Caspase-11 mediated inflammasome activation in macrophages by systemic infection of A. actinomycetemcomitans exacerbates arthritis.

Clinical studies have shown that Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) is associated with aggressive periodontitis and can potentially trigger or exacerbate rheumatoid arthritis (RA). However, the mechanism is poorly understood. Here, we show that systemic infection with A. actinomycetemcomitans triggers the progression of arthritis in mice anti-collagen antibody-induced arthritis (CAIA) model following IL-1ß secretion and cell infiltration in paws in a manner that is dependent on caspase-11-mediated inflammasome activation in macrophages. The administration of polymyxin B (PMB), chloroquine, and anti-CD11b antibody suppressed inflammasome activation in macrophages and arthritis in mice, suggesting that the recognition of lipopolysaccharide (LPS) in the cytosol after bacterial degradation by lysosomes and invasion via CD11b are needed to trigger arthritis following inflammasome activation in macrophages. These data reveal that the inhibition of caspase-11-mediated inflammasome activation potentiates aggravation of RA induced by infection with A. actinomycetemcomitans. This work highlights how RA can be progressed by inflammasome activation as a result of periodontitis-associated bacterial infection and discusses the mechanism of inflammasome activation in response to infection with A. actinomycetemcomitans.

Evaluating the transmission dynamics and host competency of aoudad (Ammotragus lervia) experimentally infected with Mycoplasma ovipneumoniae and leukotoxigenic Pasteurellaceae.

Feral populations of aoudad (Ammotragus lervia) occur in Texas bighorn sheep (Ovis canadensis) habitat and pose several conceptual ecological threats to bighorn sheep re-establishment efforts. The potential threat of disease transmission from aoudad to bighorn sheep may exacerbate these issues, but the host competency of aoudad and subsequent pathophysiology and transmissibility of pneumonic pathogens involved in the bighorn sheep respiratory disease complex is largely unknown. Because the largest population-limiting diseases of bighorn sheep involve pathogens causing bronchopneumonia, we evaluated the host competency of aoudad for Mycoplasma ovipneumoniae and leukotoxigenic Pasteurellaceae. Specifically, we described the shedding dynamics, pathogen carriage, seroconversion, clinical patterns, and pathological effects of experimental infection among wild aoudad held in captivity. We found that aoudad are competent hosts capable of maintaining and intraspecifically transmitting Mycoplasma ovipneumoniae and Pasteurellaceae and can shed the bacteria for 53 days after exposure. Aoudad developed limited clinical signs and pathological findings ranged from mild chronic lymphohistiocytic bronchointerstitial pneumonia to severe and acute suppurative pneumonia, similarly, observed in bighorn sheep infected with Mycoplasma spp. and Pasteurellaceae bacteria, respectively. Furthermore, as expected, clinical signs and lesions were often more severe in aoudad inoculated with a combination of Mycoplasma ovipneumoniae and Pasteurellaceae as compared to aoudad inoculated with only Mycoplasma ovipneumoniae. There may be evidence of interindividual susceptibility, pathogenicity, and/or transmissibility, indicated by individual aoudad maintaining varying severities of chronic infection who may be carriers continuously shedding pathogens. This is the first study to date to demonstrate that aoudad are a conceptual disease transmission threat to sympatric bighorn sheep populations due to their host competency and intraspecific transmission capabilities.

Vaginitis with purulent vaginal discharge caused by artificial insemination using frozen Histophilus somni-contaminated semen.

