Early immune response of two common carp breeds to koi herpesvirus infection.

Economic importance of common carp (Cyprinus carpio L.) increases every year. Viral diseases are major threat for carp aquaculture and cause significant economic losses. Koi herpesvirus (KHV) is one of the most serious carp diseases. Current study is focused on confirmation of possible differences in early immune response to KHV depending on level of resistance. Class I interferon signalling, complement cascade and cell-mediated cytotoxicity are hypothesized as major mechanisms of early innate immune response against KHV. Different breeds of common carp show distinct level of resistance to KHV. Two breeds of common carp with completely different susceptibility to KHV were chosen for current research: amur wild carp (AS) as highly resistant and koi carp (KOI) as very susceptible breed. KHV infection caused no mortalities, but the viral load in selected tissues increased during infection. Levels of expressions of chosen genes was examined using qRT-PCR and overall change in protein expression profiles was analysed by mass spectrometry. Significant differences in immune response between AS and KOI were detected mostly at the level of protein expression. Although cell-mediated cytotoxicity showed minimal influence during KHV infection, many immune response parameters related to class I interferon signalling pathway and complement cascade were increased earlier during KHV infection in AS comparing to KOI.

Occurrence of virulence-associated genes in Streptococcus uberis and Streptococcus parauberis isolated from bovine mastitis.

Streptococcus uberis is one of the most important mastitis-causing pathogens. Although the pathogenesis and virulence factors required for the intramammary infection development are not yet well established, several putative virulence-associated genes have been described. This work aimed to investigate the presence of ten known and putative virulence-associated genes in S. uberis isolated from subclinical or clinical mastitis and its closely related species Streptococcus parauberis in 135 dairy farms in the Czech Republic. The PCR analysis detected that all the examined isolates possessed at least four virulence genes and most isolates carried eight out of ten virulence genes. All S. uberis isolates were positive for the oppF, gapC and sua genes. Among the most prevalent virulence-associated genes skc (98%) and pauA (97%) were also found. The hasA and hasB genes were always present together in 94% of the isolates. The genes cfu and lbp were detected in 6% and 2%, respectively. In the S. uberis isolates, 14 different virulence gene profiles were observed. The most frequent profile was hasA + hasB + sua + skc + pauA + gapC + oppF with variable hasC, observed in 86% of the tested isolates, occurring in 127 out of 135 farms. S. parauberis was identified very sporadically and, although it is closely related to S. uberis, only a rare occurrence of the examined virulence-associated genes was found.

Resolution of Streptococcus suis Serotypes 1/2 versus 2 and 1 versus 14 by PCR-Restriction Fragment Length Polymorphism Method.

Streptococcus suis is an important pathogen of pigs but is also transmissible to humans, with potentially fatal consequences. Among 29 serotypes currently recognized, some are clinically and epidemiologically more important than others. This is particularly true for serotypes 2 and 14, which have a large impact on pig production and also on human health. Conventional PCR-based serotyping cannot distinguish between serotype 1/2 and serotype 2 or between serotype 1 and serotype 14. Although serotype 1/2 and serotype 2 have a very similar cps locus, they differ in a single-nucleotide substitution at nucleotide position 483 of the cpsK gene. Similarly, serotypes 1 and 14 have a very similar cps locus but also differ in the same nucleotide substitution of the cpsK gene. Fortunately, this cpsK 483G→C/T substitution can be detected by BstNI restriction endonuclease. A PCR-restriction fragment length polymorphism (RFLP) detection method amplifying a fragment of the cpsK gene digested by BstNI restriction endonuclease was developed and tested in reference strains of these serotypes and also in field isolates.

Characterization of humoral and cell-mediated immunity in rabbits orally infected with Encephalitozoon cuniculi.

