Antibiotics for Abdominal Infections

🚨 Important: Tazocin (Piperacillin/Tazobactam) is contraindicated in patients with a penicillin allergy. Always verify allergy status before prescribing.

1. Simple Gastroenteritis

• Causes: Salmonella (non-typhoid), Shigella, Campylobacter, E. coli O157.
• Features: Diarrhoea, fever, abdominal pain, dehydration.
• Management: Supportive (fluids + electrolytes). ❌ Antibiotics usually not recommended (↑ carrier risk in Salmonella, ↑ HUS in E. coli O157).
• Red flag: Severe or immunocompromised → seek Microbiology advice. Notify PHE/HPA in the UK.

2. Parasitic Infestations

• Common: Giardia, Amoeba, Cryptosporidium, Microsporidium.
• Management:
  • Giardiasis → Metronidazole 250–500 mg PO TDS × 5–7d.
  • Amoebiasis → Metronidazole 500–750 mg PO TDS × 7–10d
    ➝ then luminal agent (Paromomycin).
  • Cryptosporidium/Microsporidium → No specific drug; supportive care.

3. Viral Gastroenteritis

• Causes: Norovirus, Rotavirus, Adenovirus.
• Management: Self-limiting. Rehydration therapy is key 💧 - esp. in children & elderly.

4. Clostridioides difficile Colitis

• Mild–moderate → Metronidazole 400 mg PO TDS × 10–14d.
• Severe or recurrent → Vancomycin 125 mg PO QDS × 10–14d.
• Recurrent/complex → Consider Microbiology review ± faecal transplant.
• Always review antibiotic exposure - lifelong risk of recurrence.

5. Helicobacter pylori Eradication

• Triple Therapy (7d): PPI (e.g., Lansoprazole 30 mg BD) + Clarithromycin 500 mg BD + Amoxicillin 1 g BD.
• Penicillin allergy: Replace Amoxicillin with Metronidazole 400 mg BD.
• Stress adherence 🚨 - incomplete therapy → resistance.

6. Peritonitis & Abdominal Sepsis

• Pathogens: Mixed gut flora (coliforms, anaerobes, enterococci).
• Treatment:
  • Tazocin 2.25 g IV TDS + single IV Gentamicin if shocked.
  • Penicillin allergy → Tigecycline 100 mg IV load → 50 mg BD IV.
• Key: 🚨 Early source control (surgery/drainage).

7. Spontaneous Bacterial Peritonitis (SBP)

• Causes: E. coli, Klebsiella, Pneumococcus.
• Treatment: Tazocin 2.25 g IV TDS × 10–14d.
• Penicillin allergy: Microbiology advice.
• Prophylaxis: Norfloxacin in high-risk cirrhotic pts.

8. Liver Abscess

• Causes: Coliforms, streptococci, anaerobes ± Entamoeba histolytica.
• Treatment: Tazocin 2.25 g IV TDS (adjust after culture/drainage).
• Penicillin allergy: Microbiology advice.
• Drainage (percutaneous/surgical) often required.

9. Cholecystitis

• Cause: Coliforms + anaerobes.
• Treatment: Tazocin 2.25 g IV TDS ➝ switch to Co-amoxiclav 625 mg PO TDS if improved (after 48h).
• Allergy: Microbiology guidance.

10. Empyema of Gallbladder

• 🚨 Requires surgical drainage + antibiotics (as per liver abscess).

11. Ascending Cholangitis

• Cause: Mixed gut flora.
• Treatment: Tazocin 4.5 g IV TDS × 7–10d.
• Allergy: Consult Microbiology.
• Key: 🚨 Urgent decompression (ERCP/surgery) essential.

12. Necrotising Pancreatitis

• Antibiotics only if severe/confirmed necrosis.
• Tazocin 4.5 g IV TDS or Meropenem 500 mg IV QDS × up to 14d.
• Allergy → Microbiology review.

13. Diverticulitis

• Cause: Mixed gut flora.
• Mild: Metronidazole 400 mg PO TDS × 5d.
• Severe: Metronidazole 500 mg IV TDS (± broader cover if septic).
• Complications: Abscess/perforation → 🚨 Surgery.

14. Cirrhosis with Acute GI Bleeding

• Cause: Gut flora translocation during variceal bleed.
• Treatment: Tazocin 2.25 g IV TDS × 5d.
• Allergy: Consult Microbiology.
• Prophylaxis: Short-term prophylaxis often advised during bleed episodes.