Brucella
Brucella
• Brucellosis (undulant fever) is a zoonosis
• Members of the genus Brucella are primarily
pathogens of animals
• Different species of Brucella are each
associated with particular animal species
• B. ovis are known to cause disease in humans
General characteristics
• The brucellae are aerobic,
• facultative, intracellular parasites that can
survive and multiply within host phagocytes.
• unencapsulated
• Small coccobacilli arranged singly or in pairs
• Lipopolysaccharide is the major virulence
factor, as well as the major cell wall antigen.
Epidemiology
• Brucellosis is a chronic, lifelong infection in animals.
• Organisms localize in reproductive organs (male and
female),
• shed in large numbers in milk, urine, and the placenta
and tissues discharged during delivery or spontaneous
abortion.
• primary manifestations of infection in animals are
sterility and abortion.
• Transmission to humans via :
 direct contact with infected animal tissue
 ingestion of unpasteurized milk or milk products
Pathogenesis
• Brucellae enter the body through
 cuts and abrasions in the skin
 the gastrointestinal (GI) tract.
 Inhalation of infected aerosols
• Once the organisms gain entry,
- transported via the lymphatic system to the regional
lymph nodes, where they multiply.
- carried by the blood to organs that are involved in the
reticuloendothelial system, including the liver, spleen,
kidneys, bone marrow, and other lymph nodes
Clinical significance
• The incubation period ranges from five days to several
months, but typically lasts several weeks.
• Symptoms are nonspecific ,flu-like and GI symptoms,
and may also include depression.
• Their onset may be abrupt or insidious.
• Untreated, patients may develop an undulating
pattern of fever
• Subclinical infections occur.
• Brucellosis may involve GI tract, skeletal, neurologic,
cardiovascular, and pulmonary systems.
Laboratory identification
• history is often crucial
• The organism can be cultured from
• blood and other body fluids or from tissue
specimens.
• Multiple blood specimens should be
cultured., colonies may appear in four to five
days; cultures, examined for up to one month
before being declared negative
Treatment
• Combination therapy involving doxycycline
and gentamicin (or streptomycin) is
recommended for brucellosis
• Prolonged treatment (for example, six weeks)
is necessary to prevent relapse and reduce the
incidence of complications.
Bordetella
• Bordetella pertussis and B. parapertussis are
the human pathogens of this genus.
• Bordetella pertussis causes the disease
pertussis (whooping cough)
• Whooping cough is a highly contagious
disease and a significant cause of morbidity
and mortality worldwide.
General characteristics
• Members of the genus Bordetella
• are aerobic and Small
• encapsulated ,coccobacilli that grow singly or
in pairs.
• serotyped on the basis of cell-surface
molecules
Epidemiology
• The major mode of transmission of Bordetella
is via droplets spread by coughing
• The incidence of whooping cough among
different age-groups vary, depending on active
immunization of young children.
• In the absence of an immunization program,
disease is common among young children
(ages one to five).
Pathogenesis
• B. pertussis binds to ciliated epithelium in the
upper respiratory tract
• There, the bacteria produce a variety of toxins
and other virulence factors that interfere with
ciliary activity, eventually causing death of
these cells
Clinical significance
• The incubation period for pertussis ranges from
1-3weeks
• The disease can be divided into two phases:
 catarrhal
 paroxysmal
 Catarrhal phase:
-Runny nose
-malaise,
-mild fever
.
Clinical significance(cont’d)
Paroxysmal phase:
- Coughing
- vomiting.
- Leukocytosis
• convalescence
requires at least an additional three to four
weeks.
• Disease is generally most severe in infants
Treatment and prevention
• Erythromycin is the drug of choice for infections
with B. pertussis
• For erythromycin treatment failures,
trimethoprim-sulfamethoxazole is an alternative
choice.
• Prevention
-Pertussis vaccine is available that has had a
significant effect on lowering the incidence of
whooping cough
Legionella
• Legionellaceae are facultative intracellular
parasites
• cause primarily respiratory tract infections
• Unencapsulated,
• relatively slender rods,Coccobacillary
• Aerobic
• fastidious, with a particular requirement for Lcysteine
Epidemiology
• The Legionellaceae family includes 34 species
• normal habitat is soil and water
• 85 to 90% of human disease is caused by a
single species, Legionella pneumophila.
• Most infections result from inhalation
• occasionally from swimming in contaminated
water.
• organism is chlorine tolerant.
Pathogenesis
• The organism enter the upper respiratory tract
by aspiration of water containing the organism
• Inhalation of a contaminated aerosol.
when reached the lungs. Alveolar macrophages in
the lung do phagocytose L. pneumophila,
• the organisms multiply within phagosome until
the cell ruptures, releasing a new crop of bacteria
Clinical significance
• Legionellaceae primarily cause respiratory
tract infections.
• There are two distinctly different
presentations:
Legionnaires' disease
Pontiac fever.
Clinical significance(cont’d)
• Legionnaires' disease (LD): This is an atypical, acute
lobar pneumonia with multisystem symptoms.
• Legionellae are estimated to cause 1-5%of the cases of
community-acquired pneumonias in adults
• fatality rate for LD ranges from 5-30%
• Symptoms develop after 2-10 days.
• Early symptoms nonspecific: fever, malaise, myalgia,
anorexia, and/or headache.
• Cough, Diarrhea (watery rather than bloody stools)
Nausea, vomiting, and neurologic symptoms may also
occur
Pontiac fever
• This is an influenza-like illness
• The attack rate among those exposed to a
common source is typically 90% or more.
• Recovery is usually complete within one week.
• No specific therapy is required.
Laboratory identification
• the organism can be Gram stained, the Gimenez
stain is more useful for visualization.
• culturing of Legionella from respiratory
secretions, using buffered (pH 6.9) charcoal yeast
extract
• enriched with L-cysteine, iron, and ketoglutarate.
• Visible colonies form in three to five days.
• A urinary antigen test using an enzyme
immunoassay is available and has several
advantages over culture..
Treatment
• Macrolides, such as erythromycin or
azithromycin, are the drugs of choice for
Legionnaires disease. Fluoroquinolones are
also effective
• Pontiac fever is usually treated
symptomatically, without antibiotics.
Thanks