Pasteurellaceae
Encyclopedia
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 upper respiratory tract. The family includes several pathogens of vertebrates, most notably H. influenzae. This species causes several diseases in humans (though not flu, as was originally thought). Other Pasteurellaceae cause gingivitis and chancroid in humans and many others are important veterinary pathogens.
Pasteurellaceae are typically rod-shaped, and are a notable group of facultative anaerobes. They can be distinguished from the related Enterobacteriaceae
by the presence of oxidase
, and from most other similar bacteria by the absence of flagella
.
Bacteria in the family Pasteurellaceae have been classified into a number of genera based on metabolic properties, but these classifications are not generally accurate reflections of the evolutionary relationships between different species. H. influenzae was the first organism to have its genome
sequenced and has been studied intensively by genetic and molecular methodologies. Since 1995, the family has been expanded from three genera to the current thirteen through the use of new genetic-based classification and identification technologies. Many members of the Pasteurellaceae family make excellent natural models for the study of bacterial pathogenesis and host-pathogen-interactions thus giving valuable insights into related human diseases.
, and reproductive tracts and possibly also parts of the intestinal tract. Most taxa represent potential pathogens. Both systemic and local infections have been reported for most taxa involved in diseases. However, pneumonia
has been reported most frequently. Fossil remnants of members of Pasteurellaceae have never been reported and information on the diversification of taxa within the family can only be obtained by phylogenetic reconstruction. For more information see Christensen et al.
It has been proposed to divide the family Pasteurellaceae into at least two clades on the basis of conserved deletion mutations. One proposed clade includes Aggregatibacter
, Pasteurella
, Actinobacillus succinogenes, Haemophilus influenzae
, Haemophilus somnus and Mannheimia succiniciproducens; while the other includes Actinobacillus minor, Actinobacillus pleuropneumoniae, Haemophilus ducryi, Haemophilus parasuis and Mannheimia haemolytica.
s are bacterial pore forming toxins that are particularly abundant among pathogenic species of Pasteurellaceae where they play a major role in virulence. RTX toxins of several primary pathogens of the family of Pasteurellaceae are directly involved in causing necrotic lesions of the target organs. Many RTX toxins are mainly known as haemolysins due to their capacity to lyse erythrocytes (red blood cells) in vitro, an effect that seems to be non-specific. It is now known for many RTX toxins that their specific targets are leukocytes, where RTX toxins bind to the corresponding β subunit (CD18) of β2 integron
s and then cause a cytotoxic effect. For several RTX toxins the binding to CD18 was shown to be host specific and seems to be the basis determining the host range of a given RTX toxin. Observations on very closely related species of the Pasteurellaceae family with different RTX toxins indicate that these latter contribute to a significant part to the host specificity of the pathogen itself. RTX toxins induce a strong immunologic response generating neutralizing antibodies. They therefore constitute important antigens in modern subunit vaccines.
, Actinobacillus
, Pasteurella
, and the Mannheimia genera of organisms has highlighted several redundant iron acquisition receptors for transferrin, siderophores, and heme/heme-containing proteins. In addition, the identification of several immunogenic lipoproteins and OM proteins has driven research for an effective cross-protective vaccine for these organisms.
data are available for the following Pasteurellaceae members: Aggregatibacter actinomycetemcomitans strain HK1651, Actinobacillus pleuropneumoniae strains L20 and sv1 4074, [Haemophilus] ducreyi strain 35000HP, Haemophilus influenzae strains 86-028NP, R2846, R2866, and Rd, Histophilus somni strains 129Pt and 2336, Mannheimia haemolytica A1 strain ATCC BAA-410, Mannheimia succiniciproducens strain MBEL55E, and Pasteurella multocida strain Pm70.
Proteobacteria
The Proteobacteria are a major group of bacteria. They include a wide variety of pathogens, such as Escherichia, Salmonella, Vibrio, Helicobacter, and many other notable genera....
with members ranging from important pathogens such as Haemophilus influenzae
Haemophilus influenzae
Haemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, Gram-negative, rod-shaped bacterium first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the Pasteurellaceae family, it is generally aerobic, but can grow as a facultative anaerobe. H...
to commensals of the animal and human mucosa. Most members live as commensals on mucosal surfaces of birds and mammals, especially in the upper respiratory tract. The family includes several pathogens of vertebrates, most notably H. influenzae. This species causes several diseases in humans (though not flu, as was originally thought). Other Pasteurellaceae cause gingivitis and chancroid in humans and many others are important veterinary pathogens.
Pasteurellaceae are typically rod-shaped, and are a notable group of facultative anaerobes. They can be distinguished from the related Enterobacteriaceae
Enterobacteriaceae
The Enterobacteriaceae is a large family of bacteria that includes many of the more familiar pathogens, such as Salmonella, Escherichia coli, Yersinia pestis, Klebsiella and Shigella. This family is the only representative in the order Enterobacteriales of the class Gammaproteobacteria in the...
by the presence of oxidase
Oxidase
An oxidase is any enzyme that catalyzes an oxidation-reduction reaction involving molecular oxygen as the electron acceptor. In these reactions, oxygen is reduced to water or hydrogen peroxide ....
, and from most other similar bacteria by the absence of flagella
Flagellum
A flagellum is a tail-like projection that protrudes from the cell body of certain prokaryotic and eukaryotic cells, and plays the dual role of locomotion and sense organ, being sensitive to chemicals and temperatures outside the cell. There are some notable differences between prokaryotic and...
.