In April 2020, two cows in Japan, developed reproductive disorders accompanied by vaginitis with purulent discharge within 3 days of artificial insemination (AI) with the same lot of frozen semen. Histophilus somni was isolated from the vaginal swabs of both cows as well as from the same lot of frozen semen used for the AI. This incident marks the first reported case of H. somni infection in cattle through AI. The major outer membrane protein gene sequences and pulsed-field gel electrophoresis profiles of the isolates were identical. Moreover, we investigated the antimicrobial activity of 12 frozen semen straws against an H. somni isolate using a disk diffusion test. These straws were sourced from five AI centers and included the same lot of semen used for the AI. Although the composition of semen diluents from individual AI centers is not publicly available, both the same lot of frozen semen used in the AI and other lots produced by the same manufacturer showed lower antimicrobial activity than semen from other manufacturers. These results strongly suggest that the two vaginitis were caused by AI using H. somni-contaminated frozen semen because of insufficient antimicrobial activity to inhibit bacterial growth. The minimum inhibitory concentrations of the six antimicrobials recommended for addition to frozen semen in isolates were below the recommended concentrations, suggesting that proper addition could have prevented this incident. This highlights the importance of conducting periodical checks on the antibacterial activity of frozen semen to prevent the transmission of pathogens via AI.

Emayella augustorita, New Member of Pasteurellaceae, Isolated from Blood Cultures of Septic Patient.

We report discovery of a new bacterial genus and species of the family Pasteurellaceae by using phylogenetic and metabolic analysis. The bacterium, Emayella augustorita, was isolated from blood cultures of a patient in France diagnosed with an adenocarcinoma of the intestines and who was treated with a biliary prosthesis placement.

Aggregatibacter actinomycetemcomitans infection in children: two case reports and a review of the literature.

Aggregatibacter actinomycetemcomitans (Aa), a Gram-negative coccobacillus commonly associated with endocarditis, poses a rare diagnostic challenge in pediatric cases. The presentation of two pediatric cases-myositis and chest mass-highlights novel aspects, including unusual symptom presentations in children which can be mistaken for malignancy. The limited sensitivity of standard blood tests complicates diagnosis, leading to delayed diagnosis and treatment. Representative samples must be taken, especially if blood cultures are negative. Despite advances in detection methods, diagnosing Aa infection remains difficult due to its rarity in children and variable clinical presentation. In conclusion, a comprehensive understanding of Aa infection in children is essential for early and effective diagnostic and therapeutic management.

[Brain abscess due to Aggregatibacter aphrophilus]. / Absceso cerebral por Aggregatibacter aphrophilus.

Brain abscess is a focal suppurative process produced in most cases by bacterial agents. Aggregatibacter aphrophilus is a gram-negative bacteria belonging to the HACEK group, which causes infective endocarditis, liver abscesses, among others. Brain abscesses secondary to this germ are rare and, in most cases, it is associated with contact with pets, poor dental hygiene or dental procedures. Treatment consists of drainage of the abscess (greater than 2.5 cm) combined with antibiotic therapy, ideally beta-lactams. The case of a 64-year-old male patient with no relevant history is here presented. He was admitted to the emergency service due to headache, hemianopsia of a week's duration and later tonic-clonic seizures, in whom imaging studies and culture of a brain lesion subsequently revealed a brain abscess due to A. aphrophilus. This case aims to illustrate about the rarity of this infection, because A. aphrophilus is a normal part of the oropharyngeal flora and respiratory tract, in which it rarely causes invasive bacteremia.

El absceso cerebral es un proceso supurativo focal producido en la mayoría de los casos por agentes bacterianos. Aggregatibacter aphrophilus es una bacteria gram negativa perteneciente al grupo HACEK, causante de endocarditis infecciosa, abscesos hepáticos, entre otras. Los abscesos cerebrales secundarios a este germen son infrecuentes y en la mayoría de los casos asociados a contactos con animales domésticos, pobre higiene dental o procedimientos odontológicos. El tratamiento consiste en drenaje del absceso (mayores de 2.5 cm) combinado con terapia antibiótica, idealmente betalactámicos. Se presenta el caso de un paciente varón de 64 años sin antecedentes de relevancia quien ingresó al servicio de emergencias por cuadro de cefalea, hemianopsias de una semana de evolución y posteriormente crisis tónico clónicas, en quien posteriormente en estudios imagenológicos y cultivo de lesión cerebral se arribó al diagnóstico de absceso cerebral por A. aphrophilus. Este informe tiene como objetivo ilustrar al lector sobre la rareza de esta infección, debido a que A. aphrophilus forma parte normal de la flora orofaríngea y del tracto respiratorio, en los que rara vez ocasiona bacteriemias invasivas.

