND

Accurate measurement of disease associated with endemic bacterial agents in pig populations is challenging due to their commensal ecology, the lack of disease-specific antemortem diagnostic tests, and the polymicrobial nature of swine diagnostic cases. The main objective of this retrospective study was to estimate temporal patterns of agent detection and disease diagnosis for five endemic bacteria that can cause systemic disease in porcine tissue specimens submitted to the Iowa State University Veterinary Diagnostic Laboratory (ISU VDL) from 2017 to 2022. The study also explored the diagnostic value of specific tissue specimens for disease diagnosis, estimated the frequency of polymicrobial diagnosis, and evaluated the association between phase of pig production and disease diagnosis.

RESULTS

S. suis and G. parasuis bronchopneumonia increased on average 6 and 4.3%, while S. suis endocarditis increased by 23% per year, respectively. M. hyorhinis and A. suis associated serositis increased yearly by 4.2 and 12.8%, respectively. A significant upward trend in M. hyorhinis arthritis cases was also observed. In contrast, M. hyosynoviae arthritis cases decreased by 33% average/year. Investigation into the diagnostic value of tissues showed that lungs were the most frequently submitted sample, However, the use of lung for systemic disease diagnosis requires caution due to the commensal nature of these agents in the respiratory system, compared to systemic sites that diagnosticians typically target. This study also explored associations between phase of production and specific diseases caused by each agent, showcasing the role of S. suis arthritis in suckling pigs, meningitis in early nursery and endocarditis in growing pigs, and the role of G. parasuis, A. suis, M. hyorhinis and M. hyosynoviae disease mainly in post-weaning phases. Finally, this study highlighted the high frequency of co-detection and -disease diagnosis with other infectious etiologies, such as PRRSV and IAV, demonstrating that to minimize the health impact of these endemic bacterial agents it is imperative to establish effective viral control programs.

CONCLUSIONS

Results from this retrospective study demonstrated significant increases in disease diagnosis for S. suis, G. parasuis, M. hyorhinis, and A. suis, and a significant decrease in detection and disease diagnosis of M. hyosynoviae. High frequencies of interactions between these endemic agents and with viral pathogens was also demonstrated. Consequently, improved control programs are needed to mitigate the adverse effect of these endemic bacterial agents on swine health and wellbeing. This includes improving diagnostic procedures, developing more effective vaccine products, fine-tuning antimicrobial approaches, and managing viral co-infections.

Epidemiology and genetic diversity of Streptococcus suis in smallhold swine farms in the Philippines

This study aimed to determine the presence and characteristics of locally circulating strains of Streptococcus suis, the most important streptococcal pathogen in swine. Oral swab samples were collected from pigs from 664 representative smallhold farms across nine provinces in the Philippines. Isolates were identified and characterized using PCR assays. The study revealed an isolation rate of 15.8% (105/664, 95% CI: 13.0-18.6) among the sampled farms. Two hundred sixty-nine (269) S. suis isolates were recovered from 119 unique samples. Serotype 31 was the most prevalent (50/269, 95% CI: 13.9-23.2) among the other serotypes identified: 5, 6, 8, 9, 10, 11, 15, 16, 17, 21, 27, 28, and 29. The detection of the three 'classical' S. suis virulence-associated genes showed that 90.7% (244/269, 95% CI: 87.2-94.2) were mrp-/epf-/sly-. Multilocus sequence typing (MLST) analysis further revealed 70 novel sequence types (STs). Notably, several local isolates belonging to these novel STs formed clonal complexes (CC) with S. suis strains recovered from Spain and USA, which are major pork-exporting countries to the Philippines. This study functionally marks the national baseline knowledge of S. suis in Philippines.

Meningitis and sepsis caused by Streptococcus suis in an elderly woman: A CARE-compliant case report

RATIONALE

Streptococcus suis (S suis)-associated infections are uncommon but life-threatening diseases. The clinical manifestations vary from general symptoms of bacterial infection to fatal meningitis. The clinical manifestation and routine diagnostic testing is not specific enough to obtain well-time diagnosis.

PATIENT CONCERNS AND DIAGNOSIS

We report a case of meningitis and sepsis caused by S suis infection. A 70-year-old woman presented to our emergency department with generalized pain. After hospital admission, her condition rapidly deteriorated to fever, intracranial hypertension, and disturbance of consciousness. Examination of the blood and cerebrospinal fluid with metagenomic next-generation sequencing and bacterial cultures revealed S suis infection.

INTERVENTIONS AND OUTCOMES

After anti-infection therapy with meropenem and vancomycin, the patient recovered and was discharged from the hospital with no residual effects.

LESSONS

Human infections with S suis are extremely rare. If clinicians encounter a patient with fever, disturbance of consciousness, and intracranial hypertension, especially those who have been exposed to raw pork, S suis infection should be considered. Metagenomic next-generation sequencing can be a useful adjunct for the rapid diagnosis of S suis infection and aid in the planning of clinical treatment. Meanwhile, public health awareness is necessary to limit the risk of S suis infection.

