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PubMed1996

Differentiation of the serotype b and species-specific antigens of Actinobacillus actinobacillus actinomycetemcomitans recognized by monoclonal antibodies.

The serotype b antigens have been reported to be associated with lipopolysaccharide. Using murine monoclonal antibodies specific for either a serotype b antigen or the Actinobacillus actinomycetemcomitans species, the relationship of the two epitopes to lipopolysaccharide was determined. Both the species-specific and serotype b-specific monoclonal antibodies bound to whole cells, vesicles and conventionally isolated lipopolysaccharide and polysaccharide material derived from A. actinomycetemcomitans culture supernatants. Serotype b-specific monoclonal antibodies bound to the polysaccharide of acid-hydrolyzed lipopolysaccharide. Species-specific monoclonal antibodies bound to both the polysaccharide and the lipid A fraction of lipopolysaccharide after acid hydrolysis. Polymyxin b partially inhibited the binding of the species-specific monoclonal antibodies to lipopolysaccharide and had no effect on the binding of the serotype b-specific monoclonal antibodies to lipopolysaccharide. Lipopolysaccharide from whole bacteria and polysaccharide material isolated from culture supernatants were separated by gel filtration chromatography in deoxycholate into fractions that contained serotype b antigen, both serotype b and species-specific antigens, or species-specific antigen. SDS-polyacrylamide gel electrophoresis and Western blotting analysis of the fractions revealed that the serotype b antigen was on a high-molecular-weight polysaccharide material. The species-specific antigen was on a ladder of lower-molecular-weight polysaccharides identical to the blot pattern of lipopolysaccharide molecules separated by polyacrylamide gel electrophoresis and stained with silver stain. Chemical analysis of the polysaccharide containing serotype b antigen revealed 85% ribose, 11% glucose, and no lipid. Chemical content of the species-specific antigenic material revealed a composition typical of lipopolysaccharide. Immunoelectron microscopy using the species- or serotype b-specific monoclonal antibodies confirmed the biochemical and immunological characterization of the two antigens, showing that the species-specific epitopes were on the surface of the A. actinomycetemcomitans cell membrane and the serotype b-specific epitopes on the amorphous material extending from the cell surface. The data indicated that the serotype b antigen, detected by the antibody, was separable from lipopolysaccharide and was an A. actinomycetemcomitans capsular material. The species-specific antigen, being more conserved than the serotype antigen, was on all the lipopolysaccharide molecular species.

Aggregatibacter actinomycetemcomitans↗
PubMed2005

aroA gene PCR-RFLP diversity patterns in Haemophilus parasuis and Actinobacillus species.

The Haemophilus parasuis aroA gene encodes 5-enolpyruvylshikimate-3-phosphate synthase and participates in the aromatic amino acids and the folic acid universal metabolic pathway of bacteria. The application of aroA-based PCR-RFLP methodology yields a significant degree of diversity in H. parasuis and Actinobacillus species. PCR amplification of the aroA gene rendered a 1,067-bp fragment in all 15 H. parasuis serovars, and also in Actinobacillus pleuropneumoniae serotypes 1-12, Actinobacillus lignieresii, Actinobacillus equuli, Actinobacillus porcinus, Actinobacillus rossii, Actinobacillus suis, Actinobacillus ureae, Actinobacillus minor and Actinobacillus indolicus. Sau3AI and RsaI digestions of the aroA PCR products rendered seven different restriction fragment length polymorphism (RFLP) patterns: group I (H. parasuis serovars 1, 2, 4-6, and 8-15, A. porcinus and A. ureae), group II (H. parasuis serovars 3 and 7, and A. pleuropneumoniae serotypes 1, 4, 5, 9, 11 and 12), group III (A. lignieresii), group IV (A. pleuropneumoniae serotype 7), group V (A. pleuropneumoniae serotypes 2, 3, 6 and 8, A. equuli, A. rossii, A. minor and A. indolicus), group VI (A. suis) and group VII (A. pleuropneumoniae serotype 10). This is the first report describing the presence of aroA gene in H. parasuis, A. lignieresii, A. porcinus, A. rossii, A. suis, A. ureae, A. minor and A. indolicus and the data presented here demonstrates a significant degree of aroA genetic diversity in H. parasuis and species of the genus Actinobacillus.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗
PubMed2004

Delineation of the genus Actinobacillus by comparison of partial infB sequences.

