1/17/ Zoonotic bacteria Capnocytophaga Erysipelothrix Francisella Listeria Pasteurella Spirillum Streptobacillus Yersinia Brucella

1/17/ Brucella species Brucella abortus Brucella melitensis (most pathogenic) Brucella suis Cattle Sheep & goat Pigs

1/17/ General features Gram negative coccobacilli Non motile & non capsulated Strict aerobes & capnophilic Catalase, oxidase, urease & H2S + Facultative, intracellular Culture medium - Serum dextrose agar, trypticase soy agar, CAM Erythritol - stimulating effect on growth Addition of bacitracin, polymyxin, cycloheximide makes selective

1/17/ Mode of transmission Ingestion Inhalation Contact with tissues, blood and body fluids of infected animals Contaminated meat or unpasteurized milk when working in the laboratory

1/17/ Pathogenesis Entry into body Transported via lymphatics to regional lymphnodes Carried by blood to organs of reticuloendothelial system Liver, spleen, kidneys, bonemarrow & other LN Phagocytosed by PMNs Resist intracellular killing by inhibiting O2 burst that generate free radicals

1/17/ Who is at risk ? Occupational Disease Cattle ranchers/ dairy farmers Veterinarians Meat inspectors Lab workers Hunters Travelers Consumers of unpasteurized dairy products Zoonotic disease

1/17/ forms of human brucellosis Subclinical Serologic Bacteremic Acute systemic form Vague symptoms Presence of antibodies Localized Chronic Exacerbations and remissions occurring over months & years Granulomas in organs of RE system May develop chronic H/o contact with raw animal products or grazing animals Undulant fever, arthritis May disseminate/ chronic Complications: Meningitis, granulomatous hepatitis, abscesses of liver & spleen, cholecystitits, endocarditis, erythema nodosum, & chronic skin ulcers

1/17/ Laboratory Diagnosis SpecimensBlood, tissue, pus, MicroscopyGram negative coccobacilli Culture Serum dextrose agar – translucent & glistening IdentificationMicroscopy & slide agglutination Catalase, oxidase, urease, H2S positiveBiochemical reaction

1/17/ Blood culture Castaneda’s method – biphasic medium Trypticase Soy broth incubated at 37 0 C under 5-10% CO2. S/C on Solid media every 3-4 days Blood cultures positive in 30-50% cases Bone marrow culture gives better isolation rate Lymph node, CSF, urine, abscess aspirate culture have also been reported to give positivity Avoids contamination and infection to lab worker

1/17/ Serology Standard Tube Agglutination test (SAT) Serial dilutions of serum + Standardized suspension of B. abortus. 37 C X overnight Titre of 160 or more is significant Acute brucellosis titre could be 640 or more Prozone phenomenon very common. Blocking / Incomplete antibodies common. Important since blood cultures are often negative Remedy: Preheating serum at 55 C X 30 min / using 4% saline / Indirect Coombs’ Test Remedy: Test continued for higher dilutions

1/17/ Serological response IgM & IgG antibodies start rising in 7-10 days of onset IgM Ab decline while IgG Ab persist or continue to rise In chronic infections, IgM antibodies may often be absent. Only IgG Ab can be detected Implications High agglutinating titres especially rising titres are diagnostic. But negative agglutination test may not exclude the infection.

1/17/ Tests for animal brucellosis Above methods and in addition Rapid plate agglutination test Rose Bengal Card test In dairies, Milk Ring Test on pooled milk samples Milk + Stained brucella antigens -> Whey agglutination test for Milk Agglutination rises to top with cream to form a ring

1/17/ Prophylaxis Checking brucellosis in dairy animals Pasteurization of milk Vaccination of animals No suitable vaccine for human use Treatment Tetracyclines either alone or with Streptomycin for three weeks Brucellin test like tuberculin test indicates prior sensitization or exposure. Not useful in acute infection. The test itself converts patient into reactor. Other tests