Brucella and Brucellosis Overview

Blood Stream Infections 2

• The lecture is by Dr. Heba Ahmed, a lecturer in Medical Microbiology & Immunology.

Brucella and Brucellosis

• Brucellosis overview, pathogenesis, diagnosis, and prevention are covered.
• Brucella are short Gram-negative coccobacilli.
• They are aerobic and facultative intracellular pathogens.
• Brucella are primarily pathogens of animals.

Species of Brucella Infecting Humans

• Brucella abortus infects cattle; it causes abortion.
• Brucella melitensis infects sheep and goats.
• Brucella suis infects pigs.
• Transmission to humans occurs through contaminated milk products, and handling of infected animals.

Culture Characteristics

• Brucella species grow on enriched media.
• B. abortus requires 10% CO2 for growth.
• Culture characteristics assist in diagnosis.

Biochemical Reactions

• Biochemical tests differentiate Brucella species.
• They help in the definitive identification of Brucella species. (A table is presented showing CO2, H2S, and Urea test results for different Brucella species).

Brucellosis

• Also known as Undulant Fever or Malta Fever.
• A zoonotic disease.
• Geographic distribution of reported and human-transmitted cases is displayed.

Modes of Transmission

• Ingestion of contaminated unpasteurized milk/products.
• Direct contact with infected animals (skin abrasions).
• Inhalation of aerosols from infected animals or cultures.

Pathogenesis

• Brucella spp. enter regional lymph nodes.
• Acute lymphadenitis occurs.
• Pathogens reach the bloodstream through the thoracic duct.
• Brucella spread to various organs such as spleen, liver, bone marrow, and lymph nodes.
• The host responds with granulomas.

Clinical Manifestations

• Brucellosis symptoms include fever (undulant), chills, weakness, sweating, headache, and body aches.
• Clinical findings include enlarged lymph nodes, an enlarged spleen, and an enlarged liver.
• Complications include osteomyelitis, endocarditis, and meningitis. (Images of skin and oral manifestations are present).

Laboratory Diagnosis A. Specimens

• For acute illness, blood or bone marrow specimens are collected.
• Cultivation is rare and requires a longer incubation.
• Serologic diagnosis using STAT tests detects IgM and IgG antibodies (ELISA tests are used).
• A skin test (Brucellin test) for delayed hypersensitivity assists in diagnosis.

Prevention Strategies

• Pasteurizing milk and milk products.
• Controlling animal infections, including vaccination with live attenuated vaccines.

Hepatitis B Virus (HBV)

• HBV is a DNA virus causing serum hepatitis, belonging to the Hepadnaviridae family.
• The intact virion is known as the Dane particle (42 nm diameter).
• HBV has an outer shell (HBsAg) and a core containing HBcAg, HBeAg, DNA and a DNA polymerase .

Hepatitis B Virus Structure

• Outer shell: Lipoprotein with hepatitis B surface antigen (HBsAg).
• Excess HBsAg forms non-infectious spherical (22-25 nm) and tubular (200 nm) particles.
• Core: Contains HBcAg, HBeAg and viral DNA polymerase.
• Genome: Partially double-stranded DNA.

Modes of Transmission (HBV)

• High viral loads are present in body fluids.
• Common transmission routes include perinatal (during birth), blood-borne, and sexual transmission.
• HBV has a higher transmission rate than HIV and HCV.

Pathogenesis and Clinical Presentations (HBV)

• HBV replicates in the liver, causing dysfunction.
• Extra-hepatic manifestations include immune complex-related reactions.
• Incubation period ranges from 6 weeks to 6 months.
• Gradual onset with symptoms such as malaise, anorexia, nausea, vomiting, abdominal pain, jaundice, rashes, joint pain, and arthritis. Enlarged and tender liver are evident.

Prognosis and Outcomes (HBV)

• Fulminant hepatitis occurs in 1-2% of cases, resulting in hepatic failure (0.1-0.5%).
• Chronic infection can result in chronic active hepatitis, cirrhosis, and liver failure (possibly hepatocellular carcinoma).
• Most patients recover fully within 4-6 months.

Laboratory Diagnosis (HBV)

• Serology involves HBsAg (early marker), Anti-HBs (immunity), Antibody-HBc (recent or past infection), HBeAg (high infectivity), and Anti-HBe (recovery).
• Molecular tests include DNA polymerase activity and HBV DNA detection via PCR.
• Liver tests (ALT, bilirubin) aid in diagnosis.

Interpretation of HBV Serology

• Interpretation of HBV serologic test results are available to determine the infection's stage (acute, window, or chronic).
• Antibody status indicates immunity acquired by natural infection or vaccination.

Virus Replication (HBV)

• HBV replicates in the liver.
• Partial DNA is converted to full double-stranded DNA then to mRNA.
• Viral proteins and genome replicate, affecting clinical manifestations.

Prevention and Control (HBV)

• General measures include blood screening before transfusion and using standard precautions, including hand hygiene, gloves, and disposable syringes.
• Specific prophylactic measures include HBV vaccination with recombinant HBsAg vaccine (three doses at 0, 1, and 6 months) and hepatitis B immunoglobulin (HBIG) for post-exposure prophylaxis.

This quiz covers the essential aspects of Brucella and brucellosis, including their pathogenesis, diagnosis, and prevention. Learn about the different species of Brucella that infect humans and their culture characteristics. Test your knowledge on the biochemical reactions necessary for identifying these pathogens.