153.1 🎓 醫孞生版

153.1.0.1 📌 䞀頁重點

  • Lancefield 分矀 (A, B, C, D, F, G) + viridans group (沒 Lancefield)
  • GAS (Group A, S. pyogenes): 咜喉炎、scarlet fever、impetigo、erysipelas、necrotizing fasciitis、TSS、post-strep glomerulonephritis (PSGN)、rheumatic fever (ARF)
  • GBS (Group B, S. agalactiae): 新生兒敗血症 + 腊膜炎 #1、產婊 chorio、糖尿病人 SSTI
  • Viridans group (S. mitis, mutans, sanguinis 等): subacute IE (damaged valves)、韋霿
  • S. anginosus group (S. anginosus/intermedius/constellatus): abscess (brain, liver, abdominal)
  • S. gallolyticus (bovis): IE + 倧腞癌關聯 — 必做 colonoscopy
  • PCN 仍 universally sensitive for GAS, GBS (99%+)

153.1.0.2 1⃣ 现菌孞

  • Gram + cocci in chains (vs Staph clusters)
  • Catalase - (vs Staph +)
  • Bile esculin, NaCl tolerance, Lancefield serogrouping
  • α (viridans) / β (GAS, GBS) / γ (no) hemolysis on blood agar
153.1.0.2.1 Lancefield Groups
Group Species 臚床
A S. pyogenes 咜喉、SSTI、TSS、necrotizing fasciitis
B S. agalactiae 新生兒、產婊、糖尿病
C/G S. dysgalactiae 等 SSTI, pharyngitis (動物 reservoir)
D Enterococcus, S. bovis UTI, IE; S. bovis + 倧腞癌
F anginosus group abscess
viridans S. mitis, mutans, etc. subacute IE, 韋霿

153.1.0.3 2⃣ Group A Strep (GAS, S. pyogenes)

153.1.0.3.1 臎病因子
  • M protein: anti-phagocytic, > 200 types
  • Hyaluronic acid capsule: anti-phagocytic
  • Streptolysin O & S: cytolysin
  • SpeA, SpeB, SpeC: pyrogenic exotoxins (TSS, scarlet fever)
  • Streptokinase, hyaluronidase, DNase: tissue invasion (“flesh-eating”)
153.1.0.3.2 A. Pharyngitis (“Strep throat”)
  • 5-15 yo, winter/spring
  • Sx: sore throat, fever, anterior cervical LAP, exudates
  • Centor criteria (3-4 → test, 0-1 → skip)
  • Rapid antigen test (RADT) → if + treat, if - → throat cx (esp child)
  • Treatment: PCN VK 10d, amox 10d, benzathine PCN G IM × 1
  • Allergy: cephalexin, azithromycin
  • 目的: 預防 ARF, 瞮短 sx, 枛傳染 (NOT 預防 PSGN)
153.1.0.3.3 B. Scarlet Fever
  • Pharyngitis + 玅疹 + 草莓舌
  • SpeA toxin
153.1.0.3.4 C. Impetigo / Erysipelas / Cellulitis
  • Impetigo: è¡šçš® (honey-crust), 兒童; GAS or S. aureus
  • Erysipelas: 衚皮深局 + lymph, sharp border, 兞型臉/小腿
  • Cellulitis: 真皮深局, 玅腫熱痛; PCN/cefazolin/cephalexin
153.1.0.3.5 D. Necrotizing Fasciitis (Type II)
  • 急 + 臎呜 + 痛 disproportionate to skin
  • Crepitus, dusky skin, bullae, hemorrhagic
  • Treatment: emergent surgical debridement + Vanc + Pip-tazo + Clindamycin
    • Clindamycin: 抑制 toxin (Eagle effect, ribosome inhibitor)
  • IVIG (3 days): some evidence in toxin-mediated cases
  • Type I = polymicrobial, Type II = GAS (sometimes + S. aureus)
153.1.0.3.6 E. Streptococcal TSS
  • GAS bacteremia + multi-organ failure + 玅斑
  • 死亡 30-70%
  • IVIG + clinda + PCN
153.1.0.3.7 F. Non-Suppurative Sequelae
153.1.0.3.7.1 Acute Rheumatic Fever (ARF)
  • 2-4 weeks 埌 pharyngitis (NOT impetigo)
  • Jones criteria (2015 updated):
    • Major: carditis (echo), polyarthritis, chorea, erythema marginatum, subcutaneous nodules
    • Minor: fever, ↑ ESR/CRP, arthralgia, prolonged PR
      • Evidence of recent GAS (ASO, culture, RADT)
    • Dx: 2 major or 1 major + 2 minor + GAS evidence
  • Mitral valve > Aortic (mitral stenosis 長期)
  • 2° prophylaxis: PCN G 1.2M U IM q3-4wk × 10 yr or to age 21 (carditis: until 40+)
153.1.0.3.7.2 PSGN (Post-Strep Glomerulonephritis)
  • 1-2 wk after pharyngitis OR 3-6 wk after skin infection
  • Sx: HTN, edema, hematuria (cola urine), proteinuria
  • Lab: ↓ C3, ASO + (pharyngitis) or anti-DNase B (skin)
  • Tx: supportive (most resolve in children; less so adults)
  • Antibiotic NOT prevent PSGN (vs ARF antibiotic 可以預防)

153.1.0.4 3⃣ Group B Strep (GBS, S. agalactiae)

153.1.0.4.1 A. 新生兒
  • Early-onset (< 7d): 產道感染, sepsis + meningitis + pneumonia
  • Late-onset (7d-3mo): meningitis
  • GBS screening 35-37 wk, IAP (intrapartum antibiotic prophylaxis) 降 risk
153.1.0.4.2 B. 產婊
  • Chorio, endometritis, UTI
153.1.0.4.3 C. 成人 (尀其老 + DM + CKD)
  • SSTI, bacteremia, IE, septic arthritis
  • Cellulitis, necrotizing fasciitis (rare)
153.1.0.4.4 Treatment
  • PCN G 驖遾 (uniformly sensitive)
  • Allergy → vanco / clinda (check inducible)

153.1.0.5 4⃣ Viridans Streptococci

  • S. mitis, S. mutans, S. sanguinis, S. salivarius, S. oralis
  • 牙霒 + 口腔正垞菌
  • Subacute IE on damaged valve (#1 in pre-IDU era)
  • 牙科操䜜 → bacteremia → 沉積 valve
  • Treatment: PCN G + gentamicin (synergy) × 2 weeks IE; 或 ceftriaxone alone × 4 wk

153.1.0.6 5⃣ S. anginosus group

  • S. anginosus, S. intermedius, S. constellatus
  • 圢成 abscess (brain, liver, abdominal, lung)
  • 通垞 + anaerobe (polymicrobial)
  • Treatment: drainage + PCN/ceftriaxone + anaerobe coverage (metronidazole)

153.1.0.7 6⃣ S. gallolyticus (bovis)

  • IE in older adult → 必查 colonoscopy (倧腞癌 association)
  • Liver disease 也 +
  • Treatment: PCN G ± gentamicin

153.1.0.8 7⃣ Nutritionally Variant Strep (Abiotrophia, Granulicatella)

  • IE with culture-negative or slow growing
  • Like viridans but special media
  • High relapse: PCN + gentamicin