Microbiology Flashcards
What are the most likely pathogens responsible for a bone and joint infection?
Staph aureus
Strep A
Coliforms
What pathogens may be responsible if it is a prosthetic joint infection?
Diphtheroids
Coag neg Staph (CoNS)
How would an acute bone and joint infection present?
Pain, swelling, redness
Reduced mobility
Temperature
What is needed to diagnose Systemic Inflammatory Response Syndrome (SIRS)?
TWO OR MORE OF: Temperature >38 HR >90 RR> 20 WBC >12,000
What is septic arthritis?
An infection of the joint space
What bacteria causes septic arthritis?
MSSA
What investigations are needed if septic arthritis is suspected?
Bloods
Joint fluid aspirate
USS
Plain xray
What is the empirical therapy for septic arthritis?
Flucloxacillin
24-48 hours for lab to return sensitivities.
What antibiotic should be added if pt is under 5 for septic arthritis?
Ceftriaxone
for H flu and Kingella
What is osteomyelitis?
Inflammation of bone or medullary cavity
Where does osteomyelitis usually affect?
Long bones or vertebrae
What bacteria causes acute osteomyelitis?
MSSA
Strep
What bacteria causes chronic osteomyelitis?
M. tuberculosis, Pseudomonas, salmonella, coliforms
When is haematogenous spread more likely?
Acutely.
If osteomyelitis spreads to the joint what is it called?
Septic arthritis
Who is at higher risk of developing septic arthritis from osteomyelitis?
Infants
more vessels cross the metaphysis to the epiphysis
What antibiotics should be given for chronic osteomyelitis?
Abx should be delayed until cultures are returned.
No immediate danger
What abx are given for acute osteomyeltiis?
Flucloxacillin empirically. Tx should be modified after cultures.
What are the risk factors for developing an infection in a prosthetic joint?
Diabetes
Malnutrition
Obesity
Rheumatoid arthritis
What are the 3 types of implant infection?
Early postoperative, delayed and late.
Describe the time scale, causes and signs of early postoperative infection.
0-3 months.
Staph aureus, Strep
fever, warmth
True or False
Coagulase negative staphylococci are skin commensals
True
Why is it difficult to diagnose a prosthetic joint infection?
Caused by common contaminants
Cultures are rarely positive
What is the treatment for PJI?
removal of prosthesis and reimplantation after abx tx.
What is necrotising fasciitis?
Acute and severe infection of the subcutaneous soft tissues
Where is most commonly affected by necrotising fasciitis?
Limbs, abdominal wall, groin area, post operative wound.
What causes necrotising fasciitis?
Anaerobes.
Group A strep.
How is necrotising fasciitis diagnosed?
Pain is disproportionate to superficial appearances.
Take swabs and tissues biopsy for culture.
What is the treatment for necrotising fasciitis?
Surgical debridement
Penicillin and clindamycin
True or False
There is no need for infection control with necrotising fasciitis.
False.
Contact precautions should be taken as well as a risk assessment for droplet precautions.
How are clostridium perfringens classified?
Gram positive (purple)
Strictly anaerobes
Rods
What is gas gangrene?
Spores of C. perfringens germinate into tissue and accumulate into gas bubbles.
What is the treatment for gas gangrene?
Urgent debridement.
penicillin +/- metronizadole
Hyperbaric oxygen
What organism causes tetanus?
Clostridium tetani
How is clostridium tetani classified?
Gram positive
Strictly anaerobic
Rods
What are the symptoms of tetanus?
Spastic paralysis
Lock jaw due to muscle spasm
Stiffness of neck
What is the incubation period for tetanus?
4 days- several weeks
What is the treatment for tetanus?
Booster vaccination
Penicillin/ metronizadole
What is the antibiotic of choice to treat staph and strep?
Flucloxacillin.
Vancomycin
What antibiotic could be used for coliforms?
Gentamicin
How many samples should be taken if PJI is suspected?
3.
To exclude contaminated bacteria from the culture.
How long is the abx treatment for a hip PJI?
3 months
How long is the abx treatment for a knee PJI?
6 months
When should the first prophylactic abx be given?
Within 60 minutes of surgery
What is the most common bacteria which contaminates in trauma?
Staph aureus
What kind of patients do PVL commonly affect?
Young people with osteo infection.
What antibiotic would you use if you suspected PVL?
Clindamycin
How do CoNS affect prosthesis?
They are charged and stick to the plastic of the prosthesis and create a layer of biofilm which makes them harder to treat.
What bacteria are the most common found in osteomyelitis in children?
Pseudomonas
Kingella
True or False
BJIs never cause septic shock
False.
What do microbiology do with a joint fluid aspirate?
Look for crystals for (pseudo)gout
Check for white cells
Gram stain
What is the classic link with brucella infection?
Goats.
Especially drinking goats unpasteurised milk.
What are the downsides of gentamicin?
Nephrotoxic.
Need permission to use longer than 3 days
What kind of antibiotic is gentamicin?
Aminoglycoside
What is a DAIR procedure?
Debridement and implant retention
What blood tests need to be done if infection suspected?
CRP
PV
WCC if acute
When is acute osteomyelitis most likely to occur?
Post-trauma
Open wound
If an osteomyelitic patient has pus what is the right thing to do?
Drain the abscess
What antibiotics can be used for cellulitis?
Flucloxacillin to cover staph and strep
