Serotype diversity and antimicrobial susceptibility profiles of Actinobacillus pleuropneumoniae isolated in Italian pig farms from 2015 to 2022.

Actinobacillus pleuropneumoniae (APP) is a bacterium frequently associated with porcine pleuropneumonia. The acute form of the disease is highly contagious and often fatal, resulting in significant economic losses for pig farmers. Serotype diversity and antimicrobial resistance (AMR) of APP strains circulating in north Italian farms from 2015 to 2022 were evaluated retrospectively to investigate APP epidemiology in the area. A total of 572 strains isolated from outbreaks occurring in 337 different swine farms were analysed. The majority of isolates belonged to serotypes 9/11 (39.2%) and 2 (28.1%) and serotype diversity increased during the study period, up to nine different serotypes isolated in 2022. The most common resistances were against tetracycline (53% of isolates) and ampicillin (33%), followed by enrofloxacin, florfenicol and trimethoprim/sulfamethoxazole (23% each). Multidrug resistance (MDR) was common, with a third of isolates showing resistance to more than three antimicrobial classes. Resistance to the different classes and MDR varied significantly depending on the serotype. In particular, the widespread serotype 9/11 was strongly associated with florfenicol and enrofloxacin resistance and showed the highest proportion of MDR isolates. Serotype 5, although less common, showed instead a concerning proportion of trimethoprim/sulfamethoxazole resistance. Our results highlight how the typing of circulating serotypes and the analysis of their antimicrobial susceptibility profile are crucial to effectively manage APP infection and improve antimicrobial stewardship.

Characterization of Actinobacillus pleuropneumoniae biovar 2 isolates reportedly reacted with the serovar 4 antiserum, and development of a multiplex PCR for O-antigen typing.

We have analyzed the capsule (CPS) and the lipopolysaccharide O-Antigen (O-Ag) biosynthesis loci of twelve Spanish field isolates of Actinobacillus pleuropneumoniae biovar 2, eleven of them previously typed serologically as serovar 4 and one non-typable (NT) (Maldonado et al., 2009, 2011). These isolates have the common core genes of the type I CPS locus, sharing >98% identity with those of serovar 2. However, the former possesses the O-Ag locus as serovar 4, and the latter possesses the O-Ag locus as serovar 7. The main difference found between the CPS loci of the 11 isolates and that of serovar 2 reference strain S1536 are two deletions, one of an 8 bp sequence upstream of the coding sequence and one of 111 bp sequence at the 5' end of the cps2G gene. The deletion mutations mentioned lead to a defect in the production of CPS in these isolates, which contributed to their previous mis-identification. In order to complement the serotyping of A. pleuropneumoniae in diagnostics and epidemiology, we have developed a multiplex PCR for the comprehensive O-Ag typing of all A. pleuropneumoniae isolates.

A Florfenicol-Resistant Plasmid Shuttling Between Actinobacillus pleuropneumoniae and Glaesserella parasuis.

Porcine contagious pleuropneumonia, caused by Actinobacillus pleuropneumoniae, has resulted in significant economic losses to the swine industry. Although antibiotics are commonly employed to control this disease, their widespread use or misuse can lead to the development of antibiotic resistance in A. pleuropneumoniae. Consequently, it is crucial to conduct antimicrobial susceptibility testing on clinical isolates. In our study, we identified one strain of A. pleuropneumoniae with resistance to florfenicol and extracted a 5919 bp plasmid named pAPPJY, which confers florfenicol resistance. Sequence analysis revealed that the plasmid contains four open reading frames, namely rep, antioxin vbha family protein, floR, and a partial copy of lysr. Although a few variations in gene position were observed, the plasmid sequence exhibits a high degree of similarity to other florfenicol-resistant plasmids found in Glaesserella parasuis and A. pleuropneumoniae. Therefore, it is possible that the pAPPJY plasmid functions as a shuttle, facilitating the spread of florfenicol resistance between G. parasuis and A. pleuropneumoniae. In addition, partial recombination may occur during bacterial propagation. In conclusion, this study highlights the horizontal transmission of antibiotic resistance among different bacterial species through plasmids, underscoring the need for increased attention to antibiotic usage.

The cAMP receptor protein gene contributes to growth, stress resistance, and colonization of Actinobacillus pleuropneumoniae.

