Brucella Flashcards
Brucellosis is endemic in which country?
It is endemic in Lebanon
Are they motile? Spore forming? Do they have a capsule?
They are nonmotile, non-spore forming, non encapsulated coccobacilli
What are the results of the catalase and oxidase test?
They are catalase and oxidase positive
Are they extracellular or intracellular bacteria?
They are facultative intracellular
To what they are sensitive?
They are sensitive to direct sunlight
How are they transmitted?
By ingestion of contaminated animal products like milk or cheese
By direct contact with infected animals like a splash of blood in the conjunctiva
Laboratory infection can occur
Who are the reservoir?
Why infected individuals do not transmit the disease?
Animals are the natural reservoir, humans are not, they all accidental hosts and this is why infected individuals do not transmit the disease
What is the clinical presentation?
Brucellosis which is the Malta fever or undulating fever
What is the characteristic of brucellosis?
Night sweats are a characteristic of brucellosis and sometimes they are accompanied with chills
What is the incubation period?
1 to 6 weeks
Where do they multiply?
How do they escape phagocytosis?
They multiply at the site of entry, then they multiply into macrophages
In macrophages they block the phagosome-lysosome fusion, especially the degranulation of myeloperoxidase system
How bacteria will pass to the blood?
Bacteria will go to the lymphatic channels, then to lymph nodes, to the thoracic duct and then to blood
Where bacteria can go?
They can go to all parenchymatous organs like liver, spleen, lungs, heart, kidneys etc…
Where bacteria are multiplying wherever they are?
What do we have in parenchymatous organs?
They are multiplying in macrophages.
This is why parenchymatous organs end up having granulomas
What is the host reaction to brucellosis?
The formation of caseating granulomas (caseation=form of necrosis, destruction that appears cheese-like, typical of tuberculosis)
From what are composed caseating granulomas?
A compact layer of mononuclear cells, epithelioid cells (they resemble epithelial cells, but their origin is the monocyte macrophage), giant cells (syncytium, multinucleated cells), lymphocytes and plasma cells.
What happens in individuals who recover?
That is a deposition of fibrotic tissue on the granuloma
To what is converted the tissue fibrous tissue in advanced cases?
It is converted into a calcified area which many of them can heal spontaneously, while others stay for a longer period considered as dormant granulomas where there is a risk of relapse
Which bacteria presents a similar case?
Tuberculosis
What are the three types of symptoms?
Depending on whether there is acute, localized or chronic brucellosis
Why diagnosis is not easy in the acute brucellosis?
Because it includes general symptoms like nausea, backache, headache, fever causing night sweats which are not typical of brucellosis
Which symptoms can help in diagnosis of acute brucellosis?
Hepatomegaly, splenomegaly, lymphadenopathy although they are still not specific
What happens if it is not treated?
Individuals end up with localized brucellosis
What are the manifestations of localized brucellosis?
- Osteomyelitis, Lumbo sacral vertebrae
- Disc space infection, involving adjacent vertebrae
- septic arthritis in knees
- splenic abscesses ending with calcification
- prostatic or renal infection
- pleural effusion and pneumonia which is the most difficult thing to diagnose
- Endocarditis: Which is the worst outcome
Why endocarditis is the worst outcome?
Aortic valve is involved, it can be destroyed either by granuloma, or by the LPS which is very active during the infection.
Both valves are involved, this requires immediate surgery and replacement of both valves along with antibiotics therapy
Can we find free bacteria during the chronic brucellosis? What do we find either?
Free bacteria are no more found. We can find them only in granulomas
What are the symptoms of this stage?
Fatigue, weakness, nonspecific aches, pain, nervousness and other psychoneurotic symptoms
Fever is still present and is undulating
What is the vaccine? What are preventions?
It is live attenuated for animals
Farmers should wear protective equipment and not eat anything from an unknown origin
What do we see during the physical examination?
Splenomegaly, hepatomegaly and lymphadenopathy
In which medium does they grow?
The best medium is Castaneda bottles, they grow aerobically and anaerobically
Why culture is dangerous?
Because it can be transmitted in the lab
What is the best way for diagnosis?
Serology since culture takes a lot of time
Which test is done in serology?
Wright’s test known as Coombs test in the past which is a standard agglutination test
When IgM start to be detected? IgG and IgA?
IgM start to be detective the first week, peek at around three months weather IgA and IgG start to be deducted after the first week and stay for around eight weeks.
As long as the disease is active, we can detect IgM and IgG
What means the detection of IgM? The reduction of IgG in the brucellosis?
During brucellosis when IgM are detected this indicates the acute active infection, but IgG detection indicates whether there is a recent acute infection or a chronic infection
What does the mercaptoethanol test? For what purpose?
It destroys pentameric and dimeric IgA leaving only the monomers
This test is done to detect the agglutnating IgG which are of importance to us
What happens to the antibodies when there is progression to a chronic stage?
Agglutinating ability of Ab is lost in vitro, so we will be left with those that are not agglutinating and that can be detected by ELISA or by complement fixation
Do they give permanent immunity?
There is no permanent immunity
At which stages the treatment should be? Why?
It should be very early, at the acute and subacute stages since it is very difficult to treat chronic stages
What is the antibiotic treatment?
Doxycycline (a tetracycline) + aminoglycoside (e.g., gentamycin) for 4 weeks
Followed by doxycycline + rifampin for 4-8 weeks
What is the treatment for CNS disease?
Long-term therapy with high doses of Bactrim + rifampin
What is the treatment for children?
Bactrim + rifampin for 8-12 weeks
Is there any vaccine?
No vaccines for humans but there is a live attenuated vaccines for animals
