(10-25) Wound Infections Flashcards
1. Name one tissue component exposed by wounds to which pathogens specifically attach. 2. Describe the potentially beneficial and harmful aspects of abscess formation. 3. Define wound infections and describe their possible consequences. 4. Identify the most common bacterial causes of wound infections. 5. Outline the significance of methicillin-resistant Staphylococcus aureus (MRSA). 6. Give distinctive characteristics of three common wound infections caused by bacteria that grow in the pres
What is an abscess?
A localized collection of pus within tissue.
What is pus?
Pus is dead neutrophils, dead microorganisms, and degraded tissue
Differentiate between Pyogenic and Pyrogenic.
- Pyogenic: pus forming
2. Pyrogenic: fever forming
What helps separate the abscess from normal tissue?
An area of inflammation and clots
Why does the area of inflammation and clots separate the abscess from normal tissue?
It helps to keep the infection localized.
Is an area of inflammation and clots usually aerobic or anaerobic?
ANaerobic
Under what condition are pathogens more likely to escape an inflamed area and enter the bloodstream?
Under increased pressure (blood pressure).
How can an abscess be treated?
It must rupture or be surgically drained.
Name 4 common bacterial wound infections.
- Staphylococcus aureus
- Staphylococcus epidermidis
- Streptococcus pyogens
- Pseudomonas aeruginosa
Which Genus of bacteria are the leading cause of wound infections?
Staphylococcus
What are 2 symptoms of staphylococcus wound infections?
- Inflammation
2. Fever (in widespread infection)
Which 2 Staphylococcus species account for most human infections?
- S. aureus
2. S. epidermidis
The virulence of S. aureus is due to the production of which 4 extracellular products?
- Coagulase
- Clumping factor
- Protein A
- α toxin
What does Coagulase do in a S. aureus wound infection?
Coagulase causes blood clotting to evade phagocytosis.
What does Clumping factor do in a S. aureus wound infection?
Clumping factor aids in attachment to fibrin.
What does Protein A do in a S. aureus wound infection?
Protein A hides bacteria from phagocytic cells.
What does α toxin do in a S. aureus wound infection?
α toxin produces hole in host cell membranes.
Which bacterium has little or no invasive ability: S. aureus or S. epidermidis?
S. epidermidis
How does S. epidermidis protect itself from phagocytosis?
S. epidermidis sometimes produces a biofilm.
What are 4 measures one can take to prevent Staphylococcus wound infections?
- Cleansing wound
- Removing dirt and crushed tissue
- Prompt closure
- Pre-surgical antistaphylococcal medication
Which 3 drugs are used to treat Staphylococcus wound infections, and what are the limitations of each?
- Penicillin: most strains are resistant
- Methicillin: many strains treated, but some are resistant (MRSA)
- Vancomycin: resistant strain identified in 1997 (VRSA)
What is the primary pathogen in Streptococcal wound infections?
Group A S. pyogenes
Group A Streptococcal wound infections are common and can be treated with which drug? Why does that drug work?
- Penicillin
2. S. pyogenes does not have a lot of antimicrobial resistance
More severe wound infections are called _______.
Invasive
What are the 4 types of invasive Streptococcal infections?
- Pneumonia
- Meningitis
- Puerperal (childbirth fever)
- Necrotizing fasciitis
What is Pneumonia?
Pneumonia is an inflammation of the lungs with pus and fluid.
What is Meningitis?
Meningitis is an inflammation of the membranes of the brain and spinal cord.
What is Puerperal (childbirth) fever?
Puerperal (childbirth) fever is a bacterial infection of the uterus.
What is Necrotizing fasciitis?
Necrotizing fasciitis is when S. pyogenes releases toxinsthat kill tissue and affect blood flow to tissues. It is sometimes called “flesh-eating bacteria.”
How many people died from necrotizing fasciitis in 2002?
135
List 5 symptoms of Necrotizing fasciitis.
- Acute pain at the site of the wound
- Swelling
- Fever and confusion
- Overlying skin tightens and becomes discolored
- Shock and death in the absence of treatment
Explain the pathogenesis of Necrotizing Fasciitis. [4 Steps]
- Wound colonization enhanced through tissue binding proteins
- Subcutaneous fascia is destroyed [Muscle tissue is also destroyed when bacteria penetrate muscle tissue]
- Organisms multiply and produce toxic products
- Organisms and toxic products enter bloodstream [Can cause shock]
What is Necrotizing Fasciitis caused by?