Porcine infectious pleuropneumonia (PCP) is a severe disease of porcine caused by Actinobacillus pleuropneumoniae (APP). The spread of PCP remains a threat to the porcine farms and has been known to cause severe economic losses. The cAMP receptor protein (CRP) serves as a pivotal player in helping bacteria adapt to shifts in their environment, particularly when facing the challenges posed by bacterial infections. In this study, we investigated the role of CRP in APP. Our results revealed that crp mutant (Δcrp) strains were more sensitive to acidic and osmotic stress resistance and had lower biofilm formation ability than wild-type (WT) strains. Furthermore, the Δcrp strains showed deficiencies in anti-phagocytosis, adhesion, and invasion upon interaction with host cells. Mice infected with the Δcrp strains demonstrated reduced bacterial loads in their lungs compared to those infected with the WT strains. This study reveals the pivotal role of crp gene expression in regulating pleuropneumonia growth, stress resistance, iron utilization, biofilm formation, phagocytosis, adhesion, invasion and colonization. Our discoveries offer novel perspectives on understanding the development and progression of APP infections.

Hyper-production of porcine contagious pleuropneumonia subunit vaccine proteins in Escherichia coli by developing a bicistronic T7 expression system.

The ApxII toxin and the outer membrane lipoprotein (Oml) of Actinobacillus pleuropneumoniae are important vaccine antigens against porcine contagious pleuropneumonia (PCP), a prevalent infectious disease affecting the swine industry worldwide. Previous studies have reported the recombinant expression of ApxII and Oml in Escherichia coli; however, their yields were not satisfactory. Here, we aimed to enhance the production of ApxII and Oml by constructing a bicistronic expression system based on the widely used T7 promoter. To create efficient T7 bicistronic expression cassettes, 16 different fore-cistron sequences were introduced downstream of the T7 promoter. The expression of three vaccine antigens Oml1, Oml7, and ApxII in the four strongest bicistronic vectors were enhanced compared to the monocistronic control. Further optimization of the fermentation conditions in micro-well plates (MWP) led to improved production. Finally, the production yields reached unprecedented levels of 2.43 g L-1 of Oml1, 2.59 g L-1 of Oml7, and 1.21 g L-1 of ApxII, in a 5 L bioreactor. These three antigens also demonstrated well-protective immunity against A. pleuropneumoniae infection. In conclusion, this study establishes an efficient bicistronic T7 expression system that can be used to express recombinant proteins in E. coli and achieves the hyper-production of PCP vaccine proteins.

Native ApxIIA secreted by Actinobacillus pleuropneumoniae induces apoptosis in porcine alveolar macrophages dependent on concentration and acylation.

Actinobacillus pleuropneumoniae is an important swine respiratory pathogen causing substantial economic losses to the global pig industry. The Apx toxins of A. pleuropneumoniae belong to the RTX toxin family and are major virulence factors. In addition to hemolysis and/or cytotoxicity via pore-forming activity, RTX toxins, such as ApxIA of A. pleuropneumoniae, have been reported to cause other effects on target cells, e.g., apoptosis. A. pleuropneumoniae ApxIIA is expressed by most serotypes and has moderate hemolytic and cytotoxic activities. In this study, porcine alveolar macrophages (3D4/21) were stimulated with different concentrations of purified native ApxIIA from the serotype 7 strain AP76 which only secretes ApxIIA. By observation of nuclear condensation via fluorescent staining and detection of apoptosis and necrosis by flow cytometry, it was found that high and low concentrations of native ApxIIA mainly caused necrosis or apoptosis of 3D4/21 cells, respectively. ApxIIA purified from an AP76 mutant with a deleted acetyltransferase gene (apxIIC) did not induce necrosis nor apoptosis. Western blot analysis using specific antibodies showed that a cleaved caspase 3 and activated capase 9 was detected after treatment of cells with a low concentration of native ApxIIA, while general or specific inhibitors of caspase 3, 8, 9 blocked these effects. ApxIIA-induced apoptosis of macrophages may be a mechanism of A. pleuropneumoniae to escape host immune clearance.

Actinobacillus ureae may be a critical pathogen in patients with predispositions: A case report and review of the literature.