Bacteria in the family Pasteurellaceae have been classified into a number of genera based on metabolic properties, but these classifications are not generally accurate reflections of the evolutionary relationships between different species. H. influenzae was the first organism to have its genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
sequenced and has been studied intensively by genetic and molecular methodologies. Since 1995, the family has been expanded from three genera to the current thirteen through the use of new genetic-based classification and identification technologies. Many members of the Pasteurellaceae family make excellent natural models for the study of bacterial pathogenesis and host-pathogen-interactions thus giving valuable insights into related human diseases.
Taxonomy and biodiversity
The family Pasteurellaceae includes 38 properly classified species in addition to 24 misclassified species. The majority of taxa have been isolated from disease conditions in warm blooded animals and in particular in farm animals. These bacteria are obligate parasites or commensals of vertebrates, colonizing mainly the mucosal surfaces of the upper respiratory tract, oropharynxOropharynx
The Oropharynx reaches from the Uvula to the level of the hyoid bone.It opens anteriorly, through the isthmus faucium, into the mouth, while in its lateral wall, between the two palatine arches, is the palatine tonsil....
, and reproductive tracts and possibly also parts of the intestinal tract. Most taxa represent potential pathogens. Both systemic and local infections have been reported for most taxa involved in diseases. However, pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
has been reported most frequently. Fossil remnants of members of Pasteurellaceae have never been reported and information on the diversification of taxa within the family can only be obtained by phylogenetic reconstruction. For more information see Christensen et al.
It has been proposed to divide the family Pasteurellaceae into at least two clades on the basis of conserved deletion mutations. One proposed clade includes 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...
, 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....
, Actinobacillus succinogenes, Haemophilus influenzae
Haemophilus influenzae
Haemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, Gram-negative, rod-shaped bacterium first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the Pasteurellaceae family, it is generally aerobic, but can grow as a facultative anaerobe. H...
, Haemophilus somnus and Mannheimia succiniciproducens; while the other includes Actinobacillus minor, Actinobacillus pleuropneumoniae, Haemophilus ducryi, Haemophilus parasuis and Mannheimia haemolytica.
RTX Toxin
RTX toxinRTX toxin
The RTX toxin family is a group of exotoxins produced by gram-negative bacteria. All RTX toxins share a common gene organization and structural appearance. Gram-negative bacteria secrete the toxins into the extracellular space using the type I secretion system. RTX is an abbreviation of "repeats...
s are bacterial pore forming toxins that are particularly abundant among pathogenic species of Pasteurellaceae where they play a major role in virulence. RTX toxins of several primary pathogens of the family of Pasteurellaceae are directly involved in causing necrotic lesions of the target organs. Many RTX toxins are mainly known as haemolysins due to their capacity to lyse erythrocytes (red blood cells) in vitro, an effect that seems to be non-specific. It is now known for many RTX toxins that their specific targets are leukocytes, where RTX toxins bind to the corresponding β subunit (CD18) of β2 integron
Integron
An integron is a two component gene capture and dissemination system, initially discovered in relation to antibiotic resistance, and which is found in plasmids, chromosomes and transposons...
s and then cause a cytotoxic effect. For several RTX toxins the binding to CD18 was shown to be host specific and seems to be the basis determining the host range of a given RTX toxin. Observations on very closely related species of the Pasteurellaceae family with different RTX toxins indicate that these latter contribute to a significant part to the host specificity of the pathogen itself. RTX toxins induce a strong immunologic response generating neutralizing antibodies. They therefore constitute important antigens in modern subunit vaccines.
Iron Uptake
Outer membrane (OM) proteins for iron acquisition have roles in infection and pathogenesis and have growing appeal as novel targets for anti-infectives and therapeutics. Characterization of cell surface proteins of members of the Pasteurellaceae family including HaemophilusHaemophilus
Not to be confused with Haemophilia.Haemophilus is a genus of Gram-negative, pleomorphic, coccobacilli bacteria belonging to the Pasteurellaceae family. While Haemophilus bacteria are typically small coccobacilli, they are categorized as pleomorphic bacteria because of the wide range of shapes they...
, Actinobacillus
Actinobacillus
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 family. The bacteria are facultatively aerobic or anaerobic, capable of fermenting...
, 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....
, and the Mannheimia genera of organisms has highlighted several redundant iron acquisition receptors for transferrin, siderophores, and heme/heme-containing proteins. In addition, the identification of several immunogenic lipoproteins and OM proteins has driven research for an effective cross-protective vaccine for these organisms.
DNA sequence
DNA sequenceDNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
data are available for the following Pasteurellaceae members: Aggregatibacter actinomycetemcomitans strain HK1651, Actinobacillus pleuropneumoniae strains L20 and sv1 4074, [Haemophilus] ducreyi strain 35000HP, Haemophilus influenzae strains 86-028NP, R2846, R2866, and Rd, Histophilus somni strains 129Pt and 2336, Mannheimia haemolytica A1 strain ATCC BAA-410, Mannheimia succiniciproducens strain MBEL55E, and Pasteurella multocida strain Pm70.
See also
- Haemophilus influenzaeHaemophilus influenzaeHaemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, Gram-negative, rod-shaped bacterium first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the Pasteurellaceae family, it is generally aerobic, but can grow as a facultative anaerobe. H...
- ChancroidChancroidChancroid is a sexually transmitted infection characterized by painful sores on the genitalia...
(H. ducreyi) - MicrobiologyMicrobiologyMicrobiology is the study of microorganisms, which are defined as any microscopic organism that comprises either a single cell , cell clusters or no cell at all . This includes eukaryotes, such as fungi and protists, and prokaryotes...
- Iron in microbiologyIron in microbiologyIron is essential for almost all living organisms as it is involved in a wide variety of important metabolic processes. However, iron is not readily available and microorganisms therefore employ various iron uptake systems to secure sufficient supplies from their surroundings...