Lesson 17 - Overview of Infectious Diseases

Infectious Diseases

Caused by microbes

Microbial Intoxications

Ingestion of toxins produced outside the body (in vitro) by a pathogen.

Infectious Diseases (Infections)

Caused by colonization of a body site by a pathogen.

Infectious Diseases by Anatomical Site | Skin

• Physical barrier; prevents most pathogens.

  • Part of body’s first line of defense

Epidermis

Superficial layer of the skin.

Dermis

Inner layer of skin, containing blood and lymphatic vessels, nerves, nerve endings, glands, and follicles.

Dermatitis

Skin inflammation.

Sebaceous Glands

• Produce oily sebum (oily substance)

• Glands in the dermis that usually open into hair follicles

Common Skin Infections | Folliculitis

Inflammation of hair follicles (sac that contains a hair shaft)

Common Skin Infections | Stye (Sty)

Inflammation of sebaceous glands in eyelashes.

Common Skin Infections | Furuncle

• Localized pus-producing (pyogenic) infection usually resulting from folliculitis

  • Aka boil

Common Skin Infections | Carbuncle

Deep-seated infection from multiple furuncles.

Common Skin Infections - Surface Lesions | Macule

• a surface lesion that is flat

  • e.g., measles

Common Skin Infections - Surface Lesions | Papule

• surface lesion that is firm and raised

  • e.g., chickenpox

Common Skin Infections - Surface Lesions | Vesicle

• surface lesion that is fluid-filled blister

  • e.g., shingles and chickenpox

Common Skin Infections - Surface Lesions | Pustule

• a surface lesion that is pus-filled

Ears

• Anatomy

  • Pathogens enter via:

    • Eustachian (auditory) tube, from throat/nasopharynx

    • External ear canal.

    • Blood or lymph.

Ear Infection | Otitis Media

Middle ear infection.

Ear Infection | Otitis Externa

Outer ear canal infection.

Eyes

• Anatomy

  • Involves conjunctiva, sclera, cornea, iris, and lens.

Conjunctiva

The thin, tough lining that covers the inner wall of the eyelid and the sclera (the white of the eye)

Eye Infections | Conjunctivitis

Inflammation or infection of the conjunctiva.

Eye Infections | Keratitis

Inflammation of the cornea (domed covering over the iris and lens)

Eye Infections | Keratoconjunctivitis

infection of both cornea and conjunctiva

Eye Infections | Retinitis

• Inflammation that involves the retina

  • Often caused by viral infection

Respiratory System | Upper Respiratory Tract (URT)

consists of paranasal sinuses, nasopharynx, oropharynx, epiglottis, larynx.

Respiratory System | Lower Respiratory Tract (LRT)

• Consisting of trachea, bronchial tubes, alveoli

  • ____ infections are the most common cause of death from infectious diseases

Respiratory System Infections | Epiglottitis

• Inflammation of the epiglottis (e.g., caused by Haemophilus influenzae type b).

  • May cause respiratory obstruction

Respiratory System Infections | Laryngitis

Inflammation of the mucuous membrane of the larynx.

Respiratory System Infections | Pharyngitis

• Sore throat; commonly caused by viruses (Streptococcus pyogenes in "strep throat").

  • Inflammation of the mucuous membrane and underlying tissue of the pharynx

Respiratory System Infections | Pneumonia

• Inflammation of lungs

  • Caused by bacteria, viruses, fungi, or protozoa.

Respiratory System Infections | Sinusitis

• Inflammation of paranasal sinuses

  • Common causes:

    • Streptococcus pneumoniae.

    • Haemophilus influenzae.

Oral Hygiene | Oral Microflora

• Includes about 300 identified species of bacteria (aerobes and anaerobes) and additional unclassified species.

  • Some bacteria are beneficial, producing antagonistic secretions, while others contribute to diseases.

Common Oral Disease | Dental Carries

• Caused primarily by Streptococcus mutans, leading to tooth enamel erosion due to lactic acid production.