RATIONALE: Actinobacillus ureae (A. ureae) is an unusual commensal of human respiratory flora, rarely causing human infection. The predisposing factors, identification, clinical features, and antibiotic therapy of A. ureae are seldomly reported. Herein, we present a case of 64-year-old man affected by A. ureae pneumonia after intracranial surgery. PATIENT CONCERNS AND DIAGNOSES: A 64-year-old male was admitted with vomiting, drowsiness, and a severe disturbance of consciousness and was later diagnosed with cerebral hemorrhage by computed tomography images. After a craniocerebral surgery, the patient suffered from intractable pneumonia, experiencing treatment failure with multiple anti-bacterial agents. Sputum culture yield pure colonies of A. ureae, confirmed by matrix-assisted laser desorption/ionization time of flight and 16S rRNA gene sequencing. INTERVENTIONS: Minocycline (100 mg p.o. per 12 hours) with a course of 15 days was administrated for this patient. OUTCOMES: The respiratory symptoms, presenting as intermittent coughing with purulent and yellowish sputum, were gone. A 3-month follow-up examination showed a complete resolution of radiological findings. LESSONS: Clinically, the actual incidence of A. ureae pneumonia may be higher than that we generally recognized, and clinicians should consider A. ureae as a possible etiologic agent in patients with predispositions. Currently, A. ureae may be susceptible to penicillin, ampicillin, and third-generation cephalosporins. Other antibacterial agents, such as tetracycline, amoxicillin/clavulanic acid, and aminoglycosides also respond well and can be a choice in the treatment of A. ureae infections.

The intestinal microbiota of a Risso’s dolphin (Grampus griseus): possible relationships with starvation raised by macro-plastic ingestion / La microbiota intestinal del delfín gris (Grampus griseus): posibles relaciones con la inanición provocada por la ingestión de macroplásticos

Ingesting marine plastics is increasingly common in cetaceans, but little is known about their potential effects. Here, by utilizing 16S rRNA gene sequencing, we profiled the intestinal bacterial communities of a stranded Risso’s dolphin (Grampus griseus) which died because of the ingestion of rubber gloves. In this study, we explored the potential relationships between starvation raised by plastic ingestion with the dolphin gut microbiota. Our results showed significant differences in bacterial diversity and composition among the different anatomical areas along the intestinal tract, which may be related to the intestinal emptying process under starvation. In addition, the intestinal bacterial composition of the Risso’s dolphin showed both similarity and divergence to that of other toothed whales, suggesting potential roles of both host phylogeny and habitat shaping of the cetacean intestinal microbiome. Perhaps, the microbiota is reflecting a potentially disordered intestinal microbial profile caused by the ingestion of macro-plastics which led to starvation. Moreover, two operational taxonomic units (0.17% of the total reads) affiliated with Actinobacillus and Acinetobacter lwoffii were detected along the intestinal tract. These bacterial species may cause infections in immunocompromised dolphins which are malnourished. This preliminary study profiles the intestinal microbiota of a Risso’s dolphin, and provides an additional understanding of the potential relationships between starvation raised by ingesting macro-plastics with cetacean gut microbiota.(AU)

High-dimensional analysis reveals an immune atlas and novel neutrophil clusters in the lungs of model animals with Actinobacillus pleuropneumoniae-induced pneumonia.

Due to the increase in bacterial resistance, improving the anti-infectious immunity of the host is rapidly becoming a new strategy for the prevention and treatment of bacterial pneumonia. However, the specific lung immune responses and key immune cell subsets involved in bacterial infection are obscure. Actinobacillus pleuropneumoniae (APP) can cause porcine pleuropneumonia, a highly contagious respiratory disease that has caused severe economic losses in the swine industry. Here, using high-dimensional mass cytometry, the major immune cell repertoire in the lungs of mice with APP infection was profiled. Various phenotypically distinct neutrophil subsets and Ly-6C+ inflammatory monocytes/macrophages accumulated post-infection. Moreover, a linear differentiation trajectory from inactivated to activated to apoptotic neutrophils corresponded with the stages of uninfected, onset, and recovery of APP infection. CD14+ neutrophils, which mainly increased in number during the recovery stage of infection, were revealed to have a stronger ability to produce cytokines, especially IL-10 and IL-21, than their CD14- counterparts. Importantly, MHC-II+ neutrophils with antigen-presenting cell features were identified, and their numbers increased in the lung after APP infection. Similar results were further confirmed in the lungs of piglets infected with APP and Klebsiella pneumoniae infection by using a single-cell RNA-seq technique. Additionally, a correlation analysis between cluster composition and the infection process yielded a dynamic and temporally associated immune landscape where key immune clusters, including previously unrecognized ones, marked various stages of infection. Thus, these results reveal the characteristics of key neutrophil clusters and provide a detailed understanding of the immune response to bacterial pneumonia.

