Infectious Process and Disease.

An infection.

🎀An infection is the presence and growth of pathogenic microorganisms in a susceptible host, to the extent that tissue damage occurs. 

Disease.

🎀A disease is a condition that disrupts the normal functioning of the body or mind, leading to specific signs and symptoms.

🎀It can be caused by infection, genetics, lifestyle factors, or environmental influences.

Infectious Process and Disease.

💠Once an infection has occurred, the person is considered communicable until the host is no longer shedding infectious organisms.

💠This period of communicability varies by the type of pathogen involved and the host’s ability to fight off the infecting agent

Factors that Influence Infection and Disease

Risk of exposure

• Lifestyle
• occupation
• socioeconomic status

Host characteristics

🎗️Immunologic and nutritional status influence resistance or susceptibility to the pathogen

Environmental factors

🎗️They include sanitation, water and food safety, housing conditions, climate, pollution, and crowding, all of which can increase or reduce exposure to pathogens.

Disease-Producing Pathogens.

💎Disease-producing pathogens include any microorganism capable of producing disease

Modes of transmission.

Airborne transmission

🎀Airborne transmission occurs when tiny infectious particles remain suspended in the air and are inhaled over time.

Droplet transmission

🎀Droplet transmission occurs when large respiratory droplets spread through coughing, sneezing, or talking and enter the eyes, nose, or mouth at close range.

Contact transmission

🎀Contact transmission occurs when pathogens spread through direct physical contact or indirectly via contaminated surfaces or equipment.

Categories of Microorganisms.

• Bacteria- are single-celled microorganisms that can live independently and may cause infections or be beneficial to the body.
• Viruses -are infectious agents that require a living host cell to replicate and cause disease.
• Protozoa -are single-celled organisms, often transmitted through water or insects, that can cause parasitic infections.
• Rickettsia and chlamydia- are obligate intracellular bacteria that must live inside host cells to survive and reproduce.
• Fungi- are organisms such as yeasts and molds that can cause superficial or systemic infections, especially in immunocompromised individuals.
• Mycoplasma- are bacteria lacking a cell wall, making them resistant to certain antibiotics like penicillin.
• Helminths and prions- include parasitic worms that cause chronic infections and abnormal proteins that cause fatal neurodegenerative diseases, respectively.

The Body’s Defenses 

The Body’s Defenses Against Infection.

Skin and mucous membranes.

🎀 It acts as physical barriers that prevent microorganisms from entering the body.

 🎀They are beneficial microorganisms that inhibit the growth of harmful pathogens

Inflammatory response

🎀is the body’s immediate reaction to injury or infection to contain and eliminate pathogens.

Immune response 

🎀involves specialized cells and antibodies that recognize and destroy specific infectious agents.

Skin and Mucous Membranes

Mechanical barrier

🔷A mechanical barrier in the skin and mucous membranes refers to the physical structures and actions that block, trap, or remove microorganisms, such as intact skin, mucus, cilia, and the flushing action of tears, saliva, urine, and coughing.

🔷It Serve as portals of exit and entry

Chemical barriers

🔷A chemical barrier is the body’s defense that uses chemical substances to destroy or inhibit microorganisms, such as stomach acid, enzymes in saliva and tears, sebum on the skin, and acidic vaginal secretions.

Normal Flora.

🎗️They are beneficial microorganisms that inhibit the growth of harmful pathogens.

🎗️ They are Present on skin and in mucous membranes of the oral cavity, gastrointestinal tract, and vagina

🎗️They Help prevent excessive growth of pathogens

Inflammatory Response

Basic purposes of the inflammatory response include;

• Neutralizing and destroying harmful agents
• Limiting spread to other tissues in the body by walling off organisms
• Preparing the damaged tissues for repair

Inflammatory Changes

Inflammatory changes involve ;

• The cells of the damaged tissues and adjacent connective tissues
• The blood vessels in and near the site of injury
• The blood cells, particularly the leukocytes
• The macrophages and phagocyte activity
• The immune system

Signs and Symptoms of Inflammation 

• Systemic reactions—headache, myalgia, fever, diaphoresis, chills, anorexia, and malaise
• Chemical release and vascular changes 
• Immune response—the third line of defense
• Hormonal response
• Local reactions—redness, heat, swelling, and pain

Protective and Defensive Mechanisms Against Infection

💠Host susceptibility- Degree of susceptibility depends on general health, state of nutrition, hormone balance, immune status, and the presence of a chronic disease, such as diabetes mellitus

💠 Innate immunity- which provides immediate, natural protection present at birth, and acquired immunity, which develops over time through exposure to pathogens or vaccination.

Mechanisms Against Infection

• Antigen and antibodies
• Bone marrow 
• Leukocytosis
• Phagocytosis
• Macrophages

Antigen and Antibodies

💠An antigen is a form of protein found on the outside of cells that has the ability to identify it as “self” (native) or “non-self” (foreign) .It can stimulate the immune response to wipe out microorganisms

💠Antibodies, also known as immunoglobulins (Ig), neutralize toxins and kill invading pathogen.

Bone Marrow

💠 It plays an important role in the manufacturing of blood products that help the body defend itself against infection

Leukocytosis

💠Leukocytosis is seen more often with bacterial than viral infections

💠An increased number of leukocytes (white blood cells), usually seen at the beginning of an infection when the person’s immune system has not been overly stressed

💠When infection does occur, the bone marrow is stimulated to produce and release more leukocytes to help the body fight off, inactivate, and destroy the invading pathogens