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Gram + Cocci (Staphylococci (S. Aureus (Major clinical manifestations…

- - - - Leading pathogen in multiple types of infx
        
        bacteremia
        
        endocarditis
        
        osteoarticular infx
        
        SSTI
        
        pneumonia
        
        implanted hardware
      - Antibiotic resistance complicates therapy
    - - MRSA developed shortly after intro of methicillin, though usually in the hospital
      - epidemic of CA-MRSA
      - Bacteremia increased as medical intervention increased (central line, ICU care, transplants etc.)
    - - Toxic Shock Syndrome
        
        fever, hypotension, rash
        
        due to super antigen that results in polyclonal T cell activation
      - Food poisoning
      - Scalded skin syndrome
    - - SSTI
        
        Benign
        
        impetigo, uncomplicated abscess
        
        Severe
        
        necrotizing fasciitis, pyomyositis
      - Bacteremia
        
        Common source
        
        vascular catheter-related infx, skin infx, pulmonary infx
        
        Complicated vs uncomplicated
        
        Complicated
        
        poor outcomes, recurrence
        
        uncompleted SAB
        
        no endocarditis
        
        No implanted prosthesis
        
        Follow up blood cultures 2-4 days after initial set are neg
        
        Patient defervesces within 72 hrs of initiation of effective antibiotic therapy
        
        No evidence of metastatic sites of infx
      - Infective Endocarditis
        
        higher mortality
        
        associated with IV drug use, healthcare contact, more acute presentation, persistent bacteremia, IV device, strokes and DM
      - Bone and joint infx
        
        osteomyelitis
        
        Long bones in children, vertebral infx in adults w bacteremia, associated with diabetic foot ulcers
        
        native joint septic arthritis
        
        w bacteremia
        
        Prosthetic joint infx
        
        first month after implantation
      - Pulmonary Infx
        
        Ventilator-associated pneumonia
        
        Post-viral pneumonia
        
        CA-MRSA necrotizing pneumonia
        
        young, otherwise healthy patients, high mortality rate
        
        Empyema
        
        infected fluid outside lung, inside cavity
    - - Gram stain (+ve), grows readily in standard culture medium, PCR used increasingly for RADT and identification of antibiotic resistance
    - - Depends on site
      - Establish extent of infection, Drain pus, remove infected hardware if possible
    - - antibiotic stewardship, remove or avoid unnecessary prosthetic material, hand hygience
      - Contact precaution for MRSA
  - - - Vancomycin for empiric treatment while waiting for results and for MR-CoNS, nafcillin or oxacillin if MS-CoNS
- - - - Complete hemolysis
      - S. Pyogenes
        
        Group A
        
        Bacitracin sensitive (Antibiotic)
      - S. Agalactiae
        
        Group B
        
        Bacitracin resistant
    - - Partial Hemolysis
      - Greenish halo -> Fe metabolites from Hb
      - S. Pneumoniae
        
        Optochin (antibiotic) sensitive
        
        Capsule
        
        Quellung (+) (antibody soln, appear to swell)
      - Viridans
        
        Optochin resistant
        
        no capsule
        Quellung (-)
    - - No hemolysis
      - Enterococcus
        
        Bile esculin +ve
        
        6.5% NaCl growth
      - Non-Enterococcus
        
        Group D
        
        Bile esculin +ve
        
        6.5% NaCl no growth
  - - - Evasion
        
        Hyaluronate
        
        Protective Layer
        
        M-Protein
        
        anti-opsonization
        
        inhibits complement
        
        Auto-antibodies (facilitate auto immune response post infx)
      - Invasion
        
        Hyaluronidase
        
        break down hyaluronic acid in CT -> enter tissue and blood stream
        
        Streptokinase
        
        activates plasmin, dissolve blood clots to release additional bacteria
      - Toxins
        
        Streptolusin O (B-hemolysis)
        
        O2 labile (inactivated by O2)
        
        antigenic
        
        ASO titer to check for infx
        
        Strep pyrogenic exotoxins
        
        Erythrogenic toxin
        
        Scarlet fever
        
        Superantigens
        
        stimulate T cell nonspecifically -> Toxic shock syndrome (overwhelming inflammatory response->circulatory collapse)
    - - Strep throat
        
        Throat pain, fever, swollen lymph nodes (infx of tonsils and posterior pharynx)
      - SSTI
        
        Erysipelas, cellulitis, necrotizing fasciitis (not specific to strep)
    - - Scarlet fever
        
        head->trunks->extremeties sandpaper rash that desquamates
        
        Circumoral pallor, strawberry tongue
      - Strep toxic shock syndrome (STSS)
        
        GAS infx+hypotension+end organ dmg
        
        Skin infx
        
        Blood cultures positive (bacteremia)
        
        Erythematous rash
        
        50% mortality
    - - multiorgan inflammatory syndrome following untreated GAS pharyngitis (2-4 weeks after)
      - Autoimmune
      - 5-15y/o most affected
      - Heart, brain, skin, joints
      - Findings
        
        Subcutaneous nodules, joint pain
        
        Aschoff bodies (myocardial tissue)
        
        Erythema Marginatum (non tender, ~5%)
    - - Not reduced by antibiotic therapy
      - Follows skin or pharyngeal infx
      - Immune complex disease
      - Blood + protein in urine (tea coloured)
    - - Bacterial culture of pharynx
        
        24-48 hrs
        
        90% sensitive, >95% specific
      - Strep Rapid Antigen Detection Test (RADT)
        
        80% sensitive, 90% specific
        
        Bedside test
      - Modified Centor criteria
        
        add 1 point
        
        Temp>38C
        
        Tender or swollen anterior cervical nodes
        
        Tonsillar swelling or exudates
        
        Lack of cough
        
        3-14 y/o
        
        Subt 1 points
        
        45 y/o
        
        results
        
        0-1
        
        No further test or treatment
        
        2
        
        use RADT, treat only if +ve
        
        3-4
        
        testing preferred