Retrospective Analysis of the Detection of Pathogens Associated with the Porcine Respiratory Disease Complex in Routine Diagnostic Samples from Austrian Swine Stocks

The diagnostic workup of respiratory disease in pigs is complex due to coinfections and non-infectious causes. The detection of pathogens associated with respiratory disease is a pivotal part of the diagnostic workup for respiratory disease. We aimed to report how frequently certain viruses and bacteria were detected in samples from pigs with respiratory symptoms in the course of routine diagnostic procedures. Altogether, 1975 routine diagnostic samples from pigs in Austrian swine stocks between 2016 and 2021 were analysed. PCR was performed to detect various pathogens, including porcine reproductive and respiratory syndrome virus (PRRSV) (n = 921), influenza A virus (n = 479), porcine circovirus type 2 (PCV2) (n = 518), Mycoplasma (M.) hyopneumoniae (n = 713), Actinobacillus pleuropneumoniae (n = 198), Glaesserella (G.) parasuis (n = 165) and M. hyorhinis (n = 180). M. hyorhinis (55.1%) had the highest detection rate, followed by PCV2 (38.0%) and Streptococcus (S.) suis (30.6%). PRRSV was detected most frequently in a pool of lung, tonsil and tracheobronchial lymph node (36.2%). G. parasuis was isolated more frequently from samples taken after euthanasia compared to field samples. PRRSV-positive samples were more likely to be positive for PCV2 (p = 0.001), M. hyopneumoniae (p = 0.032) and Pasteurella multocida (p < 0.001). M. hyopneumoniae-positive samples were more likely to be positive for P. multocida (p < 0.001) and S. suis (p = 0.046), but less likely for M. hyorhinis (p = 0.004). In conclusion, our data provide evidence that lung samples that were positive for a primary pathogenic agent were more likely to be positive for a secondary pathogenic agent.

Risk factors associated with Streptococcus suis cases on pig farms in Spain

BACKGROUND

Streptococcus suis can cause meningitis, polyarthritis and acute death in piglets. However, the risk factors associated with S. suis infection remain incompletely understood. Therefore, a longitudinal study was carried out, in which six batches from two Spanish pig farms with S. suis problems were repeatedly examined to determine possible risk factors.

METHODS

A prospective case-control study was conducted, and potential risk factors were evaluated using mixed-effects logistic regression models. The explanatory variables included: (a) concomitant pathogens; (b) biomarkers associated with stress, inflammation and oxidative status; (c) farm environmental factors; and (d) parity and S. suis presence in sows. Three models were built to study the effect of these variables, including two to assess the risk factors involved in the subsequent development of disease.

RESULTS

Risk factors for S. suis-associated disease included porcine reproductive and respiratory syndrome virus co-infection at weaning (odds ratio [OR] = 6.69), sow parity (OR = 0.71), haptoglobin level before weaning (OR = 1.01), relative humidity (OR = 1.11) and temperature (OR = 0.13).

LIMITATIONS

Laboratory diagnosis was done at the batch level, with individual diagnosis based on clinical signs only.

CONCLUSIONS

This study confirms the multifactorial nature of S. suis-associated disease, with both environmental factors and factors related to the host involved in disease development. Controlling these factors may, therefore, help prevent the appearance of disease.

Interactions of Mycoplasma hyopneumoniae and/or Mycoplasma hyorhinis with Streptococcus suis Serotype 2 Using In Vitro Co-Infection Models with Swine Cells

Bacterial and/or viral co-infections are very common in swine production and cause severe economic losses. Mycoplasma hyopneumoniae, Mycoplasma hyorhinis and Streptococcus suis are pathogenic bacteria that may be found simultaneously in the respiratory tracts of pigs. In the present study, the interactions of S. suis with epithelial and phagocytic cells in the presence or absence of a pre-infection with M. hyopneumoniae and/or M. hyorhinis were studied. Results showed relatively limited interactions between these pathogens. A previous infection with one or both mycoplasmas did not influence the adhesion or invasion properties of S. suis in epithelial cells or its resistance to phagocytosis (including intracellular survival) by macrophages and dendritic cells. The most important effect observed during the co-infection was a clear increment in toxicity for the cells. An increase in the relative expression of the pro-inflammatory cytokines IL-6 and CXCL8 was also observed; however, this was the consequence of an additive effect due to the presence of different pathogens rather than a synergic effect. It may be hypothesized that if one or both mycoplasmas are present along with S. suis in the lower respiratory tract at the same time, then increased damage to epithelial cells and phagocytes, as well as an increased release of pro-inflammatory cytokines, may eventually enhance the invasive properties of S. suis. However, more studies should be carried out to confirm this hypothesis.

Serotype and multilocus sequence typing of Streptococcus suis from diseased pigs in Taiwan

Streptococcus suis (S. suis) infection can cause clinically severe meningitis, arthritis, pneumonia and septicemia in pigs. To date, studies on the serotypes, genotypes and antimicrobial susceptibility of S. suis in affected pigs in Taiwan are rare. In this study, we comprehensively characterized 388 S. suis isolates from 355 diseased pigs in Taiwan. The most prevalent serotypes of S. suis were serotypes 3, 7 and 8. Multilocus sequence typing (MLST) revealed 22 novel sequence types (STs) including ST1831-1852 and one new clonal complex (CC), CC1832. The identified genotypes mainly belonged to ST27, ST94 and ST1831, and CC27 and CC1832 were the main clusters. These clinical isolates were highly susceptible to ceftiofur, cefazolin, trimethoprim/sulfamethoxazole and gentamicin. The bacteria were prone to be isolated from cerebrospinal fluid and synovial fluid in suckling pigs with the majority belonging to serotype 1 and ST1. In contrast, ST28 strains that corresponded to serotypes 2 and 1/2 were more likely to exist in the lungs of growing-finishing pigs, which posted a higher risk for food safety and public health. This study provided the genetic characterization, serotyping and the most current epidemiological features of S. suis in Taiwan, which should afford a better preventative and treatment strategy of S. suis infection in pigs of different production stages.