Encephalitozoonosis is a common infectious disease widely spread among rabbits. Encephalitozoon cuniculi, is considered as a zoonotic and emerging pathogen capable of infecting both immunocompetent and immunocompromised hosts. The aim of the study was to describe in detail the spread of the E. cuniculi in a rabbit organism after experimental infection and the host humoral and cellular immune response including cytokine production. For that purpose, healthy immunocompetent rabbits were infected orally in order to simulate the natural route of infection and euthanised at 2, 4, 6 and 8-weeks post-infection. Dissemination of E. cuniculi in the body of the rabbit was more rapid than previously reported. As early as 2 weeks post-infection, E. cuniculi was detected using immunohistochemistry not only in the intestine, mesenteric lymph nodes, spleen, liver, kidneys, lungs and heart, but also in nervous tissues, especially in medulla oblongata, cerebellum, and leptomeninges. Based on flow cytometry, no conspicuous changes in lymphocyte subpopulations were detected in the examined lymphoid organs of infected rabbits. Cell-mediated immunity was characterized by ability of both CD4+ and CD8+ T cells to proliferate after stimulation with specific antigens. Th1 polarization of immune response with a predominance of IFN-γ expression was detected in spleen, mesenteric lymph nodes and Peyer's patches. The increased expression of IL-4 and IL-10 mRNA in mixed samples from the small intestine is indicative of balanced control of IFN-γ, which prevents tissue damage. On the other hand, it can enable E. cuniculi to survive and persist in the host organism in a balanced host-parasite relationship. The Th17 immunity lineage seems to play only a minor role in E. cuniculi infection in rabbits.

Concurrent infection with porcine reproductive and respiratory syndrome virus and Haemophilus parasuis in two types of porcine macrophages: apoptosis, production of ROS and formation of multinucleated giant cells.

Porcine reproductive and respiratory syndrome (PRRS) is one of the most significant and economically important infectious diseases affecting swine worldwide and can predispose pigs to secondary bacterial infections caused by, e.g. Haemophilus parasuis. The aim of the presented study was to compare susceptibility of two different types of macrophages which could be in contact with both pathogens during infection with PRRS virus (PRRSV) and in co-infection with H. parasuis. Alveolar macrophages (PAMs) as resident cells provide one of the first lines of defence against microbes invading lung tissue. On the other hand, monocyte derived macrophages (MDMs) represent inflammatory cells accumulating at the site of inflammation. While PAMs were relatively resistant to cytopathogenic effect caused by PRRSV, MDMs were much more sensitive to PRRSV infection. MDMs infected with PRRSV increased expression of pro-apoptotic Bad, Bax and p53 mRNA. Increased mortality of MDMs may be also related to a higher intensity of ROS production after infection with PRRSV. In addition, MDMs (but not PAMs) infected with H. parasuis alone formed multinucleated giant cells (MGC); these cells were not observed in MDMs infected with both pathogens. Higher sensitivity of MDMs to PRRSV infection, which is associated with limited MDMs survival and restriction of MGC formation, could contribute to the development of multifactorial respiratory disease of swine.

Positive selection in the SLC11A1 gene in the family Equidae.

Immunity-related genes are a suitable model for studying effects of selection at the genomic level. Some of them are highly conserved due to functional constraints and purifying selection, while others are variable and change quickly to cope with the variation of pathogens. The SLC11A1 gene encodes a transporter protein mediating antimicrobial activity of macrophages. Little is known about the patterns of selection shaping this gene during evolution. Although it is a typical evolutionarily conserved gene, functionally important polymorphisms associated with various diseases were identified in humans and other species. We analyzed the genomic organization, genetic variation, and evolution of the SLC11A1 gene in the family Equidae to identify patterns of selection within this important gene. Nucleotide SLC11A1 sequences were shown to be highly conserved in ten equid species, with more than 97 % sequence identity across the family. Single nucleotide polymorphisms (SNPs) were found in the coding and noncoding regions of the gene. Seven codon sites were identified to be under strong purifying selection. Codons located in three regions, including the glycosylated extracellular loop, were shown to be under diversifying selection. A 3-bp indel resulting in a deletion of the amino acid 321 in the predicted protein was observed in all horses, while it has been maintained in all other equid species. This codon comprised in an N-glycosylation site was found to be under positive selection. Interspecific variation in the presence of predicted N-glycosylation sites was observed.

Bovine lactoferrin free of lipopolysaccharide can induce a proinflammatory response of macrophages.

