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Brucella
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Six species of Brucella
B.melitensis, B.abortus, B.suis,
B.canis
Sir David Bruce [brucellosis],
Bernhard Bang [Bang's disease]
Undulant fever, Malta fever,
Mediterranean remittent fever
Brucella
 small (0.5 × 0.6 to 1.5 μm), nonmotile,
nonencapsulated, gram-negative
coccobacilli
 grows slowly
 strictly aerobic
 does not ferment carbohydrates
Brucella
 endotoxin is less toxic
 intracellular parasite
 the organisms are phagocytosed by
macrophages and monocytes
 phagocytosed bacteria are carried to the
spleen, liver, bone marrow, lymph nodes
 the bacteria secrete proteins that induce
granuloma formation
Brucella
 Intracellular pathogen that is resistant to
killing in serum and by phagocytes
 Smooth colonies associated with
virulence
 goats and sheep (Brucella melitensis)
 cattle (Brucella abortus)
 swine (Brucella suis)
 dogs, foxes (Brucella canis)
Brucella
 Latin America, Africa, the Mediterranean
basin, the Middle East, and Western Asia
 More than 500,000 documented cases
 Vaccination of animals
 Direct contact with the organism (e.g., a
laboratory exposure), ingestion (e.g.,
consumption of contaminated food
products), or inhalation
Brucella
 Brucella causes mild or asymptomatic
disease in the natural host
 Erythritol (breast, uterus, placenta)
 Brucellae are shed in high numbers in
milk, urine, and birth products
 B.melitensis is the most common spp
Brucella-Clinical diseases
 Brucellosis: Initial nonspecific
symptoms of malaise, chills, sweats,
fatigue, myalgias, weight loss,
arthralgias, and fever; can be intermittent
(undulant fever)
 can progress to systemic involvement
(gastrointestinal tract, bones or joints,
respiratory tract, other organs)
Brucella-Clinical diseases
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Incubation period 1-6 weeks
Fever rises in the afternoon
Falling at night by drenching sweat
Lymph nodes enlarge, SM
Hepatitis, steomyelitis
Generalized infection subsides usually
A chronic state may occur
Brucella-Diagnosis
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grow slowly
most enriched blood agars
microscopic and colonial morphology
positive oxidase and urease reactions
B. abortus and B. melitensis, B. abortus,
and B. suis will react with antisera
prepared against B. abortus or B.
melitensis
Brucella-Serology
 IgM, IgG, IgA
 Four fold increase or 1/80 indicate active
infection
 If agglutination negative “blocking
antibodies” add antihumanglobulin
Brucella-Treatment
 Doxycycline+rifampin
 Trimethoprim-sulfamethoxazole for
pregnant women and for children
younger than 8 years
 6 weeks or longer
 Fluoroquinolones, macrolides, penicillins,
and cephalosporins either ineffective or
have unpredictable activity.
Francisella
 Two species, Francisella tularensis and
Francisella philomiragia
 the causative agent of tularemia (also
called glandular fever, rabbit fever, tick
fever, and deer fly fever) in animals and
humans
 very small (0.2 × 0.2 to 0.7 μm), faintly
staining, gram-negative coccobacillus
 nonmotile
 thin lipid capsule
 fastidious requirements (most strains
require cysteine for growth)
 strictly aerobic and requires 3 or more
days
Gram stain of Francisella tularensis isolated in culture; note the extremely small coccobacilli
 Antiphagocytic capsule
 Intracellular pathogen resistant to killing in
serum and by phagocytes
 Wild mammals, domestic animals, birds, fish,
and blood-sucking arthropods are reservoirs;
rabbits and hard ticks are most common hosts;
humans are accidental hosts
 Worldwide distribution
 The infectious dose is very small
 Human tularemia is acquired most often from
the bite of an infected "hard-shell" tick (e.g.,
Ixodes, Dermacentor, Ambylomma spp.)
 or from contact with an infected animal or
domestic pet
 F. tularensis requires as few as 10 organisms
when exposure is by an arthropod bite
 Ulceroglandular tularemia: Painful papule develops
at the site of inoculation that progresses to ulceration;
localized lymphadenopathy
 Oculoglandular tularemia: Following inoculation into
the eye (e.g., rubbing eye with a contaminated finger),
painful conjunctivitis develops with regional
lymphadenopathy
 Pneumonic tularemia: Pneumonitis with signs of
sepsis develops rapidly after exposure to contaminated
aerosols; high mortality unless promptly diagnosed and
treated
 Ulceroglandular tularemia is the most common
manifestation
Francisella-Diagnosis
 F. tularensis are hazardous for both the physician and
the laboratory worker
 Microscopy is insensitive due yo small size and faintly
staining
 Fluorescein-labeled antibodies
 PCR
 F. tularensis can grow on chocolate agar or buffered
charcoal yeast extract (BCYE) agar, media
supplemented with cysteine
 a fourfold or greater increase in the titer of antibodies
during the illness or a single titer of 1:160 or greater