What is the Bartonella birtlesii pathogen?
Bartonella birtlesii is a facultative intracellular bacterium. Specifically, this means that the intracellular bacteria can enter their target cells and multiply in the cytoplasm. The Bartonella birtlesii pathogen was isolated for the first time from wood mice of the genus Apodemus in France and the United Kingdom. Through experimental trials, laboratory mice also became infected with the pathogen and subsequently formed a bacteraemia lasting about 5 to 10 weeks. A bacteraemia is the presence of bacteria in the bloodstream.
Like other Bartonella species, the Bartonella birtelesii pathogen uses a parasitism strategy in which red blood cells are infiltrated by the transmission of arthropods. Scientists assume that fleas and ticks act as vectors of the Bartonella birtlesii pathogen.
How can the Bartonella birtlesii pathogen be characterised?
The Bartonella birtlesii pathogen belongs to the genus Bartonella and is therefore a gram-negative bacterium. The bacterium is a parasite that lives inside the host cell (intracellular). In the case of the Bartonella birtlesii pathogen, this host cell is usually the red blood cells (erythrocytes). The vector of the Bartonella birtlesii pathogen is fleas and ticks.
From a biochemical point of view it can be described as an oxidase and catalase bacterium. The oxidase is an enzyme that catalyses oxidation-reduction reactions. This includes above all reactions in which disoxygen (O 2 ) is involved as an electron acceptor . Catalase is also an enzyme that is widespread and occurs in almost all living organisms that are exposed to oxygen . In this process, the catalase bacterium catalyses the decomposition of hydrogen peroxide to oxygen and water and is important for protecting from oxidative damage, which can be caused, for example, by reactive oxygen species (ROS). The Bartonella birtlesii pathogen was isolated from Apodemus. Apodemus is a genus of the Muridae. These are real mice and rats.
How dangerous is the Bartonella birtlesii pathogen for humans?
The pathogenicity of the Bartonella birtlesii pathogen, i.e. its ability to cause pathological changes in humans, is still largely unknown. For the Central Commission for Biological Safety (ZKBS), Bartonella birtelsii is to be assigned to risk group 2 as a donor and recipient organism for genetic engineering work. This classification recommendation is based on the fact that the bacterium has a low pathogenic potential and its host range is, as things stand at present, very limited. Risk group 2 means that it is a notifiable disease according to Section 6 of the Infection Protection Act.
Studies of the Bartonella birtlesii pathogen in mice
The bacterium Bartonella birtelesii is mainly used to study long-term bacteraemia, erythrocyte adhesion as well as invasion in mice. Here, the main focus is on how the mouse-adapted Bartonella birtlesii pathogen affects the viability of Balb/C mouse red blood cells (erythrocytes). The study proceeded as follows:
- Bacterial strains and their growth conditions: 5 days Bartonella birtlesii pathogen was grown at 35 ° C on blood agar . Blood agar is a culture medium for microorganisms, of which 5 per cent came from defibrinated sheep blood (CBA) in the experiment conducted here.
- Animal husbandry: The laboratories of Charles River in Lyon/France housed the Balb/C mice in two mouse cages. Before the start of the experiment, all animals showed no signs of illness and were allowed to acclimatise to the facility as well as the diet under the later experimental supervision for at least 5 days prior to blood collection .
- In vitro incubation of Bartonella birtlesii pathogens with rodent blood cells (erythrocytes): The red blood cells (erythrocytes) from peripheral mouse blood were isolated . Using the Ficoll gradient centrifugation method, was then purified and cultured for 5 days on CBA plates.
- Evaluation of the erythrocyte lysis: After 3 days of incubation, 100 microlitres of erythrocytes and Bartonella birtlesii pathogens were detected under the microscope.
What were the study results of the Bartonella birtlesii pathogen in mice?
Regarding the effect of Bartonella birtlesii pathogens on the viability of red blood cells, the study revealed that according to the scale moi of 0.01, 0.1 and 1, the bacterium did not affect the cell viability. Even after 3 days of incubation and the scale moi 10, 2 percent of red blood cells (erythrocytes) were still intact. Compared to red blood cells present in RPMI without bacteria, no significant effect on cell viability of red blood cells (erythrocytes) was observed with a complete RPMI medium. After an initial infection with the Bartonella birtlesii pathogen, it was quickly removed from the blood of the rodents.
How does the Bartonella birtlesii pathogen affect the red blood cells (erythrocytes)?
In order to survive in the host animal at all, the Bartonella birtlesii pathogen must outsmart the host's immune response, thereby not only enabling its extracellular survival, but also enabling it to approach the red blood cells (erythrocytes). Which bacterial factors are decisive for outwitting the immune system of the host animal, and which ultimately make replication of the bacterium possible in the first place, is still unknown to the scientists. However, to prevent the spread of Bartonella birtlesii infection, it is important for scientists to continue to investigate the mechanisms of Bartonella infection. In addition to the question of replication of the pathogen in the host animal, gene expression and the regulation and signal transduction pathways of the Bartonelaa bacteria also play an important role here in the scientific understanding of the Bartonella pathogen. Incidentally, these considerations do not explicitly apply only to the Bartonella birtlesii pathogen, but also to other Bartonella species.