Microbiology Flashcards
What is osteomyelitis?
Inflammation of the bone and medullary cavity, usually located in one of the long bones
How can osetomyelitis be classified?
Acute vs chronic
Contiguous vs haematogenous
Host status - presence of vascular insufficiency
What is an example of how the host status can change oestomyelitis?
Those with sickle cell are susceptible to salmonella ostemomyelitis
What is the gold standard for diagnosis of oesteomyelitis?
Bone biopsy
MRI
If you can see bone or tendon this is DEFINITELY osteomyelitis
When should antibiotics be prescribed for oestomyelitis?
AFTER CULTURES
NEVER EMPIRICAL unless septic or there is systemic upset
What are the hallmarks of inflammation?
Color Dolor Tumor Rubor Function lasea
What risk factors predispose to osteomyelitis?
Open fractures Diabetes/ vascular insufficiency Haematogenous osteomyelitis Vertebral osteomyelitis Prosthetic joint infection Specific hosts and pathogens
When is osteomyelitis likely to occur?
Bone is highly resistant to infection and therefore, will only occur with necrosis +/- high inoculum
How long does an infection bone take to heal?
Debrided bone takes 6 weeks to be revascularised with soft tissue
How long should antibiotics be given for in osteomyelitis?
6 weeks
What bacterium is likely to affect prosthetic joints?
Staphylococcal coagulase negative - staphylococcal epidermidis
How are open fractures managed?
Aggressive debridement
Fixation
Soft tissue cover
What bacteria are likely to infect an open fracture?
Staphylococcus aureus and aerobic gram negative bacteria (pseudomonas, neisseria, e.coli, salmonella, kelbsiella, proteus, shigella)
What is the treatment for diabetic ulcers?
Surgical debridement and antimicrobial’s
Antibiotics CANNOT penetrate abscesses or necrotic tissue - these need surgical removal
What are the three markers you need to evaluate for the presence of osteomyelitis?
Chronic, indolent or deep ulcer
Positive probe-to-bone test
Elevated levels of inflammatory markers (CRP, PV)
What radiological investigations are best for osteomyelitis?
X-ray
Gold standard is MRI
What are appropriate cultures for osteomyelitis?
Per-cutaneous aspirate
Bone biopsy surgically
What is the definition of a mild diabetic foot ulcer?
2 or more: pus, erythema, pain, tender, warmth, in-duration
OR
Cellulitis <2cm confined to skin or subcutaneous
What is the treatment for a mild ulcer?
Flucloxacillin (oral)
What are the main bacterial causes for mild diabetic feet ulcers?
MSSA
MRSA
Streptococci
How long is treatment for feet ulcers?
7 days
10 days if severe
14 days IV if S.aureus bacteraemia
What are the main bacterial causes for moderate and severe diabetic feet ulcers?
MSSA MRSA Streptococci Enterobacteriacae Obligate anaerobes
How are moderate diabetic feet ulcers treated?
Flucloxacillin and metrondiazole (oral)
How are severe diabetic feet ulcers treated?
Flucloxacillin
Metrondiazole
Gentamicin or aztreonam (IV)
What is the alternative for penicillin allergic patients with a mild diabetic foot ulcer?
Doxycycline
Co-trimoxazole
What is the alternative for penicillin allergic patients with a moderate diabetic foot ulcer?
Doxyxycline and metrondiazole
What is the alternative for penicillin allergic patients with a severe diabetic foot ulcer?
Vancomycin
Gentamicin/ aztreonam
Metrondiazole
Who is susceptible to haematogenous osteomyelitis?
Prepubertal children
PWID
Central lines/ dialysis
Elderly
What is gaucher’s disease?
Lysosomal storage disorder that can mimic a bone crisis
Often affects tibia
What can vertebral osteomyelitis be associated with?
Epidural abscess
Psoas abscess
Who is susceptible to vertebral osteomyelitis?
PWID IV site infections GU infections STI Post operative
What are the clinical symptoms of osteomyelitis?
50% fever 90% insidious pain and tenderness 15% neurological signs 90% raised inflammatory markers 32% abnormal plain film NEED to do MRI
How is vertebral osteomyelitis treated?
Drain lare paravertebral abscesses
Antibiotics for 6 weeks
ONLY repeat MRI if: unexplained increase in inflammatory markers, increasing pain, new anatomical signs
What is Potts disease?
Skeletal TB
Less than half have pulmonary TB
What are risk factors for developing an infection in prosthetic joints?
RA
Diabetes
Malnutrition
Obesity
What unusual organisms are likely in PWIF haematogenous osteomyelitis?
Candidia = heroin Eikenella = those who lick needles before injection
What additional test should be done in those who present with TB?
HIV test
What is the mechanism of prosthetic joint infection?
Direct inoculation at time of surgery
Manipulation of joint at time of surgery
Seeding of a joint at a later time
What can PVL staph auerus cause?
Skin infections
Necrotising pneumonia
Bacteraemia
Septic arthritis
What will sessile bacteria form?
A biofilm
What are organisms that indicate a very bad infection?
Fungal is BAD
Mycobacteria is even WORSE
How is prosthetic joint osteomyelitis diagnosed?
Culture perioperative tissue
Blood cultures
CRP
Radiology
How is prosthetic joint osteomyelitis treated?
Remove prosthesis and cement
Therapy for 6 weeks
Re-implant device after aggressive antibiotic treatment
How is staphylococcus epidermidis treated?
Vancomycin IV
Where can septic arthritis originate from?
Direct invasion through a penetrating wound
Haematogenous spread
Spread from infectious focus (cellulitis abscess)
Spread from focus of osteomyelitis in adjacent bone
How is septic arthritis diagnosed?
Severe pain, red, hot, swollen
Joint fluid - microscopy, C&S
Blood culture if pyrexial
Exclude crystals
What viruses can cause viral arthritis?
Alphavirus
Hep B
Rubella virus
Parovirus B19
What is pyomisitis?
Bacterial skeletal muscle infection which results in pus filled abscesses
How is clostridium tetani classed?
Gram positive, strictly anaerobic spore forming bacillus
What is the incubation period of tetanus?
4 days to several weeks
What can tetanus infection cause?
Spastic paralysis Trismus Risus sardonicus Dysphagia Complete tetanic spasm
How is tetanus treated?
Surgical debridement
Antitoxin
Supportive measures
Booster vaccination - toxoid
What can cause myositis (inflammation of muscles)?
Viral - HIV, influenza, CMV, rabies, chikungunya
Protozoa
Fungal
Schistomsoma, taenia
