Bartonella is a genus of bacteria consisting of many different species out of which almost eight species have been recognized as potentially harmful or pathogenic towards human beings. Due to its ability to reproduce either within or outside the cell, the Bartonella species is also considered as ‘facultative intracellular,’ while its ability to resist the ‘gram stain’ makes the bacteria to be considered a ‘gram negative’ bacteria. Among the Bartonella species, the most notable is Bartonella henselae, which causes the cat scratch disease largely in the young and in immune-compromised individuals. However, the bacterium is also responsible for diseases such as bacillary epithelioid angiomatosis, bacillary peliosis hepatic, and bacteremia as well.
The Bartonella is an aerobic organism, which means the bacteria depend on oxygen to maintain its life. It extends to about 1 micrometer in length while it could measure up to 0.5 micrometers in diameter. A slightly curved appearance is a possibility for most Bartonella species and it can also make jerky movements, even in the absence of whips as with certain other bacteria. The optimal growing conditions for Bartonella has been recognized as blood with a moist atmosphere, rich CO2 count and a temperature of 35% Celsius. It should also be remembered that Bartonella species, such as Bartonella henselae, responds to Warthin-Starry silver stain and is therefore used as the method of detection for Bartonella.
The Bartonella is believed to be transmitted through blood-sucking arthropod vectors and the usual reservoir host has been recognized as a mammal. At the beginning, Bartonella colonizes within the endothelial cells and at frequent intervals, multiple bacteria are released into the circulation where they infect the circulating erythrocytes or the red blood cells. The bacteria can replicate within the red blood cell until it reaches a critical density, after which it can be sucked in by a blood sucking arthropod. Among the vectors that are being studied for transmitting Bartonella, ticks, lice, fleas and sandflies are prominent. However, the spread of cat scratch disease or ‘bartonellosis’ can take place following a scratch from a kitten, because kittens lack the immunity to resist Bartonella and therefore are made to be reservoirs for Bartonella henselae.
Bartonella spp. can cause multiple diseases related to humans and the symptoms that are associated with these diseases are usually none specific. However, in cat scratch disease, fever, malaise and headache predominate, while within 3 to 10 days the local lymph nodes begin to swell. Complications related to cat scratch fever and other Bartonella related diseases include endocarditis and myocarditis, although many of the diseases resolve by themselves after few days.
As mentioned earlier, most Bartonella infections will resolve themselves unless the patient is a immune-compromised individual. However, antibiotics can be given for a quick recovery along with other supportive measures. The effectiveness of antibiotic treatment in immune-compromised individuals are not certain, although the chances of developing systemic illnesses and bacteremia would be rather less among those who are given antibiotics compared to the ones who await self-resolution. In addition, aspiration of infected lymph nodes may also have to be performed in certain instances.