Role of Metabolic Adaptation of Streptococcus suis to Host Niches in Bacterial Fitness and Virulence

Streptococcus suis, both a common colonizer of the porcine upper respiratory tract and an invasive pig pathogen, successfully adapts to different host environments encountered during infection. Whereas the initial infection mainly occurs via the respiratory tract, in a second step, the pathogen can breach the epithelial barrier and disseminate within the whole body. Thereby, the pathogen reaches other organs such as the heart, the joints, or the brain. In this review, we focus on the role of S. suis metabolism for adaptation to these different in vivo host niches to encounter changes in nutrient availability, host defense mechanisms and competing microbiota. Furthermore, we highlight the close link between S. suis metabolism and virulence. Mutants deficient in metabolic regulators often show an attenuation in infection experiments possibly due to downregulation of virulence factors, reduced resistance to nutritive or oxidative stress and to phagocytic activity. Finally, metabolic pathways as potential targets for new therapeutic strategies are discussed. As antimicrobial resistance in S. suis isolates has increased over the last years, the development of new antibiotics is of utmost importance to successfully fight infections in the future.

Novel Multiplex PCR Assay and Its Application in Detecting Prevalence and Antibiotic Susceptibility of Porcine Respiratory Bacterial Pathogens in Guangxi, China

Porcine respiratory disease complex (PRDC) is a serious disease caused by multiple pathogens which inflicts huge economic losses on the pig industry. Investigating the epidemiology of porcine respiratory bacterial pathogens (PRBPs) in specific geographic areas and exploring the antibiotic susceptibility of local strains will contribute to the prevention and control of PRDC. However, the epidemiology of PRBPs in Guangxi Province remains unclear, and existing diagnostic methods have multiple limitations, such as high costs and the detection of only a single pathogen at a time. In this study, we developed a multiplex PCR assay for Streptococcus suis, Glaesserella parasuis, Actinobacillus pleuropneumoniae, Pasteurella multocida, and Mycoplasma hyopneumoniae, and investigated the prevalence of PRBPs in pigs with respiratory symptoms in Guangxi Province. The isolates from positive samples were subjected to susceptibility tests to 16 antibiotics. Our results indicated that of the 664 samples from pigs with respiratory symptoms, 433 (65.21%), 320 (48.19%), 282 (42.47%), 23 (3.46%), and 9 (1.36%), respectively, carried each of these 5 pathogens; 533 samples were positive; and 377 (56.78%) carried multiple pathogens simultaneously. The dominant PRBPs in pigs with respiratory symptoms in Guangxi province were S. suis, G. parasuis, and A. pleuropneumoniae, which frequently co-infected swine herds. Most of the isolates (A. pleuropneumoniae, G. parasuis, S. suis, and P. multocida) were sensitive to cefquinome, ceftiofur, trimethoprim-sulfamethoxazole (TMP-SMX), and tiamulin antibiotics. We developed a rapid specific multiplex PCR assay for PRBPs. Our findings provide new information on the epidemiology of PRBPs in Guangxi Province and offer a reference for developing drug targets against PRDC. IMPORTANCE Pigs are closely associated with humans as the most common food animals and the vectors of numerous pathogens. PRDC, caused by multiple pathogens, is a serious disease that can cause growth retardation in swine and even sudden death. Due to the droplet transmission of PRBP and the similar clinical signs of different pathogen infections, most pig farms struggle to identify and control PRBPs, leading to the abuse of antibiotics. In addition, some PRBPs have the potential to infect humans and threaten human health. Therefore, this study developed a multiplex PCR method targeting PRBPs, investigated the prevalence of these pathogens, and tested their antibiotic susceptibility. Our studies have important implications for public health safety and the development of the pig industry.

Viral and Bacterial Profiles in Endemic Influenza A Virus Infected Swine Herds Using Nanopore Metagenomic Sequencing on Tracheobronchial Swabs

Swine influenza A virus (swIAV) plays an important role in porcine respiratory infections. In addition to its ability to cause severe disease by itself, it is important in the multietiological porcine respiratory disease complex. Still, to date, no comprehensive diagnostics with which to study polymicrobial infections in detail have been offered. Hence, veterinary practitioners rely on monospecific and costly diagnostics, such as Reverse Transcription quantitative PCR (RT-qPCR), antigen detection, and serology. This prevents the proper understanding of the entire disease context, thereby hampering effective preventive and therapeutic actions. A new, nanopore-based, metagenomic diagnostic platform was applied to study viral and bacterial profiles across 4 age groups on 25 endemic swIAV-infected German farms with respiratory distress in the nursery. Farms were screened for swIAV using RT-qPCR on nasal and tracheobronchial swabs (TBS). TBS samples were pooled per age, prior to metagenomic characterization. The resulting data showed a correlation between the swIAV loads and the normalized reads, supporting a (semi-)quantitative interpretation of the metagenomic data. Interestingly, an in-depth characterization using beta diversity and PERMANOVA analyses allowed for the observation of an age-dependent interplay of known microbial agents. Also, lesser-known microbes, such as porcine polyoma, parainfluenza, and hemagglutinating encephalomyelitis viruses, were observed. Analyses of swIAV incidence and clinical signs showed differing microbial communities, highlighting age-specific observations of various microbes in porcine respiratory disease. In conclusion, nanopore metagenomics were shown to enable a panoramic view on viral and bacterial profiles as well as putative pathogen dynamics in endemic swIAV-infected herds. The results also highlighted the need for better insights into lesser studied agents that are potentially associated with porcine respiratory disease. IMPORTANCE To date, no comprehensive diagnostics for the study of polymicrobial infections that are associated with porcine respiratory disease have been offered. This precludes the proper understanding of the entire disease landscape, thereby hampering effective preventive and therapeutic actions. Compared to the often-costly diagnostic procedures that are applied for the diagnostics of porcine respiratory disease nowadays, a third-generation nanopore sequencing diagnostics workflow presents a cost-efficient and informative tool. This approach offers a panoramic view of microbial agents and contributes to the in-depth observation and characterization of viral and bacterial profiles within the respiratory disease context. While these data allow for the study of age-associated, swIAV-associated, and clinical symptom-associated observations, it also suggests that more effort should be put toward the investigation of coinfections and lesser-known pathogens (e.g., PHEV and PPIV), along with their potential roles in porcine respiratory disease. Overall, this approach will allow veterinary practitioners to tailor treatment and/or management changes on farms in a quicker, more complete, and cost-efficient way.

