Brucella 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 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 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