Characterization of Actinobacillus pleuropneumoniae isolated from pigs in Japan using whole genome sequencing.

We conducted whole-genome sequencing to investigate the serotypes, the presence of virulence and antimicrobial resistance genes, and the genetic relationships among isolates of Actinobacillus. pleuropneumoniae derived from diseased pigs. Serotype 2 (71.2%) was the most common, but the prevalence of serotypes 6 (13.6%) and 15 (6.8%) increased. Existing vaccines are considered ineffective on the isolates belonging to serotypes 6 and 15. The phylogenetic tree based on core genome single nucleotide polymorphisms showed that the isolates were clustered by serotype. Of the isolates, 62.5% did not have an antimicrobial resistance gene, including a florfenicol resistance gene, but 32.2% had a tetracycline resistance gene. The antimicrobial resistant phenotype and genotype were almost identical. The plasmid-derived contigs harbored resistance genes of aminoglycosides, tetracyclines, ß-lactams, phenicols, or sulfonamides. It has been suggested that isolates with different genetic properties from vaccine strains are circulating; however, antimicrobial resistance may not be widespread.

Pulmonary lesions with asteroid bodies in a pig experimentally infected with Actinobacillus pleuropneumoniae serovar 15.

Five pigs experimentally infected with Actinobacillus pleuropneumoniae serovar 15 isolated in our previous study were pathologically examined. One pig died at 2 days post inoculation (dpi) and four pigs were euthanized at 7 dpi. Autopsy revealed fibrinohemorrhagic pleuropneumonia in all pigs. Histopathologically, the lesions were characterized by extensive hemorrhage and necrosis, fibrin deposition, and multifocal abscesses composed of numerous neutrophils including oat cells and numerous Gram-negative bacilli. In one survived pig, asteroid body formation was confirmed in the lung. The bacteria within the abscesses and asteroid bodies were immunohistochemically positive for antiserum raised against A. pleuropneumoniae serovar 15. This is the first report describing porcine pleuropneumonia with asteroid bodies in a pig experimentally infected with A. pleuropneumoniae serovar 15.

Characterization of nonencapsulated Actinobacillus pleuropneumoniae serovar K12:O3 isolates.

Three Actinobacillus pleuropneumoniae isolates from clinical cases of porcine pleuropneumonia were positive by capsular serovar 12-specific PCR assay, but not reactive to antiserum prepared against serovar 12 using the rapid slide agglutination (RSA) test. The isolates were positive for apxIICA, apxIIICA, apxIBD, apxIIIBD, and apxIVA in the PCR toxin gene assay, which is the profile seen in serovars 2, 4, 6, 8, and 15, and reacted with antisera against serovars 3, 6, 8, 15, and 17. Nucleotide sequence analysis revealed that genes involved in the biosynthesis of capsular polysaccharide of the 3 isolates were identical or nearly identical to those of serovar 12. However, genes involved in the biosynthesis of O-polysaccharide of the 3 isolates were highly similar to those of reference strains of serovars 3, 6, 8, 15, 17, and 19. In agreement with results from the RSA test, transmission electron microscopic analysis confirmed the absence of detectable capsular material in the 3 isolates. The existence of nonencapsulated A. pleuropneumoniae serovar K12:O3 would hamper precise serodetection.

Tea Polyphenols Protects Tracheal Epithelial Tight Junctions in Lung during Actinobacillus pleuropneumoniae Infection via Suppressing TLR-4/MAPK/PKC-MLCK Signaling.