Paeoniflorin combined with norfloxacin ameliorates drug-resistant Streptococcus suis infection

BACKGROUND

The increased resistance of bacterial pathogens to fluoroquinolones (FQs), such as norfloxacin and ciprofloxacin, supports the need to develop new antibacterial drugs and combination therapies using conventional antibiotics. The LuxS/AI-2 quorum sensing (QS) system can regulate the complex group behaviour of Streptococcus suis and impact its susceptibility to FQs.

OBJECTIVES

We investigated the combination of paeoniflorin and norfloxacin as a novel and effective strategy against FQ-resistant S. suis.

METHODS

FIC, AI-2 activity assay, real-time RT-PCR and biofilm inhibition assays were performed to investigate the in vitro effect of paeoniflorin combined with norfloxacin. Mouse protection and mouse anti-infection assays were performed to investigate the in vivo effect of paeoniflorin combined with norfloxacin.

RESULTS

FIC results showed that paeoniflorin and norfloxacin exert a synergistic bactericidal effect. Evidence was brought that paeoniflorin reduces the S. suis AI-2 activity and significantly down-regulates the transcription of the FQ efflux pump gene. In addition, paeoniflorin can inhibit biofilm formation, thereby promoting the ability of norfloxacin to kill S. suis. Finally, we showed in a mouse model that paeoniflorin in association with norfloxacin is effective to treat S. suis infections.

CONCLUSIONS

This study highlighted the inhibitory potential of paeoniflorin on the LuxS/AI-2 QS system of S. suis, and provided evidence that it can inhibit the FQ efflux pump and prevent biofilm formation to cooperate with norfloxacin in the treatment of resistant S. suis-related infections.

Revealing the Changes in Saliva and Serum Proteins of Pigs with Meningitis Caused by Streptococcus Suis: A Proteomic Approach

Meningitis due to Streptococcus suis causes high mortality and morbidity on pig farms and has increasing zoonotic potential worldwide. Saliva proteome analysis would potentially be useful in elucidating pathophysiological changes and mining for new biomarkers to diagnose and monitor S. suis infection. The objective of this study was to investigate the changes in the salivary and serum proteome profile of piglets with meningitis. The LC-MS/MS TMT proteomic approach was used to analyze saliva and serum samples from 20 male piglets: 10 with meningitis and 10 healthy. In saliva, 11 proteins had higher and 10 had lower relative abundance in piglets with meningitis. The proteins with the highest relative abundance were metavinculin (VCL) and desmocollin-2 (DSC2). Adenosine deaminase (ADA) was selected for validation using a spectrophotometric assay and demonstrated excellent performance in the differentiation between healthy and pigs with meningitis due to S. suis. In serum, the most protruding changes occurred for one SERPIN and haptoglobin (HP). In saliva and serum, the highest number of proteins with altered abundance were linked, via the enrichment analysis, with platelet and neutrophil pathways. Overall, meningitis caused by S. suis resulted in specific proteome changes in saliva and serum, reflecting different pathophysiological mechanisms, and marking new potential biomarkers for this infection.

Diversity of respiratory viruses present in nasal swabs under influenza suspicion in respiratory disease cases of weaned pigs

Respiratory diseases in weaned pigs are a common problem, with a complex etiology involving both viruses and bacteria. In the present study, we investigated the presence of eleven viruses in nasal swabs, collected from nurseries (55 cases) under the suspicion of swine influenza A virus (swIAV) and submitted by swine veterinarians for diagnosis. The other ten viruses included in the study were influenza B (IBV) and D (IDV), Porcine reproductive and respiratory syndrome virus (PRRSV), Porcine respiratory coronavirus (PRCV), Porcine cytomegalovirus (PCMV), Porcine circovirus 2 (PCV2), 3 (PCV3) and 4 (PCV), Porcine parainfluenza 1 (PPIV1) and Swine orthopneumovirus (SOV). Twenty-six swIAV-positive cases and twenty-nine cases of swIAV-negative respiratory disease were primarily established. While IBV, IDV, PCV4 and PPIV1 were not found in any of the cases, PRCV, SOV, and PCMV were more likely to be found in swIAV-positive nurseries with respiratory disease (p < 0.05). Overall, PCV3, PRRSV, and PCMV were the most frequently detected agents at herd level. Taken individually, virus prevalence was: swIAV, 48.6%; PRCV, 48.0%; PRRSV, 31.6%; SOV, 33.8%; PCMV, 48.3%, PCV2, 36.0%; and PCV3, 33.0%. Moreover, low Ct values (<30) were common for all agents, except PCV2 and PCV3. When the correlation between pathogens was individually examined, the presence of PRRSV was negatively correlated with swIAV and PRCV, while was positively associated to PCMV (p < 0.05). Also, PRCV and SOV were positively correlated between them and negatively with PCMV. Besides, the analysis of suckling pig samples, collected in subclinically infected farrowing units under an influenza monitoring program, showed that circulation of PRCV, PCMV, SOV, and PCV3 started during the early weeks of life. Interestingly, in those subclinically infected units, none of the pathogens was found to be correlated to any other. Overall, our data may contribute to a better understanding of the complex etiology and epidemiology of respiratory diseases in weaners. This is the first report of SOV in Spain and shows, for the first time, the dynamics of this pathogen in swine farms.

