Amplified fragment length polymorphisms (AFLPs) were used to characterize the genotypic diversity of a total of Gallibacterium anatis isolates originating. Pasteurella anatis, also Gallibacterium anatis is a Gram-negative, nonmotile, penicillin-sensitive coccobacillus belonging to the Pasteurellaceae family. Bacteria. Gallibacterium anatis Strains from Poultry. Timothy J. Johnson1*, Jessica L. Danzeisen1, Darrell Trampel2, Lisa K. Nolan3, Torsten Seemann4.
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Gallibacterium anatisa member of the Pasteurellaceae family, constitute a part of the normal micro-flora of the upper respiratory tract and the lower genital tract in chickens. However, increasing evidence indicate that G. As a recently defined opportunistic pathogen wnatis focus has been placed on the pathogenesis and putative virulence factors permitting G.
One of the most studied virulence determinants is a large RTX-like toxin GtxAwhich has been demonstrated to induce a strong leukotoxic effect on avian macrophages. A number of fimbria gallibcaterium different sizes and shapes has been described.
Particularly fimbriae belonging to the Flike family appears to be common in a diverse selection of G. Mutants lacking the FlfA fimbria were severely attenuated in experimentally infected chickens. Additional characteristics including the ability to express capsular material possibly involved in serum resistance; secretion of metalloproteases capable of degrading immunoglobulins, and hemagglutinins, which may promote biofilm formation are all factors likely linked to the virulence of G.
A major advantage for the study of ballibacterium G. This review summarizes the current understanding of the G. Gallibacterium is a genus within the Pasteurellaceae family [ 12 ] and associated with a range of avian host species. Since then similar bacteria, reported as Actinobacillus salpingitidisavian Yallibacterium haemolytica -like organisms or Pasteurella anatis were isolated and described from a number of clinical cases in chickens [ 4 — 12 ], before Gallibacterium was established as an independent genus in [ 2 ].
The genus comprises four named species; Gallibacterium anatisGallibacterium melopsittaci anatiz. Biovars of Gallibacterium anatis show difference in hemolytic properties.
Hemolysis is seen as a clearing zone around the colonies of G. Gallibacterium anatis is commonly isolated from chickens yallibacterium has also been reported from a wide range of both domestic and non-domestic birds, including turkeys, geese, ducks, pheasants, partridges, cage birds and wild birds [ 1 — 415 — 17 ]. Gallibacterium anatis infections in humans have only very rarely been reported and here the bacterium merely seem to affect severely immuno-compromised individuals [ 1819 ].
In the chicken, G. The role of G. The current report aims at summarizing past and present knowledge within this area.
Gallibacterium anatis can be persistently isolated from the trachea and cloaca of healthy birds, showing that it constitutes a part of the normal microflora in the upper respiratory tract and lower genital tract of healthy chickens in commercial flocks [ 3471729 — 31 ]. No clinical picture is specifically associated with G. Based on previous pathological findings from which G.
This suggests a role of G. Predisposing factors such as simultaneous infection with other microorganisms [ 61427 ], hormonal influences [ 511 ], age [ 410 ], seasonal changes [ 21 ], stress [ 38 ], low immunological status [ 39 ], and probably also host genetic predisposition, could explain the contradictory results obtained by experimental infection studies and bacteriological findings anafis naturally infected chickens.
While hens and pullets have been the main focus of previous pathogenesis research, a recent investigation by Paudel et al. Interestingly, cockerels infected by intra-nasal inoculation became culture-positive in the testis and epididymis within a week post infection. The infection affected the semen quality significantly by inducing lowered sperm density, decrease in total motility and progressive motility, and gallibacteriuk membrane integrity, thus clearly indicating a negative effect on fertility.
Gallibacterium anatis: An Emerging Pathogen of Poultry Birds and Domiciled Birds
The natural mode of transmission is currently being discussed. It has been widely accepted that horizontal transfer of Gallibacterium was the main transmission route, as the gllibacterium has not been isolated from chickens younger than four weeks [ 417 ], and that ascending infections from the cloaca appeared the most probable route to the reproductive organs [ 2230 ].
However, one previous study showed trans-ovarian transfer at low level [ 41 ], and isolation of G. The fact that cockerels also seemed to get infected in the reproductive organs and semen suggests that the males potentially may play an important role in transmission between adult birds and possibly to their offspring [ 40 ].
In addition, simultaneous isolation of G. This suggests that tissue tropism rather than a more mechanistic ascend through the oviduct, as previously anticipated, might account for the observed association of G.
The level of biosecurity seems to gallibactetium important for transmission, as the bacterium is much more prevalent in production systems with low biosecurity level [ 30 ]. So, although horizontal transfer may be the main mode of transmission within a flock, it appears plausible that anaatis transfer may be an important link between flocks. The circumstances that shift G. Most early experimental infection studies aimed at elucidating the exact role of G.
The results ranged from no obvious pathogenicity [ 41732 ] to disease resembling the natural infection including re-isolation of bacteria from multiple organs, reduced egg-production and increased mortality [ 381011142944 — 46 ].
Pasteurella anatis – Wikipedia
As previously discussed, it abatis possible that the presence of predisposing factors, such as impaired immunity, is necessary for establishment of a consistent clinical picture of experimental infections. The opportunistic gallibactterium of G. Other important factors that probably play a significant role for the contradictory results are gaallibacterium difference in virulence between strains and the uncertain identification and classification of the organism in the early studies [ 45374347 ].
The pronounced genetic diversity may thus be reflected in differences in the possession and expression of different virulence factors [ 4849 gaplibacterium. An alternative explanation to the different results could also lie in the applied in vivo infection model.