Virulent strains of S. pyogenes
Which 2 extracellular products are responsible for virulence, and what do each of them do?
- Pyrogenic exotoxin A: causes streptococcal toxic shock.
2. Exotoxin B: destroys tissue through protein breakdown.
Which preventative measure is proven to be effective against Necrotizing Fasciitis?
There are none.
Which 2 mechanical therapeutic measures are taken for Necrotizing Fasciitis infections, and why?
- Urgent surgery required due to rapidity of toxin spread
2. Amputation is sometimes required
Explain the effectiveness and limitations of Penicillin use in treating Necrotizing Fasciitis.
- Must be given early
- Has little or no effect on bacteria in necrotic tissues
- No effect on toxin
- Surgery may still be necessary
P. aeruginosa is a/an __________ pathogen.
Opportunistic
Which bacterium is a major cause of nosocomial infections?
P. aeruginosa
Which 2 characteristics contribute to the virulence of Pseudomonas aeruginosa?
- Toxins
2. Multi-drug antibiotic resistance
Where do nosocomial Pseudomonas aeruginosa lung infections originate?
From contaminated respirator water
How do Pseudomonas aeruginosa burn Infections present?
They release pigments that often color tissues green.
What is the treatment protocol for Pseudomonas aeruginosa wound infections?
Treatment is prompt wound care and high doses of antibiotics (carefully monitored for resistance)
List 3 anaerobic bacterial wound infections.
- Tetanus (Lockjaw)
- Gas Gangrene
- Lumpy Jaw
Which anaerobic bacterium causes Tetanus (Lockjaw)?
Clostridium tetani
Which anaerobic bacterium causes Gas Gangrene?
Clostridium perfringens
Which anaerobic bacterium causes Lumpy Jaw?
Actinomycosis israelii
What is Lumpy Jaw?
Gram-positive filamentous anaerobic bacterium, Actinomycosis israelii, forms abscesses.
What is Tetanus?
Sustained painful and uncontrollable cramplike muscle spasms.
Which muscle does Tetanus usually start with?
The Mastoid.
What is the severity and prevalence of Tetanus in the developed world?
- Tetanus is frequently fatal
2. It is rare in the developed world
Describe 4 bacterial characteristics of Clostridium tetani.
- Gram-positive
- anaerobic
- rod-shaped
- endospore-forming
Where are Clostridium tetani endospores prevalent?
In dust and soil
Describe the invasiveness and pathogenesis of Clostridium tetani.
- Not invasive– remains localized to wound
2. Pathogenesis is due to tetanus toxin
How does Tetanus toxin spread?
Tetanus toxin spreads via blood stream to central nervous system.
How does Tetanus toxin affect the body?
Tetanus toxin blocks inhibitory neurons so muscles contract out of control.
~ If inhibitory neurons of brain first affected, muscles of the jaw are first to become spastic
How does Clostridium tetani kill?
Death is often from paralysis of respiratory muscles or stomach contents regurgitated into the lungs.
How can Tetanus be prevented?
Immunization with (inactivated) tetanus toxin is protective for 10 years.
What is the treatment for Tetanus?
Passive immunization with antibodies from a person who has been immunized against tetanus toxin.
~ Tetanus immune globulin (TIG)
Gas gangrene of the uterus is common after what?
Self-induced abortion.
Gas Gangrene is primarily a disease of wartime due to what?
Neglected wounds, containing debris
Describe 5 bacterial attributes of C. perfringens.
- Gram-positive
- anaerobic
- rod-shaped
- endospore-forming
- found in soil
What is C. perfringens’ pathogenesis?
- Symptoms begin abruptly with rapidly increasing pain localized to area of wound
- Swelling due to gas production and tissue breakdown
Describe the action of the α toxin produced by C. perfringens.
- α toxin kills cells by attacking host membranes.
2. Spread of α toxin to blood stream leads to red blood cell destruction.
How can Gas Gangrene be prevented?
Prompt wound cleaning
What is the treatment for Gas Gangrene?
- Antibiotics work against bacterium but do not stop toxin
2. Amputation often necessary