Detection of Porcine Circovirus Type 2a and Pasteurella multocida Capsular Serotype D in Growing Pigs Suffering from Respiratory Disease

In order to diagnose a respiratory disease in a pig farm, the lungs, spleen, and lymph nodes of three dead pigs were collected for pathogen detection by PCR and isolation on the basis of preliminary clinical diagnosis. The virus isolate was identified by gene sequence analysis and Immunoperoxidase monolayer assay (IPMA). The bacterial isolate was identified by biochemical tests, 16S rDNA sequence analysis, and species- and serotype-specific PCR, and the pathogenicity was analyzed. Porcine circovirus type 2a (PCV2a) genotype from the lungs, spleen, and lymph nodes and Pasteurella (P.) multocida capsular serotypes D from the lungs were found. The PCV2a isolates could specifically bound the anti-PCV2-Cap polyclonal antibody. The 16S rDNA sequence of P. multocida isolates had 99.9% identity with that of the strain from cattle, and the isolate was highly pathogenic to mice. The results showed that the co-infection of PCV2a and P. Multocida capsular serotypes D should be responsible for the disease. The uncommon PCV2a is still prevalent in some pig farms besides the dominant PCV2d genotype. This study could provide important etiological information for effective control and treatment of the disease in pig farms.

From Farm to Fork: Streptococcus suis as a Model for the Development of Novel Phage-Based Biocontrol Agents

Bacterial infections of livestock threaten the sustainability of agriculture and public health through production losses and contamination of food products. While prophylactic and therapeutic application of antibiotics has been successful in managing such infections, the evolution and spread of antibiotic-resistant strains along the food chain and in the environment necessitates the development of alternative or adjunct preventive and/or therapeutic strategies. Additionally, the growing consumer preference for “greener” antibiotic-free food products has reinforced the need for novel and safer approaches to controlling bacterial infections. The use of bacteriophages (phages), which can target and kill bacteria, are increasingly considered as a suitable measure to reduce bacterial infections and contamination in the food industry. This review primarily elaborates on the recent veterinary applications of phages and discusses their merits and limitations. Furthermore, using Streptococcus suis as a model, we describe the prevalence of prophages and the anti-viral defence arsenal in the genome of the pathogen as a means to define the genetic building blocks that are available for the (synthetic) development of phage-based treatments. The data and approach described herein may provide a framework for the development of therapeutics against an array of bacterial pathogens.

Vaccination with an Escherichia coli F4/F18 Vaccine Improves Piglet Performance Combined with a Reduction in Antimicrobial Use and Secondary Infections Due to Streptococcus suis

Simple Summary

Post-weaning diarrhea (PWD) due to Escherichia coli (E. coli) remains a major cause of economic losses for the pig industry. Therapy to combat PWD typically consists of antibiotic treatment or supplementation of zinc oxide to the feed. The emergence of antimicrobial resistance and new EU regulations prompt the need for alternative control strategies, such as immunization. The aim of the field study was to evaluate the effect of an oral live non-pathogenic E. coli vaccine on piglet performance, health, and antimicrobial use. We compared 10 batches receiving a standard antimicrobial control treatment to 10 batches vaccinated with the oral E. coli vaccine. The vaccine-treated groups demonstrated a significant improvement in performance, mortality weight, and antimicrobial use. In addition, secondary infections due to Streptococcus suis in the second part of nursery were reduced, as indicated by the reduction in amoxicillin use. In conclusion, the present study demonstrates the efficacy of an oral live non-pathogenic E. coli vaccine for the active immunization of piglets against PWD under field conditions. Therefore, vaccination against PWD may be considered a valuable alternative for strengthening piglet performance while meeting the new EU requirements concerning the prudent use of antimicrobials in intensive pig production.

Abstract

Post-weaning diarrhea (PWD) due to Escherichia coli (E. coli) remains a major cause of economic losses for the pig industry. Therapy to combat PWD typically consists of antibiotic treatment or supplementation of zinc oxide to the feed. The emergence of antimicrobial resistance to E. coli and new EU regulations prompt the need for alternative control strategies, such as immunization. The aim of the field study was to evaluate the effect of an oral live non-pathogenic E. coli vaccine on piglet performance, health, and antimicrobial use. We evaluated vaccination with an oral live non-pathogenic E. coli F4/F18 under field conditions in 10 consecutive batches against a standard antimicrobial treatment in 10 historical control batches. The vaccine-treated groups demonstrated a significant improvement in feed conversion rate, mortality weight, and antimicrobial use. From a general health perspective, secondary infections due to Streptococcus suis (S. suis) in the second part of nursery were markedly reduced, as indicated by the reduction in amoxicillin use. In conclusion, the present study demonstrates the efficacy of an oral live non-pathogenic E. coli vaccine for active immunization of piglets against PWD under field conditions. The vaccine-treated groups showed an improvement in several economically important performance parameters while reducing the overall antimicrobial use and infection pressure due to S. suis. Therefore, vaccination against PWD may be considered a valuable alternative for consolidating piglet performance while meeting the new EU requirements concerning the prudent use of antimicrobials in intensive pig production.