Mannheimia haemolytica-associated fibrinonecrotizing abomasitis in lambs.

Mannheimia haemolytica-associated abomasitis has been clinically described as a cause of sudden death in lambs, but it is poorly characterized. We describe the pathological features of a severe fibrinonecrotizing abomasitis in 3 lambs that died suddenly. All 3 abomasums had a thickened submucosa due to edema and necrotic areas delimited by bands of degenerate neutrophils with slender nuclei (oat cells) and angiocentric distributions. The overlying mucosa was congested. Myriads of gram-negative coccobacilli were observed within the oat cell bands. M. haemolytica was isolated from the abomasum in all 3 animals and was serotyped as A2 in one of them. Pericarditis and pleuritis were observed in 2 of the lambs. Clostridium spp. were isolated in 1 lamb and detected by immunohistochemistry in the 3 animals, suggesting clostridial co-infection. M. haemolytica should be considered among the differential diagnoses of necrotizing abomasitis in lambs.

Atypical post-infectious glomerulonephritis with c-ANCA positivity followed by endocarditis.

Post-infectious glomerulonephritis (PIGN), an uncommon variety of glomerulonephritis (GN), is characterized by emergence of nephritic syndrome within a few weeks following an infectious event. PIGN typically presents as a mild condition and tends to resolve by the time of diagnosis for GN. Aggregatibacter actinomycetemcomitans belongs to the HACEK group of bacteria, which constitutes less than 3% of bacteria responsible for community-acquired infective endocarditis. We present a case of 29-year-old man suspected of lymphoma with B-symptoms along with severe splenomegaly and nephromegaly. Shortly after, he developed an episode of nephritic syndrome accompanied by acute kidney injury (AKI) and high titers of cytoplasmic ANCA (c-ANCA)-positivity. Kidney biopsy revealed PIGN with tubulointerstitial nephritis. Despite treatment with antibiotics and corticosteroid, he visited the emergency room due to worsening dyspnea and multi-organ failure. An echocardiogram showed a bicuspid aortic valve with vegetation unseen on previous echocardiogram. He underwent aortic valve replacement immediately without adverse events. Four months after valve replacement, his renal function and cardiac performance have remained stable. We report a case of PIGN with AKI and high titers of c-ANCA appearing later as an infective endocarditis due to Aggregatibacter actinomycetemcomitans. With careful clinical observation and appropriate and timely management, satisfactory outcomes for patient health are possible.

Gallibacterium anatis infection in poultry: a comprehensive review.

Gallibacterium anatis (G. anatis), a member of the Pasteurellaceae family, normally inhabits the upper respiratory and lower genital tracts of poultry. However, under certain circumstances of immunosuppression, co-infection (especially with Escherichia coli or Mycoplasma), or various stressors, G. anatis caused respiratory, reproductive, and systemic diseases. Infection with G. anatis has emerged in different countries worldwide. The bacterium affects mainly chickens; however, other species of domestic and wild birds may get infected. Horizontal, vertical, and venereal routes of G. anatis infection have been reported. The pathogenicity of G. anatis is principally related to the presence of some essential virulence factors such as Gallibacterium toxin A, fimbriae, haemagglutinin, outer membrane vesicles, capsule, biofilms, and protease. The clinical picture of G. anatis infection is mainly represented as tracheitis, oophoritis, salpingitis, and peritonitis, while other lesions may be noted in cases of concomitant infection. Control of such infection depends mainly on applying biosecurity measures and vaccination. The antimicrobial sensitivity test is necessary for the correct treatment of G. anatis. However, the development of multiple drug resistance is common. This review article sheds light on G. anatis regarding history, susceptibility, dissemination, virulence factors, pathogenesis, clinical picture, diagnosis, and control measures.

Development of a new multiplex quantitative PCR for the detection of Glaesserella parasuis, Mycoplasma hyorhinis, and Mycoplasma hyosynoviae.

