Diseases

Overview Of Diseases

  • Discussion of diseases can be approached in different ways:

    • By specific pathogens (e.g., E. Coli, Staphylococcus aureus)

    • By parts of the human body (this approach will be used)

  • Focus will be on diseases categorized by body region, beginning with skin infections.

Skin Infections

  • Definition: Infections that affect the skin, which has two main layers:

    • Epidermis:

    • Composed of dead cells

    • Contains keratin; serves as a water-repelling barrier

    • Dermis:

    • Contains living cells, hair follicles, sebaceous glands, and sweat glands

    • Sebaceous Glands: Release oils

    • Sweat Glands: Release water and salt, serving as nutrients for bacteria

  • Characteristics of Skin:

    • Slightly acidic pH range: 4-6.8

    • Skin surface is dry, salty, and unstable

    • Major component of household dust: dead skin cells

Normal Skin Flora

  • Diphthroids:

    • Reside in hair follicles

    • Break down sweat leading to body odor and are involved in acne

  • Staphylococcus:

    • Halo tolerant; includes species such as Staphylococcus epidermis and Staphylococcus aureus that reside on skin surface

  • Fungi:

    • Malassezia is commonly found on the skin

Acne Formation

  • Caused by diphthroids when they penetrate from the surface into hair follicles, resulting in pimples (whiteheads, blackheads, cystic acne).

  • Staphylococcus bacteria can lead to deeper infections if they infect hair follicles:

    • Folliculitis: Infection of the hair follicle

    • Furuncle: Progression from hair follicle into surrounding tissue, resulting in a boil

    • Carbuncle: Further progression into organs, is more serious

  • Requires incision and drainage, along with antibiotics; cannot simply be popped.

Bacterial Skin Diseases

  • Staphylococcus aureus:

    • Hair follicle infections lead to swelling, redness, boils, and carbuncles

    • In the past, these infections were common among people who worked outdoors, but are less frequent now due to better hygiene

    • Treatment includes incision and drainage, and antibiotic therapy

Borrelia burgdorferi

  • Characteristics:

    • Spiral-shaped with a linear genome (unlike most bacteria which have circular DNA)

  • Disease Caused: Lyme disease, transmitted by ticks

  • Symptoms include:

    • Rash, fever, muscle pains

    • Dizziness and headaches weeks later

    • Joint pain and arthritis months later

  • Life Cycle of Lyme Disease: Ticks feed on deer and mice before infecting humans

  • Cases have increased due to human encroachment on wildlife habitats

  • Hallmark symptom: a circular red rash around the tick bite

Viral Skin Diseases

  • Chickenpox:

    • Caused by a double-stranded DNA virus (herpes family)

    • Characterized by red spots, bumps, and blisters; can cause shingles later in life if contracted as a child

    • Vaccination available since 1995; awareness of vaccination leads to reduced cases among younger populations

  • Measles:

    • An RNA virus leading to fever, cough, swollen eyes, and a fine red rash

    • Vaccine has been around since 1968; vaccination leads to a significant decline in cases

  • Risks of Measles:

    • 0.2% death rate in developed countries, up to 33% in developing countries

    • Can cause encephalitis and damage immune system memory

  • Outbreaks and vaccination resistance issues lead to renewed cases, including a public health emergency in 2019 due to a community outbreak in New York

  • German Measles (Rubella):

    • Mild disease but highly dangerous for pregnant women, leading to congenital defects in the fetus

Respiratory System Diseases

  • Divided into upper and lower respiratory systems:

    • Upper Respiratory System: Includes eyes, nose, mouth, ears, throat

    • Generally less severe conditions (e.g., common cold)

    • Lower Respiratory System: Includes trachea, bronchi, and lungs

    • Conditions are more serious and rarer

Upper Respiratory Bacterial Infections

  • Streptococcus pyrogenes:

    • Causes strep throat (sore throat, fever) and can spread easily through coughing

    • Treated with antibiotics; is significant due to potential for developing necrotizing fasciitis (flesh-eating disease)

  • Necrotizing Fasciitis:

    • Symptoms include severe pain, swelling, and fever; can be life-threatening and requires urgent medical intervention

    • Death occurs typically via tissue destruction and requires amputation in many cases

Other Bacterial Infections in Upper Respiratory System

  • Diphtheria:

    • Caused by Corynebacterium diphtheriae; leads to sore throat, fever, swollen neck

    • Characterized by a gray membrane in throat which can lead to suffocation

    • Death typically results from suffocation due to obstruction of airway

Viral Infections of Upper Respiratory System

  • Rhinovirus:

    • Causes the common cold; no effective treatment as you're simply advised to let it run its course

Lower Respiratory System Diseases

  • Pneumonia:

    • Inflammation of the lungs caused by different pathogens; symptoms include cough, fever, and difficulty breathing

  • Bacteria Causing Pneumonia:

    • Streptococcus pneumoniae: Common cause with treatable symptoms

    • Klebsiella pneumoniae: More severe with bloody sputum; dangerous for the immunocompromised

    • Mycoplasma pneumoniae: Known as walking pneumonia; doesn't incapacitate individuals but is contagious

    • Legionella pneumophila: Waterborne bacterium; leads to serious infection with pneumonia and requires careful environmental controls to eradicate

Viral Infections of Lower Respiratory System

  • Hantavirus:

    • Highly lethal with no treatment; symptoms include fever, cough, and abdominal pain

    • Transmitted through inhalation of contaminated rodent waste

Conclusion

  • Discussed various bacterial and viral diseases affecting the skin and respiratory systems, their characteristics, and prevention/treatment methods. More will be covered in subsequent lectures.