Actinobacillus pleuropneumoniae (APP) is the causative pathogen of porcine pleuropneumonia, a highly contagious respiratory disease in the pig industry. The increasingly severe antimicrobial resistance in APP urgently requires novel antibacterial alternatives for the treatment of APP infection. In this study, we investigated the effect of tea polyphenols (TP) against APP. MIC and MBC of TP showed significant inhibitory effects on bacteria growth and caused cellular damage to APP. Furthermore, TP decreased adherent activity of APP to the newborn pig tracheal epithelial cells (NPTr) and the destruction of the tight adherence junction proteins ß-catenin and occludin. Moreover, TP improved the survival rate of APP infected mice but also attenuated the release of the inflammation-related cytokines IL-6, IL-8, and TNF-α. TP inhibited activation of the TLR/MAPK/PKC-MLCK signaling for down-regulated TLR-2, TLR4, p-JNK, p-p38, p-PKC-α, and MLCK in cells triggered by APP. Collectively, our data suggest that TP represents a promising therapeutic agent in the treatment of APP infection.

TurboID screening of ApxI toxin interactants identifies host proteins involved in Actinobacillus pleuropneumoniae-induced apoptosis of immortalized porcine alveolar macrophages.

Actinobacillus pleuropneumoniae (APP) is a gram-negative pathogenic bacterium responsible for porcine contagious pleuropneumonia (PCP), which can cause porcine necrotizing and hemorrhagic pleuropneumonia. Actinobacillus pleuropneumoniae-RTX-toxin (Apx) is an APP virulence factor. APP secretes a total of four Apx toxins, among which, ApxI demonstrates strong hemolytic activity and cytotoxicity, causing lysis of porcine erythrocytes and apoptosis of porcine alveolar macrophages. However, the protein interaction network between this toxin and host cells is still poorly understood. TurboID mediates the biotinylation of endogenous proteins, thereby targeting specific proteins and local proteomes through gene fusion. We applied the TurboID enzyme-catalyzed proximity tagging method to identify and study host proteins in immortalized porcine alveolar macrophage (iPAM) cells that interact with the exotoxin ApxI of APP. His-tagged TurboID-ApxIA and TurboID recombinant proteins were expressed and purified. By mass spectrometry, 318 unique interacting proteins were identified in the TurboID ApxIA-treated group. Among them, only one membrane protein, caveolin-1 (CAV1), was identified. A co-immunoprecipitation assay confirmed that CAV1 can interact with ApxIA. In addition, overexpression and RNA interference experiments revealed that CAV1 was involved in ApxI toxin-induced apoptosis of iPAM cells. This study provided first-hand information about the proteome of iPAM cells interacting with the ApxI toxin of APP through the TurboID proximity labeling system, and identified a new host membrane protein involved in this interaction. These results lay a theoretical foundation for the clinical treatment of PCP.

Testosterone and estradiol modify the expression of adhesins and biofilm formation in Actinobacillus seminis.

Actinobacillus seminis is the causal agent of epididymitis and has other effects on the reproductive tracts of small ruminants and bovines. This bacterium causes infection when luteinizing (LH) or follicle-stimulating hormones increase, and hosts reach sexual maturity. LH induces female ovulation and male testosterone production, suggesting that these hormones affect A. seminis pathogenicity. In the present study, we evaluated the effect of testosterone (1-5 ng/ml) or estradiol (5-25 pg/ml) added to culture medium on the in vitro growth, biofilm production, and adhesin expression of A. seminis. Estradiol does not promote the growth of this bacterium, whereas testosterone increased A. seminis planktonic growth 2-fold. Both hormones induced the expression of the elongation factor thermo unstable (EF-Tu) and phosphoglycerate mutase (PGM), proteins that A. seminis uses as adhesins. Estradiol (5 or 10 pg/ml) decreased biofilm formation by 32%, whereas testosterone, even at 5 ng/ml, showed no effect. Both hormones modified the concentrations of carbohydrates and eDNA in biofilms by 50%. Amyloid proteins are characterized by their capacity to bind Congo red (CR) dye. Actinobacillus seminis binds CR dye, and this binding increases in the presence of 5-20 pg/ml estradiol or 4 ng/ml testosterone. The A. seminis EF-Tu protein was identified as amyloid-like protein (ALP). The effect of sexual hormones on the growth and expression of virulence factors of A. seminis seems to be relevant for its colonization and permanence in the host.

The morphology and metabolic changes of Actinobacillus pleuropneumoniae during its growth as a biofilm.

