Brucella melitensis
From DrugPedia: A Wikipedia for Drug discovery
Brucella melitensis
Brucella sp. is a small, Gram-negative coccobacillus, which can be grown slowly in vitro, and causes brucellosis. Brucellosis can be described as a "zoonotic disease that causes systemic symptoms and can involve many organs and tissues." This disease is not very common in the United States, but has plagued many countries where there is a lack of good standardized and effective public health systems. Countries currently high at risk include the Mediterrean Basin area, South and Central America, Eastern Europe, Asia, Africa, and the Middle East. The Brucella species acts as a pathogen that can induce "abortion and sterility in domestic mammals and chronic infections in humans known as Malta fever." These infections could easily be contracted through "consumption of unpasteurized dairy products and occupational contact." The Brucella species may also be used as agricultural, civilian, or military bioterrorism agents.
| Kingdom | Bacteria |
|---|---|
| Phylum | Proteobacteria |
| Class | Alphaproteobacteria |
| Order | Rhizobiales |
| Family | Brucellaceae |
| Genus | Brucella |
| Species | B. melitensis |
| Binomial | Brucella melitensis |
Contents |
[edit] Surface Characteristics
Brucella is a Gram-negative coccobacilli pathogenic bacteria that adapts to an intracellular lifestyle, is non-spore-forming and is non-motile. These organisms are mainly aerobic but some may require an atmosphere containing about 5-10% of carbon dioxide. The growth of the Brucella species is slow, sometimes taking as long as 2-3 days and an enriched medium is needed for optimal growth at 37°C. Experiments suggested that in Brucella melitensis strains, the expression of a fatty tissue called O-polysaccharides (OPS) on the outer membrane of the bacterium controls whether the bacterium will look smooth or round. O-polysaccharide is a homopolymer of 4,6-dideoxy-4-formamidoct-D-mannopyranose residues. The absence of these O-polysaccharide chains turns the organism into a rough variant. This layer is important in identifying whether a pattern of species-specific flagellar gene inactivations and flagellum gene clusters exist, because this would give a better understanding of host specificity and virulence. The need for these species to survive in a species-specific environment provides an explanation that the adaptation of the Brucella species requires an "intracellular life-style in a protected and more stable local environment or niche that provides a constant supply of nutrients." . Currently, little is known about their chromosomal exchange, and there is no evidence of plasmids or bacteriophages in these species.
[edit] Pathogenic Activity
Brucella melitensis mainly interacts with animals such as goat and sheep in domestic or wild animal reservoirs. Infectious food-borne diseases usually result in humans when contaminated or poorly pasteurized or unpasteurized milk and cheese products are consumed because of the ability for the organism to colonize in the udder of animals. These organisms thrive in the phagocytic cells of its host. However, the main sources of infection and the routes of contamination are variable because each of the Brucella species has distinctive factors controlling the presence or absence of a disease, which adds complexity when trying to identify interactions between the organism, its environment, and its host. Also, because of the rapidly changing environment in different aspects, whether it be social, cultural, or agricultural, new Brucella strains may emerge
[edit] Virulence
Brucella melitensis is one of the six species that causes Brucellosis, which can be described as a fatal zoonotic disease that affects multiple body systems. B. melitensis was originally found as a pathogen that mainly affected goats and sheep, which caused a decrease in fertility, loss of young, and a decrease in milk production. However, there has been more recent cases where this species has also been a highly pathogenic cause of human brucellosis. Brucellosis is common in many parts of the world, but is rare in the United States. This disease is mainly caused by the transfer of bacteria from farm animals to humans, usually through unpasteurized, contaminated goat milk, in which the bacteria can localize itself intracellularly once inside a host. (9). People can become infected through ingestion, inhalation, or direct contact.
Symptoms in Human Brucellosis include:
Anorexia Back pain Headache (cephalgia) Fatigue Fever Muscle pain (myalgia) Sweating Weight loss Feeling of general discomfort or uneasiness (often one of the first indications of an infection or disease) B. melitensis increases its survival and replication in phagocytic cells by minimizing the activation of the defense system of the host. This bacteria is also known for its macrophage infections. Macrophage function is responsible for many pathways important in apoptosis. Because apoptosis kills off infected cells to prevent the spread of infection, disruption in these pathways allows for pathogen survival. (9).
To eliminate the infection in hosts, hygiene, vaccine, and pasteurization of dairy products should be implemented. Hygienic precautions are especially important because contraction of Brucellosis may be induced by skin contact of infected materials. Vaccines in humans "have had limited efficacy and have been associated with serious medical reactions. Vaccines developed to prevent and control livestock infection are effective in reducing the incidence of human brucellosis." (11).
The virulence factors of B. melitensis are variable. The best known factors include the Type IV secretion system (responsible for signal delivery into host eukaryotic cells), flagella, and other regulatory elements.
Treatment of Brucellosis depends on the age of the patient and whether the patient is pregnant or not. Various treatments include the combination of antibiotics such as Rifampicin, Trimethoprim, Doxycycline, Gentamicin, and Ciprofloxacin.
