169.1 🎓 醫孞生版

169.1.0.1 📌 䞀頁重點

  • Salmonella enterica — gram - rod, motile, lactose -, oxidase -
  • 2 ç—…çš® categories:
    1. Typhoidal: S. Typhi, S. Paratyphi A/B/C → enteric fever (systemic), 人傳人 (人 only host)
    2. Non-typhoidal Salmonella (NTS): > 2000 serovars (e.g. Typhimurium, Enteritidis) → gastroenteritis ± invasive disease; zoonotic (poultry, eggs, reptile, dairy)
  • Typhoid fever:
    • 望䌏 5-21 d (avg 8-14)
    • Step-wise fever, 盞對 bradycardia (Faget sign), abdominal pain, rose spots, hepatosplenomegaly
    • 通報 (notifiable globally)
    • Complications: intestinal perforation (3rd wk Peyer’s patch), hemorrhage, sepsis
    • 5% chronic carrier (gallbladder; “Typhoid Mary”)
    • Treatment: ceftriaxone or azithromycin (FQ 抗藥升 — S Asia XDR)
    • Vaccines: Ty21a (oral, live), Vi polysaccharide (IM), Typbar-TCV (Vi-TT conjugate, ≥ 6 mo, WHO prequalified 2018)
  • NTS gastroenteritis:
    • 6-72 hr onset, 氎瀉/血䟿, 腹痛, 燒 24-48 hr
    • Healthy adult: NO antibiotic (prolongs carriage)
    • Invasive: bacteremia, endovascular focus (mycotic aneurysm in elderly atherosclerotic aorta!), osteomyelitis (sickle cell, infant)
    • Indications for antibiotic: > 50, immunocompromise, sickle cell, prosthetic, severe, bacteremia
    • Treatment: ceftriaxone or azithromycin

169.1.0.2 1⃣ 现菌孞

  • Salmonella enterica — most clinical; S. bongori rare
  • > 2500 serovars within S. enterica
  • 名皱 e.g. S. enterica serovar Typhi (= “S. Typhi” 簡寫)
  • Gram - rod, motile (flagella), facultative anaerobe
  • Lactose - (most), H2S + (most NTS), urea -
  • Antigens: O (somatic LPS), H (flagellar), Vi (capsule, Typhi)
169.1.0.2.1 臎病機蜉 — Typhoid
  • 口服 → 䞊腞 → Peyer’s patch invasion → mesenteric LN → blood → liver/spleen/marrow → 再 secrete to gallbladder + small bowel (relapse → continued bacteremia)
  • Vi antigen (capsule) — anti-phagocytic, immunoprotection target
169.1.0.2.2 NTS
  • 通垞 limited to small/large bowel mucosa + lymph
  • Invasive forms breach (immunocompromise, infants, elderly)

169.1.0.3 2⃣ Typhoid Fever (Enteric Fever)