  • Tooth decay or cavities

Common Oral Disease | Gingivitis

Inflammation of the gums.

Common Oral Disease | Periodontis

Advanced gum disease that can result in tooth loss.

Common Oral Disease | Thrush

Infection of the oral tissues with Candida albicans that occurs mainly in immunocompromised patients

Oral Infections

They result from a combination of the unique microbial population, reduced host defenses, improper diet, and poor dental hygiene

Gastrointestinal (GI) Tract

• The ______ is designed for food digestion, nutrient absorption, and waste elimination.

  • Most ingested microorganisms are destroyed by stomach acid (pH ~1.5) or expelled via defecation.

Gastrointestinal (GI) Tract | Colitis

Inflammation of the colon (large intestine)

Gastrointestinal (GI) Tract | Diarrhea

• Abnormally frequent discharge of semi-solid or liquid stool, often due to infection.

  • “stool specimens that conform to the shape of the container”

Gastrointestinal (GI) Tract | Dysentery

• Severe diarrhea with blood or mucus.

  • Accompanied by abdominal pain, fever, and dehydration

Gastrointestinal (GI) Tract | Enteritis

Inflammation of the small intestine.

Gastrointestinal (GI) Tract | Gastritis

Stomach lining inflammation.

Gastrointestinal (GI) Tract | Gastroenteritis

Infection that involves both the stomach and intestines.

Gastrointestinal (GI) Tract | Hepatitis

Liver inflammation, often viral in origin.

Genitourinary Tract (GU) Tract | Urinary Tract Infections (UTIs)

• Divided into upper UTIs (e.g., nephritis, pyelonephritis) and lower UTIs (e.g., cystitis, urethritis).

  • Common causes include E. coli, Chlamydia trachomatis, and other bacteria or fungi.

  • Prevention involves good hygiene and maintaining the urinary tract's natural defenses.

Genital Infections

Indigenous microflora of the genital area can lead to infections if disrupted (e.g., Candida albicans causing yeast vaginitis).

Genital Infection | Bartholinitis

Bartholin’s gland (which produces mucus to lubricate the vagina) inflammation in women.

Genital Infection | Cervicitis

Cervix inflammation.

Genital Infection | Pelvic Inflammatory Disease (PID)

• Inflammation of fallopian tubes, often due to sexually transmitted pathogens.

  • Aka salpingitis

Genital Infection | Vaginitis

Caused by yeast (C. albicans), protozoans (Trichomonas vaginalis), or bacteria (as in bacterial vaginosis).

Genital Infection | Sexually Transmitted Diseases

• Include infections transmitted via sexual contact, such as HIV/AIDS, gonorrhea, chlamydia, and syphilis.

• ______ can affect various systems, not just the genital tract.

• Previously known as venereal disease

Circulatory System | Cardiovascular System

Composed of the heart, arteries, capillaries, veins, and blood.

Circulatory System Infections | Endocarditis

Inflammation of the endocardium (endothelial membrane that lines the cavities of the heart)

Circulatory System Infections | Myocarditis

Inflammation of the heart's muscular walls (myocardium)

Circulatory System Infections | Pericarditis

Inflammation of the pericardium (membranous sac around the heart)

Circulatory System Infections - Bloodstream Infections | Bacteremia

presence of bacteria in the blood, often transient (e.g., from dental procedures).

Circulatory System Infections - Bloodstream Infections | Septicemia

A serious systemic infection with bacteria/toxins in the bloodstream, leading to chills, fever, and exhaustion.

Blood Donation Screening

Routine testing for pathogens like HIV, hepatitis, and syphilis in donor blood.

Lymphatic System

Includes lymph vessels, nodes, tonsils, thymus, and spleen.

Lymphatic System Infections | Lymphadenitis

Inflamed lymph nodes.

Lymphatic System Infections | Lymphangitis

Inflamed lymph vessels.

Lymphatic System Infections | Lymphadenopathy

Diseased lymph nodes

CNS Components

• CNS (brain, spinal cord, meninges) is protected by the blood-brain barrier.