Actinobacillus pleuropneumoniae is an important swine respiratory pathogen. Previous studies have suggested that growth as a biofilm is a natural state of A. pleuropneumoniae infection. To understand the survival features involved in the biofilm state, the growth features, morphology and gene expression profiles of planktonic and biofilm A. pleuropneumoniae were compared. A. pleuropneumoniae in biofilms showed reduced viability but maintained the presence of extracellular polymeric substances (EPS) after late log-phase. Under the microscope, bacteria in biofilms formed dense aggregated structures that were connected by abundant EPS, with reduced condensed chromatin. By construction of Δpga and ΔdspB mutants, polymeric ß-1,6-linked N-acetylglucosamine and dispersin B were confirmed to be critical for normal biofilm formation. RNA-seq analysis indicated that, compared to their planktonic counterparts, A. pleuropneumoniae in biofilms had an extensively altered transcriptome. Carbohydrate metabolism, energy metabolism and translation were significantly repressed, while fermentation and genes contributing to EPS synthesis and translocation were up-regulated. The regulators Fnr (HlyX) and Fis were found to be up-regulated and their binding motifs were identified in the majority of the differentially expressed genes, suggesting their coordinated global role in regulating biofilm metabolism. By comparing the transcriptome of wild-type biofilm and Δpga, the utilization of oligosaccharides, iron and sulfur and fermentation were found to be important in adhesion and aggregation during biofilm formation. Additionally, when used as inocula, biofilm bacteria showed reduced virulence in mouse, compared with planktonic grown cells. Thus, these results have identified new facets of A. pleuropneumoniae biofilm maintenance and regulation.

Condenações de carcaça suínas devido a doenças respiratórias revisão bibliográfica / Pork carcass condemnation due to respiratory diseases bibliographic review / Condena de canales de cerdo por enfermedades respiratorias revisión bibliográfica

As doenças respiratórias são um problema significativo na produção suína e podem levar à condenação de carcaças no abate. Entre os agentes causadores dessas doenças destacam-se o Actinobacillus pleuropneumoniae, Mycoplasma hyopneumoniae e a Pasteurella multocida. O Actinobacillus pleuropneumoniae é um patógeno altamente contagioso, que ocasiona hemorragia, pleuropneumonia purulenta e fibrosa. A Pleuropneumonia é amplamente distribuída e gera graves prejuízos para a suinocultura. O Mycoplasma hyopneumoniae ocasionador da pneumonia por micoplasma, doença respiratória crônica. As infecções originadas podem regular negativamente o sistema imunológico do hospedeiro e aumentar a infecção e assim a replicação de outros patógenos. A Pasteurella multocida é o agente causador de uma ampla gama de infecções levando a alto impacto econômico. Patógeno comensal e oportunista da boca, nasofaringe e trato respiratório superior. A identificação precoce e o manejo adequado desses agentes causadores de doenças respiratórias são fundamentais para minimizar a incidência de carcaças suínas. A adoção de medidas preventivas, como a vacinação e práticas de manejo adequadas, pode ajudar a prevenir a propagação dessas doenças e garantir a produção de carne suína segura e de alta qualidade para o consumo humano.(AU)

Respiratory diseases are a significant problem in pork production and can lead to condemnation of carcasses at slaughter. Among the causative agents of these diseases are Actinobacillus pleuropneumoniae, Mycoplasma hyopneumoniae and Pasteurella multocida. Actinobacillus pleuropneumoniae is a highly contagious pathogen that causes hemorrhage, purulent and fibrous pleuropneumonia. Pleuropneumonia is widely distributed and causes serious damage to pig farming. Mycoplasma hyopneumoniae causes mycoplasma pneumonia, a chronic respiratory disease. Originating infections can down-regulate the host's immune system and increase infection and thus replication of other pathogens. Pasteurella multocida is the causative agent of a wide range of infections leading to high economic impact. Commensal and opportunistic pathogen of the mouth, nasopharynx and upper respiratory tract. Early identification and proper management of these agents that cause respiratory diseases are essential to minimize the incidence of swine carcasses. Adopting preventive measures, such as vaccination and proper management practices, can help prevent the spread of these diseases and ensure the production of safe, high-quality pork for human consumption.(AU)

