Antiretroviral Therapy and Acute Diseases Quiz

Microbiology Lecture 10: Infection & Disease

• Host-Microbe Relationship: Microbes live on and in the human body. Microbiota is the population of microbes that inhabit the body without causing disease. Some are permanent (e.g., Escherichia coli and Candida albicans in the large intestine) while others are transient (e.g., Streptococcus in the large intestine).
• Symbiosis: The relationship between a host and its microbiota; can be beneficial to both (mutualism), beneficial to only one (commensalism), or harmful to the host (parasitism).
• Opportunistic Infections: Indigenous microbiota can cause infections if the host's immune system is weakened (e.g., AIDS).
• AIDS (Acquired Immunodeficiency Syndrome): A severe stage of HIV (Human Immunodeficiency Virus) infection, marked by a weakened immune system that allows opportunistic infections to develop.
• Kaposi's Sarcoma (KS): A type of cancer caused by Kaposi's sarcoma herpesvirus (KSHV), appearing as abnormal blood vessels on the skin. Severe cases can be life-threatening.
• Pneumonia: Infection in the lungs caused by bacteria, viruses, or fungi, characterized by symptoms like coughing, fever, and breathing problems, potentially life-threatening in people with compromised immune systems due to other conditions, like HIV infections.

Infection and Disease Mechanism

• Infection: Multiplication of microbes within a host.
• Disease: A change in the normal state of health caused by an infection or physical injury, but infection alone does not always result in disease.
• Pathogenicity: Microbes' ability to cause disease.
• Virulence: Degree of pathogenicity (i.e., the severity of the damage). Highly virulent microbes cause disease regularly. Moderately virulent ones cause disease sometimes, and avirulent ones don't generally cause disease.
• Pathogenicity Islands: Clusters of genes on a chromosome or plasmid that can encode virulence factors.

Virulence Factors

• Adhesion: Factors (e.g., capsules, pili) that enable pathogens to attach to host cells.
• Enzymes: Factors (e.g., hyaluronidase) that aid in the invasion of host tissues.
• Invasiveness: Capability of pathogens to penetrate tissues.
• Toxicity: Production of toxins (endotoxins or exotoxins) that harm the host, causing intoxication.

Infective Dose

• Infective dose refers to the number of microbes entering the body. Infections will only develop when the infectious dose is exceeded.

Potential Pathogen Interactions

• Potential pathogens may colonize with the host's existing microbiota, remain transient, or become commensal. Pathogens may need to cross a host barrier (skin) and penetrate host defenses to cause disease.
• Some pathogens don't need to penetrate cells or tissues to cause disease. e.g., cholera attaches to intestinal surfaces to produce toxins

Portal of Entry and Exit

• Pathogens enter the body through various portals (i.e., wounds, respiratory system, mouth, eyes).
• Pathogens leave the body through various portals (i.e., coughing, sneezing, in the urine & stool).

Nosocomial Infections

• Infections that develop during a hospital stay. Three key elements: (1) Compromised host (hospital patients), (2) Source of hospital pathogens (other patients or staff), and (3) Chain of transmission (direct contact, shared equipment, poor hygiene).

Stages of Disease

• Incubation period: Time from infection to the appearance of first symptoms.
• Prodromal phase: A short period with mild signs and symptoms marking the early stages of the primary period of disease.
• Acute period (Climax): The period of most intense symptoms.
• Decline period: Symptoms start to diminish.
• Convalescence period (Recovery period): Recovery from the infection, with symptoms disappearing.

Types of Disease

• Local diseases: Affect a specific part of the body.
• Systemic diseases: Spread throughout the body (e.g., septicemia)

Chronic disease

• A disease that persists for a long time (e.g., years).