Infection Control: Course of Infection By Stage Flashcards
What is the incubation period of an infection?
- Interval between pathogen entering the body and first symptoms appearing
- Examples: Chickenpox 2-3 weeks, common cold 1-2 days, influenza 1-3 days, mumps 15-18 days
What is the prodromal stage?
- Interval from onset of nonspecific symptoms (malaise, low fever, fatigue) to more specific symptoms
- Microorganisms grow and multiply, patient may be more contagious
What is the illness stage?
- Interval when patient shows signs/symptoms specific to the infection type
- E.g. cold: sore throat, congestion; mumps: earache, fever, swollen glands
What is the convalescence stage?
- Acute symptoms disappear, body replenishes resources to return to homeostasis
- Length depends on infection severity and patient’s overall health, can take days to months
Where does the body normally contain microorganisms (normal flora)?
- On the skin surface and deep layers
- In the saliva and oral mucosa
- In the gastrointestinal and genitourinary tracts
What role do the normal flora play?
- Do not typically cause disease in their usual areas
- Participate in maintaining health
- Assist in fighting infection and inflammation
- Maintain homeostasis
How do gut microorganisms benefit the host?
- Convert dietary fiber into fatty acids reabsorbed by bowel
- Synthesize vitamins B, K, bile acids, and sterols
What protects against pathogens invading when normal flora are disrupted?
- Bile’s antibacterial properties
- Fatty acids stabilizing normal flora populations
What can disrupt the balance of normal flora?
- Acquiring new microorganisms (e.g. in hospital)
- Use of broad-spectrum antibiotics
What is a risk of using broad-spectrum antibiotics?
- Can lead to superinfection like Clostridioides difficile (C. diff)
- Eliminates normal flora, reducing body’s defenses
What body systems have unique defenses against infection?
- Skin
- Respiratory tract
- Gastrointestinal tract
Why are these systems easily accessible to microorganisms?
- Pathogens can adhere to skin surface
- Pathogens can be inhaled into lungs
- Pathogens can be ingested with food
How are the defenses suited to each system’s structure and function?
- Each system has physiologically suited defense mechanisms
- E.g. Airways lined with cilia to move mucus/trapped organisms
What increases susceptibility to infection?
- Conditions that impair an organ system’s specialized defenses
What is inflammation?
- The body’s cellular response to injury or infection
- A protective vascular reaction delivering fluid, blood products, and nutrients to injured area
- Neutralizes and eliminates pathogens or dead tissues
- Establishes means of repairing cells and tissues
What are signs of localized inflammation?
- Swelling
- Redness
- Heat
- Pain or tenderness
- Loss of function in affected area
What are signs of systemic inflammation/infection?
- Fever
- Leukocytosis
- Malaise
- Anorexia
- Nausea/vomiting
- Lymph node enlargement
What can trigger the inflammatory response?
- Physical agents (trauma, temperature extremes, radiation)
- Chemical agents (irritants, poisons, gastric acid)
- Microorganisms
What events occur after tissue injury in the inflammatory response?
- Vascular and cellular responses
- Formation of inflammatory exudates (fluid/cells discharged)
- Tissue repair
What are the vascular and cellular responses in acute inflammation?
- Arteriole dilation allowing more blood flow to area
- Increased redness from more local blood circulation
- Localized warmth from greater blood volume
- Vasodilation enables blood/WBCs to travel to injured tissues
What chemical mediators are released by the body in response to tissue injury?
- Histamine
- Bradykinin
- Prostaglandins
- Serotonin
What do these chemical mediators cause?
- Increase permeability of small blood vessels
- Allow fluid, protein, and cells to enter interstitial spaces
- Result in localized swelling (edema)
What symptom of inflammation results from swelling of tissues?
- Pain, due to increased pressure on nerve endings
- Chemical substances like histamine stimulate nerve endings
What other effect can inflammation have?
- Temporary loss of function in the involved body part
- E.g. Swollen, painful, discolored fingers from hand infection
What is the cellular response in inflammation?
- WBCs (neutrophils and monocytes) arrive at site
- Pass through blood vessels into tissues
- Ingest and destroy microbes/particles by phagocytosis
What systemic signs develop as inflammation becomes systemic?
- Leukocytosis (increased circulating WBCs)
- Normal WBC count 5000-10000/mm3, can rise to 15000+
- Fever from phagocytic release of pyrogens causing hypothalamic change
What forms at the site of inflammation?
- Accumulation of fluid
- Dead tissue cells
- White blood cells (WBCs)
- Together forming an exudate
What types of exudates can form?
- Serous (clear, watery plasma)
- Sanguineous (bloody drainage)
- Serosanguineous (thin, watery, blood-tinged)
- Purulent (thick drainage containing pus)
How is the exudate eventually cleared?
- Through lymphatic drainage
What forms a meshlike matrix at the inflammation site?
- Platelets
- Plasma proteins like fibrinogen
What is the purpose of this matrix?
- To prevent the spread of infection
What stages are involved in tissue healing after injury?
- Inflammation
- Proliferation
- Remodeling
What happens to damaged cells during healing?
- They are eventually replaced with healthy new cells
- The new cells undergo gradual maturation
- They take on same structural characteristics as previous cells
Does the healed wound regain full tensile strength?
- Unless the wound is minor
- The healed wound usually does not regain full tensile strength of replaced tissue
- Scarring may occur