BACKGROUND: Lactoferrin (LF) is an 80 kDa glycoprotein which is known for its effects against bacteria, viruses and other pathogens. It also has a high potential in nutrition therapy and welfare of people and a variety of animals, including piglets. The ability to bind lipopolysaccharide (LPS) is one of the described anti-inflammatory mechanisms of LF. Previous studies suggested that cells can be stimulated even by LPS-free LF. Therefore, the aim of our study was to bring additional information about this possibility. Porcine monocyte derived macrophages (MDMF) and human embryonic kidney (HEK) cells were stimulated with unpurified LF in complex with LPS and with purified LF without bound LPS. RESULTS: Both cell types were stimulated with unpurified as well as purified LF. On the other hand, neither HEK0 cells not expressing any TLR nor HEK4a cells transfected with TLR4 produced any pro-inflammatory cytokine transcripts after stimulation with purified LF. This suggests that purified LF without LPS stimulates cells via another receptor than TLR4. An alternative, TLR4-independent, pathway was further confirmed by analyses of the NF-kappa-B-inducing kinase (NIK) activation. Western blot analyses showed NIK which activates different NFκB subunits compared to LF-LPS signaling via TLR4. Though, this confirmed an alternative pathway which is used by the purified LF free of LPS. This stimulation of MDMF led to low, but significant amounts of pro-inflammatory cytokines, which can be considered as a positive stimulation of the immune system. CONCLUSION: Our results suggest that LF's ability is not only to bind LPS, but LF itself may be a stimulant of pro-inflammatory pathways.

A proteomic approach to the development of DIVA ELISA distinguishing pigs infected with Salmonella Typhimurium and pigs vaccinated with a Salmonella Typhimurium-based inactivated vaccine.

BACKGROUND: Salmonella enterica serovar Typhimurium is one of the most common enteropathogenic bacteria found in pigs in Europe. In our previous work, we demonstrated the protective effects in suckling piglets when their dams had been vaccinated with an S. Typhimurium-based inactivated vaccine. This study is focused on a procedure leading to serological discrimination between vaccinated and infected pigs. As we supposed, distinct environment during natural infection and in bacterial cultures used for vaccine preparation led to a slightly different spectrum of expressed S. Typhimurium proteins. The examination of porcine antibodies produced after the experimental infection with S. Typhimurium or after vaccination with S. Typhimurium-based inactivated vaccine by affinity chromatography and mass spectrometry revealed differences in antibody response applicable for serological differentiation of infected from vaccinated animals. RESULTS: Antibodies against Salmonella SipB, SipD and SseB proteins were detected at much higher levels in post-infection sera in comparison with control and post-vaccination sera. On the other hand, proteins BamB, OppA and a fragment of FliC interacted with antibodies from post-vaccination sera with a much higher intensity than from control and post-infection sera. In addition, we constructed ELISA assays using post-infection antigen - SipB protein and post-vaccination antigen - FliC-fragment and evaluated them on a panel of individual porcine sera. CONCLUSIONS: The analysis of antibody response of infected and vaccinated pigs by proteomic tools enabled to identify S. Typhimurium antigens useful for distinguishing infected from vaccinated animals. This approach can be utilized in other challenges where DIVA vaccine and a subsequent serological assay are required, especially when genetic modification of a vaccine strain is not desirable.

Characterization of Gallibacterium anatis Isolated from Pathological Processes in Domestic Mammals and Birds in the Czech Republic.

Gallibacterium anatis, recognized as a resident and opportunistic pathogen primarily in poultry, underwent investigation in unwell domestic mammals and birds. The study encompassed the mapping and comparison of G. anatis isolates, evaluation of their genetic diversity, and determination of their susceptibility to antimicrobials. A total of 11,908 clinical samples were analyzed using cultivation methods and MALDI-TOF. Whole-genome sequencing was performed on seven calf isolates and six hen isolates. Among mammals, G. anatis was exclusively detected in 22 young dairy calves, while among domestic birds, it was found in 35 individuals belonging to four species. Pathological observations in calves were predominantly localized in the digestive tract, whereas in birds, multi-organ infections and respiratory system infections were most prevalent. Distinct groups of genes were identified solely in calf isolates, and conversely, those unique to hen isolates were also recognized. Novel alleles in the multilocus sequence typing scheme genes and previously unidentified sequence types were observed in both calf and hen isolates. Antimicrobial susceptibility exhibited variation between bird and calf isolates. Notably, G. anatis isolates from calves exhibited disparities in genotype and phenotype compared to those from hens. Despite these distinctions, G. anatis isolates demonstrated the capability to induce septicemia in both species.