Glaesserella parasuis, Mycoplasma hyorhinis, and Mycoplasma hyosynoviae are important porcine pathogens responsible for polyserositis, polyarthritis, meningitis, pneumonia, and septicemia causing significant economic losses in the swine industry. A new multiplex quantitative polymerase chain reaction (qPCR) was designed on one hand for the detection of G. parasuis and the virulence marker vtaA to distinguish between highly virulent and non-virulent strains. On the other hand, fluorescent probes were established for the detection and identification of both M. hyorhinis and M. hyosynoviae targeting 16S ribosomal RNA genes. The development of the qPCR was based on reference strains of 15 known serovars of G. parasuis, as well as on the type strains M. hyorhinis ATCC 17981T and M. hyosynoviae NCTC 10167T . The new qPCR was further evaluated using 21 G. parasuis, 26 M. hyorhinis, and 3 M. hyosynoviae field isolates. Moreover, a pilot study including different clinical specimens of 42 diseased pigs was performed. The specificity of the assay was 100% without cross-reactivity or detection of other bacterial swine pathogens. The sensitivity of the new qPCR was demonstrated to be between 11-180 genome equivalents (GE) of DNA for M. hyosynoviae and M. hyorhinis, and 140-1200 GE for G. parasuis and vtaA. The cut-off threshold cycle was found to be at 35. The developed sensitive and specific qPCR assay has the potential to become a useful molecular tool, which could be implemented in veterinary diagnostic laboratories for the detection and identification of G. parasuis, its virulence marker vtaA, M. hyorhinis, and M. hyosynoviae.

Clinical-pathological findings induced by Histophilus somni isolated in subacute cardiac death in feedlot cattle.

The purpose of this report is to provide information about the different presentations of cardiac and extra-cardiac histophilosis and, to assess the antimicrobial (ATM) susceptibility of Histophilus somni isolated from these cardiac lesions to different ATM agents commonly used for treating bovine bacterial respiratory pathogens. Eight feedlot calves, which died after suffering from food rejection, apathy, hyperthermia, cough and nasal mucous discharge, and lack of response to ATM therapy, were studied. Cardiac lesions observed at necropsy included valvular/mural endocarditis, myocardial infarction, and necrotizing myocarditis, miliar non-suppurative myocarditis, myocardic necrotic sequestrum, and/or pericarditis. Histopathological, bacteriological and molecular studies confirmed the presence of a fastidious microorganism in the affected organs. H. somni showed no resistance to most ATM tested (ceftiofur, gamithromycin, enrofloxacin, florfenicol, tilmicosin). The results obtained in this study confirmed that H. somni was the main cause of the subacute cardiac lesions associated with hyperthermia, apathy and respiratory signs observed in cattle examined in this research. These presentations must be considered by veterinary practitioners in order to establish a rational therapeutic.

Brain abscess due to Aggregatibacter aphrophilus in association with atrial septal defect：Case report and literature review.

BACKGROUND: Aggregatibacter aphrophilus（A. aphrophilus）is one of the organisms of the HACEK group. Previously reported cases of brain abscesses caused by A. aphrophilus infection have occurred in children with a basis for congenital heart disease, or in adults with a basis for dental disease. Rare cases of brain abscess caused by A. aphrophilus have been reported in adults with congenital heart disease or in patients without dental disease history. Herein we present a rare case of brain abscess caused by A. aphrophilus, who was in association with atrial septal defect for more than 20 years, and had no dental disease and did not develop infective endocarditis. CASE PRESENTATION: A 51-year-old female was admitted due to progressively worsening headache and left limb weakness for more than 10 days. She denied the history of chronic diseases such as hypertension and diabetes, and no periodontal disease. While she had a history of atrial septal defect, a form of congenital heart disease with severe pulmonary hypertension for more than 20 years. After admission, echocardiographic illustrated congenital heart disease with severe pulmonary hypertension. CT and MRI showed brain abscess. Cerebrospinal fluid (CSF) results also confirmed the presence of intracranial infection. Empirical therapy with vancomycin 1.0 g i.v q12h and meropenem 2.0 g i.v q8h was initiated from the day of admission. On the fourth day after admission, brain abscess resection and decompressive craniectomy were performed, and the pus drained on operation were cultured and Gram-negative bacilli grew, which was identified as A.aphrophilus. Vancomycin was discontinued and meropenem was continued（2.0 g i.v q8h）for 5 weeks, followed by oral levofloxacin 0.5 qd for 4 weeks of out-patient antibiotics. The patient recovered fully within 9 weeks of treatment. CONCLUSIONS: This is the first case of A. aphrophilus to cause brain abscess in adult with a history of congenital heart disease for more than 20 years, who had no dental disease and did not develop infective endocarditis. We also highlight the value of bacterial 16 S rDNA PCR amplification and sequencing in identifying bacteria in abscesses which are culture-negative, and prompt surgical treatment，choosing effective antibiotics and appropriate course of treatment will get better clinical effect.