A 426 bp fragment of infB, a housekeeping gene that encodes translation initiation factor 2, was sequenced from 59 clinical isolates and type strains of Actinobacillus species and sequences were compared. Partial sequences of 16S rRNA genes were also obtained. By comparing infB sequences, Actinobacillus pleuropneumoniae, Actinobacillus equuli, Actinobacillus suis, Actinobacillus ureae, Actinobacillus arthritidis, Actinobacillus hominis and two unnamed genomospecies showed more than 85 % similarity to the type strain of the type species of the genus, Actinobacillus lignieresii. The taxonomic position of Actinobacillus capsulatus was unresolved; this species is more remotely related to A. lignieresii. The two species A. lignieresii and A. pleuropneumoniae could not be clearly separated by infB sequence analysis. The phylogeny of the genus Actinobacillus based on infB analysis was essentially congruent with relationships inferred from 16S rRNA sequence comparisons and DNA hybridization studies. Discrepancies were encountered with single strains or taxa at the periphery of the genus. Greater intraspecies variation was observed with infB sequences than with 16S rRNA gene sequences, with notable exceptions. The apparent subdivision of some species by 16S rRNA analysis was most likely caused by RNA operon heterogeneity.

Actinobacillus↗
PubMed1999

Extracts of Actinobacillus actinomycetemcomitans induce apoptotic cell death in human osteoblastic MG63 cells.

Whether an extracellular component of periodontal-disease-causing bacteria induces apoptotic cell death in bone-related cells is unknown. To study the effects on osteoblasts of extracts obtained from sonicated Actinobacillus actinomycetemcomitans and Prevotella intermedia, we cultured human osteoblastic cell lines MG63 and Saos-2 cells and mouse osteoblastic cell line MC3T3-E1 cells in the presence of such extracts. The addition of the extracts from Actinobacillus actinomycetemcomitans induced cell death in MG63 cells in a dose- and time-dependent fashion over the concentration range of 0.1 to 10 microg/mL. By contrast, the extracts from Prevotella intermedia did not induce cell death in these cells, even in the presence of 10 microg/mL protein. By using the Hoechst 33342 staining technique, we observed marked nuclear condensation and fragmentation of chromatin in MG63 cells treated with the extracts of Actinobacillus actinomycetemcomitans. DNA ladder formation, a hallmark of apoptosis, also was detected in MG63 cells treated with extracts from Actinobacillus actinomycetemcomitans. In MG63 cells, DNA ladder formation was dose-dependent, with a maximal effect at a concentration of 10 microg/mL, and time-dependent, from 12 to 48 hrs. However, the extracts from Prevotella intermedia did not induce DNA fragmentation in MG63, Saos-2, or MC3T3-E1 cells. The extracts from Actinobacillus actinomycetemcomitans did not induce cell death and DNA fragmentation in Saos-2 and MC3T3-E1 cells. Sonicated extracts of Actinobacillus actinomycetemcomitans that had been treated with heat and trypsin did not induce DNA ladder formation in MG63 cells, suggesting that the apoptosis-inducing factors are proteinaceous. Cycloheximide prevented the Actinobacillus actinomycetemcomitans-induced DNA ladder formation in MG63 cells in a dose-dependent fashion, suggesting that new gene transcription and protein synthesis are regulated for Actinobacillus actinomycetemcomitans-induced apoptosis in MG63 cells. Our results indicate that apoptosis in alveolar bone cells induced by Actinobacillus actinomycetemcomitans plays an important role in periodontal diseases.

3T3 Cells↗
PubMed1985

Serological cross-reactivity between a porcine Actinobacillus strain and Haemophilus pleuropneumoniae.