Streptococcus suis strains with novel and previously undescribed capsular loci circulate in Europe.

Streptococcus suis (S. suis) causes serious diseases in pigs, and certain serotypes also pose a risk to humans. The expression of capsular polysaccharides (CPS) is considered an important virulence property of the pathogen. Recently, some serotypes have been reclassified as other organisms, while novel S. suis serotypes are being described. Although the CPS can be typed by serological methods using antisera, the presence of unique sequences for each capsular polysaccharide synthesis locus (cps locus) enables convenient PCR-based serotyping. In this study, we characterized 33 non-serotypeable S. suis strains obtained from diseased pigs in the Czech Republic by sequencing and analyzing the cps locus. Phylogenetic analysis of cpn60 confirmed that all isolates belong to the S. suis species. Four isolates had cps loci similar to the previously described reference S. suis serotypes. Eleven isolates were classified as recently described novel cps loci (NCLs). Nine isolates had substitutions, insertions and/or deletions in their cps loci and showed only partial similarity to the already described NCLs. Another eight isolates had previously undescribed cps locus structures and were proposed as novel NCLs. One isolate had lost the genes encoding capsule biosynthesis. Only four sequence types (ST) had two isolates each; the rest had unique STs. Two isolates harbored the classical virulence associated genes (VAGs) mrp and sly. Another isolate had only the mrp gene, while a different isolate harbored only the sly gene. This study provides insight into untypeable isolates in the Czech Republic, highlighting the genetic diversity and potential for novel serotype identification.

Antimicrobial Susceptibility and Resistance Genes in Streptococcus uberis Isolated from Bovine Mastitis in the Czech Republic.

Streptococcus uberis is one of the most important causative agents of mastitis and is a common reason for the use of antimicrobials in dairy cows. In this study, we assessed the antimicrobial susceptibility of 667 S. uberis isolates originating from 216 Czech dairy farms collected between 2019 and 2023 using the broth microdilution method. We tested 140 of the isolates for the presence of antimicrobial genes using whole-genome sequencing and evaluated their relationship with phenotypic resistance. Streptococcus uberis isolates showed high levels of resistance to tetracycline (59%), followed by streptomycin (38%) and clindamycin (29%). Although all of the isolates were susceptible to beta-lactams, a relatively high percentage of intermediately susceptible isolates was recorded for ampicillin (44%) and penicillin (18%). The isolates were mainly resistant to tetracycline alone (31.3%); the second most frequent occurrence of the phenotypic profile was simultaneous resistance to tetracycline, streptomycin, and clindamycin (16.6%). The occurrence of antibiotic resistance genes did not always match the phenotypic results; in total, 36.8% of isolates that possessed the ant(6)-Ia gene did not show phenotypic resistance to streptomycin. To a lesser extent, silent genes were also detected in clindamycin and tetracycline. This study confirmed the high susceptibility of S. uberis to penicillins used as first-line antimicrobials for S. uberis mastitis treatment.

Salmonella Typhimurium-based inactivated vaccine containing a wide spectrum of bacterial antigens which mimics protein expression changes during different stages of an infection process.

