1. Chapter 24 Wound Infections
Bio 261
Medgar Evers College, CUNY
Prof. Santos

2. Classification of wounds
Incisions: produced by knife or other sharp object
Punctures: result from penetration by small sharp object
Lacerations: occur when tissue is torn
Contusions: produced by blow that crushes tissue
Abrasions: occur when epidermis is scraped off
Gunshot wounds: caused by bullets, other projectiles
Burns: caused by heat, electricity, chemicals, radiation, or friction

3. Anatomy and Physiology
1- Tissue components exposed during a wound (break in skin or damage to skin) include collagen, fibronectin, fibrin, and fibrinogen.
2-They provide receptors to which potential pathogens can attach to.
3- Collagen is a fibrous material that is the main supportive protein in skin, tendons, scars, and other body components.

4. 4- Fibronectin is a glycoprotein that both circulates the body and is a component of body tissue. In a tissue, it binds cells together.
5- Fibrinogen is a soluble blood protein that is converted to a fibrous material called fibrin after a wound occurs. This results in the formation of clots in the damaged vessels.

5. This stops the flow of blood as the first step in the repair process.
6- Wound healing begins with the outgrowth of connective tissue cells called fibroblasts and capillaries from the surface of wound to form nodular, red, translucent material called granulation tissue. Granulation tissue is bright red, differentiates into new capillaries and bleeds easily.

6. 7- granulation tissue fills the void created by the wound, contracts, and is converted to collagen that composes the scar tissue and eventually covered by skin or mucous membrane.

8. Abscess formation
An abscess is a localized collection of pus surrounded by a body tissue. It is composed of living and dead white blood cells, components of tissue breakdown, and infecting organisms.
There are no blood vessels in an abscess since they have been pushed aside or destroyed. This results in poor delivery of medication or antimicrobial drugs to the area.
An area of inflammation separates the abscess from normal tissue. This localizes the infection.

9. Microorganisms stop multiplying in an abscess so antimicrobial drugs such as penicillin has no effect.
The chemical nature of pus interferes with antimicrobial drugs.
An abscess must burst to surface or be drained surgically in order to effect a cure.

10. Copyright © The McGraw-Hill Companies, Inc
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Microorganisms
Epidermis
Dermis
Capillary
Neutrophils 1
Microorganisms enter the tissue from
a wound or from the bloodstream. 2
Blood vessels dilate, and leukocytes migrate
to the area of the developing infection.
Pus
Blood clots
Blood clots 3
Pus forms and an abscess develops;
clotting occurs in adjacent blood vessels. 4
Buildup of pressure causes the abscess to expand in
the direction of least resistance; if it reaches a body
surface, it may rupture and discharge its contents. 10

11. Anaerobic wounds
Allow anaerobic organisms such a Clostridium tetani to colonize and cause infection.

12. Staphylococcal wound infections
2 species of Staphylococci account for most human wound infections; Staphylococcus aureus and Staphylococcus epidermidis
Symptoms include the discharge of pus, inflammatory reaction with swelling, redness, and pain
Epidemiology; Staph is a normal habitant of the skin and nasal carriers have a greater chance of infection than noncarriers.

13. Old age, poor health, prolonged hospital stay, immuno-supression also contribute to the progression of disease.
Treatment; cleaning and removing dirt, and anti Staph medication given to eliminate nasal carrier state or prior to surgery.

14. Group A Streptococcal flesh eaters
Streptococcus pyogenes can colonize wounds and cause severe infections such as necrotizing fasciitis or flesh eating disease or worst streptococcal toxic shock.
Symptoms; severe pain, swelling, fever and confusion. The overlying skin becomes stretched and discolored due to swelling. Shock and death will follow if treatment is not received shortly after infection.

15. Causative agent is S. pyogenes
Causative agent is S. pyogenes. It is a beta hemolytic, aerotolerant, gram positive chain forming coccus with Lancefield group A cell wall polysaccharide.
They possess at least 2 extracellular products; pyrogenic exotoxin A and exotoxin B.

16. Exotoxin A is a superantigen that causes shock and Exotoxin B is a protease that destroys tissue by breaking its proteins.
Pathogenesis; S. pyogenes bind to fibronectins in tissue that help in colonization. They destroy Fascia or bands of fibrous tissues that underlie the skin and surround muscle and body organs. Intense swelling occurs due to fluid entering the area as a result of increased osmotic pressure from tissue breakdown into small molecules.

17. Prevention; urgent surgery is needed to relieve the pressure of the swollen tissue and remove dead tissue. Amputation is sometimes needed to rid patient of toxin.

19. Pseudomonas aeruginosa infections
Agent of infection: P. aeruginosa is aerobic, gram negative, rod shaped with a single flagellum. It produces 2 pigments that often color the area of infection green.
Symptoms; green coloration, chills, fever, skin lesions, and shock.
Prevention; carefully remove dead tissue from wound, clean area, application of antibacterial cream and antibiotics.

21. Anaerobic bacterial infections
Disease
Cause
Symptoms
treatment
Tetanus or lockjaw
Clostridium tetani
*release of tatanospasmin, a toxin that acts against nerve cells
Restlessness, irritability, difficult swallowing, muscle pain and spasm in jaw, abdomen, or entire body
Tetanus antitoxin

22. Anaerobic bacterial infections
Disease
Cause
Symptoms
treatment
Gas gangrene
(clostridial myonecrosis)
Clostridium perfringens
*secretion of alpha toxin that kills wbc’s and tissues
Severe pain, gas and fluid seep from wound, blackening of skin, shock and death follows!
Clean wounded area, surgical removal of dirt and dead tissue, oxygen, antibiotics.

24. Anaerobic bacterial infections
Disease
Cause
symptoms
pathogenesis
treatment
Lumpy Jaw or actinomycosis
Actinomyces israelii
Chronic disease, painful swellings under the skin, involves face and neck, chest or in the genital tract of women. These swellings can open to release pus.
Usually begins in mouth area and extends outward.
Long treatment due to slow growth, a number of antibacterial medications can be given.

25. Bacterial bite wound infections
Disease
Cause
Symptoms
treatment
Pasteurella multocida infections from dog, cat, monkey, human bite.
Pasteurella multocida
*gram – coccobacillus lives in mouth
Spreading redness, tenderness, swelling, discharge of pus
Treatment with penicillin is effective if given early

26. Bacterial bite infections
Disease
Cause
Symptoms
treatment
Cat scratch disease
Bartonella henselae
Pimple appears at the bite, local lymph node enlargement, fever, and convulsions
Avoid rough play with pet cat, flea control in cats, apply antiseptic, and antimicrobial treatment

27. Bacterial bite infections
Disease
Cause
Symptoms
treatment
Streptobacillary rat bite infection
Streptobacillus moniliformis
*some develop L- form variants which lack a cell wall
Chills, fever, muscle aches, headache, vomiting, rash and pain in the large joints
Penicillin and control rat population

28. Bacterial bite infections
Disease
Cause
Symptoms
treatment
Human bite infection
Mixed mouth flora including staph, anaerobic streptococcus
Pain, swelling, drainage of foul smelling pus
Avoid human altercations that might lead to biting.

29. Fungal wound infections
Disease
Cause
Symptoms
treatment
Rose Gardener’s disease
Sporothrix schenckii
Painless, ulcerating nodules appearing in a linear fashion
Protective clothing, amphotericin B or itraconazole