New Insights into Neutrophil Extracellular Trap (NETs) Formation from Porcine Neutrophils in Response to Bacterial Infections

Actinobacillus pleuropneumoniae (A.pp, Gram negative) and Streptococcus (S.) suis (Gram positive) can cause severe diseases in pigs. During infection, neutrophils infiltrate to counteract these pathogens with phagocytosis and/or neutrophil extracellular traps (NETs). NETs consist of a DNA-backbone spiked with antimicrobial components. The NET formation mechanisms in porcine neutrophils as a response to both of the pathogens are not entirely clear. The aim of this study was to investigate whether A.pp (serotype 2, C3656/0271/11) and S. suis (serotype 2, strain 10) induce NETs by NADPH oxidase- or CD18-dependent mechanisms and to characterize phenotypes of NETs in porcine neutrophils. Therefore, we investigated NET induction in porcine neutrophils in the presence and absence of NET inhibitors and quantified NETs after 3 h. Furthermore, NETosis and phagocytosis were investigated by transmission electron microscopy after 30 min to characterize different phenotypes. A.pp and S. suis induce NETs that are mainly ROS-dependent. A.pp induces NETs that are partially CD18-dependent. Thirty minutes after infection, both of the pathogens induced a vesicular NET formation with only slight differences. Interestingly, some neutrophils showed only NET-marker positive phagolysosomes, but no NET-marker positive vesicles. Other neutrophils showed vesicular NETs and only NET-marker negative phagolysosomes. In conclusion, both of the pathogens induce ROS-dependent NETs. Vesicular NETosis and phagocytosis occur in parallel in porcine neutrophils in response to S. suis serotype 2 and A.pp serotype 2.

Comparative Analysis of the Upper Respiratory Bacterial Communities of Pigs with or without Respiratory Clinical Signs: From Weaning to Finishing Phase

Simple Summary

In this work, we performed a prospective study to compare bacterial communities in the nasal and laryngeal cavities of pigs with or without clinical signs of respiratory disease which were followed in a longitudinal fashion, at three critical phases of production, from weaning to the finishing phase. The findings reported here provide evidence that the composition of the upper respiratory tract bacterial microbiota differs significantly when comparing pigs with or without respiratory clinical signs after weaning; these differences were maintained in the nursery phase but were not observed at the finishing phase. Our results contribute to the knowledge of the porcine microbiota at different stages of production, providing new insights into the role of bacteria in the early stages of respiratory diseases.

Abstract

A prospective study was conducted to identify bacterial communities in the nasal and laryngeal cavities of pigs with or without clinical signs of respiratory disease in a longitudinal fashion, from weaning to the finishing phase. Nasal and laryngeal swabs were collected from asymptomatic pigs (n = 30), as well as from pigs with clinical signs of respiratory disease (n = 30) at the end of the weaning (T1—33 days) phase, end of the nursery phase (T2—71 days), and finishing (T3—173 days). Total DNA was extracted from each sample, and the V4 hypervariable region of the 16S rRNA gene was amplified and sequenced with the Illumina MiSeq platform. Principal coordinates analysis indicated no significant differences between the nasal and laryngeal bacterial communities. Nevertheless, the microbiota composition in the upper respiratory tract (URT) was clearly distinct between animals, with or without signs of respiratory disease, particularly at post-weaning and the end of nursery. In pigs with clinical signs of respiratory disease, Actinobacillus, Streptococcus Porphyromonas, Veillonella, and an unclassified genus of Pasteurellaceae were more abundant than in pigs with no signs. Metabolic prediction identified 28 differentially abundant pathways, mainly related to carbohydrate, energy, amino acid, anaerobic, and nucleotide metabolism in symptomatic pigs (especially in T2). These findings provide evidence that the composition of the URT bacterial microbiota differs significantly when comparing pigs with or without respiratory clinical signs after weaning, and this difference is maintained in the nursery phase; such differences, however, were not evident at the finishing phase.

A Proteomic Approach to Elucidate the Changes in Saliva and Serum Proteins of Pigs with Septic and Non-Septic Inflammation

Sepsis is a systemic inflammatory response triggered by an infectious agent and is recognized by the World Health Organization as a global concern, since it is one of the major causes of severe illness in humans and animals. The study of the changes that can occur in saliva and serum in sepsis can contribute to a better understanding of the pathophysiological mechanisms involved in the process and also to discover potential biomarkers that can help in its diagnosis and monitoring. The objective of this study was to characterize the changes that occur in the salivary and serum proteome of pigs with experimentally-induced sepsis. The study included five pigs with sepsis induced by LPS administration and five pigs with non-septic inflammation induced by turpentine for comparative purposes. In saliva, there were eighteen salivary proteins differentially expressed in the sepsis condition and nine in non-septic inflammation. Among these, significant increments in aldolase A and serpin B12 only occurred in the sepsis model. Changes in aldolase A were validated in a larger population of pigs with sepsis due to Streptococcus suis infection. In serum, there were 30 proteins differentially expressed in sepsis group and 26 proteins in the non-septic group, and most of the proteins that changed in both groups were related to non-specific inflammation. In the saliva of the septic animals there were some specific pathways activated, such as the organonitrogen compound metabolic process and lipid transport, whereas, in the serum, one of the main activated pathways was the regulation of protein secretion. Overall, saliva and serum showed different proteome variations in response to septic inflammation and could provide complementary information about the pathophysiological mechanisms occurring in this condition. Additionally, salivary aldolase A could be a potential biomarker of sepsis in pigs that should be confirmed in a larger population.