During serological screening of a closed SPF-herd free of pleuropneumonia, more than half of the pigs were positive for complement-fixing antibodies to Haemophilus pleuropneumoniae. Actinobacillus bacteria closely related to A. suis were isolated from tonsillar tissue of 14 out of 20 slaughtered pigs submitted for pathological and bacteriological evaluation. None of the pigs had evidence of respiratory disease. Two pigs inoculated endobronchially with a selected Actinobacillus strain developed mild focal pneumonia and complement-fixing antibodies cross-reacting with H. pleuropneumoniae. Five pigs exposed and vaccinated with the Actinobacillus strain and five pigs spontaneously infected with the strain also developed complement-fixing antibodies against H. pleuropneumoniae and appeared to be less susceptible to experimental Haemophilus pleuropneumonia than pigs not exposed to the Actinobacillus infection. The agglutination test applied on serum treated with 2-mercaptoethanol detected antibodies against H. pleuropneumoniae serotype 5 but not against serotype 1 in pigs exposed to the Actinobacillus strain. Antibodies reactive with the Actinobacillus strain were also found in pigs hyperimmunized against H. pleuropneumoniae serotypes 1-5 in 2-mercaptoethanol tube agglutination test and rabbits hyperimmunized against serotypes 1,2 and 7, and strain 73567 in the immunodiffusion test. Conversely rabbits immunized against the Actinobacillus strain had antibodies against H. pleuropneumoniae serotypes 1, 3, 4, 5 and 6. It is concluded that pigs infected with Actinobacillus organisms may become false positive reactors against H. pleuropneumoniae.

Actinobacillus↗
PubMed1995

[The prognostic significance of the presence of Actinobacillus actinomycetemcomitans in the subgingival plaque of young orthodontic patients].

The aim of present study was to evaluate the prognostic significance of the presence of Actinobacillus actinomycetemcomitans in subgingival plaque from young patients wearing fixed orthodontic appliances. Fifteen orthodontic patients, 3 males and 12 females, aged 10 to 27, systemically healthy, participated in the study. First examination took place in the spring of 1992 (T1) and consisted in the collection of clinical (pocket depth, PD; Gingival Index, GI; Plaque Index, P1I; Gingival Bleeding Index, GBI) and microbiological (Actinobacillus actinomycetemcomitans presence) parameters in 4-8 periodontal sites in each patient. The same clinical and microbiological parameters were collected again in the spring of 1994 (T2). Results showed that the presence of Actinobacillus actinomycetemcomitans in the examined periodontal sites underwent fluctuation, 25% of sites being positive for the sought after bacterium in T2 whereas the percentage of Actinobacillus actinomycetemcomitans positivity in T1 was 47.5% with a statistically significant difference (p < 0.005). On the contrary clinical parameters did not show significant modifications through the study period T1-T2. Differential analysis of clinical parameter modifications in relation to Actinobacillus actinomycetemcomitans positivity in T1 or Actinobacillus actinomycetemcomitans-positivity fluctuations in T1-T2 period did not evidence any significant difference among various microbiological conditions. The authors conclude that the mere presence of Actinobacillus actinomycetemcomitans in subgingival plaque from specific periodontal sites in young orthodontic patients does not seem sufficient to consider those sites at risk for periodontal destruction in the medium-short term.

Adolescent↗
PubMed2004

Revised definition of Actinobacillus sensu stricto isolated from animals. A review with special emphasis on diagnosis.

The taxonomy of the members of the genus Actinobacillus associated with animals has been reviewed with focus on classification and identification including molecular based characterization, typing and identification. Out of the 22 species or species like taxa reported as Actinobacillus, 19 are associated with animals. When classified on the basis of 16S rRNA sequence based phylogenetic analysis, DNA-DNA hybridizations and phenotypic analysis, Actinobacillus sensu stricto is restricted to include A. lignieresii, A. pleuropneumoniae, A. equuli subsp. equuli, A. equuli subsp. haemolyticus (taxon 11 of Bisgaard), A. hominis, A. suis, A. ureae, A. arthritidis (taxon 9 of Bisgaard), Actinobacillus genomospecies 1 and 2 and the taxa 8 and 26 of Bisgaard. The remaining 11 species of Actinobacillus are unrelated to A. sensu stricto and should consequently be grouped with other genera or be renamed as new genera depending on new data. Identification of members of Actinobacillus at species level is possible through phenotypic characterization combined with information on host of isolation. PCR tests are available for specific detection of A. pleuropneumoniae. Only A. pleuropneumoniae is presently considered as a primary pathogen. Based on different types of RTX genes it is possible to PCR type A. pleuropneumoniae to serotype level. PCR might also be used for the specific detection of A. equuli subsp. haemolyticus. Epidemiological investigations and surveillance have so far included serotyping, multilocus enzyme electrophoresis (MLEE), ribotyping and restriction fragment length profiling.

Actinobacillus↗
PubMed2002

Postoperative infection with Actinobacillus spp in horses: 10 cases (1995-2000).