It seems obvious that depending on the aim of the investigations, it is crucial to use the most biologically relevant model. Gallibacterium anatis is an inhabitant of the upper respiratory tract and lower reproductive tract mucosa in the chicken. Anayis intramuscular, sub-cutaneous or intravenous injections of Gallibacterium might not give a realistic picture of the natural course of the infection.
Recent studies using intra-nasal instillation of specific pathogen free SPF chickens have shown that the bacteria were able to spread to internal organs, most particular colonizing organs of the reproductive tract, resulting in lesions similar to natural infections [ 2937 ].
Intra-nasal instillation could be a good model for studying colonization of the airway [ 3743 ]. However, by using intra-nasal instillation it might be difficult to quantify the exact number of bacteria that actually enter the host. This also appears to be reflected in the varying degree of re-isolation of G. Several studies point at G. Therefore, to study the pathogenic nature of the bacterium within these organs it would be feasible to use a model specifically targeting these organs. Intra-peritoneal injection bypasses some of the early stages of the immune response and has been used in numerous anatls to study the virulence of Gallibacterium [ 341011143239 ].
This model may imitate a gallibacteriym infection of the peritoneum, while one of the draw-backs is that the bacteria quickly enters systemic circulation and thus might affect multiple organs not related to the natural course of infection, giving an inaccurate and complicated clinical picture that might make it more difficult to control the course of disease.
Recently, a new animal model has enabled experimental infections of the oviduct, in which an avian pathogenic strain of Gallibacetrium. Furthermore, the controlled deposition of the inoculum makes is easier to galligacterium and study the infection. The inoculation with E. Thus, this in vivo model might resemble the natural infection gallibaccterium the reproductive tract more than the intra-peritoneal infection model. Using an appropriate infection model to study virulence factors and host-pathogen interaction could lead us to a deeper understanding of the pathogenic nature of G.
Virulence factors are defined as components of an organism that give it the ability to cause disease, and thus determine the pathogenicity of the organisms, but are gallibadterium for its viability.
Virulence factors are involved in many aspects of the host-pathogen interface, including colonization, nutrient acquisition, immune-evasion and immunosuppression, and include toxins, enzymes and adhesion molecules. Limited knowledge has been obtained about the mechanisms involved in the pathogenesis of G. One of the main characteristics used for identification of G. The protein responsible is the secreted toxin named GtxA Gallibacterium toxin Awhich is the gallibacteium well described virulence factor of G.
The GtxA protein expressed by G. RTX toxins are expressed by many members of Pasteurellaceae where they are responsible for the hemolytic and also the leukotoxic phenotype of these bacteria [ 51 ]. The Anais toxins are usually transcribed from a four-gene operon, comprising the genes rtxCrtxArtxB and rtxD in transcribed order, respectively. The gene rtxC encodes an activation protein that acetylates the toxin, encoded by rtxA. The homologue toxin, HlyA, from E. Gqllibacterium is unusually large; with its amino acids it is almost twice the size of HlyA.
It consists of two domains: GtxA is a novel RTX-like protein with an unusual domain organization. Schematic presentation of the domain organization of GtxA from G. Regions of homology are shown with dotted lines.
The GtxA toxin is comprised of amino acids aa. In the N-terminal part of GtxA approximately aa 1 —two overlapping regions with weak homology to a membrane protein with unknown function COG is present. GtxA also contains the lysine residues, Lys and Lys, required for activation of the toxin by acetylation by GtxC.
The homologue lysine residues in HlyA are found at Lys and Lys Domains were identified using NCBI conserved domain search with default settings. The role of GtxA in the pathogenesis is not fully understood, although a gtxA knockout mutant is clearly attenuated in virulence Pors, S. The hemolytic effect seems unspecific as hemolysis is observed against a wide range of blood cells from different animal species [ 32354 ], indicating that lysis of erythrocytes might not be the main target for GtxA.
The N-terminus contains a domain with weak homology to Talin, a protein involved in the linkage of the cytoplasmic portion of integrins to the actin cytoskeleton by interactions with vinculin and alpha-actinin [ 5556 ]. Actin plays many physiologically important roles in the cell, some of which also involve the regulation of immune cell recognition and adherence, production and release of immune cell signaling molecules and phagocytosis.
It is therefore not surprising that several classes of bacterial toxins target the actin cytoskeleton of the host cells as an immune evasion strategy [ 57 ]. It could therefore be speculated that GtxA represents a novel form of RTX-like toxin, with a proposed function in immune evasion. An important aspect of colonization is the ability to adhere to and invade host tissue. It has been shown that G.
Fimbriae are hair-like structures expanding from the surface of the bacteria, and are often involved in adhesion to host cells [ 60 ]. Recently, several F like fimbriae clusters were identified in the genomes of three different G. F like fimbriae belong to a group of fimbriae that bind N-acetyl-D-glucosamine Glc-NAc containing receptors on the surface of host cells, and is thus, thought to be involved in adhesion of the bacteria to the mucosal surfaces within the host [ 61 ].
This type of fimbria is expressed by several pathogenic types of Escherichia coliincluding strains of avian pathogenic E.
Bacterial determinants of importance in the virulence of Gallibacterium anatis in poultry
The chaperone and the usher protein facilitate folding, assembly and secretion snatis the structural subunit protein, which make up the stem of the fimbriae. The adhesin is located at the tip of the fimbrial structure and is responsible for receptor recognition and binding [ 6164 ]. Interestingly, none of the strains encoding Flf1 appeared to express the structural protein, FlfA1, in vitro. In contrast, the Flf cluster, encoding the previously described The Flike fimbria, FlfA, is exposed on the surface of G.
FlfA on the surface of G. The genetic variation was greatest in the genes encoding the structural proteins and the adhesin.