Brucella Species

by Sean Elliott, MD

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    00:01 Brucella Species, a bacteria.

    00:04 Brucella are gram-negative coccobacilli as you see on the image here.

    00:09 They’re aerobic, facultative and intracellular bacteria.

    00:14 Also, they’re non-encapsulated.

    00:17 This means that they have somewhat difficult or fastidious growth requirements.

    00:22 The Brucella are interesting because they are one of several that cause zoonotic diseases or as we like to say in the world of infectious diseases, they’re fascinomas, the zebras.

    00:33 Zonoses typically come from known animal sources such as in the case of Brucella, cattle, goats, sheep, and dogs.

    00:43 One can acquire Brucella by ingesting unpasteurized dairy products from for example, goats or cattle, as well as contact with an infected animal host.

    00:55 As you see on the top image, the young lady is playing with the very cute goat.

    01:00 You know for a fact that she will soon be swapping saliva by kissing or licking with the same goat and potentially being exposed to Brucella.

    01:09 The image on the lower is cheese which maybe if it’s coming from goats or chèvres, may be unpasteurized and in certain parts of the world, unpasteurized dairy coming from goats is a known source of Brucella.

    01:26 But also, farmers, veterinarians, slaughterhouse workers, anybody who works with the zoonotic animals you see listed above are all at risk for acquiring Brucella either through direct contact or through inhalation of airborne disease.

    01:42 How does Brucella cause its disease? This is yet another example of the organism entering into a white blood cell to escape detection.

    01:51 And in this case as you see on the image, Brucella is ingested by or phagocytosed by a macrophage.

    01:59 However, it again is resistant to intracellular killing.

    02:04 It prevents the fusion of a lysosome or an enzyme-containing vacuole with the phagosome and thus, it’s able to replicate itself while also evading immune control.

    02:16 This replication or growth continues and then, allows it to spread within its carrier to other parts of the body, typically, in immune tissues such as the spleen, liver, lymph nodes, and bone marrow.

    02:29 Ultimately, it exits its host macrophage and then, so, doing, causes cell death.

    02:36 This finally is the trigger for other immune cells including the TH1 or T Helper 1 response to be activated and to respond to the Brucella with antibody production, with cytokine production and ultimately, creating a granuloma around the site of the infection.

    02:57 What does Brucella disease look like? Well, Brucellosis is the typical description, although, there are many different words for Brucella associated disease around the world.

    03:08 Some call Brucellosis undulant fever which is a reference to the undulating pattern of the fever.

    03:15 It’s a cyclical process.

    03:17 Typical patients with Brucellosis have malaise, fever, and rigors or chills, night sweats, and fatigue.

    03:25 Along with that, they may have weight loss and many of them have reactive arthritis or arthralgias.

    03:31 The arthritis as you see on the image many times is of the small joints and it may resemble rheumatoid arthritis such as older individuals experience later in life.

    03:43 The undulating fever pattern along with the reactive arthritis is a suggestion that Brucella is the likely diagnosis, although, not specific to that diagnosis, the combination of those two is quite striking.

    03:58 A way for me to remember undulating fever is to think of the udder of a cow as the cow walks back and forth and underneath the udder, you can see the swinging pattern back and forth, a cyclical pattern of the fever.

    04:12 Brucellosis exists primarily in an acute form although, there can be a subacute onset, a slow onset but it is especially problematic when it occurs in a chronic form and in fact, chronic Brucellosis is one of the many, many known causes of fever of unknown origin.

    04:31 Prevention and treatment, most importantly, is to prevent disease in the animals and if that’s not possible, to at least pasteurize the dairy products.

    04:42 Again, it is unpasteurized goat and cow associated dairy products which are the primary risk for Brucellosis.

    04:50 Treatment for non-pregnant adults consists of an oral regimen of doxycycline and an aminoglycoside.

    04:56 However, for women in early pregnancy, they should be treated with rifampin plus trimethoprim sulfamethoxazole, while those in late stage pregnancy receive only rifampin until delivery.

    05:07 The trimethoprim Sulfamethoxazole is avoided in late pregnancy to prevent any risk of neonatal or chronic stress.

    05:14 Remember, however, to also give a folic acid supplement when treating those pregnant women with late stage pregnancy.

    05:21 Relapses can occur and if you think about where Brucella hides, it’s hiding within immunologic tissue, within macrophages, within the spleen, within lymph nodes and, so, it makes sense that one would have to treat a long time to gain entry into those protected immunologic sources.

    05:40 Thus, prolonged therapy is the way to go.

    05:43 So, Brucella is definitely a zoonotic process.

    05:47 It is something to consider for that patient with prolonged fevers and it is one of the reasons that in infectious diseases, we ask the interesting questions, not what did you have for breakfast, but how much goat cheese did you have?

    About the Lecture

    The lecture Brucella Species by Sean Elliott, MD is from the course Bacteria.

    Included Quiz Questions

    1. Granulomas
    2. Bruises
    3. Petechiae
    4. Hematomas
    5. Ulcers
    1. Brucellosis
    2. Hemolytic disease of the newborn
    3. Typhoid
    4. Malaria
    5. AIDS
    1. Undulating pattern
    2. Continuous pattern
    3. Step ladder pattern
    4. Remittent pattern
    5. Relapsing pattern

    Author of lecture Brucella Species

     Sean Elliott, MD

    Sean Elliott, MD

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