OBJECTIVE: To determine features of postoperative wound infection caused by Actinobacillus spp in horses undergoing clean, elective surgery and to evaluate bacterial susceptibility profiles of bacteria isolated. DESIGN: Retrospective study. ANIMALS: 10 horses. PROCEDURE: Data were retrieved from medical records and the microbiology laboratory database. RESULTS: 1,604 horses underwent clean, elective surgical procedures during the study period. Of these, 23 (1.43%) had postoperative wound infections, and Actinobacillus spp was isolated from 10 of these 23 (43%). Surgical procedures in these 10 horses included laryngoplasty with ventriculocordectomy (n = 3), arthroscopy (3), desmotomy of the accessory ligament of the superficial digital flexor tendon (2), removal of laryngoplasty prostheses (1), and hygroma resection (1). Seven horses survived, and 3 were euthanatized. All 10 Actinobacillus isolates were resistant to penicillin, and 6 were resistant to trimethoprim-sulfamethoxazole. All isolates were susceptible to ceftiofur and gentamicin. During the 5-year period of the study, Actinobacillus organisms were isolated from 35 of 513 (6.8%) samples from the general hospital population submitted for bacterial culture and antimicrobial susceptibility testing. CONCLUSIONS AND CLINICAL RELEVANCE: During the study period, Actinobacillus spp was isolated from a higher than expected percentage of horses that developed postoperative wound infections after clean, elective surgery. Susceptibility profiles for these isolates were different from typical susceptibility profiles for Actinobacillus isolates, suggesting that a pattern of resistance may be emerging.

Actinobacillus↗
PubMed2001

The transferrin receptor of Actinobacillus pleuropneumoniae: quantitation of expression and structural characterization using a peptide-specific monoclonal antibody.

When Actinobacillus pleuropneumoniae (A. pp) is grown under iron-restricted conditions in vitro, transferrin binding proteins (Tbps) are induced. The functional transferrin receptor of A. pp is composed of two outer membrane proteins (Tbp1 and Tbp2) and shows an exquisite specificity for porcine transferrin. This complex was studied using a monoclonal antibody (Mab 1.48) raised against a synthetic peptide corresponding to a hydrophilic domain of Tbp2 common to several A. pp serotypes. The antibody reacted specifically with a 60-70kDa Tbp2-antigen found in all serotypes of A. pp obtained from iron-restricted culture. It was found that Tbp2 was not expressed in iron replete medium by any serotype except serotypes 5a, 5b and 6 where a weak expression was seen. There was a weak expression of related antigens in Actinobacillus indolicus and Actinobacillus suis under iron-depleted conditions while no similar antigens were detected with the Mab in iron-starved Actinobacillus lignieresii, Actinobacillus porcinus, Actinobacillus minor, Haemophilus influenzae, and Haemophilus parasuis. Using an enzyme-linked immunosorbent assay (ELISA) based on the Mab 1.48, Tbp2 could be detected in both recombinant E. coli expressing Tbp2 and in wild type A. pp grown under iron restricted conditions. The subcellular location of Tbp2 in A. pp was studied by immunoelectron microscopy using the Mab 1.48. Interestingly, all antibody binding was found inside the A. pp cells, while Tbp2 expressed in recombinant E. coli was found both in the cytosol and on the outer membrane. These results indicate that the Mab 1.48-reactive epitope of Tbp2 is surface exposed when it is expressed without Tbp1 in E. coli while the inaccessibility of this epitope of Tbp2 in A. pp could be due to shading by the association between Tbp2 and Tbp1.

Actinobacillus pleuropneumoniae↗
PubMed1996

Serological and biochemical properties of the major outer membrane protein within strains of the genus Actinobacillus.

Sarcosyl-extracted outer membrane preparations of organisms of the genus Actinobacillus were investigated with regard to heat-modifiable and serological properties as well as N-terminal amino acid sequencing of the isolated major outer membrane protein (Omp). The major Omp of Actinobacillus lignieresii was recognized by a monoclonal antibody with specificity towards Proteus mirabilis OmpA. Moreover, N-terminal amino acid sequencing revealed strong homology to OmpA of enterobacteriaceae, on the contrary, no reaction of the Proteus mirabilis OmpA monoclonal antibody was detectable when investigating the outer membrane preparations of Actinobacillus suis and Actinobacillus equuli in Western blot analyses. N-terminal amino acid sequencing of the major Omp of these two species showed homologies to OmpC or OmpF of the enterobacteriaceae. In accordance with these results, a polyclonal antibody with specificity for the major Omp of Pasteurella multocida cross-reacted with the major Omps of Actinobacillus suis and Actinobacillus equuli. The relationship of the major Omp of Pasteurella multocida and OmpC and OmpF had been verified in recent studies.

