Flashcards in Infections and treatments Deck (94):
What are the most common microorganisms infecting prosthetic joints?
CoNS, staph aureus, strep spp. And propriobacterium acnes.
What are the most common microorganisms causing septic arthritis?
Staph aureus and streptococci
What are the most common microorganisms causing post traumatic infections?
Staph aureus, polymicrobial coliforms and pseudomonas.
What are the most common microorganisms causing vertebral osteomyelitis?
Staph aureus, coliforms, streptococcus spp. And mycobacterium tuberculosis.
What are the most common microorganism causing osteomyelitis?
What are the most common microorganisms causing diabetic foot infection?
Staph aureus, streptococcus spp. Coliforms, pseudomonas and anaerobes.
What antibiotics should we use for staphs or streps?
Flucloxacillin or vancomycin (used if penicillin allergic).
What properties does clindamycin have?
It has antitoxin properties (PVL, group A strep) it also can penetrate deep into tissues.
What antibiotics are used for diptheroids, CoNS or MRSA?
Flucloxacillin or vancomycin.
What antibiotics are used for coliforms?
Gentamicin, sometimes a cephalosporin like ceftriaxone and sometimes oral ciprofloxacin.
What are the three most likely causative organisms of bone and joint infections?
Staph aureus (rarely MRSA or PVL), streptococci like group A and coliforms.
What serious side effects can gentamicin have?
It is ototoxic and nephrotoxic.
What does CoNS stand for?
Coagulase negative staphylococci. Also called CNS on occasion.
What are the most likely causative organisms of PJI's?
CoNS, proprionobacteria and pseudomonas aeruginosa.
What are the uncommon but important to remember causative organisms of BJI's?
Kingella in children under 5 and pseudomonas aeruginosa.
What might children with BJI's present with?
Listlessness, crankiness and not feeding/playing.
What might adults with bone and joint infections present with?
The cardinal signs of inflammation.
What does SIRS stand for?
Systemic inflammatory response syndrome.
What four criteria do we use to diagnose SIRS? (Patients must have two or more)
Temp over 38 or under 36
HR over 90
Resp rate over 20 or PaCO2 under 4.3
WBC over 12000 or under 4000
How might organisms be introduced to the joint space to cause septic arthritis?
By haematogenous spread
Or direct inoculation
What are some primary causes of haematogenous spread of infection and what should we do if we suspect blood borne infection?
An STI e.g. Gonorrhoea or an infection from being an IVDU.
If we think it's blood borne we should look for another focus of infection.
What does contiguous spread mean in BJI's?
E.g. Into a joint space from an infected bone beside it.
What kind of staph aureus mostly causes septic arthritis?
What two organisms can rarely cause septic arthritis?
Haemophillus influenzae and neisseria
What tests should we do for septic arthritis?
Blood cultures if pyrexial.
CRP and plasma viscosity (very useful)
FBC, U and E, ESR etc.
Culture of joint aspirate
Crystals, WCC and gram stain.
Ultrasound, plain Xray MRI, CT, technetium scan.
How useful is CRP when looking for infection?
It may not always indicate infection as in chronic infections it may not be raised. It can be influenced by underlying disease of surgery and so may not be indicative of infection. It is however very good for monitoring the course of an infection in the absence of surgery etc.
What is empiric treatment for an infection?
Done before culture is taken, it covers the most likely organisms.
What empiric treatment is given for septic arthritis?
High dose IV flucloxacillin.
Ceftriaxone for under 5s (to cover Kingella and H influenzae).
How should we manage septic arthritis other than the empiric antibiotic treatment?
Look for source of organisms and adjust antibiotics when cultures are taken.
How long should septic arthritis treatment last?
What are the two most likely causative organisms of acute osteomyelitis in adults?
MSSA or streptococci
What can be an additional causative organism of acute osteomyelitis in children?
What organisms can cause chronic osteomyelitis?
Mycobacterium tuberculosis, pseudomonas aeruginosa, salmonella, brucellosis and coliforms.
In what ways can osteomyelitis be spread?
Haematogenous, contiguous, from PVD ulcer or form a prosthesis.
It can commonly be post traumatic from direct inoculation.
What kind of spread is most likely in acute osteomyelitis?
Haematogenous especially the femur/tibia
What special features of the shoulder, ankle, hip and elbow joints are important in acute osteomyelitis?
The metaphysis are intracapsular and so infection may extend into the joint space.
What are infants at risk of from acute osteomyelitis and why?
Septic arthritis as vessels cross the metaphysis to the epiphysis.
What can a delay in treatment of acute osteomyelitis cause?
It to turn chronic and gives a higher risk of abscess, permanent damage or septicaemia etc.
What should be the treatment strategy for osteomyelitis?
Don't give antibiotic treatment if SIRS is absent. We can wait for ortho samples and go straight to targeted.
What tests should we get for osteomyelitis?
Blood culture if pyrexial.
Bone biopsy/washout for microscopy and culture.
What empiric treatment should we give for acute osteomyelitis? How long for?
High dose flucloxacillin for 4-8 weeks.
What is an involucrum?
Sometimes seen in osteomyelitis. Periosteum is stripped off by pus within the bone and new bone then grows from the periosteum.
What organisms normally cause type 1 necrotising fasciitis?
Anaerobes plus multiple other bacteria causing a synergistic gangrene.
What organisms normally cause type 2 necrotising fasciitis?
Group A strep (flesh eating) either alone or in combination with staph aureus.
