What kind of bacteria is Brucella?

Brucellas are Gram – negative bacteria. They are small coccobacilli, measuring about 0.6 to 1.5 μm by 0.5-0.7 μm. They do not form spores and are non motile due to lack of capsules and flagella. They function as facultative intracellular parasites. They do produce endospores, which enable survival under long-term starvation. This heterotrophic bacterium carries out either aerobic or anaerobic respiration because it is a facultative bacterium. This means that they can survive with or without oxygen.

Brucellas rarely form capsules, which is usually immediately lost in breeding grounds. In common breeding grounds they grow very slowly. They have a better growth in enriched growing grounds. Brucellas are catalase positive.

The metabolism of the brucella is mainly oxidative and they show little action on carbohydrates in conventional media. They are aerobes but some species require an atmosphere with added CO2. Multiplication is slow at the optimum temperature of 37°C and enriched medium is needed to support adequate growth.

Brucella colonies become visible on suitable solid media in 2-3 days. The colonies of smooth strains are small, round and convex.

Today there are 6 species of Brucellas known:

  • Brucella melitensis
  • Brucella abortus
  • Brucella suis
  • Brucella ovis
  • Brucella canis
  • Brucella neotomae

Only Brucella melitenisi, abortus and suis are pathogenic for humans. Brucella melitensis B. with 3 serovars, as the source of infection sheep and goats, causes a serious form of the disease.  B. abortus with 9 serovars, as the source of infection cattle, causes mild form of the disease, but with intention to chronicity. Brucella suis, with 5 serovars has pigs as the source of infection. Brucella canis has dogs as the source of infection.

Brucellas do not produce protein toxins, but their pathogenic effect depends from their ability to resist phagocytosis, the ability to survive in the interior of monocytes, and the toxic action of lipopolysaccharides.

On the surfaces of Brucella, there are two antigenic determinants present, antigens A and M. In Brucella abortus and Brucella suis, the determinant is the antigen A, so the antigenic formula is Am. In Brucella melitensis the determinant is the antigen M, so the antigenic formula is aM.

Brucellas are able to live for a long time in the outer world. In milk, brucellas can survive for weeks, while in chees or other dairy products, from 1-3 months. Brucellas are sensitive to heat, and they are usually destroyed within 10 minutes in 60 degrees.

Brucellas were first described in 1887 and were named after the person who first discovered them, David Bruce.

What kind of infection is Brucellosis?

Brucellosis is a bacterial infection caused by bacterium Brucella. Humans get infected with Brucella from animals. There are three main ways how a human gets infected:

  • Raw dairy products – humans do get infected from consuming unpasteurized milk, cheese, butter, yogurt, ice cream, etc.  The bacteria can also be transmitted in raw or undercooked meat from infected animals.
  • Inhalation – Brucella bacteria spread easily in the air. Farmers, laboratory technicians and slaughterhouse workers can inhale the bacteria.
  • Direct contact – Bacteria in the blood, semen or placenta of an infected animal can enter thr bloodstream through a cut or a wound.

Normally, brucellosis is not transmitted from human to human, but however, there have been cases reported of infants who were infected from their mothers during breastfeeding.

Countries with high rates of Brucellosis include: Asia, Africa, Middle East, Latin America, around the Mediterranean Sea, etc.

People, who are at a greater risk to get infected are the once who have daily contact with animals like farmers, veterinarians, ranchers, hunters, microbiologists, etc.

Signs and symptoms of Brucellosis

The incubation period is usually long, and is characterized by high fever which comes and goes. Brucellosis can affect every part and organ of the body. Usually, signs and symptoms of Brucellosis include: high fever, chills, weakness, headache, fatigue, nausea, vomiting, diarrhea, joint pain, muscle pain, etc. These symptoms may be recurrent and appear from time to time. Brucellosis could also be chronic, when these symptoms are present for years, even after good treatment. Brucellosis abortus usually causes the chronic form of the disease, even though the onset might be mild. Possible complications of an infection with Brucellosis include:

  • Endocarditis – infection of endocardium of the heart. It is a very serious complication, because the infection can destroy the heart valves and lead to heart failure and death.
  • Arthritis – every joint can be affected, but usually signs and symptoms occur in the ankle, knee, hips, wrists and spine. Joints are painful, stiffed and swollen.
  • Splenomegaly – infection and inflammation of the spleen and liver, causing them to enlarge beyond their normal size.
  • CNS – central nervous system infections are very dangerous and life threatening. Meningitis – inflammation of the meninges that surround the brain, or Encephalitis – inflammation of the brain may occur.
  • Orchitis and Epididimitis – infection and inflammation of the male reproductive system. This leads to infertility.

How is Brucellosis diagnosed?

Brucellosis is usually diagnosed by testing a sample of blood or bone marrow for the brucella bacteria or by testing blood for antibodies to the bacteria. Other tests and examinations like Ultrasound, X-Rays, CT-Scan and Echocardiography may be needed to determine if any organ in the body is affected.

How is Brucellosis treated?

Treatment is supportive against the signs and symptoms of the disease. Treatment also tries to prevent complications, which can be life threatening sometimes.

Therapy with Antibiotics is required for couple of weeks and maybe months. Even with good treatment, in some cases the disease can reoccur and even become chronic.

Can Brucellosis be prevented?

It is very important to keep in mind some simple things that prevent Brucellosis, like:

  • Never consume unpasteurized dairy food, like milk, yogurt, cheese, etc.
  • Never consume undercooked meat.
  • Wear gloves when working with animals, especially if you are a farmer, rancher, veterinarian, etc.
  • Vaccinate domestic animals.