Actinobacillus↗
PubMed2006

Classification of Actinobacillus spp isolates from horses involved in mare reproductive loss syndrome.

OBJECTIVE: To identify Actinobacillus spp isolates recovered from fetuses and pericardial fluid from horses affected with mare reproductive loss syndrome (MRLS) and determine whether these bacterial species are the same as those isolated from clinically normal horses. SAMPLE POPULATION: Isolates of actinobacilli recovered from 18 horses with pericarditis and 109 fetuses aborted by mares affected by MRLS. Procedures-Actinobacillus spp isolates were identified to the level of species or subspecies by use of conventional phenotypic tests and biochemical and enzyme test kits. The 16S rRNA gene from selected isolates was amplified, purified, and sequenced. Sequence data were compared with sequence data for actinobacilli in GenBank. RESULTS: Of the 109 isolates obtained from fetuses, 14 were Actinobacillus equuli subsp equuli, 65 were A equuli subsp haemolyticus, 28 were Bisgaard taxon 10-like bacterium, and 2 were Actinobacillus genomospecies 1. Of the 18 isolates from horses with pericarditis, 4 were A equuli subsp equuli, 13 were A equuli subsp haemolyticus, and 1 was Bisgaard taxon 10-like bacterium. Comparisons with published data and GenBank data revealed that the isolates recovered from horses with MRLS were the same as those isolated from the oral cavity or alimentary tract of healthy horses. CONCLUSIONS AND CLINICAL RELEVANCE: Actinobacillus spp isolates recovered from fetuses and pericardial fluid samples of horses affected by MRLS in 2001 to 2003 were identical to Actinobacillus spp found in the oral cavity and alimentary tracts of healthy horses.

Aborted Fetus↗
PubMed1988

Comparison and partial characterization of the protein profiles and outer membrane antigens of Actinobacillus species isolated from ram lambs with epididymitis.

Three monoclonal antibodies (LG17, LG30, LG33) were used in the indirect fluorescent antibody test, the ELISA, and the immunoelectrotransfer blot technique to identify group-specific and strain-specific epitopes on the outer membranes of Actinobacillus seminis, A actinomycetemcomitans, and 17 field isolates of Actinobacillus spp. The field isolates had been obtained by bacteriologic culture of specimens from ram lambs with epididymitis. Only antibody LG33 consistently had specificity for an outer membrane epitope shared by most of the bacterial isolates tested. Staining of polyacrylamide gels with periodic acid-Schiff reagent, Sudan black B, and Coomassie brilliant blue R250 indicated that target antigens for antibodies LG17 and LG33 contained carbohydrate and lipoprotein components, respectively. The chemical composition of the LG30 target antigen was not determined because of its instability after exposure to sodium dodecyl sulfate. Discontinuous-gradient polyacrylamide gel electrophoresis in sodium dodecyl sulfate and spectrophotometric scans of the gels were used to analyze n-octyl-beta-D-glucopyranoside protein extracts from A seminis, A actinomycetemcomitans, and 13 representative field isolates of Actinobacillus spp. Bacterial isolates could be grouped according to their protein profiles. The first group consisted of A seminis, A actinomycetemcomitans, and 7 field isolates of Actinobacillus spp, all of which shared common protein bands with molecular masses of approximately 94 kilodaltons (kD), 64 kD, 60 kD, 52 kD, 44 kD, and 26 kD. The second group was composed of 6 field isolates, each with unique protein profiles; isolates had relatively few protein bands in common. These data suggested that members of the genus Actinobacillus cultured from ram lambs with epididymitis probably include a number of various strains.

Actinobacillus↗
PubMed1997

Strains of Actinobacillus spp. from diseases of animals and ostriches in Zimbabwe.