What tests should we do for necrotising fasciitis?
Swabs and tissue biopsy for gram stain and culture.
CRP, U and E etc.
What antibiotics should we give for necrotising fasciitis caused by strep pyogenes? Why?
Penicillin and clindamycin.
Pen kills actively multiplying bacteria in the exponential growth phase.
Clindamycin stops bacterial protein production and so switches off its toxin.
What treatment should we give for synergistic necrotising fasciitis?
Pip-taz, clindamycin and gent.
What organism causes gas gangrene?
What type of bacteria is clostridium perfringens and where is it normally found?
Gram positive strictly anaerobes rods commonly found in the bowel.
What can predispose to gas gangrene?
Dead tissue and anaerobic conditions.
What is the pathophysiology of gas gangrene?
Spores of clostridium perfringens can get into tissues. The spores germinate and accumulation of gas bubbles in tissues cause crepitus.
What is the treatment of gas gangrene?
Urgent debridement as can get antibiotics to dead tissues.
High dose antibiotics: penicillin or metronidazole or both.
Hyperbaric oxygen may be needed.
What kind of organism is clostridium tetani?
Gram positive strictly anaerobic rods.
Where is clostridium tetani found?
Soil, gardens and animal bites.
What kind of toxin does clostridium tetani have and what does it do?
A neurotoxin which binds to inhibitory neurones preventing release of neurotransmitter causing spastic paralysis
Is clostridium tetani invasive?
No all symptoms are caused by toxin release.
What is the incubation period of clostridium tetani?
4 days to several weeks.
What does tetanus cause?
Lock jaw and muscle spasms.
How is tetanus managed?
Surgical debridement, antitoxin, supportive measures and antibiotics (penicillin /metronidazole)
A toxoid booster vaccine should also be given.
What are the risk factors for PJI's?
RA, diabetes, malnutrition and obesity.
What tests should we do for PJI's?
CRP, joint aspiration, technetium 99 and Xray.
What are the three types of implant infection?
Early postoperative, delayed (low grade) and late.
How are early postoperative and delayed implant infections contracted?
How is a late implant infection contracted?
By haematogenous spread.
What are the signs of early postoperative implant infection?
Fever, effusion, warmth and drainage.
What are the causative organisms of early postoperative implant infection?
Staph aureus, streptococci and enterococci
What are the signs of delayed implant infection?
Persians pain and device loosening.
What are the causative organisms of delayed implant infection?
Coagulase negative staphylococci and p.acnes.
What are the causative organisms of late implant infection?
Staph aureus and E. coli.
What are the signs of late implant infection?
Can be the same as the acute or subacute infections.
What features of bacteria in abscesses or biofilms make treatment difficult?
They gain acquired resistance to antibiotics.
Where are CoNS found?
As part of normal skin flora.
What happens when CoNS come into contact with a prosthetic joint?
They form a biofilm which is protected from the immune system and antibiotics.
What do biofilms consist of?
Bacteria coated in a slimy mixture of proteins and polysaccharides.
What features of biofilms allow bacteria to proliferate on the hostile environment of an implant?
It lowers the pH, reduces the oxygen and provides nuclei can acids and other cell products.
What is the management of PJI?
Removal of prosthesis and cement. Definitely remove dead tissue and pus.
Antibiotic treatment for 6 weeks after and reimplantation of joint.
What different surgeries do we do for prosthetic joint infections?
DAIR - retention of prosthesis.
One stage or two stage removal.
When do we give antibiotics for two stage prosthesis removals?
Don't give any for healthy patients before the first stage as they cannot penetrate the biofilm. Usually give for 6 weeks before the second stage.
What kind of prosthetic joint revision is not commonly done?
What antibiotics are given for gram positive PJIs?
Flucloxacillin or vancomycin then on to teicoplanin.
What antibiotics are given for gram negative PJIs?
Cotrimoxazole, amoxicillin, ciprofloxacin or Ceftriaxone.
What is the duration of antibiotic treatment for a DAIR procedure?
4 + 8 weeks.
What is the duration of antibiotic treatment for a One stage implant revision procedure?
4 + 8 weeks
What is the duration of antibiotic treatment for a two stage implant revision procedure?
6 + 6 weeks
What is the duration of antibiotic treatment for a hip implant revision procedure?
What is the duration of antibiotic treatment for a Knee implant revision procedure?
How long should treatment be continued after resolution of clinical sign of PJI?
How long do we need to wait before we can be sure they a PJI has been cured?
What is the tayside protocol for PJI's?
No antibiotic preoperatively while infected joint still in.
A minimum of three bone/pus samples must be taken.
Minimum 6 weeks antibiotic treatment before the next clean surgery.
What prophylaxis treatments are given to avoid PJI's?
24 hours of antibiotics starting with induction. Also antibiotics are added to the cement.
Patients are also screened and recolonised of MRSA.
What antibiotics are usually given as prosthetic joint infection prophylaxis and for what time scale?
Co-amoxiclav perioperatively and 2 post op doses.
If there is a penicillin allergy, give co-trimoxazole.
Prophylactic Antibiotics should be given under an hour before surgery and not continued after 24 hours.
Where can we catch brucella from?
Unpasteurised cow or goats milk.
Why is the timing of preop prophylactic antibiotics for PJI so important?
They have to be in the tissues at the time of the surgery in order to work. They also must be timed properly with the tourniquet to ensure they reach tissues.