Mycoplasma gallisepticum (MG) is a prokaryote from the class of Mollicutes and the family of Mycoplasmataceae and inhabits the upper respiratory tract. MG is different bacteria due to the lack of a cell wall. The genome of this kind was completely sequenced in 2012.
- 3.1 Sources of infection and infectious diseases
- 3.2 pathogenicity
- 3.3 therapy
Mycoplasma gallisepticum as a pathogen is respiratory diseases in poultry, such as Chickens and turkeys before and can be isolated from the respiratory tract. Upon infection, there is frequently a mixed infection with other viral or bacterial pathogens.
Species of the genus Mycoplasma ( also referred to as mycoplasma ) have the peculiarity that they do not otherwise typical for bacterial cell wall. Thus, they are more like a protoplast, which is also reflected in cell morphology: they are of more varied ( pleomorphic ), variable, vesicular shape. Their growth is carried out aerobically to facultative anaerobes, and although they are presented as part of a Gram stain as gram- negative because they lack the cell wall, have genetic research indicates that they are related to gram- positive cocci with low GC content in the DNA.
The cells because of the lack murein layer, although vulnerable to osmotic variations of the surrounding medium, but, in comparison with a less labile protoplasts. This is due to the presence of sterol in the cytoplasmic membrane, Mycoplasma gallisepticum therefore requires cholesterol ( cholesterol) in the medium, in order to grow. But since they normally colonize parasite a host organism, they receive from the cells of sterols and other essential metabolic components. In addition, there are still Lipoglycane in the cell membrane, as these are to be found also in the thermal plasma Tales, an order within the Archaea. They enable bacterial cells to adhere to the cell surface receptors of host animal cells, similarly as is the case with the lipopolysaccharides of Gram-negative bacteria.
Mycoplasma gallisepticum is to be regarded as all members of this genus as " metabolic cripple ". In the course of evolution, the bacterium has lost a lot of non- essential genes, on the one hand for the formation of a cell wall, but also for the synthesis of many metabolites, it has to be asked by the host cells. This is also reflected in the very small genome of this kind, which has just 986 kilobase pairs (kb ), which is less than one-fifth the size of the genome of Escherichia coli. Required metabolic components, it must either be obtained from the host cells or they must be added to the nutrient medium.
In the isolation of the pathogen is important to note that it can not survive long in the environment because of its properties, so for example, swabs of the infected tissue must be kept with a swab in a sterile nutrient solution in order to protect the cells against dehydration.
On solid media containing agar, Mycoplasma gallisepticum forms colonies that look like a fried egg. This typical appearance is due to the fact that the cells are grown so that they are embedded in the medium. If you would like to be cultured on a nutrient medium that satisfy end complete media for bacteria not, as they have because of their small genome size lost the ability to synthesize a number of metabolic components. The cultivation of M. gallisepticum is therefore complicated, because it must be very complex culture media are used, such as a yeast extract - peptone - beef heart infusion medium, which includes the addition of fresh serum to meet the needs of sterols and unsaturated fatty acids.
Evidence of infection with Mycoplasma gallisepticum are therefore usually by detection of antibodies formed in the infected organism by means of the ELISA method to continue is still a real-time multiplex PCR test kit approved to directly detect the DNA of the bacterium.
Sources of infection and infectious diseases
The infection is considered preparer of the CRD ( Chronic Respiratory Disease ) arising by secondary pathogens a clinical picture. An infection caused by Mycoplasma gallisepticum in chicken is done as a smear on the stables facility, as a droplet infection and direct by the hen to the embryo. The disease ( mycoplasmosis ) manifests itself usually by first dry short sneezing, which is expelled through the nostrils on beak closed. In a progressive spread in the respiratory tract also clear discharge from the nostrils is in the form of a moist film towards the tip of the beak visible. This film is especially noticeable when uneaten food and litter sticking around the openings.
In turkeys, the symptoms are similar, and in some cases be referred to as infectious sinusitis, it also changes in the joints, and thus motor has been described.
Although M. gallisepticum can only survive a short time in the environment, it is possible the pathogen to rapidly transferred to a new host. Factory farming in poultry breeding favored this. It needs to be further examined to what extent wild birds with contact with infected animals within the poultry farming as vectors for the transmission of Mycoplasma gallisepticum act.
The pathogenicity of mycoplasmas has not yet been sufficiently clarified, it is believed that the Lipoglycane contained in the cell membrane are involved as they trigger the production of antibodies in experimental animals. M. gallisepticum can attach to the animal cells of the target tissue, penetrate into it and remain intracellularly. In addition, they are capable of the three-dimensional structure of their surface antigens to change, it is believed that they are the immune response of the host organism deal by this mechanism, in order to survive in the host. The exact processes at the cellular and molecular level, leading to the clinical symptoms are still unclear, it is likely that the pathogenic structures of the cell membrane act as endotoxin, they will be free after the cell is destroyed. These toxins accumulate in the respiratory tract, thus making the animal for consumption of limited use.
A refurbishment of the portfolio concerned is only possible via the interruption of the chain of infection by a sufficiently long depopulation. Mycoplasma gallisepticum respond to tylosin, an antibiotic. The symptoms can thus be pushed back in the short term, the reinfection occurs but promptly at continuous stall stocking because the bacteria outside the body in the environment ( stable outlet ) for a limited time receives its infectivity. The occurrence of symptoms facilitates infection by other economically significant respiratory disease such as Infectious bronchitis (IB) and avian rhinotracheitis (ART).
In Austria, there are moves that are strengthened by research of the University of Veterinary Medicine in Vienna, to get poultry flocks free of Mycoplasma gallisepticum by targeted stable management. Reason, the zoonotic suspicion. So the bacteria in humans, among other irritation of the conjunctiva (conjunctivitis) to evoke.
- Klaus Damme, Ralf -Achim Hildebrand: poultry farming. Ulmer 2002, ISBN 978-3800139293
- Lecture by Detlef Bibl as part of the training for veterinarians at the Vet.med. Univ. Vienna