Actinobacillus
Encyclopedia
Actinobacillus is a genus of gram-negative, immotile and nonspore-forming, oval to rod-shaped bacteria occurring as parasites or pathogens in mammals, birds, and reptiles. It is a member of the Pasteurellaceae
Pasteurellaceae
Pasteurellaceae comprise a large and diverse family of Gram-negative Proteobacteria with members ranging from important pathogens such as Haemophilus influenzae to commensals of the animal and human mucosa. Most members live as commensals on mucosal surfaces of birds and mammals, especially in the...

family. The bacteria are facultatively aerobic or anaerobic, capable of fermenting carbohydrates (without production of gas) and of reducing nitrates. The genomic DNA contains between 40 and 47 mol % guanine plus cytosine.

Actinobacillus (Pasteurella
Pasteurella
Pasteurella is a genus of Gram-negative, facultatively anaerobic bacteria. Pasteurella species are non-motile and pleomorphic. Most species are catalase-positive and oxidase-positive....

) ureae
and A. hominis occur in the respiratory tract of healthy humans and may be involved in the pathogenesis of sinusitis
Sinusitis
Sinusitis is inflammation of the paranasal sinuses, which may be due to infection, allergy, or autoimmune issues. Most cases are due to a viral infection and resolve over the course of 10 days...

, bronchopneumonia
Bronchopneumonia
Bronchopneumonia or bronchial pneumonia or "Bronchogenic pneumonia" is the acute inflammation of the walls of the bronchioles...

, and meningitis. Actinobacillus actinomycetemcomitans occurs in the human oral microflora
Oral microbiology
Oral microbiology is the study of the microorganisms of the oral cavity and the interactions between the oral microorganisms with each other and with the host. Of particular interest is the role of oral microorganisms in the two major dental diseases: dental caries and periodontal disease.The mouth...

, and together with anaerobic or capnophilic organisms (HACEK group organisms) may cause endocarditis. Actinobacilli are susceptible to most antibiotics of the beta-lactam family, aminoglycoside
Aminoglycoside
An aminoglycoside is a molecule or a portion of a molecule composed of amino-modifiedsugars.Several aminoglycosides function as antibiotics that are effective against certain types of bacteria...

s, tetracyclines, chloramphenicol
Chloramphenicol
Chloramphenicol is a bacteriostatic antimicrobial that became available in 1949. It is considered a prototypical broad-spectrum antibiotic, alongside the tetracyclines, and as it is both cheap and easy to manufacture it is frequently found as a drug of choice in the third world.Chloramphenicol is...

, and many other antibacterial chemotherapeutics.

An analysis of Actinobacillus actinomycetemcomitans indicated that it was monophyletic
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...

 with Haemophilus aphrophilus and Haemophilus segnis, and it was proposed that they be reclassified as a new genus, Aggregatibacter
Aggregatibacter
Aggregatibacter is a genus in the phylum Proteobacteria , which contains three species, namely* A. actinomycetemcomitans Aggregatibacter is a genus in the phylum Proteobacteria (Bacteria), which contains three species, namely* A. actinomycetemcomitans Aggregatibacter is a genus in the phylum...

(from the Latin, "aggregare", meaning "to come together").
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