Salmonella infections are still considered a persistent problem in veterinary medicine. Vaccination is one of the tools for decreasing the burden of many pathogens on animals. However, the efficiency of available commercial or experimental vaccines against non-typhoid Salmonella strains is not yet sufficient. We followed the path of an inactivated vaccine that is safe and well accepted, but whose presented antigen spectrum is limited. We improved this issue by using diverse cultivation conditions mimicking bacterial protein expression during the natural infection process. The cultivation process was set up to simulate the host environment to enhance the expression of SPI-1 (Salmonella pathogenicity island) proteins, SPI-2 proteins, siderophore-related proteins, and flagellar proteins. Three different cultivation media were used and subsequent cultures were mixed together, inactivated, and used for the immunization of post-weaned piglets. A mixture of recombinant Salmonella proteins was also used as a recombinant vaccine for comparison. The clinical symptoms during the subsequent experimental infection, antibody response, and organ bacterial loads were examined. One day after the infection, we observed an increased rectal temperature in the group of unvaccinated animals and the animals vaccinated with the recombinant vaccine. The increase in the temperature of the pigs vaccinated with the inactivated Salmonella mixture was significantly lower. In the same group, we also found lower bacterial loads in the ileum content and the colon wall. The IgG response to several Salmonella antigens was enhanced in this group, but it did not reach the titers of the group vaccinated with the recombinant vaccine. To summarize, the pigs vaccinated with an inactivated mixture of Salmonella cultures mimicking protein expression changes during the natural infection exhibited less serious clinical symptoms and lower bacterial load in the body after the experimental infection compared to the unvaccinated pigs and the pigs vaccinated with a mixture of recombinant Salmonella proteins.

Survey of Genotype Diversity, Virulence, and Antimicrobial Resistance Genes in Mastitis-Causing Streptococcus uberis in Dairy Herds Using Whole-Genome Sequencing.

Streptococcus uberis is one of the primary causative agents of mastitis, a clinically and economically significant disease that affects dairy cattle worldwide. In this study, we analyzed 140 S. uberis strains isolated from mastitis milk samples collected from 74 cow herds in the Czech Republic. We employed whole-genome sequencing to screen for the presence of antimicrobial resistance (AMR) genes and genes encoding virulence factors, and to assess their genetic relationships. Our analysis revealed the presence of 88 different sequence types (STs), with 41% of the isolates assigned to global clonal complexes (GCCs), the majority of which were affiliated with GCC5. The STs identified were distributed across the major phylogenetic branches of all currently known STs. We identified fifty-one putative virulence factor genes, and the majority of isolates carried between 27 and 29 of these genes. A tendency of virulence factors and AMR genes to cluster with specific STs was observed, although such clustering was not evident within GCCs. Principal component analysis did not reveal significant diversity among isolates when grouped by GCC or ST prevalence. The substantial genomic diversity and the wide array of virulence factors found in S. uberis strains present a challenge for the implementation of effective anti-mastitis measures.

Interleukin-17 producing cells in swine induced by microbiota during the early postnatal period - a brief research report.

Interleukin-17A (IL-17) is a pro-inflammatory cytokine involved in the immune response to many pathogens playing also a role in certain chronic and autoimmune diseases. The presented study focused on the early postnatal development of IL-17 producing cells in swine. In agreement with previous studies, αß T-helper (CD3+CD4+) and γδ T (CD3+TCRγδ+) cells were found to be the major producers of IL-17. In newborn conventional piglets, αß T-helper cells positive for IL-17 were almost undetectable, but their frequency increased markedly with age in all issues examined, i.e., blood, spleen, and mesenteric lymph nodes (MLN). Additional analyses of CD8 and CD27 expression showed that the main αß T-helper producers of IL-17 has CD8+CD27- phenotype in all tissues. IL-17 positive CD8+CD27+ αß T-helper subpopulation was found only in blood and spleen. The production of IL17 in CD8-CD27+ αß T-helper cells was always minor. In contrast, γδ T cells positive for IL-17 did not show a similar age-dependent increase in blood and spleen, whereas they increased in MLN. Because of the age-dependent increase in conventional animals, we included a comparison with germ-free piglets to show that the increase in IL-17 positive cells was clearly depended on the presence of the microbiota as the production in germ-free animals was negligible without any age-dependent increase.

Genomic analysis of Paenibacillus larvae isolates from the Czech Republic and the neighbouring regions of Slovakia.

