What should one know about the devious bacteria Bartonella? Well, first of all, there are two serotypes of it: Seroptype I is Houston-1 and Serotype 2 is Marseille. The different classifications are based on the slight but still significant differences in the 16S ribosomal DNA sequences. The full name of the bacteria itself is Bartonella henselae, but it has only been called this since 1993, before which it had been titled Rochalimaea henselae.
Bartonella is an oxidase-negative, aerobic, and relatively slow growing Gram negative rod. Its features are that its shape is very slightly curved and it does not have flagella to stimulate its movement. It also requires very fastidious and precise conditions to fully grow in vitro. For instance, the temperature for the best growth of this bacterium is 37 degrees Celsius. Besides that, Bartonella is highly dependent on the amount of heme available for its development. With a high sensitivity to changes in pH it has an explicit pH range of 6.8 to 7.2. All in all, what does it look like? Generally, examination under the microscope provides cauliflower-like structures.
The first time Bartonella henselae was discovered was actually in a patient who had been suffering from Cat Scratch Disease in 1950. The bacterium today is found and can successfully be isolated from erythrocytes of cats and also the nodes of humans.
Typically, colonies of Bartonella take about two to six weeks to form. It is for this reason that it is frequently misdiagnosed – its slow development is difficult to judge. The slow growth contributes to frequent misdiagnosis. Though taking part in the Cat Scratch Disease, it was also discovered that this bacterium is involved in numerous other symptoms, such as those found in HIV-positive individuals.
Finally, it is interesting to discover how this bacterium’s invasion mechanisms function. The first one involves Bartinella eliciting a large rearrangement of the actin cytoskeleton and is called the invasome-mediated uptake. The process causes aggregation and once the bacteria is swallowed up by host cell membranes, it eventually enters the endothelial cells as well. This entire event occurs within 24 hours and then the invasion is successful, and may cause swelling for those who bear the bacteria in their system in the form of bacillary angiomatosis or peliosis hepatitis. The second mechanism for the bacterium’s invasion was discovered later than the first. The invasion of Barticella drives HUVEC into the cell. The vasoproliferative lesions that are caused by Bartonella species are normally surrounded by neutrophils. It is these that contribute to an inflammatory response involving endothelial cell activation. The bacterium is then allowed to enter the tissues and follows up with the involvement of other adhesion molecules, resulting in invasion of the organism.