Comparative study of antibacterial activity and stability of D-enantiomeric and L-enantiomeric bovine NK-lysin peptide NK2A.

L-enantiomers of antimicrobial peptides (AMPs) are sensitive to proteolytic degradation; however, D-enantiomers of AMPs are expected to provide improved proteolytic resistance. The present study aimed to comparatively investigate the in vitro antibacterial activity, trypsin and serum stability, toxicity, and in vivo antibacterial activity of L-enantiomeric bovine NK2A (L-NK2A) and its D-enantiomeric NK2A (D-NK2A). Circular dichroism spectroscopy of D-NK2A and L-NK2A in anionic liposomes showed α-helical structures and the α-helical conformation of D-NK2A was a mirror image of L-NK2A. Both D-NK2A and L-NK2A displayed minimal in vitro and in vivo toxicities. RP-HPLC and mass spectrometry analyses revealed that D-NK2A, but not L-NK2A, was resistant to trypsin digestion. D-NK2A and L-NK2A showed similar in vitro bacterial killing activities against Histophilus somni. Slightly reduced antibacterial activity was observed when D-NK2A and L-NK2A were pre-incubated with serum. Confocal and transmission electron microscopic findings confirmed that both peptides induced disruption of bacterial inner- and outer-membranes. Improved survivals with D-NK2A treatment were observed when compared to L-NK2A in a murine model of acute H. somni septicemia. We conclude that antibacterial activity and mode of action of NK2A are not chiral specific. With further optimization, D-NK2A may be a viable AMP candidate to combat bacterial infections.

Aggregatibacter actinomycetemcomitans as the Aetiological Cause of Rheumatoid Arthritis: What Are the Unsolved Puzzles?

Leukotoxin A (LtxA) is the major virulence factor of an oral bacterium known as Aggregatibacter actinomycetemcomitans (Aa). LtxA is associated with elevated levels of anti-citrullinated protein antibodies (ACPA) in rheumatoid arthritis (RA) patients. LtxA targets leukocytes and triggers an influx of extracellular calcium into cytosol. The current proposed model of LtxA-mediated hypercitrullination involves the dysregulated activation of peptidylarginine deiminase (PAD) enzymes to citrullinate proteins, the release of hypercitrullinated proteins through cell death, and the production of autoantigens recognized by ACPA. Although model-based evidence is yet to be established, its interaction with the host's immune system sparked interest in the role of LtxA in RA. The first part of this review summarizes the current knowledge of Aa and LtxA. The next part highlights the findings of previous studies on the association of Aa or LtxA with RA aetiology. Finally, we discuss the unresolved aspects of the proposed link between LtxA of Aa and RA.

A Conserved Histophilus somni 23S Intervening Sequence Yields Functional, Fragmented 23S rRNA.

