Lecture 21: Wound and Device Infections

(Wound and Device Infections) Lecture 21 Device Related Infections · risk for infection increases with insertion of protheses (eg. artificial joints, pacemakers, intravenous lines) ↳ biofilms commonly grow · one of the most common causes is normal skin flora: ↳ Staphylococcus epidermidis ↳ Staphylococcus aureus · treatment: removal of device and antibiotics Intravenous Catheters · peripheral and central venous catheters, total parenteral nutrition catheters, arterial lines · 4 sources of infection Infections of Vascular Grafts · eg. CABG (coronary artery bypass graft) · results from: ↳ intraoperative contamination ↳ extension from nearby infected tissue ↳ hematogenous seeding (bacteria floating in bloodstream) - S. aureus most common pathogen Dialysis · dialysis: a method of removing the toxic wastes from the body in patients with renal failure · two major methods: ↳ intravenous or "hemodialysis"→go to hospital ↳ peritoneal dialysis → permanently attached hemodialysis: at risk for blood born infections Peritoneal Dialysis 1. have permanent connection in abdomen 2. drain all fluid out first 3. perfuse with new fluid 4. wait 5 hours, then drain Infection Risks with both Types of Dialysis: · hemodialysis: contamination of equipment with hepatitus B, C, HIV, (bloodborne pathogens) · perioneal dialysis: risk for contamination of abdominal cavity Peritonitis with bacteria of the skin · inflammation of the peritoneal cavity ↳ retains fluid ↳ peritonitis: infection and inflammation of the peritoneal cavity (major complication of peritoneal dialysis) · symptoms: ↳ moderately severe abdominal pain* ↳ pain aggravated by motion, even breathing ↳ anorexia, nausea, vomiting, fever, abdominal distention · complication: development of intra-peritoneal abscess Abscess · localized lesion with pus anywhere on body · result of external or internal infection · internal abscesses are often polymicrobial · skin abscesses commonly from S. aureus Osteomyelitis · infection/abscess of the bone by nearby site of infection, after trauma (like a fracture, or from circulating microbes) · most common cause from blood: S. aureus · most common cause from nearby site: Polymicrobial (G +/-) · difficult to treat, bone is difficult to get antibiotics into ↳ long treatment periods Acute Osteomyelitis Chronic Osteomyelitis · bone lesions very painful, fever debridement necessary with prolonged antibioties · often end of long bones, typically in children · usually with necrotic bone fragments, surgical · amputation may be needed to prevent spread · mainly elderly patients Surgical Infections · contamination of the surgical site during operation OR infection of the site after surgery · associated with hygienic conditions in the operating room, immune status of the patient, and often the competence of the surgeon · common to have normal skin flora infecting a surgical site ↳ can't remove them completely Consequences of Wounds ① delayed healing ② formation of abscesses ③ dissemination or spread of infection to nearby tissues, blood, or lymph ↳ leads to septicemia or shock Pre- and per-operative antibiotics used in "dirty" surgery (abdominal surgery) Snake Bites Human Bites where infection can develop · Eikonella corrodens signifies human bite · venom causes tissue necrosis · pseudomonas aeruginosa, Salmonella species (any dirt bacterium) · more often infected than animal bites · both aerobic and anaerobic bacteria implicated (oral flora) Cellulitis · rapid acute spreading infection of deep subcutaneous tissues · causes redness, swelling, pain · can progress to necrotizing fasciitis, gangrene · originates from superficial skin lesions or trauma ↳ boils, ulcers, pimples, sores · main cause: S. aureus and S. pyogenes · must be treated immediately with antibiotics · intravenous drug users: ↳ many are immunocompromised and have many infections ↳ often get cellulitis or lymphangitis with S. aureus due to sharing injection needles · anaerobic cellulitis: ↳ areas of traumatized tissue or poor blood circulation - diabetics prone to cellulitis of the feet ↳ infections in lower half of body: fecal flora ↳ infections in upper half of body: oral flora ↳ foul smelling pus, marked swelling, gas ↳ treatment: IV antibiotics and surgical debridement of wound Gas Gangrene · usually caused by Clostridium perfringens ↳ G + anaerobic spore forming bacilli ↳ found in soil and feces · usually a result of traumatized tissue with poor blood supply, with anaerobic conditions in the wound · pathogens multiply in subcutaneous tissues and invade deeper, thrives on dead tissue · produces gas as a byproduct of metabolism → crackling sound on palpitation · a-toxin destroys tissue cells and WBC, collagenase, hyaluronidase further break down tissue Tetanus or "Lockjaw" · caused by Clostridium tetani ↳ anaerobic spore forming G+ bacillus, often found in soil · neurotoxin tetanospasmin ↳ enters CNS via peripheral nerves or blood (bloodstream/tissues) ↳ blocks release of inhibitory neurotransmitters (glycine and GABA) → causes spasms · death usually from spasms of respiratory muscles, pneumonia, or regurgitating stomach contents into the lungs · Neonatal Tetanus: ↳ >50% of cases due to puncture wounds ↳ usually due to nonvaccinated mothers, filling umbilical cord w/dirt, and nonsterile instruments · toxoid vaccine and antitoxin (TIG) exist Burns · mortality rate higher the more burns across the body · important to maintain blood flow to the area · necrotic tissue good medium for growth of bacteria · decreased immune defense in large burns (cells burn out) · treatment: close burn wound ASAP and use topical antibiotics prophylactically (as prevention) as well as surgical excision of necrotic tissue · hemorrhage, eschar formation (black scabs) or greenish decolorization indicate infection · polymicrobial infections include G+ and G- · Pseudomonas aeruginosa commonly infects burn wounds Pseudomonas aeruginosa · widespread in nature, water, soil · very common in wounds and hard to treat due to antibiotic resistance · motile G-bacteria, grows in almost everything (including disinfectant), anaerobic or aerobic · causes tissue damage and prevents healing, increased risk for septic shock · endotoxin in cell wall (G -) · pyocyanin for blue green pus, toxic for WBC · exotoxins: exoenzyme S, toxin A, proteases, hemolysins, phospholipase C