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: 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