Antimicrobial Therapy Flashcards
What is the other name for skeletal tuberculosis?
Pott’s disease
What is unusual about skeletal tuberculosis?
Often has no systemic manifestations and is not infectious
What are some features of skeletal tuberculosis?
50% have skin and soft tissue infections, <50% have pulmonary TB, travel history is important, crushes bone and causes wedge-compressions that lead to kyphosis
What should be checked in children when considering skeletal TB?
Check reduced receptors for IFN-gamma RI and IL-12 beta 1
What should adults with suspected skeletal TB always be check for?
HIV
What are the risk factors for prosthetic limb infections?
Obesity, diabetes, malnutrition, rheumatoid arthritis
How can bacteria spread in prosthetic limb infections?
Direct inoculation during surgery, limb manipulation during surgery, seeding of joint at later time
What are features of early and late prosthetic limb infections?
Early (within a month) = haematoma, wound sepsis
Late (>month) = contamination at time of operation
What type of infections do planktonic bacteria cause?
Bacteraemia = presence of bacteria in blood
What are some features of sessile bacteria?
Phenotypic transformation of planktonic bacteria, form biofilm, extracellular matrix, need surgical removal
What drug is used to remove biofilms form prosthetic limb infections?
Rifampicin
What are some gram positive organisms that can cause prosthetic limb infections?
Staph. aureus, staph. epidermidis, Propionibacterium acnes (upper limb), rarely strep. sp and enterococcus sp
What are some gram negative organisms that cause prosthetic joint infections?
E.coli, pseudomonas aeruginosa
What are some non-bacterial causes of prosthetic limb infections?
Fungi, myobacteria sp
How can prosthetic limb infections be diagnosed?
Culture samples taken from perioperative tissue (multiple), blood culture, CRP, radiology (x-rays)
What are some features of staph. epidermidis prosthetic limb infections?
Coagulase negative staph, forms slime, treated with vancomycin initially, usually swap to doxycycline or clindamycin orally as out-patient
How should prosthetic limb infections be treated?
Remove prosthesis and cement, treat with antibiotics for at least 6 weeks, re-implantation of joint after aggressive antibiotic therapy
What are some ways to reduce risk of infection in orthopaedics?
Anti-infective implants and cement, antibiotic prophylaxis, laminar flow, hydrogels, surgical aftercare
How can bacteria spread in septic arthritis?
Direct invasion, haematogenous spread, rarely spread from adjacent osteomyelitis
What is septic arthritis?
Inflammation of joint space caused by infection
What bacteria cause septic arthritis?
Staph. aureus (most common), strep, coagulase negative staph. in prosthetics, Neisseria gonorrhoeae in sexually active, h.influenzae in pre-schoolers (rare)
What are some features of PVL producing staph. aureus?
Both MSSA and MRSA, rare, skin infections, necrotising pneumonia, invasive infections (e.g. septic arthritis)
How can PVL producing staph. aureus be treated?
Flucloxacillin, clindamycin, linezolid
How is septic arthritis diagnosed?
Joint fluid for microscopy, culture and sensitivity, blood culture if pyrexial, exclude crystals
How is septic arthritis treated?
High dose flucloxacillin for staph. aureus, add ceftriaxone in children <5 to cover haemophilis influenzae
What are some causes of viral arthritis?
Hep B, parovirus B19, rubella, alphavirus = all treated supportively
What is pyomyositis?
Muscle inflammation with pus
What are some causes of bacterial pyomyositis?
90% are staph. aureus, some site specific (e.g GNB perineum), treated with surgery
Tropical variant = MSSA (immune competent)
Temperate variant = pseudomonas, beta haemolytic strep, enterococcus (immunosuppressed)
Clostridial infections = contaminated wounds
What are some causes of diffuse viral pyomyositis?
HIV, HTLV, influenza, CMV, rabies, Chikungunya and other arboviruses (travel history important)
What are some features of fungal pyomyositis?
Often focal
What parasites can cause pyomyositis?
Schistosoma, taenia, trichinella, echinococcus (travel history important)
What can pyomyositis lead to?
Myonecrosis = treated by surgery
What bacteria causes tetanus-toxin mediated illness?
Clostridium tetani
What are some features of clostridium tetani?
Gram positive, strictly anaerobic rods, forms spores, found in soil, non-invasive, all toxin related
How does clostridium tetani cause illness?
Produces neurotoxin = causes spastic paralysis by preventing muscle relaxation
What is the incubation period for tetanus?
4 days to several weeks
What is the classic symptom of tetanus?
Lock jaw
How is tetanus diagnosed?
Culture = difficult, anaerobic gram positive, terminal spore
Serum and urine toxin assays exist
How is tetanus treated?
Surgical debridement, antitoxin
Antibiotics = 7-10 days, penicillin, metronidazole
What are some supportive treatments for tetanus?
Early initiation, beta blockers, benzodiazepines for reflex spasms, need some neuromuscular blockade
What are some features of the tetanus vaccine?
Survivors not immune so need booster vaccination
Routine vaccination = toxoid vaccine (2,3,4 months)