Histophilus somni is a Gram-negative bacterial organism that acts as an opportunistic pathogen and is a fastidious member of the Pasteurellaceae family associated with diseases of respiratory, reproductive, cardiac, and other tissues of ruminants. We identified an intervening sequence (IVS) embedded in all five copies of the 23S rRNA gene in the closed genome sequence of the H. somni isolate USDA-ARS-USMARC-63250 that may play an important role in affecting the biology of the organism. Sequencing the RNA from this isolate shows that most of the IVS is cleaved from the transcript, resulting in independent fragments of this structural rRNA that remain functional within the bacterial ribosome. The IVS lies between positions 1170 and 1278 bp of the 3,017-bp gene and exhibits self-complementarity between its 5' and 3' ends that predicts a stem-loop structure interrupting helix-45 in the transcribed 23S rRNA. Excision removes a 94-nucleotide (nt) stem-loop structure that displays an unusual 1-nt 3' end overhang instead of the more typical 2-nt overhang commonly observed at the ends of other excised IVS stem-loops. A comparison with genomes of other H. somni isolates indicates that this IVS is highly conserved, with 31 of 32 complete genomes having similar interruptions of canonical 23S rRNA genes. The potential biological effects of either the released IVS or the fragmentation of the functional 23S rRNA are unknown, but fragmentation may enhance rRNA degradation in ways that contribute to the regulation of gene expression. IMPORTANCE The genome biology underlying H. somni virulence, pathogenicity, environmental adaptability, and broad tissue tropism is understood poorly. We identified a novel H. somni 109-nt IVS stem-loop structure, of which the central portion is excised from the 23S rRNA transcript, resulting in the fragmentation of this rRNA in the H. somni isolate USDA-ARS-USMARC-63250 and the release of a 94-nt structured RNA of unknown function. We determined that this peculiar rRNA biology is widespread among sequenced H. somni isolates, suggesting it has importance to organism biology. The fragmented 23S rRNA molecules remain functional in the ribosome, given that the isolate grows in culture. The structured excised portion of the IVS, presumably due to the action of the endoribonuclease III, has an unusual 1-nt 3' end overhang. This newly discovered H. somni 23S rRNA fragmentation may enhance rRNA degradation providing a previously unrecognized avenue for regulating H. somni biological processes.

An improved multiplex PCR for Actinobacillus pleuropneumoniae, Glaesserella australis and Pasteurella multocida.

Glaesserella australis, a newly described bacterial species, has been isolated from pig lungs that displayed lesions very similar to those caused by Actinobacillus pleuropneumoniae, prompting the need for a validated diagnostic tool. In this work, we have altered a multiplex PCR used for the identification of cultures of G. australis, A. pleuropneumoniae and Pasteurella multocida to be more sensitive and then evaluated the use of the altered diagnostic tool on cultures and directly on tissues. The altered multiplex PCR was validated using 47 related species, both type/reference strains and field isolates. The sensitivity was assessed by serial dilutions and used a mixture of target bacteria in different concentrations. Further, 166 lung samples from 54 farms from four Australian States were used to validate the ability of the multiplex PCR to detect bacteria in lung swabs. The multiplex PCR was specific for the three target species. The assay could detect a minimum of 40 colony forming units (CFU) of G. australis, 786 CFU of A. pleuropneumoniae and 238 CFU of P. multocida. The multiplex PCR yielded more positives than coventional bacteriological examination. From a total of 166 lung samples, 51.9%, 51.9% and 5.6% of farms were PCR positive for P. multocida, A. pleuropneumoniae and G. australis, respectively. The results suggested that the new multiplex PCR was specific, sensitive and out performed traditional culture. The prevalence of G. australis was not very high, but it was the dominant pathogen in infected pigs.

On-farm colorimetric detection of Pasteurella multocida, Mannheimia haemolytica, and Histophilus somni in crude bovine nasal samples.

