6: Microbiology Part 2 Flashcards
The fitting of which materials may lead to infection?
Prosthetic joints
What are some risk factors for prosthetic joint infection?
Immunosuppression - rheumatoid arthritis
Diabetes
Malnutrition
Obesity
What is a biofilm?
Community of different organisms getting up in there and having fun etc.
Orthopaedic theatres are strictly controlled to prevent infection.
What are two mechanisms of prosthetic joint infection at the time of surgery?
Direct inoculation using instruments
Manipulation of joint by surgeons
Seeding of joint by something else
If prosthetic joint occurs early (i.e within a month), what is it likely associated with?
Haematoma / sepsis
If prosthetic joint infection occurs late (i.e after a month), what is the likely cause?
Contamination during surgery (?why)
Biofilms produce a thick ___ which antibiotics struggle to penetrate?
mucus
Which organisms tends to cause prosthetic joint infection?
Staph. aureus still
but also Staph. epidermidis due to involvement of prosthesis
Which organism, found in the skin of the upper limb, may rarely be responsible for upper limb prosthetic joint infections?
Proprionibacterium spp.
Before antibiotics are given, what should be taken from a suspected prosthetic joint infection?
Biopsy (as always)
Coagulase negative Staph. tend to be treated as contaminants unless the patient has what?
Prosthesis
How are prosthetic joint infections treated?
Remove / replace the joint
Antimicrobial therapy (fluclox for the Coag +ve, vancomycin for Coag -ve)
If a patient with prosthetic joint infection is elderly and can’t tolerate surgery, what may be done to treat them?
Cleaning / debridement
prognosis is poor
DAIR
Which drug is added to normal antibiotic therapy for prosthetic joint infections?
Why?
Is the drug ever used by itself?
Rifampicin
Helps other antibiotic to penetrate slime produced by biofilm
No, as Staph. aureus will develop resistance to it
(rearrange) How is septic arthritis diagnosed?
Aspiration of joint fluid via needle
r From which other infections can septic arthritis develop?
Cellulitis
Osteomyelitis
r What is the duration of antibiotic therapy for septic arthritis?
4 weeks
What is septic arthritis?
Inflammation of joint space due to infection
What organisms tend to cause septic arthritis?
Staph. aureus
Streptococci
Coagulase negative Staph. (prosthetic joints)
Neisseria gonorrhoea
Which specific toxin, produced by both MSSA and MRSA, makes patients very sick?
PVL
What drug is used to treat PVL-producing Staph. aureus?
Flucloxacillin
What is sent to the lab for microscopy to diagnose septic arthritis?
Joint fluid
Which metabolic diseases mimic septic arthritis?
How would you tell from the fluid?
Crystal arthropathy (gout and pseudogout)
Crystals in the fluid
What drug is used to treat septic arthritis?
Flucloxicillin (Vancomycin in MRSA, clindamycin in allergies)
+/- ceftriaxone in patients < 5yrs to cover Haemophilus influenzae
What other pathogen can cause arthritis?
Viruses
People with viral arthritis will present with ___ symptoms.
viral
look up what these are, presumably fever
What is pyomyositis?
Muscle inflammation caused by infection
90% of pyomyositis cases are caused by (Staphylococci / Streptococci).
Staphylococci
How is pyomyositis treated?
Surgery to debride as much pus / necrotic tissue as possible
Why are antibiotics an afterthought in severe pyomyositis?
Antibiotics don’t penetrate necrotic tissue and pus
What is the main symptom of pyomyositis?
Pain
Redness
What is the difference between pyomyositis and myositis?
Pyomyositis - bacterial, focal
Myositis - viral, diffuse
Tetanus is mainly a (bacterial / toxin) - mediated disease.
Toxin-mediated
What is the organism responsible for tetanus?
Clostridium tetani
more on c. tetani
What are the classic symptoms of tetanus?
Lockjaw and muscle spasm
triggered by loud noises and bright lights
How is tetanus treated?
Surgical debridement of wound(s)
Antitoxin
Supportive - benzodiazepines, anaesthetics, nutrition & fluids
Are tetanus survivors immune to the disease?
What should the next step be?
No
Tetanus vaccination