Paenibacillus larvae is the causative agent of American foulbrood (AFB), a devastating disease of honeybee larvae. In the Czech Republic, two large infested regions were recognised. This study aimed to analyse P. larvae strains occurring in the Czech Republic in the years 2016-2017 and to characterise the genetic structure of their population with the use of Enterobacterial Repetitive Intergenic Consensus genotyping (ERIC), multilocus sequence typing (MLST) and whole genome sequence (WGS) analysis. The results were complemented by the analysis of isolates collected in the year 2018 in areas of Slovakia located near the Czechia-Slovakia border. ERIC genotyping revealed that 78.9% of tested isolates belonged to the ERIC II genotype and 21.1% to ERIC I genotype. MLST showed six sequence types with ST10 and ST11 being the most frequent among isolates. Within six isolates we found discrepancies in correlations between MLST and ERIC genotypes. The use of MLST and WGS analysis of isolates revealed that each of the large infested geographic regions had its own dominating P. larvae strains. We assume that these strains represented primary sources of infection in the affected areas. In addition, the sporadic presence of strains identified by core genome analysis as genetically related was unveiled in geographically distant regions suggesting possible human-mediated transmission of AFB.

Gordonia species as a rare pathogen isolated from milk of dairy cows with mastitis.

While Gordonia species have long been known to cause severe inflammation in humans, the pathogenic effects of Gordonia species in veterinary medicine have rarely been described. Between 2010 and 2019, we collected microorganisms of the genus Gordonia isolated from milk samples from dairy cows with mastitis. We describe the growth properties of these microorganisms and their prevalence, virulence factors and susceptibility to antimicrobial agents. From 31,534 quarter milk samples processed by standard culture methods, 27 isolates of Gordonia species (0.086% prevalence) were identified by a molecular phenotyping method. The isolates originated from 17 farms in 12 districts of the Czech Republic. Twenty-one isolates were tested for susceptibility to 7 antimicrobials by the disc diffusion method. Notably, 100% of these isolates were susceptible to streptomycin and neomycin, 85.7% to cefovecin and tetracycline, 76.2% to penicillin G, 47.6% to trimethoprim/sulfamethoxazole and 0% to clindamycin. The species was determined to be Gordonia paraffinivorans by whole genome sequencing for 9 isolates (from 8 farms in 7 districts). These isolates showed the highest similarity to two reference strains from the environment. In all these isolates, we identified genes encoding virulence factors that are very similar to genes encoding virulence factors expressed in Mycobacterium tuberculosis and Mycobacterium smegmatis. However, genome analysis revealed 61 unique genes in all 9 sequenced isolates.

Multilocus Sequence Genotype Heterogeneity in Streptococcus uberis Isolated from Bovine Mastitis in the Czech Republic.

The ubiquitous occurrence and high heterogeneity of Streptococcus uberis strains cause difficulties in the development and implementation of effective control strategies in dairy herds. In this study, S. uberis strains from 74 farms, obtained predominantly from subclinical, acute, and chronic recurrent mastitis, as well as from udder surface swabs and milk from healthy udders, were analysed for their genetic diversity using multilocus sequence typing (MLST). Isolates were tested for the presence of the genes encoding the virulence factors using polymerase chain reaction. Antibiotic susceptibility testing was performed using a microdilution assay including 14 antimicrobials. The virulence profiles and antimicrobial (AMR) profiles of the isolates were assembled and the overall heterogeneity was evaluated. Among the 124 isolates, 89 MLST genotypes, 7 different virulence profiles, and 12 AMR profiles were identified. The large number of different MLST allelic profiles in this study points to the high heterogeneity of strains in dairy herds in the Czech Republic. Isolates of a certain MLST genotype may possess a different set of virulence factor genes. We detected up to three different resistance profiles within a single MLST genotype. The results of our study showed that fully susceptible isolates coexisted with resistant or even multiresistant isolates in the same herd. Multiple genotypes within a herd were detected on many farms (up to seven MLST genotypes and four AMR profiles in one herd). This heterogenic population structure might suggest that environmental transmission is the predominant route of infection in herds in the Czech Republic.

Resistance of Streptococcus suis Isolates from the Czech Republic during 2018-2022.

