Microbiology Flashcards
Name four underlying risk factors for bone joint infection (BJI)?
- Implants
- Immunosuppressed
- Diabetes
- IVDU
Name three bacterium causing prosthetic-joint infection?
- CoNS, S. aureus
- Streptococcus spp.
- Propionibacterium acnes
Name two organisms causing septic arthritis?
S. aureus
Streptococci
Name three organisms causing post-traumatic infection?
- S.aureus
- Polymicrobial coliforms
- Pseudomonas
Name four organisms causing vertebral osteomyelitis?
- S.aureus
- Coliforms
- Streptococcus spp.
- Mycobacterium tuberculosis
Name 4 organisms causing diabetic foot infection?
- S.aureus
- Streptococcus spp.
- Coliforms, pseudomonas
- Anaerobes
What is the most common causative pathogen of osteomyelitis?
S. aureus
What bacterium should you consider in children with BJI?
Kingella in children
What are teh clinical presentations of acute BJIs?
Signs of infection - temperature, systemic sign, pain swelling redness over area and reduced motility of joint
What is the criteria for diagnosing systemic inflammatory response syndrome? (SIRS)
Two or more of:
- temperature >38 or 90
- RR > 20 or PaCO2 12000 or
What is the term for infection of joint space?
Septic arthritis
What are the three ways organisms are introduced in septic arthritis?
- Haematogenous spread
- Contiguous spread
- Direct inoculation
How to diagnose acute septic arthritis?
- Blood culture if pyrexial
- CRP, FBC etc
- Joint fluid aspirate
- Crystals white cells and gram stain
- Ultrasound scan
What is the emperic treatment for septic arthritis in children
Flucloxacillin and ceftriaxone for 2-4 weeks
What is the term for inflammation of bone and medullary cavity, usually in long bones or vertebrae?
Osteomyelitis
In acute osteomyelitis what will the two organisms likely be>
Staph aureus MSSA
Streptococci
In chronic osteomyelitis what might the organisms be?
M. tuberculosis, pseudomonas aeruginosa, salmonella, brucella, coliforms
What are the four methods of spread in osteomyelitis?
- Haematogenous
- Contiguous
- Peripheral vascular disease
- Prosthesis associated - prostehtic joint
What is the incubation for acute osteomyelitis?
Few days -
Why are infants more at risk of septic arthritis?
Due to vessels crossing metaphysis to epiphysis
In chronic osteomyelitis should you use antibiotics immediatly?
No - wait for specimens from culture
What is the treatment for osteomyelitits?
- Blood culture if pyrexial
- Bone biopsy
- Empiric high dose flucloxacillin 4-8 weeks
What are the four risk factors for infection in prosthetic joints?
- Rheumatoid arthritis
- Diabetes
- Malnutrition
- Obesity
What is the implant infection at 0-3 months?
Early postoperative
What is the implant infection at 3-24 months?
Delayed (low grade)
What is the implant infection at >24 months?
Late
In CoNs and PJI what is there a presence of?
Biofilm
What culture should be done in PJI diagnosis?
Tissue and bone
Give two treatments for PJI?
Removal of prosthesis and cement
Re-implantation of joint after antibiotic treatment
What is uncommon but an acute or severe infection of the subcutaneous soft tissues?
Necrotising fasciitis
What are the common areas of necrotising fasciitis?
Limbs, abdominal wall, perineal and groin area and post-operative wound
What are three clinical clues for necrotising faasciitis?
- Highly painful with signs of inflammation
- Spread through tissues rapidly
- Systemic toxiciy
Agony with no visible signs - pain disproportionate to superficial appearances?
Necrotising fasciitis
What is type I necrotising fasciitis
Anerobes plus multiple other bacteria “synergistic gangrene”
What is type II necrotising fasciitis?
Flesh-eating bacteria - group A streptococcus
What is the main treatment for necrotising fasciitis?
Surgical debridement
What antibiotics are used to treat strep pyogenes in necrotising fasciitis?
Penicillin + clindamycin
What class of antibiotics kills actively multiplying bacteria in exponential growth phase?
Penicillin
What antibiotic stops bacterial protein production and switches off bacterial toxin?
Clindamycin
Name three antibiotics used for synergistic necrotising fassciitis?
Pip-taz, clindamycin and gentamicin
Name the organism in Gas Gangrene?
Clostridium perfringens (part of normal bowel flora), gram positive strictly anaerobic rods
What is produced by clostridium perfringens in gas gangrene?
Spores
What is the pathogenesis of gas gangrene?
Spores germinate and accumulation of gas bubbles in tissues space gas gangrene crepitus occurs
What is the three step treatment for gas gangrene?
- Urgent debridement
- Antibiotics high dose - penecillin, metronidazole
- Hyperbaric oxygen
What disease is characterised by Clostridium tetani, gram positive stricly anaerobic rods and spores found in soil, garden and animal bites?
Tetanus
What does the neurotoxin cause in tetanus?
Spastic paralysis
What is the incubation for tetanus?
4 days to several weeks
What disease is lock jaw found in?
Tetanus
What are the treatment steps for tetanus?
- Surgical debridement
- Antitoxin
- Penicillin + metronidazole
- Booster vaccination toxoid
In BJI staph what is used instead of flucloxacillin if pen allaergic?
Vancomycin
In BJI what is clindamycin used for?
Antitoxin properties (PVL, group A strep), penetration into tissue
Name a few antibiotics used for coliforms in BJI?
Gentamicin
Cephalosporin like ceftriaxone
Sometimes ciprofloxacin oral
In infections of implanted devices what, produced by bacteria, allows microorganisms to proliferate in a hostile environment?
Biofilm - slime (protein + polysaccharide)
What is the route for early postoperative and delayed (late) implant infection?
Perioperative
What is hte route for late implant infection?
Haematogenous
Name three organisms in early postoperative implant infection?
Staph aureus
Streptococci
Enterococci
Name two organisms in delayed (late) implant infection?
Coagulase negative staphylococci
P.acnes
Name two organisms in the late implant infection stage?
S.aureus and E.coli
Bacteria in abscesses or biofilms are phenotypically resistnat to what>
Antibiotics
Name three antibiotics given for PJI gram positive bacteria?
Flucloxacillin
Vancomycin
Teicoplanin
Name four antibiotics given for PJI gram negative bacteria?
Clotrimazole
Amoxicillin
Ciprofloxacin
Ceftriaxone
What is the duration treatment for knee PJI?
6 months
What is the duration for hip PJI?
3 months
How to image the response of PJI?
MRI or CT