Helicobacter pylori
Overview
H. pylori is a bacterium found in the gastric mucous layer or attached to the stomach lining.
-Transmission: Likely faecal-oral
-Survival: Enabled by urease enzyme, motility, and epithelial adherence
-Guidelines: Maastricht 2016 – H. pylori causes chronic active gastritis in all colonised adults
Diagnosis
Non-invasive:
- Stool antigen test
- Blood IgG
- Urea breath test
Invasive (biopsy):
- Histology
- Culture & sensitivity
- PCR
Treatment
Treat all infected adults, regardless of symptoms.
Recommended for:
- Active or past peptic ulcers
- Post-gastric cancer resection
- Gastric MALT lymphoma
- Asymptomatic with positive test
Initial therapy:
- Triple therapy (2 antibiotics + PPI) for 14 days
- Quadruple therapy in high resistance areas or prior antibiotic exposure
Clostridium difficile (CDAD)
Pathogenesis
C. difficile produces toxins A & B → colitis and diarrhoea
-Hypervirulent strain: NAP1/BI/027 with binary toxin
Risk Factors
- Antibiotics (e.g. fluoroquinolones, clindamycin)
- PPIs and H2 blockers
- Chemotherapy
- GI surgery or stem cell transplant
Clinical Presentation
- Watery diarrhoea, abdominal pain, fever
- Leukocytosis (>15,000/µL)
- Can progress to toxic megacolon
Diagnosis
- PCR for toxin genes (first-line at Ampath)
- Only test symptomatic patients
Treatment
- Stop inciting antibiotic
- Mild: Metronidazole
- Severe: Vancomycin
- Fulminant: Vancomycin + IV Metronidazole
- Relapse: Vancomycin taper or faecal transplant
Salmonella Infection
Types
- Typhoidal: S. typhi, S. paratyphi
- Non-typhoidal (NTS): S. enteritidis, S. typhimurium
Clinical
- NTS: Gastroenteritis (nausea, vomiting, diarrhoea)
- Typhoid: Fever, rose spots, hepatosplenomegaly
- Invasive: Endocarditis, osteomyelitis (esp. in HIV)
Diagnosis
- Stool & blood cultures
- PCR panel available at Ampath
Treatment
- Fluids & electrolytes
- Antibiotics for high-risk or severe cases
- Typhoid: Avoid quinolones in Asia due to resistance
Shigella Infection
Clinical
- High fever, cramps, bloody/mucoid stools
- Highly transmissible
Diagnosis
- Stool culture & PCR
Treatment
- Avoid anti-motility drugs
- Antibiotics for severe cases, elderly, malnourished, healthcare workers
- Oral: Ciprofloxacin, Azithromycin
- IV: Ceftriaxone
Campylobacter Infection
Clinical
- Diarrhoea (may be bloody), cramps
- Complications: Reactive arthritis, Guillain-Barré
Diagnosis
- Stool culture & PCR
Treatment
- Supportive care
- Antibiotics for severe cases
- Oral: Azithromycin, Ciprofloxacin
- IV: Carbapenem or fluoroquinolone
Escherichia coli Infection
Pathogenic Strains
- ETEC: Traveller’s diarrhoea
- EPEC: Infant diarrhoea
- EHEC/STEC: Haemorrhagic colitis, HUS
- EIEC: Dysentery
- EAEC: Persistent diarrhoea
Diagnosis
- Stool PCR (Ampath panel)
Treatment
- Hydration is key
- Antibiotics for severe cases or specific strains
- Avoid antimotility agents in children
Cholera Infection
Clinical
- Severe watery diarrhoea ("rice-water stools")
- Risk of dehydration and shock
Diagnosis
- Stool microscopy & culture
Treatment
- Rehydration
- Antibiotics: Doxycycline, Azithromycin
Yersinia Infection
Clinical
- Diarrhoea, pseudoappendicitis, pharyngitis
- Extra-intestinal complications possible
Diagnosis
- Culture & serology
Treatment
- Only for severe disease
- Oral: Ciprofloxacin
- IV: Ceftriaxone + Gentamicin
Viral Gastroenteritis
Common Viruses
- Rotavirus
- Norovirus
- Sapovirus
- Astrovirus
- Adenovirus 40/41
Clinical
- Nausea, vomiting, diarrhoea, fever
- Duration: 3–7 days
Diagnosis
- Stool PCR (Ampath viral panel)
Treatment
- Supportive care
- No antibiotics unless bacterial cause confirmed
- Probiotics may help
Parasitic Infections
Amoebiasis (Entamoeba histolytica)
- Diarrhoea, liver abscess
- Diagnosis: Stool microscopy, serology, PCR
- Treatment: Metronidazole or Tinidazole + cyst eradication therapy
Giardiasis (Giardia lamblia)
- Diarrhoea, steatorrhoea
- Diagnosis: Stool microscopy, antigen, PCR
- Treatment: Metronidazole, Tinidazole, Albendazole
Cryptosporidiosis
- Severe in HIV patients
- Diagnosis: Stool PCR
- Treatment: ART + supportive care ± antimicrobial agents
Blastocystis hominis
- Controversial pathogen
- Diagnosis: Stool microscopy
- Treatment: Only if symptomatic
Intra-abdominal Infections (IAI)
Causes
- GI tract disruption
- Polymicrobial infections
Treatment
- Fluid resuscitation
- Surgical intervention
- Empiric antibiotics based on risk level
Low-risk:
- Ertapenem, piperacillin-tazobactam
- Ceftriaxone + Metronidazole
High-risk:
- Meropenem, Imipenem
- Add antifungals if Candida is present
Healthcare-associated:
- Tailored to local resistance patterns
- Include vancomycin or teicoplanin for MRSA