Antimicrobial Susceptibility Testing of Porcine Bacterial Pathogens: Investigating the Prospect of Testing a Representative Drug for Each Antimicrobial Family

Antimicrobial susceptibility testing is necessary to carry out antimicrobial stewardship but a limited number of drugs belonging to each antimicrobial family has to be tested for technical limitations and economic resources. In this study, we have determined the minimal inhibitory concentration, using microdilution following international standards (CLSI), for 490 Actinobacillus pleuropneumoniae, 285 Pasteurella multocida, 73 Bordetella bronchiseptica, 398 Streptococcus suis and 1571 Escherichia coli strains from clinical cases collected in Spain between 2018 and 2020. The antimicrobial susceptibility pattern was deciphered using a principal component analysis for each bacterium and a matrix correlation (high > 0.8, medium 0.5−0.8 and low < 0.5) was obtained for each pair of antimicrobials. No significant associations were observed between MIC patterns for different antimicrobial families, suggesting that co-selection mechanisms are not generally present in these porcine pathogens. However, a high correlation was observed between the fluroquinolones (marbofloxacin and enrofloxacin) for all mentioned pathogens and for ceftiofur and cefquinome for E. coli and S. suis. Moreover, a significant association was also observed for tetracyclines (doxycycline and oxytetracycline) and B. bronchiseptica and tildipirosin/tulathromycin for P. multocida. These results suggest that generally, a representative drug per antimicrobial class cannot be selected, however, for some drug−bug combinations, MIC values from one representative drug could be extrapolated to the whole antimicrobial family.

Measurement of procalcitonin in saliva of pigs: a pilot study

Background

Procalcitonin (PCT) is a widely used biomarker of sepsis in human medicine and can have potential applications in the veterinary field. This study aimed to explore whether PCT could be measured in the saliva of pigs and whether its concentration changes in sepsis. Therefore, a specific assay was developed and analytically validated, and changes in PCT concentration were evaluated in two conditions: a) in an experimental model of sepsis produced by the administration of lipopolysaccharide (LPS) to pigs (n = 5), that was compared with a model of non-septic inflammation induced by turpentine oil (n = 4), and b) in healthy piglets (n = 11) compared to piglets with meningitis (n = 20), a disease that usually involves sepsis and whose treatment often requires large amounts of antibiotics in farms.

Results

The assay showed coefficients of variation within the recommended limits and adequate linearity after serial sample dilutions. The method's detection limit was set at 68 μg/L, and the lower limit of quantification was 414 μg/L. In the LPS experiment, higher concentrations of PCT were found after 24 h in the animals injected with LPS (mean = 5790 μg/L) compared to those treated with turpentine oil (mean = 2127 μg/L, P = 0.045). Also, animals with meningitis had higher concentrations of PCT (mean = 21515 μg/L) than healthy pigs (mean = 6096 μg/L, P value < 0.0001).

Conclusions

According to these results, this assay could be potentially used as a tool for the non-invasive detection of sepsis in pigs, which is currently a topic of high importance due to antibiotic use restriction.

Compositional analysis of the tonsil microbiota in relationship to Streptococcus suis disease in nursery pigs in Ontario

BACKGROUND

The tonsil of the soft palate in pigs is the colonization site of both commensal and pathogenic microbial agents. Streptococcus suis infections are a significant economic problem in the swine industry. The development of S. suis disease remains poorly understood. The purpose of this study was to identify whether the tonsillar microbiota profile in nursery pigs is altered with S. suis disease. Here, the dynamics of the tonsillar microbiota from 20 healthy pigs and 43 diseased pigs with S. suis clinical signs was characterized.

RESULTS

Based on the presence or absence of S. suis in the systemic sites, diseased pigs were classified into confirmed (n = 20) or probable (n = 23) group, respectively. Microbiota composition was assessed using the V3-V4 hypervariable region of the 16S rRNA, and results were analyzed to identify the diversity of the tonsillar microbiota. The taxonomic composition of the tonsil microbiota proved to be highly diverse between individuals, and the results showed statistically significant microbial community structure among the diagnosis groups. The confirmed group had the lowest observed species richness while the probable group had higher phylogenetics diversity level compared to the healthy group. Un-weighted Unifrac also demonstrated that the probable group had a higher beta diversity than both the healthy and the confirmed group. A Dirichlet-multinomial mixture (DMM) model-based clustering method partitioned the tonsil microbiota into two distinct community types that did not correspond with disease status. However, there was an association between Streptococcus suis serotype 2 and DMM community type 1 (p = 0.03). ANCOM-BC identified 24 Streptococcus amplicon sequence variants (ASVs) that were differentially abundant between the DMM community types.

CONCLUSIONS

This study provides a comprehensive analysis of the structure and membership of the tonsil microbiota in nursery pigs and uncovers differences and similarities across varying S. suis disease status. While the overall abundance of Streptococcus was not different among the diagnosis groups, the unique profile of DMM community type 1 and the observed correlation with S. suis serotype 2 could provide insight into potential tonsillar microbiota involvement in S. suis disease.

Distribution and characterization of Streptococcus suis serotypes isolated from January 2015 to June 2020 from diseased pigs in Québec, Canada

Streptococcus suis is one of the most important swine bacterial pathogens causing economic losses. This report presents the serotype distribution of S. suis recovered from diseased pigs in Québec from January 2015 to June 2020. Serotypes 1/2 and 2 predominated, followed by serotypes 7, 3, 5, 4, 9, 1, and 14. Compared to previously reported data, very few changes could be observed concerning the serotype distribution, indicating a relative stability. Half of the untypable isolates did not belong to the species S. suis sensu stricto, as determined by recN polymerase chain reaction. Less than 10% of "real S. suis" isolates were untypable. The genetic diversity of S. suis serotypes 1, 2, and 14, as analyzed by multilocus sequence typing, was mainly represented by sequence type (ST)1, ST28, ST25, and ST94. All ST1 isolates (considered highly virulent) belonged to either serotype 1 or 14.

