Small gram neg rods. Without capsule.
B.melitensis(goats and sheep).
Are human pathogens
Cause Brucellosis or undulant fever(rise and fall pattern)
B.melitensis infections more severe and prolonged
whereas B.abortus infections are self limited.
Prevention: Pasteurization of milk.
F.tularensis causes Tularemia.
Small pleomorphic gm neg rods.
Granuloma infection due to endotoxin.
Most of them are ulceroglandular, the site of entry
(usually the skin)ulcerates and the regional lymph
nodes are swollen and painful.
Prevention: avoid bitten by ticks(insect vector) and
handling wild animals.
Y.pestis cause Plague also known as black death.
Is a small gm neg rod that exhibits bipolar staining
(resembles a safety pin).
Freshly isolated samples possess a polysaccharide-protein
complex capsule. These may be lost. Virulence is lost as
One of the most virulent bacteria known. Even 1-10 orgs
can cause disease.
Rat flea is the vector and endemic in wild rodents.
The orgs at the time of the bite spread to the regional
lymph nodes, which swell and become tender. They are
known as buboes and hence the name Bubonic plague.
5. The orgs, reach high concentrations in blood 9bacteremia)
and disseminate to form abscesses in many organs.
The endotoxin related symptoms including DIC and
cutaneous haemorrhages lead to the name Black death.
Several virulent factors. They have an envelope capsular
antigen called F-1 which protects against phagocytosis.
Endotoxin, an exotoxin and 2 special proteins V and Wantigens that allow the org to survive and grow
intracellularly. Mode of action of these antigens and of the
exotoxin is unknown.
A group of virulent factors called “Yops” (yersinia outer
proteins). These are injected into the human cell by the
typeIII secretion system and inhibit phagocytosis and
cytokine production by macrophages and neutrophils.
6. One of the Yops proteins is a protease(YopJ), that
cleaves 2 signal transduction pathway proteins
required for the induction of TNF synthesis. This
inhibits the action of host defense and contribute to
the ability of the org to replicate rapidly.
7. Clinical findings:
Bubonic plague is the most frequent form.
It begins with pain and swelling of the lymph nodes and
systemic symptoms such as high fever, myalgias and
The affected nodes become large and exquisitely tender. The
buboes are early characteristic finding.
Septic shock and pneumonia are the main life threatening
Pneumonic plague arises from inhalation of an aerosol or from
septic emboli that reaches the lungs.
Untreated bubonic plague fatal in half the cases, and
pneumonic plague is 100% fatal.
8. Lab findings:
Smear and culture of blood or pus from the bubo is
the best diagnostic procedure.
Care should be taken during aspiration or doing the
culture not to create an aerosol that might transmit
Giemsa or Wayson stain reveals the typical safety pin
appearance better than gm stain.
Fluorescent antibody staining to identify orgs in
A combination of Streptomycin and Tetracycline. Streptomycin can be
As disease progresses rapidly should not wait for bacteriological
Incision and drainage of the buboes not usually necessary.
Control the spread of rats and avoid rat flea bites.
A patient with plague should be kept in strict isolation for 72 hours
after starting treatment.
Reporting cases is mandatory.
A formalin killed organism vaccine is available but offers only partial
protection against bubonic plague but not pneumonic plague.
P.multocida causes wounds (rapidly spreading
cellulitis at the site of animal bite) associated with cat
and dog bites.
Treatment of choice is Penicillin G.
Prevention: Cat bite cases should be given Ampicillin
to prevent infection.
Cat bites especially should not be sutured.
B.henselae cause of cat-scratch disease (CSD),
especially in immunocompetent people.
Characterized by fever, and tender enlarged lymph
nodes typically on the same side as the scratch.
In immunocompromised cases such as AIDS,
B.henselae can cause bacillary
angiomatosis(BA)characterized by cherry red vascular
lesions in the skin and visceral organs.
CSD no antibiotics required.For BA: Doxycycline or