This work modifies a loop-mediated isothermal amplification (LAMP) assay to detect the bovine respiratory disease (BRD) bacterial pathogens Pasteurella multocida, Mannheimia haemolytica, and Histophilus somni in a colorimetric format on a farm. BRD causes a significant health and economic burden worldwide that partially stems from the challenges involved in determining the pathogens causing the disease. Methods such as polymerase chain reaction (PCR) have the potential to identify the causative pathogens but require lab equipment and extensive sample processing making the process lengthy and expensive. To combat this limitation, LAMP allows accurate pathogen detection in unprocessed samples by the naked eye allowing for potentially faster and more precise diagnostics on the farm. The assay developed here offers 66.7-100% analytical sensitivity, and 100% analytical specificity (using contrived samples) while providing 60-100% concordance with PCR results when tested on five steers in a feedlot. The use of a consumer-grade water bath enabled on-farm execution by collecting a nasal swab from cattle and provided a colorimetric result within 60 min. Such an assay holds the potential to provide rapid pen-side diagnostics to cattle producers and veterinarians.

Glaesserella parasuis serotype 4 HPS4-YC disrupts the integrity of the swine tracheal epithelial barrier and facilitates bacterial translocation.

Glaesserella parasuis (G. parasuis) is a commensal bacterium in the upper respiratory tract of pigs that can also cause the swine Glässer disease, which induces an intensive inflammatory response and results in significant economic losses to the swine industry worldwide. G. parasuis can cause disease through infection of the respiratory tract, resulting in systemic infection, but the mechanism is largely unknown. Recently we showed that Glaesserella parasuis serotype 4 (GPS4) increased swine tracheal epithelial barrier permeability, resulting in easier bacterial translocation. Tight junction proteins (TJ) play a crucial role in maintaining the integrity and impermeability of the epithelial barrier. GPS4 decreased the expression of the TJ ZO-1 and occludin in swine tracheal epithelial cells (STEC). Furthermore, the proinflammatory cytokines IL-6, IL-8 and TNF-α were significantly upregulated in GPS4-infected STEC, and both the MAPK and NF-κB signaling pathways were activated and contributed to the expression of TNF-α. We demonstrate that the production of proinflammatory cytokines, especially TNF-α, during GPS4 infection was involved in barrier dysfunction. Additionally, animal challenge experiments confirmed that GPS4 infection downregulated TJ in the lungs of piglets and induced a severe inflammatory response. In general, G. parasuis infection downregulated the expression of TJ and induced massive secretion of proinflammatory cytokines, resulting in epithelial barrier disruption and favoring bacterial infection. This study allowed us to better understand the mechanism by which G. parasuis crosses the respiratory tract of pigs.

The Hunger Games: Aggregatibacter actinomycetemcomitans Exploits Human Neutrophils As an Epinephrine Source for Survival.

Aggregatibacter actinomycetemcomitans is a gram-negative facultative anaerobe and an opportunistic oral pathogen, strongly associated with periodontitis and other inflammatory diseases. Periodontitis is a chronic inflammation of the periodontium resulting from the inflammatory response of the host towards the dysbiotic microbial community present at the gingival crevice. Previously, our group identified catecholamines and iron as the signals that activate the QseBC two-component system in A. actinomycetemcomitans, necessary for the organism to acquire iron as a nutrient to survive in the anaerobic environment. However, the source of catecholamines has not been identified. It has been reported that mouse neutrophils can release catecholamines. In periodontitis, large infiltration of neutrophils is found at the subgingival pocket; hence, we wanted to test the hypothesis that A. actinomycetemcomitans exploits human neutrophils as a source for catecholamines. In the present study, we showed that human neutrophils synthesize, store, and release epinephrine, one of the three main types of catecholamines. Human neutrophil challenge with A. actinomycetemcomitans induced exocytosis of neutrophil granule subtypes: secretory vesicles, specific granules, gelatinase granules, and azurophilic granules. In addition, by selectively inhibiting granule exocytosis, we present the first evidence that epinephrine is stored in azurophilic granules. Using QseC mutants, we showed that the periplasmic domain of the QseC sensor kinase is required for the interaction between A. actinomycetemcomitans and epinephrine. Finally, epinephrine-containing supernatants collected from human neutrophils promoted A. actinomycetemcomitans growth and induced the expression of the qseBC operon under anaerobic conditions. Based on our findings, we propose that A. actinomycetemcomitans promotes azurophilic granule exocytosis by neutrophils as an epinephrine source to promote bacterial survival.