Among the Actinobacillus spp. only A. lignieresii represents a homogenous and well studied taxon. However, haemolytic and non-haemolytic strains of A. equuli and A. suis are also isolated from a wide range of diseases in a variety of hosts. These isolates often pose problems in definitive identification. Consequently, several studies have been published, emphasizing the need for detailed studies to reclassify various members of this genus and also to assess their disease significance. We isolated 48 strains of Actinobacillus from clinical cases in horses, cattle, sheep, cat, pigs and ostrich. In order to investigate the association of various taxa of Actinobacillus in different pathological conditions in these hosts, the Zimbabwean isolates were characterized in detail and assigned to the recently described taxa of Actinobacillus. Representative strains of different taxa were also confirmed at the Department of Veterinary Microbiology, Frederiksburg C, Denmark. Of the 48 isolates, 22 were identified as A. lignieresii, 13 as A. equuli; 6 as A. suis, four as belonging to Taxon 11 and one as belonging to Taxon 9. These two taxa were recently described. Details of pathological conditions in the respective hosts and the significance of isolation, are discussed. We have reported for the first time isolation of A. lignieresii from a post-operative wound in a cat and there is also a first report of isolation from an ostrich. We considered A. equuli to be the primary cause of equine abortion and septicaemia, and Taxon 9 as causing "sleepy foal" disease. We did not encounter any case of "wooden tongue", but isolated A. lignieresii from cases of superficial lymphadenitis in cattle and sheep. This appears to be a first report of detailed descriptions of Zimbabwean strains of Actinobacillus spp.

Actinobacillus↗
PubMed1997

Environmental and physiological factors affecting the succinate product ratio during carbohydrate fermentation by Actinobacillus sp. 130Z.

Actinobacillus sp. 130Z fermented glucose to the major products succinate, acetate, and formate. Ethanol was formed as a minor fermentation product. Under CO2-limiting conditions, less succinate and more ethanol were formed. The fermentation product ratio remained constant at pH values from 6.0 to 7.4. More succinate was produced when hydrogen was present in the gas phase. Actinobacillus sp. 130Z grew at the expense of fumarate and l-malate reduction, with hydrogen as an electron donor. Other substrates such as more-reduced carbohydrates (e.g., d-sorbitol) resulted in higher succinate and/or ethanol production. Actinobacillus sp. 130Z contained the key enzymes involved in the Embden-Meyerhof-Parnas and the pentose-phosphate pathways and contained high levels of phosphoenolpyruvate (PEP) carboxykinase, malate dehydrogenase, fumarase, fumarate reductase, pyruvate kinase, pyruvate formate-lyase, phosphotransacetylase, acetate kinase, malic enzyme, and oxaloacetate decarboxylase. The levels of PEP carboxykinase, malate dehydrogenase, and fumarase were significantly higher in Actinobacillus sp. 130Z than in Escherichia coli K-12 and accounted for the differences in succinate production. Key enzymes in end product formation in Actinobacillus sp. 130Z were regulated by the energy substrates.

Actinobacillus↗
PubMedDate not supplied

Phylogenetic relationship of equine Actinobacillus species and distribution of RTX toxin genes among clusters.

Equine Actinobacillus species were analysed phylogenetically by 16S rRNA gene (rrs) sequencing focusing on the species Actinobacillus equuli, which has recently been subdivided into the non-haemolytic A. equuli subsp. equuli and the haemolytic A. equuli subsp. haemolyticus. In parallel we determined the profile for RTX toxin genes of the sample of strains by PCR testing for the presence of the A. equuli haemolysin gene aqx, and the toxin genes apxI, apxII, apxIII and apxIV, which are known in porcine pathogens such as Actinobacillus pleuropneumoniae and Actinobacillus suis. The rrs-based phylogenetic analysis revealed two distinct subclusters containing both A. equuli subsp. equuli and A. equuli subsp. haemolyticus distributed through both subclusters with no correlation to taxonomic classification. Within one of the rrs-based subclusters containing the A. equuli subsp. equuli type strain, clustered as well the porcine Actinobacillus suis strains. This latter is known to be also phenotypically closely related to A. equuli. The toxin gene analysis revealed that all A. equuli subsp. haemolyticus strains from both rrs subclusters specifically contained the aqx gene while the A. suis strains harboured the genes apxI and apxII. The aqx gene was found to be specific for A. equuli subsp. haemolyticus, since A. equuli subsp. equuli contained no aqx nor any of the other RTX genes tested. The specificity of aqx for the haemolytic equine A. equuli and ApxI and ApxII for the porcine A. suis indicates a role of these RTX toxins in host species predilection of the two closely related species of bacterial pathogens and allows PCR based diagnostic differentiation of the two.

Actinobacillus↗