Genomic and pathogenic investigations of Streptococcus suis serotype 7 population derived from a human patient and pigs

Streptococcus suis is one of the important emerging zoonotic pathogens. Serotype 2 is most prevalent in patients worldwide. In the present study, we first isolated one S. suis serotype 7 strain GX69 from the blood culture of a patient with septicemia complicated with pneumonia in China. In order to deepen the understanding of S. suis serotype 7 population characteristics, we investigated the phylogenetic structure, genomic features, and virulence of S. suis serotype 7 population, including 35 strains and 79 genomes. Significant diversities were revealed in S. suis serotype 7 population, which were clustered into 22 sequence types (STs), five minimum core genome (MCG) groups, and six lineages. Lineages 1, 3a, and 6 were mainly constituted by genomes from Asia. Genomes of Lineages 2, 3b, and 5a were mainly from Northern America. Most of genomes from Europe (41/48) were clustered into Lineage 5b. In addition to strain GX69, 13 of 21 S. suis serotype 7 representative strains were classified as virulent strains using the C57BL/6 mouse model. Virulence-associated genes preferentially present in highly pathogenic S. suis serotype 2 strains were not suitable as virulence indicators for S. suis serotype 7 strains. Integrative mobilizable elements were widespread and may play a critical role in disseminating antibiotic resistance genes of S. suis serotype 7 strains. Our study confirmed S. suis serotype 7 is a non-negligible pathotype and deepened the understanding of the population structure of S. suis serotype 7, which provided valuable information for the improved surveillance of this serotype.

The Role of Pathology in the Diagnosis of Swine Respiratory Disease

The definition “porcine respiratory disease complex” (PRDC) is used to indicate the current approach for presenting respiratory pathology in modern pig farming. PRDC includes pneumonias with variable pictures, mixed with both aerogenous and hematogenous forms with variable etiology, often multimicrobial, and influenced by environmental and management factors. The notion that many etiological agents of swine respiratory pathology are ubiquitous in the airways is commonly understood; however, their isolation or identification is not always associable with the current pathology. In this complex context, lung lesions registered at slaughterhouse or during necropsy, and supplemented by histological investigations, must be considered as powerful tools for assigning a prominent role to etiologic agents. In recent years, the goal of colocalizing causative agents with the lesions they produce has been frequently applied, and valid examples in routine diagnostics are those that indicate pulmonary involvement during porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) infections.

Experimental evaluation of protection and immunogenicity of Streptococcus suis bacterin-based vaccines formulated with different commercial adjuvants in weaned piglets

Streptococcus suis is an important swine pathogen responsible for economic losses to the swine industry worldwide. There is no effective commercial vaccine against S. suis. The use of autogenous (“bacterin”) vaccines to control S. suis outbreaks is a frequent preventive measure in the field, although scientific data on immunogenicity and reduction in mortality and morbidity are scarce. The goal of our study is to experimentally evaluate the immunogenicity and protective efficacy against homologous challenge in weaned piglets of a S. suis serotype 2 bacterin-based vaccine formulated with six different commercial adjuvants (Alhydrogel®, Emulsigen®-D, Quil-A®, Montanide™ ISA 206 VG, Montanide™ ISA 61 VG, and Montanide™ ISA 201 VG). The vaccine formulated with Montanide™ ISA 61 VG induced a significant increase in anti-S. suis antibodies, including both IgG1 and IgG2 subclasses, protected against mortality and significantly reduced morbidity and severity of clinical signs. Vaccines formulated with Montanide ISA 206 VG or Montanide ISA 201 VG also induced a significant increase in anti-S. suis antibodies and showed partial protection and reduction of clinical signs severity. Vaccines formulated with Alhydrogel®, Emulsigen®-D, or Quil-A® induced a low and IgG1-shifted antibody response and failed to protect vaccinated piglets against a homologous challenge. In conclusion, the type of adjuvant used in the vaccine formulation significantly influenced the immune response and efficacy of the vaccine against a homologous challenge.

Adding value to food chain information: using data on pig welfare and antimicrobial use on-farm to predict meat inspection outcomes

BACKGROUND

Using Food Chain Information data to objectively identify high-risk animals entering abattoirs can represent an important step forward towards improving on-farm animal welfare. We aimed to develop and evaluate the performance of classification models, using Gradient Boosting Machine algorithms that utilise accurate longitudinal on-farm data on pig health and welfare to predict condemnations, pluck lesions and low cold carcass weight at slaughter.

RESULTS

The accuracy of the models was assessed using the area under the receiver operating characteristics (ROC) curve (AUC). The AUC for the prediction models for pneumonia, dorsocaudal pleurisy, cranial pleurisy, pericarditis, partial and total condemnations, and low cold carcass weight varied from 0.54 for pneumonia and 0.67 for low cold carcass weight. For dorsocaudal pleurisy, ear lesions assessed on pigs aged 12 weeks and antimicrobial treatments (AMT) were the most important prediction variables. Similarly, the most important variable for the prediction of cranial pleurisy was the number of AMT. In the case of pericarditis, ear lesions assessed both at week 12 and 14 were the most important variables and accounted for 33% of the Bernoulli loss reduction. For predicting partial and total condemnations, the presence of hernias on week 18 and lameness on week 12 accounted for 27% and 14% of the Bernoulli loss reduction, respectively. Finally, AMT (37%) and ear lesions assessed on week 12 (15%) were the most important variables for predicting pigs with low cold carcass weight.

CONCLUSIONS

The findings from our study show that on farm assessments of animal-based welfare outcomes and information on antimicrobial treatments have a modest predictive power in relation to the different meat inspection outcomes assessed. New research following the same group of pigs longitudinally from a larger number of farms supplying different slaughterhouses is required to confirm that on farm assessments can add value to Food Chain Information reports.