Infection of soft tissue and MSS

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  1. 4 normal defense mechanism of the skin
    • normal skin flora
    • skin integrity
    • rapid cell turnover
    • antimicrobial effect of the lipid layer (pH 5.5)
  2. 4 most common resident skin flora
    • SCMP
    • Staphylococcus
    • Corynebacterium
    • Micrococcus
    • Propionibacterium acnes
  3. 4 ways of pathogenesis of skin and soft tissue infections
    • breach of normal skin integrity
    • alteration of normal skin flora
    • change in local environment of the tissues
    • introduction of exogenous/endogenous microbial flora
  4. 3 microorganisms causing Dermatophytosis
    • MET
    • microsporum spp.
    • epidermophyton floccosum
    • trichophyton spp.
  5. Causative agent of Dermatomycosis
    non-dermophytic fungi e.g. candida albicans
  6. typical presentation of dernatophytosis
  7. how to make diagnosis of dermatophytosis?
    • KOH wet mount
    • fungal culture
  8. treatment for dermatophytosis
    topical/ systemic antifungal agent
  9. what is dermatophytosis?
    superficial infection of keratinized tissue by dermatophytes
  10. what is Paronychia?
    superficial infection of the nail fold
  11. what are causative agents of paronychia?
    • acute: S. aureus
    • chronic: Candida spp. esp. Candida albicans
  12. what is Impetigo?
    superficial intra-epidermal unilocular veicopustule
  13. 2 common pathogens leading to impetigo
    • Streptococcus pyogenes
    • Staphylococcus aureus
  14. Impetigo most common in which age group?
  15. Epidemiology of impetigo
    highly communicable
  16. what are the presentations of impetigo?
    • vesicles -> pustule -> golden-yellow crust in exposed areas e.g. forearm, face
    • heals without scarring
  17. Laboratory diagnosis of impetigo
    culture of exudate beneath crust
  18. what is folliculitis?
    abscess formation around hair follicles
  19. what is the most common causative agent of folliculitis?
    S. aureus
  20. what is furnacles?
    subcutaneous abscess
  21. what is cellulitis?
    acute spreading infection of the skin involving the subcutaneous tissues
  22. what are the causative agents of cellulitis?
    • Streptococcus pyogenes
    • Staphylococcus aureus
    • Vibrionaceae
    • Enterobacteriaceae
  23. Predisposing factors of cellulitis
    • trauma
    • underlying skin lesions
  24. What is the clinical presentation of cellulitis?
    • local signs of inflammation
    • ill-defined margin of inflammation
    • local abscess
    • fever
    • chills 
    • bacteraemia
  25. how to make diagnosis of cellulitis?
    clinical diagnosis
  26. What is erysipeals?
    superficial, dermarcated infection involving lymphatics, epidermis
  27. What causes erysipeals?
    group A streptococcus
  28. who is more prone to erysipeals?
    e.g. DM patients
  29. what are the common sites of erysipeals?
    • face (swollen regions with distinct borders)
    • lower limb
  30. what are the clinical presentations of erysipeals?
    • painful red lesions with distinct border spreading rapidly
    • marked subepidermal oedema with heavy infiltration of PMNs
  31. Treatment of pyoderma
    beta lactam antibiotics
  32. treatment of cellulitis
    beta lactum antibiotics
  33. treatment of erysipeals
    beta lactam antibiotics
  34. treatment for MSSA
    • cloxacillin
    • beta-lactam-beta-lactamase inhibitor
  35. treatment of MRSA
    • vancomycin
    • non-beta-lactam antibiotics
  36. treatment for beta haemolytic antiboitics
  37. what will increase the risk of HA-MRSA infection?
