Blood Stream Infections 2 Lecture Notes PDF

Blood Stream Infections 2 Dr. Heba Ahmed Lecturer of Medical Microbiology & Immunology Brucella and Brucellosis Overview of Characteristics, Pathogenesis, Diagnosis, and Prevention Characteristic Features Short Gram-negative coccobacilli Aerobic and facultative intr...

Blood Stream Infections 2 Dr. Heba Ahmed Lecturer of Medical Microbiology & Immunology Brucella and Brucellosis Overview of Characteristics, Pathogenesis, Diagnosis, and Prevention Characteristic Features Short Gram-negative coccobacilli Aerobic and facultative intracellular pathogens Primarily pathogens of animals Species of Brucella Infecting Humans 1.Brucella abortus: Infects cattle; causes abortion 2.Brucella melitensis: Infects sheep and goats 3.Brucella suis: Infects pigs Culture Characteristics Grows on enriched media B. abortus requires 10% CO2 for growth Importance: Assists in diagnosis Biochemical Reactions Biochemical tests differentiate genus Brucella and species Helps in definitive identification Brucellosis Also known as Undulant Fever or Malta Fever Zoonotic disease  Modes of Transmission 1.Ingestion: Contaminated unpasteurized milk/products 2.Direct contact: Skin abrasions during handling of infected animals 3.Inhalation: Aerosols from infected animals or cultures Pathogenesis Clinical Manifestations Symptoms: Fever (undulant), chills, weakness, sweating, headache, body aches Findings: Enlarged lymph nodes, liver, spleen Complications: Osteomyelitis, endocarditis, meningitis Laboratory Diagnosis A. Specimens A. Specimens: Blood or bone marrow (acute illness) B. Cultivation: Rare due to risk, long incubation (6-7 weeks) C. Serologic Diagnosis: STAT: Detects IgM + IgG antibodies ELISA for IgG or IgM D. Brucellin Test: Skin test for delayed hypersensitivity Prevention Strategies 1.Pasteurization of milk and products 2.Control of animal infections Vaccination with live attenuated vaccine (e.g., for cattle) Hepatitis B Virus Hepatitis B Virus (HBV) Structure, Transmission, Pathogenesis, and Management Hepatitis B Virus (HBV) Definition: HBV is a DNA virus causing serum hepatitis. Family: Hepadnaviridae Intact Virion: Known as the Dane particle (42 nm diameter). Structure: Composed of an outer shell (HBsAg) and a core containing HBcAg, HBeAg, DNA- dependent DNA polymerase, and partially double-stranded DNA.  Hepatitis B Virus Structure Outer Shell: Lipoprotein with hepatitis B surface antigen (HBsAg). Excess HBsAg released as non-infectious particles (spherical: 22-25 nm; tubular: 200 nm). Function: Stimulates production of neutralizing antibodies for long-term protection. Core: Contains HBcAg, HBeAg, and viral DNA polymerase. Genome: Partially double-stranded DNA. Modes of Transmission Body Fluids: High viral load (~10ⁱ⁰ copies/mL of serum). Main Routes: Perinatal transmission Blood and percutaneous transmission Sexual transmission Comparison: Higher transmission rate (30%) than HIV (0.3%) and HCV (3%). Pathogenesis and Clinical Presentations Pathogenesis: HBV replicates in the liver, causing hepatic dysfunction. Extra-Hepatic Manifestations: Immune complex-related (rash, urticaria, poly-arthralgia, vasculitis, glomerulonephritis). Incubation Period: 6 weeks to 6 months. Clinical Onset: Gradual. Symptoms: Malaise, anorexia, nausea, vomiting, abdominal pain. Jaundice, rashes, joint pain, arthritis. Enlarged, tender liver. Prognosis and Outcomes Fulminant Hepatitis: Occurs in 1-2%; hepatic failure in 0.1-0.5%. Chronic Infection: Chronic active hepatitis Cirrhosis and liver failure Hepatocellular carcinoma Recovery: Most patients recover fully within 4-6 months Laboratory Diagnosis Serology: HBsAg: Early marker, indicates infection. Anti-HBs: Immunity marker. Anti-HBc: IgM (recent infection); IgG (past infection). HBeAg: High infectivity. Anti-HBe: Recovery marker. Molecular Tests: DNA polymerase activity. HBV DNA via PCR. Liver Tests: ALT, bilirubin. Interpretation of HBV Serology Test Results and Interpretation: HBsAg (+), Anti-HBc (+), Anti-HBs (−): Acute infection. HBsAg (−), Anti-HBc (+), Anti-HBs (−): Window phase. HBsAg (+), Anti-HBc IgG (+), Anti-HBs (−): Chronic infection. Anti-HBc IgG (+), Anti-HBs (+): Immunity from natural infection. Anti-HBs (+) only: Immunity from vaccination. Virus Replication Replication Site: Liver. Process: Partial DNA converted to full double-stranded DNA -> mRNA -> viral proteins and genome replication. Significance: Replication level affects clinical manifestations. Prevention and Control General Measures: Blood screening before transfusion. Standard precautions (hand hygiene, gloves, disposable syringes). Specific Prophylaxis: HBV Vaccine: Recombinant HBsAg vaccine. Three doses (0, 1, 6 months). Hepatitis B Immunoglobulin (HBIG): Post-exposure prophylaxis.