Transcript Wound Infections

Wound Infections
Chapter 23
Introduction
 Many people obtain wounds that produce breaks in the
skin or mucous membranes
 Microorganisms have the ability to invade and attempt
to colonize within these breaks
 The ability of them to cause disease is dependent on:
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How virulent they are
How many there are
Status of host defenses
Nature of the wound (crush, break, puncture, etc.)
 Clean wounds often heal uneventfully even if there was
an attempt at microbial colonization
 Occasionally, however, trivial wounds have resulted in
fatal events
Classification of wounds
 Incised – produced by a sharp object (like in surgery)
 Puncture – penetration of a small, sharp object
(stepping on a nail)
 Laceration – tissue is torn
 Contused – caused when tissue is crushed
 Burns
23.1 Anatomy and Physiology
 Wounds expose tissues that are normally protected from
outside contact
 Healing begins when connective tissue starts to fill the
void created by the wound
 In the absence of infection, the void is quickly filled and
covered by skin and other tissues
 An abscess is a localized collection of pus surrounded by
tissues, components of tissue breakdown, and infecting
organisms
 Abscess formation helps to localize the infection and
prevent spread
 Many times antimicrobial medications do not work on
abscesses because they diffuse poorly into the area
 Effective treatment is to drain the abscess
 Many wounds are anaerobic and allow for the
colonization of dangerous anaerobic bacteria like
Clostridium tetani
 Dirty wounds are the ideal place for these bacteria to
develop – punctures, bullet wounds, or other projectile
wounds produce tissue damage that is conducive for the
entrance of microbes
23.2 Common Bacterial Wound
Infections
 Possible consequences of infection include
 Delayed healing
 Formation of abscesses
 Extension of infection into adjoining tissues
 Staphylococcal infection can be from surgical or
accidental wounds
 Will cause the production of pus
 Can cause inflammation, redness, and pain
 Can lead to toxic shock syndrome from certain strains
 Causative agents include
 S. aureus
 S. epidermis, which is normally not invasive
 Group A Steptococcal “Flesh Eaters”
 Common cause of wound infection, but generally destroyed
by penicillin
 However, S. pyogenes can progress quickly and lead to
death despite treatments
 Pseudomonas aeruginosa infections
 Opportunistic pathogen and most common cause of
nosocomial infections
 Can be a community acquired infection – meaning it comes
from something outside of a hospital (most commonly from
a contaminated hot tub or swimming pool)
 Has been contracted into foot bones from stepping on a
nail, or caused eye infections from contaminated contacts
23.3 Diseases due to anaerobic bacterial
wound infections
 Wounds that provide anaerobic conditions allow
colonization by strict anaerobic species of bacteria
1. Lockjaw – caused by tetanus, which is often fatal.
Characterized by sustained, painful cramp like muscle
spasms. Death is usually caused by pneumonia from
stomach contents entering the lungs. Active
immunization with tetanus toxoid is the best
preventative treatment (usually immunization begins
in infancy). Treatment after exposure includes
administering the tetanus antitoxin and administering
the antibacterial medication, metronidazole, which
cannot kill endospores or nongrowing bacteria.
2. Gas Gangrene – Usually a disease of wartime and found
in wounds that have been neglected. Symptoms include
pain, leakage of a brown fluid. Skin becomes stretched
and mottled. Victim will be alert until late in the infection
when they may become delerious or lapse into a coma.
Prevention includes immediate care of wounds and
surgical removal of dead or damaged tissue as well as any
debris that may have entered the wound. Antibiotics
(penicillin) may be administered to help stop bacterial
growth, but they are ineffective against the toxins
produced.
3. Lumpy Jaw – Slowly progressive and painful swellings
under the skin that eventually open and drain pus. They
may heal, but will reappear in the near future. Generally,
the bacteria (Actinomycees israelii) cannot enter the skin,
but it can establish an infection if introduced into a
wound. No preventions are available, but penicillin and
tetracycline given over several weeks or months can treat
the infection.
23.4 Bacterial bite wound
infections
 More than 3 million animal bite wounds occur in the US
yearly. The most feared result is rabies.
 Bite wound infection is dependent on the type of
infectious agent found in the mouth of the animal that
did the biting
 Bacterial infections from biting animals are much more
common than rabies
 Pasteurella multocida – can be passed from dogs, cats,
monkeys, and humans
 Symptoms include redness, tenderness, swelling,
discharge of pus
 No vaccine is available for human use
 Treatment includes prompt cleaning of the bite and
administration of antibiotics that have a beta-lactamase
inhibitor with amoxicillin, the pill form is called
Augmentin
 Streptobacillary Rat Bite Fever – as many as 1 in 10 rat
bites result in rat bite fever
 Symptoms – usually the bite heals without any
problems, but 2-10 days later, other symptoms develop.
These include fever, chills, muscle aches, and vomitting
 Causative agent is Streptobacillus moniliformis
 Prevention – keeping rats under control
 Treatment includes intravenous dosage of penicillin
 Human bites – fairly common and can be very serious
 Symptoms – pain and massive swelling. Pus that is
discharged will have a foul odor. Movement may be
affected in the bitten area, especially in the hands
 Prevention – avoid a situation where biting could occur.
Prompt cleaning of the wound
 Treatment – opening of the area surgically and washing
with with sterile fluid to remove dirt and dead tissue.
Antibiotics will need to be effective against anaerobes
23.5 Fungal Wound Infections
 Fungal infections of wounds are normally found in
economically challenged areas.
 They can present however, in conjunction with other
burns or in the presence of other diseases such as
diabetes or cancer
 Rose Gardener’s Disease (Sporotrichosis) – caused by puncture
wounds from vegetation.
 Symptoms – a chronic ulcer forms at the wound cite and is
followed by a progressing series of ulcerating nodules. Most
patients do not become ill, but if the patient is already
suffering from AIDS or immunodeficiency, then it can be life
threatening.
 Prevention – protective gloves and long sleeves while working
with plants, especially evergreens and sphagnum moss.
 Treatment – oral administration of a compound containing
potassium iodide, which helps the body reject the fungus.
Itraconazole is used in rare cases when the fungus spreads