    • use of antibiotics
    • frequent hospitalisation
  38. Clinical presentations of CA-MRSA infection
    • soft tissue abscess e.g. furuncles
    • fulminant and rapidly fatal pneumonia (necrotising pneumonia)
  39. treatment for CA-MRSA
    • resistant to beta-lactam antibiotics
    • susceptible to other agents like clindamycin
  40. Characteristics of CA-MRSA
    • different antibiogram from HA-MRSA
    • special genetic elements
    • Panton-Valentine leukocidin
  41. 3 Features of necrotising soft tissue infections
    • multiple tissue levels involvement
    • thromobosis of BV perforating hte dascial envelope
    • extension of necrosis under the skin
  42. Aetiology of Type I necrotizing fasciitis
    anaerobes e.g. bacteriodes and clostridium + facultative anaerobes e.g. streptococci, enterobacteriaceae
  43. predisposing factor of Type I necrotising fasciitis
    after intra-abdominal or pelvic surgery before the days of peri-operative antibiotic prophylaxis
  44. Aetiology of type II necrotising fasciitis
    • Streptococcus pyogenes
    • Staphylococcus aureus may be involved
  45. Aetiology of type III necrotising fasciitis
    vibrio spp. esp. vibrio vulnificus
  46. predisposing factor of Type III necrotising fasciitis
    • exposure to water
    • consumption of seafood containing the pathogens
  47. Clinical presentation of Necrotising fasciitis
    • fever
    • pain
    • oedema
    • skin become cyanotic and finally dusky and black (full thickness necrosis of skin)
    • septic shock
  48. appearance of lesion
    • tender esp. at the spreading edge
    • central part become anasthetic
  49. Management of necrotising fasciitis
    • surgical emergency
    • supportive treatment for sepsis
    • early and aggresive surgical debridement
    • antibiotics
  50. Microbiology of Clostridial myonecrosis (gas gangrene)
    • Clostriduim perfringens (85-90%)
    • other clostridium spp.
    • can be mixed with other facultative anaerobes
  51. Pathogenesis of Gas gangrene
    muscle injury and contamination with soil or other foreign material containing spores of Clostridium perfringenes -> coagulative necrosis of muscle fibers
  52. 4 Clinical features of gas gangrene
    • local tense oedema
    • serosanguineous discharge
    • foul odor of wound
    • crepitus
  53. Lab diagnosis of gas gangrene
    • Gram smear of wound discharge (numerous bacteria but few leukocytes)
    • aerobic and anaerobic culture
  54. Difference between surgical wound and surgical site
    • surgical wound: skin incision
    • surgical site: organ space deep to the skin and soft tissue e.g. peritoneum and bone
  55. 4 indications of wound infection
    • pus from the incision
    • pain, tenderness, localized swelling, redness, dehiscence of wound and sometimes with fever
    • organisms isolated from an aseptically obtained culture of tissue or fluid from the wound
    • Gram smear of the soft tissue/ fluid/ swab may reveal numerous leukocytes and bacteria
  56. 4 wound classes
    • clean 
    • clean contaminated
    • contaminated
    • dirty
  57. Aetiology of surgical wound infection
    depending on the type of operation
  58. what is Osteomyelitis?
    an infectious process involving the various components of bone, i.e. periosteoum, medullary cavity and cortical bone
  59. 3 types of osteomyelitis
    • acute osteomyelitis 
    • chronic osteomyelitis
    • prosthesis-related infection
  60. route of infection of acute osteomyelitis
    • haematogenous osteomyelitis (monomicrobial)
    • contiguous focus osteomyelitis (polymicrobial)
  61. route of infection of chronic osteomyelitis
    untreated or inadequately treated acute osteomyelitis
  62. route of infection of prosthesis-related infection
    • pathogens are usually introduced during operation or from post-operative wound infection
    • haematogenous spread
  63. pathology of osteomyelitis
    • acute inflammation -> obliteration of vascular channels -> ischaemia and necrosis
    • subperiosteal extension of infection -> lifting of periosteum away from bone -> bone formation
    • ischaemic segments of bone separated to form the sequestrum
  64. Causative agent of acute haematogenous osteomyelitis in infants
    • S. aureus
    • S. agalactiae
    • E. coli
  65. Causative agent of acute haematogenous osteomyelitis in children > 1 y.o.
    • S. aureus
    • S. pyogenes
    • Haemophilus influenzae (uncommon after 4 y.o.)
