In-Depth Notes on Microbial Diseases

Microbial Diseases

Tuberculosis (TB)

  • Causative Agent: Caused by the bacterium Mycobacterium tuberculosis (M. tuberculosis).

    • Over 9 million new cases and 2 million deaths annually worldwide.
    • 1/3 of the global population is infected.

  • Transmission:

    • Airborne disease spread from person to person through respiration.
    • Droplet nuclei containing tubercle bacilli are inhaled.

  • Pathophysiology:

    • Highly aerobic, primarily infects the lungs.
    • Divides every 15-20 hours.
    • Resistant to many disinfectants (acid, alkali, drying).
    • More easily contracted with a weakened immune system.

  • Symptoms:

    • Cough (possibly with blood), loss of appetite, fever, weight loss, night sweats.
    • Can spread to other organs, leading to additional symptoms.

  • Diagnosis:

    • Tuberculin Skin Test.
    • Chest X-rays.
    • Sputum analysis.

  • Treatment/Prevention:

    • Positive Skin Test, Negative X-Ray: Isoniazid (Antibiotic).
    • Positive Skin Test, Positive X-Ray: Combination of Isoniazid, Rifampin, Ethambutol, and Pyrazinamide.
    • Prevention through the BCG vaccine.

  • Epidemiology:

    • Second most common cause of death from infectious diseases, after HIV/AIDS.
    • Significant decline in cases since 2005, particularly notable in China with an 80% reduction in mortality (1990-2010).
    • More prevalent in developing nations, with about 80% of populations in some countries testing positive.
Human Immunodeficiency Virus (HIV)

  • Definition: HIV is an RNA virus responsible for causing AIDS.

    • Attacks the immune system and destroys the body’s disease defenses, making the host vulnerable to infections and cancers.

  • Structure:

    • Diameter of 100-120 nm with a spherical shape.
    • Contains a cone-shaped core surrounded by a lipid matrix with surface glycoproteins and essential enzymes like reverse transcriptase.

  • Transmission Mechanism:

    • Requires infected body fluids and entry into the body.

  • Infection Transmission:

    • Fluids that transmit HIV:
    • Blood, Semen, Vaginal secretions, Breast milk.
    • Fluids that do not transmit HIV:
    • Saliva, Urine, Sweat, Tears.

  • Modes of Infection:

    • Most common: Unprotected sex, sharing needles, from mother to infant.
    • Rare transmission includes blood transfusions or in healthcare settings.

  • Symptoms of HIV:

    • Chronic stage: Symptoms include fatigue, fever, weight loss, dry cough, night sweats, and swollen lymph nodes, among others.

  • Treatment:

    • Highly Active Antiretroviral Therapy (HAART) is the most effective treatment, involving multiple antiretroviral drugs to control viral load.

  • Diagnosis:

    • Blood tests to detect antibodies to HIV, generally within 3-6 months post-infection.
    • Techniques include ELISA and Western Blots.
    • PCR can be used to identify HIV DNA in white blood cells, which amplifies small quantities of HIV DNA for detection.

  • Prevention:

    • Practice safe sex and reduce the number of sexual partners.
    • Communicate sexual histories with partners.
    • Do not share IV needles or personal hygiene items that could be contaminated.
    • Safe sex practices include using condoms and avoiding blood/tissue donation if at risk.
Malaria

  • Definition: Malaria is a vector-borne infectious disease caused by protozoan parasites from the genus Plasmodium.

    • Transmitted through the bite of infected female Anopheles mosquitoes.

  • Global Impact:

    • More deaths annually from malaria than from AIDS, with malaria causing 50 deaths for every one from HIV/AIDS.
    • Increasing drug resistance to malaria treatments presents a major challenge.

  • Symptoms:

    • Key clinical manifestations include fever, sweating, anemia, splenomegaly, irritability, coma, and respiratory distress syndrome.

  • Diagnosis:

    • Microscopic examination of blood smears, both thick and thin, is the gold standard. Thick smears are typically used for sensitivity.

  • Epidemiology:

    • Affects over 40% of the global population residing in malaria-prone regions (e.g., parts of Africa, Asia).

  • Control Measures:

    • Elimination of mosquito breeding sites, improved health and hygiene practices.
    • Use of treated mosquito nets and repellents.