A determination of susceptibility/resistance to antimicrobials via serotype was carried out in 506 field isolates of Streptococcus suis, originating from pig farms in the Czech Republic in the period 2018-2022. A very high level of susceptibility of S. suis isolates was found to amoxicillin, in combination with clavulanic acid and sulfamethoxazole potentiated with trimethoprim. None of the tested isolates were resistant to these antimicrobial substances. Only two isolates were found to be intermediately resistant to enrofloxacin in 2020. With regard to ceftiofur, one isolate was intermediately resistant in 2020 and 2022, and two isolates were intermediately resistant in 2018 and 2021. A low level of resistance was detected to ampicillin (0.6% in 2021) and to florfenicol (1.15% in 2019; 1.3% in 2022). With regard to penicillin, a medium level of resistance was detected in 2018 (10.6%), but a low level of resistance was found in the following years (7.0% in 2019; 3.1% in 2020; 3.3% in 2021; 3.9% in 2022). On the contrary, a high or very high level of resistance was found to tetracycline (66.0% in 2018; 65.1% in 2019; 44.35% in 2020; 46.4% in 2021; 54.0% in 2022). Using molecular and serological methods, serotype 7 (16.4%) was determined to be predominant among S. suis isolates, followed by serotypes 1/2, 2, 9, 4, 3, 1, 29, 16, and 31 (10.7%; 8.5%; 5.7%; 5.5%; 4.5%; 4.3%; 3.6%; 3.4%; 3.4%, respectively). Other serotypes were identified among the investigated strains either rarely (up to 10 cases) or not at all. A relatively high percentage of isolates were detected as non-typeable (79 isolates; 15.6%). Dependence of resistance upon serotype assignment could not be proven in all but serotype 31, wherein all isolates (n = 17) were resistant or intermediately resistant to clindamycin, tilmycosin, tulathromycin, and tetracycline. The resistance to clindamycin and tetracycline may be related to the high consumption of these antibiotics on pig farms at present or in previous years. Macrolides (tilmicosin and tulathromycin) and tiamulin are not suitable for the treatment of streptococcal infections, but are used on pig farms to treat respiratory infections caused by gram-negative bacteria, so they were included in the study.

Vaccine against Streptococcus suis Infection in Pig Based on Alternative Carrier Protein Conjugate.

Streptococcus suis is a serious pathogen in the pig industry with zoonotic potential. With respect to the current effort to reduce antibiotic use in animals, a prophylactic measure is needed to control the disease burden. Unfortunately, immunization against streptococcal pathogens is challenging due to nature of the interaction between the pathogen and the host immune system, but vaccines based on conjugates of capsular polysaccharide (CPS) and carrier protein were proved to be efficient. The main obstacle of these vaccines is manufacturing cost, limiting their use in animals. In this work, we tested an experimental vaccine against Streptococcus suis serotype 2 based on capsular polysaccharide conjugated to chicken ovalbumin (OVA) and compared its immunogenicity and protectivity with a vaccine based on CRM197 conjugate. Ovalbumin was selected as a cheap alternative to recombinant carrier proteins widely used in vaccines for human use. We found that the ovalbumin-based experimental vaccine successfully induced immune response in pigs, and the IgG antibody response was even higher than after immunization with capsular polysaccharide-CRM197 conjugate. Protectivity of vaccination against infection was evaluated in the challenge experiment and was found promising for both conjugates.

Characterisation of Streptococcus suis Isolates in the Czech Republic Collected from Diseased Pigs in the Years 2018-2022.

As in other countries, in the Czech Republic, Streptococcus suis infection in pigs is considered an economically significant disease for the pig industry, though little is known about its population structure. We collected S. suis isolates from 144 farms in the years 2018-2022. All samples were taken from animals suffering from symptoms indicating possible S. suis infection. Serotyping revealed the presence of 23 different serotypes, and 18.94% were non-typable strains. The most common was S7 (14.96%), while other serotypes had frequencies of less than 10%. Sequence typing identified 56 different sequence types, including 31 newly assigned sequence types together with 41 new alleles in genes in the MLST schema. A large portion of isolates (25.70%) were of unknown sequence type. The most common sequence types were ST29 (14.77%) and ST28 (10.04%); the other sequence types had frequencies of less than 10%. In total, 100 different combinations of serotypes and sequence types were identified. Among them, S7ST29 was found in 72 isolates, representing 13.63% of all isolates, and was significantly associated with the central nervous system. Many other isolates of particular serotype and sequence type combinations were found in a few cases, and a number of isolates were non-typable.