Las enfermedades respiratorias son un problema importante en la producción porcina y pueden provocar el decomiso de las canales en el matadero. Entre los agentes causantes de estas enfermedades se encuentran Actinobacillus pleuropneumoniae, Mycoplasma hyopneumoniae y Pasteurella multocida. Actinobacillus pleuropneumoniae es un patógeno altamente contagioso que causa hemorragia, pleuroneumonía purulenta y fibrosa. La pleuroneumonía está ampliamente distribuida y causa graves daños a la cría de cerdos. Mycoplasma hyopneumoniae causa neumonía por micoplasma, una enfermedad respiratoria crónica. Las infecciones que se originan pueden regular a la baja el sistema inmunitario del huésped y aumentar la infección y, por lo tanto, la replicación de otros patógenos. Pasteurella multocida es el agente causal de una amplia gama de infecciones que tienen un alto impacto económico. Patógeno comensal y oportunista de la boca, nasofaringe y tracto respiratorio superior. La identificación temprana y el manejo adecuado de estos agentes causantes de enfermedades respiratorias son fundamentales para minimizar la incidencia de las canales porcinas. La adopción de medidas preventivas, como la vacunación y prácticas de manejo adecuadas, puede ayudar a prevenir la propagación de estas enfermedades y garantizar la producción de carne de cerdo segura y de alta calidad para el consumo humano.(AU)

Characterization of an atypical Actinobacillus pleuropneumoniae serovar 2 isolate with a rough-type lipopolysaccharide.

We describe phenotypic and genetic characterization of an atypical Japanese Actinobacillus pleuropneumoniae isolate OT761. Nucleotide sequence analysis revealed that gene clusters involved in capsular polysaccharide and O-polysaccharide (O-PS) biosynthesis of the isolate were nearly identical to those of serovar 2 reference strain. The main difference found between the O-PS loci is the shortening of 31 amino acids from the C terminus of WcaJ in the atypical isolate due to a 93 bp deletion at the 3' end of wcaJ gene. Immunoblot analysis revealed that this isolate could not produce O-PS. Taken together, our results showed that the C-terminal domain of the A. pleuropneumoniae WcaJ plays a critical role in enzyme function of WcaJ involved in the biosynthesis of O-PS.

Effects of oil-based adjuvants on the immune response of pigs after dermal administration of antigen and evaluation of the immunization level after a subsequent Actinobacillus pleuropneumoniae challenge in pigs.

Route of vaccine delivery can greatly impact the immunogenicity, efficacy and safety of the vaccine. Four groups of piglets were immunised transdermally (t.d.), intradermally (i.d.) or intramuscularly (i.m.) with the same doses of antigen in combination with a water-in-oil-in-water emulsion adjuvant Montanide™ ISA 201 VG or with a microemulsion adjuvant Montanide™ IMS 1313 VG N ST (Seppic, France). The last group was left without vaccination as a control group. All animals were subsequently exposed to the infection induced by Actinobacillus pleuropneumoniae (App). The immune response was evaluated with respect to the intensity of systemic and mucosal antibody formation, their isotype characterisation and rate of cell-mediated immunity. These findings were compared with the intensity of adverse local reactions and level of protection in experimental challenge. Monitoring of the local reaction at the injection site after each administration showed that microemulsion adjuvant IMS 1313 was less reactogenic than the water-in-oil-in-water emulsion ISA 201. In terms of efficacy, both dermal administrations were less immunogenic than the i.m route. The i.m. injection induced higher anti-App9 IgG and IgM titres. Nevertheless, IgG1 and IgG2 isotypes analysis revealed a close immunological profile between i.m. and i.d. routes. The concentration of IFN-γ from peripheral blood after in vitro restimulation with the specific antigen was only increased in the i.m. group at the day of challenge (D35) and two weeks after (D49). Interestingly, the smallest gross pulmonary lesions were observed in the i.d. vaccinated group (3.4%) compared to the control group (39.4%) and to groups with other routes of administration. Taken together, these results suggest that i.d. administration of vaccines is a promising approach. Even the i.d. vaccine was more reactogenic and slightly less immunogenic than the i.m. vaccine, its protection effectiveness seemed to be superior.

[Case report of fatal sepsis caused by Actinobacillus suis/equuli in an adult male].

This is a case report of sepsis caused by the species Actinobacillus suis/equuli in a male agriculture worker that ended fatally. The article also contains information on identification and results of antibiotic susceptibility testing. This is a rare case of human infection and probably the first case of a human being infected by this species in the Czech Republic.