Inflammation and Infection

• Inflammation


  1. Heat = inflammatory response

  2. It is the primary response to foreign substances entering the body – part of the immune response

  3. Inflammation can arise from many conditions

  4. Physiological inflammatory response example – response to surgery indicates wound is healing (homeostasis)

  5. Pathological inflammatory response destructive process = disease process example – atherosclerosis in coronary heart disease
• Acute inflammation


  • Rapid response – seconds to minutes
  • Defence mechanism in response to injury and infection
  • Inflammation occurs only in vascularised tissues, example – with a blood supply
• Five cardinal signs/symptoms of acute inflammation

  • Redness – due to vasodilation, increased blood supply to area
  • Swelling – due to fluid and cell accumulation in tissues
  • Heat – only of extremities, due to vasodilation, increased blood supply to area
  • Pain – due to swelling, stretching
  • Loss of function – decreased joint mobility due to swelling/pain; or result of scar tissue
• Chronic inflammation


  • Slow, long-term inflammation
  • Main difference is duration (2 weeks or longer)
  • Sometimes preceded by unsuccessful acute phase of inflammatory phase
  • Extent and effects vary depending on cause of inflammation
• Causes of chronic inflammation

  • Failure to eliminate the original pathogen that caused the inflammation, example – parasite
  • Exposure to an irritant/foreign material that cannot be eliminated via normal inflammatory processes, example – long-term industrial exposure
  • Autoimmune disorder where the immune system attacks healthy tissues
  • Auto-inflammatory disorders where there is a defect in the cells responsible for resolve inflammatory responses – instead persists, and reoccurs
  • Recurrent episodes of acute inflammation
  • Other mechanisms triggering cellular stress/dysfunction
• Common chronic inflammatory diseases

  • Diabetes
  • Cardiovascular disease
  • Rheumatoid arthritis
  • Chronic obstructive pulmonary disease
  • Allergies
  • Cancer
  • Obesity
• Common signs and symptoms of chronic inflammation

  • Muscular/joint/body pain
  • Chronic fatigue, insomnia
  • Depression, anxiety
  • Gastrointestinal complications
  • Weight gain/loss
  • Frequent infections
  • Oedema
• Granulomatous inflammation


  • Specific type of chronic inflammation
  • Granulomas may form in sites of chronic inflammation caused by certain specific infections (TB, syphilis, cat-scratch disease) or foreign objects
  • Pockets of infected tissues are essentially 'walled off' and surrounded by white blood cells
• Infection


  Invasion of pathogenic microorganisms, example – bacteria, viruses, fungi and parasites
• Pathogen


  A microorganism that causes disease, example – common cold
• Opportunistic infection


  • Caused by microorganisms that normally don't cause disease in a healthy person
  • In immune compromised persons they can cause disease, example – infections in people having chemotherapy, or people with AIDS
• Virus entering body, cells, and replication to become a disease

  Flu Attack! How A Virus Invades Your Body | Krulwich Wonders | NPR
• Infection transmission


  • Direct contact, example – hands touching, sexual intercourse
  • Inhalation, example – TB, pneumonia, influenza
  • Ingestion, example – eating/drinking the microorganism (e.g. giardia from Bali)
  • Penetration of skin, example – spider bite, dog bite, needles
• Barriers that a successful infection must overcome

  • Protective barriers, example – skin, mucosal secretions, hairs in nose, tears in eyes
  • Stomach acids
  • Antibacterial enzymes (produced by natural/normal flora)
• Clinical manifestation of infection

  • Depends on type of pathogen and organ affected
  • Majority of symptoms result from host's inflammatory response and immune response
• Typical early symptoms of infectious diseases

  • Fever – hallmark characteristic
  • Non-specific general symptoms, example – fatigue, malaise
  • Weakness, loss of appetite
  • Loss of concentration
  • General aching
• Predictable stages of infection trajectory

  1. Infection – point of transmission/exposure

  2. Incubation (latency) - time between infection and onset of symptoms, pathological changes are occurring but asymptomatic, often infectious in this stage

  3. Onset of symptoms – clinical signs/symptoms become present, generally when diagnosis takes place

  4. Shedding of microorganism – body cells release infectious particles which are released into the greater environment (via exhalations, droplets when sneezing/coughing, stools)
• Pathogenic infection


  • Myobacterium tuberculosis
  • Rheumatic Heart Disease