169.1.0.3.1 流行病孞
  • 11-21 million 病䟋 /yr globally, 110,000 死亡
  • 高負擔: South Asia (India, Pakistan, Bangladesh), Sub-Saharan Africa
  • Spread: 食氎 fecal contamination; 人 only reservoir
  • Typhoid Mary (1900s NY cook, asymptomatic carrier)
169.1.0.3.2 臚床 — Week-by-week (classic)
Week Sx
1 Step-wise fever 1°C/d, headache, malaise, relative bradycardia (Faget)
2 Rose spots (trunk, faint blanching macules), abdominal pain, splenomegaly, hepatomegaly, mental cloudiness
3 Complications: intestinal perforation (Peyer’s patch in distal ileum), hemorrhage, sepsis, encephalopathy, myocarditis
4 Resolution or relapse (~ 5-15%)
169.1.0.3.3 Complications
  • Intestinal perforation (1-5%) — 急 abdomen, peritonitis; surgical emergency
  • Hemorrhage (lower GI, melena/hematochezia)
  • Sepsis, shock, myocarditis, encephalopathy
  • Pneumonia, meningitis, osteo, IE — rare
  • Chronic carrier (5%): gallbladder, > 1 yr stool/urine carriage; risk of gallbladder CA
169.1.0.3.4 Dx
  • Blood culture — best yield Week 1 (50-80% +); decreases later
  • Stool culture — yield ↑ Week 2-3 (~ 30%)
  • Bone marrow culture — highest yield (90%+; gold standard) but invasive
  • Widal test (serology) — limited utility, false +/- common
  • PCR / Typhi Detect — emerging
  • Blood + stool 同 send
169.1.0.3.5 Treatment
  • Ceftriaxone 2 g IV qd × 10-14 d (first-line in resistant regions)
  • Azithromycin 1 g PO qd × 5-7 d (uncomplicated)
  • Fluoroquinolone — resistance 圚 S Asia 高 (50%+ in some)
  • XDR S. Typhi (Pakistan 2016-): 對 1st-line, FQ, 3rd-gen ceph 郜 R — 必 azithromycin (some R emerging) or carbapenem
  • Dexamethasone adjunct for severe (Hoffman 1984): 3 mg/kg → 1 mg/kg q6h × 8 doses — 降 mortality
  • Surgical: perforation
  • Treat carrier: ciprofloxacin × 4 wk OR cholecystectomy
169.1.0.3.6 Prevention — Vaccines (2024)
Vaccine Type Route Schedule Efficacy
Ty21a (Vivotif) Live oral PO 4 doses every other day ~ 50-60% over 5y
Vi polysaccharide (Typhim Vi) IM IM Single, booster q2y ~ 50-60% over 2y
Vi-TT conjugate (Typbar-TCV) Conjugate IM Single ≥ 6 mo ~ 80% (children)
Tybar-TCV WHO prequalified 2018 Booster decade
  • 旅遊 to S Asia, Africa
  • Endemic area children — WHO掚
  • 高 risk lab worker

169.1.0.4 3⃣ Non-Typhoidal Salmonella (NTS)

169.1.0.4.1 Source
  • Poultry, eggs (S. Enteritidis) — biggest
  • Beef, pork, dairy, produce
  • Reptiles (S. Typhimurium, Java) — pet turtle / iguana
  • Pet 食 / 飌料 outbreaks
  • Person-person rare (䜎-medium dose)
169.1.0.4.2 A. Gastroenteritis
  • 望䌏 6-72 hr
  • 氎暣 → 血䟿 ± mucus, 急 cramping, 燒, vomiting
  • Self-limit 3-7 d
  • Healthy adult: NO antibiotic (prolongs carriage + R selection)
169.1.0.4.3 B. Bacteremia (Invasive)
  • 5-10% NTS gastroenteritis → bacteremia
  • 高 risk: 老 / 嬰 / immunocompromise / HIV / sickle cell / IBD / steroid / 化療
  • Sx: 持續 fever + chills + 無 GI sx (sometimes)
  • Endovascular focus 倧譊: mycotic aneurysm (atheromatous aorta), IE on damaged valve
169.1.0.4.4 C. Endovascular (Aortic Mycotic Aneurysm)
  • Older atherosclerotic male — bacteremia → seed atheroma → mycotic aneurysm
  • Sx: persistent bacteremia despite abx, back pain, pulsatile mass
  • CT angiogram — emergent
  • Surgical repair + 6 wk abx mandatory
  • High mortality if missed (rupture)
169.1.0.4.5 D. Osteomyelitis
  • Sickle cell disease — Salmonella is the most common cause (vs S. aureus in normals)
  • Infant
  • Vertebra in elderly atherosclerosis
169.1.0.4.6 E. Localized
  • Cholecystitis (gallstone disease — carrier potential)
  • Splenic abscess
  • Septic arthritis
  • Meningitis (neonates)
  • Lung abscess (rare)
  • UTI rare
169.1.0.4.7 Treatment — When + What
Situation Antibiotic?
Healthy adult gastroenteritis NO
Age < 3 mo or > 50 YES (prevent invasive)
Immunocompromise YES
Sickle cell, prosthetic, atherosclerosis YES
Severe sepsis YES
Bacteremia YES
  • Drugs: Ceftriaxone or ciprofloxacin (community); ESBL → carbapenem
  • 持續 bacteremia → endovascular workup (CT angio aorta + TEE)
  • Aortic mycotic aneurysm: 6 wk abx + surgical repair
  • Osteo: 4-6 wk
  • Bacteremia: 14d (uncomplicated)