Microbiology Flashcards
What is the treatment for a Staphylococcus epidermidis infection?
Vancomycin.
What is the treatment for a Staphylococcus aureus infection?
Flucloxacillin.
What is the treatment for an infection of gram-negative microorganisms?
Doxycycline/clindamycin.
What is osteomyelitis?
Inflammation of bone and medullary cavity, usually located in one of the long bones.
How is osteomyelitis in patients classified?
By time - acute/chronic.
By spread - contiguous/haematogenous.
Host status - presence of vascular insufficiency, host susceptibility.
What is contiguous spread of an organism?
Spread is from a site adjacent to where you think the infection started e.g. diabetic with superficial ulcer and the infection from the ulcer spreads down into the bone.
What is haematogenous spread of an organism?
Secondary spread of infection from blood to the bone.
E.g. drugs user gets a bacteraemia and the infection spreads to the bone from elsewhere in the body from the primary infection site.
How can you get indirect and direct confirmation of infection in the bone?
Indirect - scan.
Direct - sample from the bone itself.
What is the best clinical indicator that there may be osteomyelitis from an open wound?
If you can see tendon/bone or you can probe the bone the open wound.
When is osteomyelitis a medical emergency?
If there is sepsis or the patient is clinically unstable.
You also give antimicrobials before culturing if it is a soft tissue infection.
What is the treatment plan for osteomyelitis?
No empiric antibiotics (guessing what the infection is and prescribing antibiotics without confirmed cultures).
Culture the bone first, await results and prescribe based on those results.
Acute/chronic osteomyelitis is not a medical emergency.
AND surgical debridement of pus, dead bone.
Why should a patient have 6 weeks of antibiotic therapy for osteomyelitis?
It takes 6 weeks for debrided bone to be covered by vascularised soft tissue.
When is coagulase negative staphylococcus (staph. epidermidis) likely to cause infection in the body?
If there are metal or plastic prosthesis surgically implanted into the body.
What spread is likely to cause vertebral osteomyelitis?
Haematogenous.
How best should you culture for osteomyelitis?
Percutaneous aspirate or deep surgical cultures, NOT swabbing top of a sinus.
Who is likely to get osteomyelitis?
Open fractures.
Diabetes/vascular insufficiency.
Haematogenous osteomyelitis.
Vertebral osteomyelitis (specific case of haematogenous spread).
Prosthetic joint infection.
Specific hosts and pathogens.
What is the clinical clue that someone has developed osteomyelitis following an open fracture?
Non-union and poor wound healing.
What microorganism tends to be causative in open fracture osteomyelitis?
Staph. aureus.
Gram-negative bacteria.
What microorganism tends to be causative in diabetic/vascular insufficiency osteomyelitis?
Polymicrobial (often staph. aureus).
What is the rule of thumb for when it is likely to get infection from an open wound?
If you have a wound >2cm for >2 months, then it is at high risk of infection.
If there is osteomyelitis following a diabetic foot ulcer, what is the best treatment?
Flucloxacillin (staph. aureus and stept. cover).
Gentamicin (gram-negative cover).
Metronidazole (anaerobic cover).
How long would you prescribe antibiotics for a skin and soft tissue infection?
7 days.
How long would you prescribe antibiotics for a bacteraemia?
14 days by IV.
How long would you prescribe antibiotics for osteomyelitis?
6 weeks.
When is oral vancomycin only ever given?
To treat C. difficile because orally it is not absorbed by the gut so it becomes a topical treatment in the gut.
How long would you prescribe antibiotics for endocarditis?
6 weeks IV therapy.
Which bacteria when cultured should never be ignored?
Staph. aureus.
Group A, B, C, or G strept.
Milleri group.
Anaerobes.
Which patients are likely to get haematogenous osteomyelitis?
Prepubertal children.
People who inject drugs.
Central lines/dialysis/elderly.
When treating osteomyelitis when is day 1 of treatment?
The first day you get negative cultures for the organism you are treating for.
What organisms can cause osteomyelitis in people who inject drugs?
Staphylococcus.
Streptococci.
Pseudomonas.
Candida.
Eikenella corrodens (needle lickers).
Mycobacterium tuberculosis.
Which organisms can cause osteomyelitis in dialysis patients?
Staphylococcus aureus.
Aerobic gram negatives.
Which organisms are likely causative in sickle cell osteomyelitis?
Salmonella.
Staphylococcus aureus.
What is synovitis acne pustulosis hyperostosis osteitis (SAPHO)?
Chronic lytic lesions that when seen on MRI look like osteomyelitis.
Raised inflammatory markers.
Antibiotic and non-antibiotic treatments.
What is chronic recurrent multifocal osteomyelitis (CRMO)?
Chronic lytic lesions that when seen on MRI look like osteomyelitis.
Raised inflammatory markers.
Antibiotic and non-antibiotic treatments.
What abscesses may be associated with vertebral osteomyelitis?
Epidural abscess.
Psoas abscess.
What conditions are risk factors of infection in prosthetic joints?
Rheumatoid arthritis.
Diabetes.
Malnutrition.
Obesity.
What is dehiscing of a wound?
The wound doesn’t heal properly, instead, there are little punctures of pus seeping from it
What type of infection do planktonic bacteria cause?
Bacteraemia.
What type of infection do sessile bacteria cause?
Bacteria form a layer really close to prosthetic material that grows very slowly forming an extracellular matrix of biofilm meaning it can’t be targeted well by antibiotics.
What bacteria may cause infection following a shoulder replacement?
Propionibacterium acnes.
What is the best treatment for infection following a prosthetic joint replacement?
Ideally, remove prosthesis and cement.
Antimicrobial therapy for at least 6 weeks.
Re-implantation of the joint after aggressive antibiotic therapy.
What is septic arthritis?
Inflammation of the joint space caused by infection.
Can be from blood-borne organisms, an extension of local infection (e.g. complication of infection in adjacent bone), or introduced by direct inoculation (e.g. following injection of joint or trauma).
What can be the bacterial causes of septic arthritis?
Staph. aureus.
Stept.
Coagulase-negative staph.
Neisseria gonorrheae (sexually active, not common).
Haemophilus influenzae (pre-school, not common).
What are the symptoms of PVL producing staph. aureus?
Skin infections.
Necrotising pneumonia.
Invasive infections, e.g. bacteraemia, septic arthritis.
What is the treatment for PVL producing staph. aureus?
Flucloxacillin, clindamycin, linezolid, depending on sensitivities.
What is pyomyositis?
Bacterial infection of the skeletal muscles resulting in pus-filled abscesses.
Which patients are more at risk of pyomyositis?
Immunocompromised patients.
What is the treatment of tetanus infection?
Surgical debridement.
Antitoxin.
Supportive measures (early intubation, beta blockers, avoid light, benzodiazepines for reflex spasms).
Antibiotics 7-10 days.
Booster vaccination (toxoid).
Survivors are not immune.
