Brucella abortus

From DrugPedia: A Wikipedia for Drug discovery

Brucella abortus

Brucella abortus is a gram-negative bacterium that is found in cattle populations. This intracellular parasite is a blood borne pathogen that causes premature abortion of a cattle fetus. What makes this bacterium so dangerous is that it is zoonotic, meaning it can be transferred from an animal to a human host and still remain pathogenic. In humans this disease cause both acute and chronic symptoms, but can be treated with antibiotics. Because of this economic effect on the cattle business and the disease potential in humans, the US has spent close to $3.5 billion trying to vaccinate the cattle herds in the US. It is possible for B. abortus to be spread from wild populations of elk and bison into domestic cattle herds and this is why the US government continues to be vigilant in tracking potential cases within herds.

[edit] Surface Characteristics

Brucella abortus consists of a characteristic lipopolysaccharide [LPS] on its outer surface. LPS carries the A (B. abortus-type) and M (B. melitensis-type) epitopes, respectively. In addition, there is at least one common (C) epitope restricted to the smooth brucellae and a second common epitope (C/Y) shared with Yersinia enterocolitica O:9. O-polysaccharide consists of an unbranched linear homopolymer of 10 to 100 α-1,2-linked 4-formamido-4,6-dideoxy-D-mannose (N formylperosamine) residues. The O-polysaccharide is covalently linked to a core oligosaccharide. Core oligosaccharide is composed of mannose, glucose, 2-amino-2,6-dideoxyglucose (quinovosamine), 2-amino-2-deoxyglucose (GlcN),3-deoxy-D-manno-2-octulosonic acid (KDO), and unidentified sugars. The core is linked to the lipid A, which in contrast to most LPS studied, contains both GlcN and 2,3- diamino-2,3-dideoxyglucose (GlcN3N) as backbone sugars and amide- and ester-linked long-chain saturated (C16:0 to C18:0) and hydroxylated (3-OH-C12:0, to 29-OH-C30:0) fatty acids

[edit] Pathogenic Activity

Brucella abortus is an intracellular bacteria, which means that it does not replicate outside the host organism. This bacterium, as an intracellular pathogen, enters phagocytes, such as macrophages, in humans and in cows. It attaches to the endoplasmic reticulum of these cells. These smooth bacteria enter macrophages and then live in compartments of vacuolar space along the ER. The few cells that make it to these vacuolar spaces down regulate apoptosis genes within the macrophage and therefore cause the cell to resist self-death and these pathogens become resistant within these cells of the immune system. These resistant bacterium are what go on to cause chronic disease in human hosts.

In bovine species the bacteria also infects the trophoblast epithelial cells, which are the cells that provide nutrition to the embryo (8). After a number of rounds of cellular replication in the trophoblast the cells lyse, causing more bacteria cells to enter the blood stream of the developing embryo (1). These cells in the blood stream go on to colonize the placenta and fetus in pregnant female cows, and will go on to induce abortion of the fetus (7).

Though Brucella abortus is an intracellular bacterium it can remain alive outside the host without replicating. This bacterium can remain in the excrement of cattle and the aborted fetuses of the cattle for quite some time depending on the exact conditions; thought the average time is around 30 days. Outside the host the bacteria cells are affected by direct sunlight; the pathogen can be eliminated by pasteurization, and can be killed by disinfectants.

[edit] Virulence

Brucella abortus causes a disease called brucellosis, which used to be referred to as Malta Fever because it was first discovered in soldiers who were living on the island of Malta by Dr. David Bruce, for whom the pathogen gets its name. B. abortus is originally found in cattle and causes problems with fetus development and viability, but this pathogen can be passed to humans. It is uncommon in the US; most cases emerge from slaughterhouse workers, meat packers, or large animal veterinarians, but in the developing world the disease is much more common because their cattle herds are not vaccinated. In these cases the most common mode of transmission is through unpasteurized milk and cheese products because the bacteria is present it the milk glands of a female cow.

In humans the disease has both an acute and a chronic phase. The chronic phase will last as long as the host is alive without treatment. Acute symptoms include fever, chills, headache, backache, weakness, and weight loss. The chronic symptoms are usually recurring joint pain, fatigue, and headaches.

There is an antibiotic regiment for humans who come in contact with the disease that includes the antibiotics rifampin and doxycycline together

[edit] References

MicrobeWiki