Makindo Medical Notes

📖 About

• Salmonella enterica → a highly motile, Gram-negative bacterium in the Enterobacteriaceae family.
• Non-lactose fermenting;>2000 serotypes (e.g. Typhimurium, Enteritidis, Dublin, Choleraesuis).
• Major global cause of foodborne gastroenteritis.

🔬 Characteristics

• Motile Gram-negative rods; facultative anaerobes.
• Ferment glucose but not lactose → pale colonies on MacConkey agar.
• 🧪 Oxidase-negative, catalase-positive, reduce nitrates → nitrites.
• Antigens:
  • H antigen: flagellar, motility.
  • O antigen: somatic, LPS-related.
  • Vi antigen: capsular virulence factor (esp. *S. Typhi*).
• Bile salt resistant → survival in intestinal tract.

🏠 Source

• Foodborne: undercooked poultry, raw eggs, unpasteurised milk.
• Risk groups: infants 👶, elderly 👵, reduced gastric acid (e.g. PPI users).
• ⚠️ Sickle cell disease → predisposes to invasive salmonella infection, esp. osteomyelitis.

⚠️ Pathogenicity

• Most commonly → gastroenteritis (self-limiting).
  • Watery diarrhoea (may be inflammatory with mucus/blood).
  • Abdominal cramps, nausea, vomiting, fever.
• Septicaemia → uncommon but can occur in immunocompromised (HIV, malignancy, extremes of age).
• Focal infections (rare): osteomyelitis, meningitis, endocarditis.

💊 Sensitivities

• Traditionally sensitive to ciprofloxacin & fluoroquinolones.
• ⚠️ Increasing resistance (MDR *Salmonella*) → culture and sensitivity essential.

🩺 Management

• 💧 Supportive therapy → oral rehydration/IV fluids mainstay in gastroenteritis.
• 💊 Antibiotics:
  • Not required in most cases (may prolong carriage).
  • Indicated if severe/systemic disease, immunocompromised, infants, elderly.
  • Agents: Ciprofloxacin, ceftriaxone, azithromycin (guided by sensitivity).
• 🛡️ Prevention: safe food handling, proper cooking, pasteurisation, hand hygiene.

⚠️ Exam pearl: Salmonella enterica (non-typhoidal) → foodborne gastroenteritis, usually self-limiting. In sickle cell disease, it is the classic cause of osteomyelitis.