• Peripheral nerves branch from the CNS.

CNS Infection | Meningitis

Inflammation of the meninges, caused by various pathogens, drugs, or toxins.

CNS Infection | Viral Meningitis

Often referred to as "aseptic meningitis" and less severe than bacterial meningitis.

CNS Infection | Bacterial Meningitis

Caused by H. influenzae, Neisseria meningitidis, S. pneumoniae, among others.

CNS Infection | Parasitic Causes

Protozoa (Naegleria, Acanthamoeba) and fungal pathogens (Cryptococcus neoformans).

CNS Infection | Toxins

Bacterial neurotoxins (e.g., botulinum toxin) and fungal toxins (e.g., ergot).

Opportunistic Infections (OIs)

• Affect immunosuppressed individuals more severely.

  • Examples include:

    • Aspergillosis, Candidiasis, Cytomegalovirus, and Herpes Simplex Virus.

    • Pneumocystis pneumonia, Toxoplasmosis, and Tuberculosis.

Emerging Causes

• Changes in demographics, climate change, international travel, and misuse of antibiotics.

  • Examples: Avian influenza, SARS, Lyme disease, Ebola, and West Nile virus.

Re-emerging Causes

• Pathogen mutations, acquired drug resistance, and reduced vaccination compliance.

  • Examples: Cholera, malaria, TB, yellow fever, and MRSA infections.

Upper UTI | Nephritis

• Inflammation of kidneys

  • Most common cause is E. coli

Lower UTI | Cystitis

• Inflammation of the urinary bladder

  • Most common type of UTI

Lower UTI | Urethritis

inflammation of the urethra (a tube that carries urine out of the body)

Uretetitis

Inflammation of one or both ureters

Atypical Pneumonia

Has more insidious (slower) onset than typical pneumonia

Periodontium

They are tissues that surround and support the teeth, including the gingiva and supporting bone

Periodontal Diseases

Oral diseases such as gingivitis, periodontitis, and trench mouth

Cervix

Part of the uterus that opens into the vagina

Endometritis

Inflammation of the endometrium (the inner layer of the uterine wall)

Epididymitis

Inflammation of the epididymis (an elongated structure connected to testis)

Opportunistic Infection | Aspergillosis and other mould infections

an opportunistic infection that can become a systemic infection in immunosuppressed individuals

Opportunistic Infection | Candidiasis

an opportunistic infection that refers to a yeast infection of the mouth (thrush), throat, or vagina

• can become a systematic infection in immunosuppressed individuals

Opportunistic Infection | Cytomegalovirus Infection

an opportunistic infection that can cause eye disease that can lead to blindness

Opportunistic Infection | Herpes simplex virus infections

• an opportunistic infection that refers to the cause of oral herpes (cold sores) and genital herpes

  • can occur in immunocompetent individuals but more frequent and severe in immunosuppressed

Opportunistic Infection | Malaria

• an opportunistic infection that refers to a parasitic infection that occurs in immunocompetent individuals, but is more common and severe in immunosuppressed individuals

  • caused by plasmodium spp.

Opportunistic Infection | Mycobacterium avium complex

an opportunistic infection that refers to a bacterial infection that can cause recurring fevers, problems with digestion, and serious weight loss

Opportunistic Infection | Pneumocystis pneumonia

• an opportunistic infection that refers to a fungal infection that can cause a fatal pneumonia

  • was once the major killer of AIDS patients

Opportunistic Infection | Toxoplasmosis (“toxo”)

an opportunistic infection that refers to a protozoal infection of the eyes and brain

Opportunistic Infection | Tuberculosis (TB)

• an opportunistic infection that refers to a bacterial lower respiratory infection

  • can cause meningitis

CNS Infection | Encephalitis

Inflammation of the brain

CNS Infection | Encephalomyelitis

Brain and spinal cord inflammation

CNS Infection | Meningoencephalitis

Brain and meninges inflammation

CNS Infection | Myelitis

Inflammation of the spinal cord