  66. Causative agent of acute haematogenous osteomyelitis in adults
    S. aureus
  67. route of infection of vertebral osteomyelitis
  68. Involvement of vertebral osteomyelitis
    • usu 2 adjacent  IV disc
    • as segmental arteries supplying vertebrae and the IV disk
  69. 4 Predisposing factors of contiguous focus osteomyelitis
    • trauma
    • surgical operations of bone
    • open fractures 
    • chronic soft tissue infections
  70. Pathogenesis of contiguous focus osteomyelitis
    vascular insufficiency
  71. Causative agent of contiguous focus osteomyelitis
    • Polymicrobial
    • S. aureus
    • Gram -ve bacilli
    • strep
    • enterococci
    • anaerobes
  72. Commonest causative agent of skeletal mycobacterial infection
    Mycobacterium tuberculosis
  73. route of infection of skeletal mycobacterial infection
    • haematogenous spread during primary infection
    • contiguous lymphadenitis
  74. Pathological changes of chronic osteomyelitis
    • a nidus of infected, ishaemic, dead bone (sequestrum)
    • local infection -> local bone loss, persistent drainage, local abscess or adjacent soft tissue inflammation, sinus tract formation
  75. Clinical features of acute osteomyelitis
    • fever
    • chills 
    • leukocytosis
    • pain
    • local swelling
    • (signs may be non-specific/ minimal)
  76. Clinical features of chronic osteomyelitis
    • chronic pain and drainage
    • low grade fever
    • (could be mild)
  77. clinical diagnosis of osteomyelitis
    • Radiological: Plain X-ray (change lags at least 2 weeks), CT, MRI
    • Radionuclide imaging (bone scan)
  78. Microbiological diagnosis of osteomyelitis
    • blood culture
    • operative biopsy of bone lesion for culture
    • (in case of chronic osteomyelitis, culture of sinus tract is not reliable for predicting the organisms causing osteomyelitis)
  79. Treatment for osteomyelitis
    • prolonged course of treatment
    • surgical debridement (removal of dead bone essential in chronic osteomyelitis)
  80. route of infection of infective arthritis
    • haematogenous seeding
    • direct inoculation
  81. pathology of infective arthritis
    • synovium is highly vascular and lacks a basement membrane -> susceptible to bacterial seeding
    • intra-articular inflammation -> destruction of articular cartilage
  82. Clinical features of infective arthritis
    • pain and decreased ROM
    • fever, swollen joint, leukocytosis
    • usu. large joints but all joints will be affected
  83. infective causes of polyarthritis
    • virus
    • Neisseria gonorrhoeae
  84. Causative agents in acute infective arthritis in infants <1 month
    • S. agalactiae
    • S. aureus
    • aerobic Gram -ve bacilli e.g. E. Coli
  85. Causative agents in acute infective arthritis in children <2 y.o.
    H. influenzae B
  86. Causative agents in acute infective arthritis in children >2 y.o. and adults
    S. aureus
  87. Causative agents in acute infective arthritis in young sexually active adults
    Neisseria gonorrhoeae: part of gonococcal infection and usually polyarticular
  88. Causative agents in acute infective arthritis in IV drug addicts
    • S. aureus
    • Pseudomonas aeruginosa
  89. Diagnosis of infective arthritis
    • blood culture
    • diagnostic synovial fluid aspirate: leukocyte count, crytals, Gram stain, culture
    • synovial biopsy
  90. treatment of infective arthritis
    • antibiotics
    • surgical drainage
Card Set:
Infection of soft tissue and MSS
2013-11-09 10:37:14
MSS mic bio

MSS mic bio
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