IM26.15-16 | Gram Negative Nonfermenter and Helicobacter Infections — Summary & Reflection

KEY TAKEAWAYS

Helicobacter pylori: spiral urease-producing Gram-negative bacillus; infects 70–80% of adults in India; causes antral gastritis (high acid → duodenal ulcer) or corpus atrophy (low acid → gastric ulcer/carcinoma/MALT lymphoma); virulence factors CagA (oncogenic) and VacA (vacuolating cytotoxin); diagnosis: RUT/UBT/stool antigen (non-invasive) or histology/culture (endoscopic); eradication in high clarithromycin resistance areas (>15%): 14-day bismuth quadruple therapy (PPI + bismuth + metronidazole + tetracycline); confirm eradication with UBT or stool antigen ≥4 weeks post-treatment; MALT lymphoma Stage I: eradication first-line.

Pseudomonas aeruginosa: aerobic non-fermenter, intrinsically resistant to many antibiotics; opportunistic pathogen in neutropenia, burns, ventilated patients, cystic fibrosis; ecthyma gangrenosum (necrotic eschar) = pathognomonic of Pseudomonas bacteraemia; malignant otitis externa in elderly diabetics (cranial nerve palsy, granulation tissue in auditory canal) requires IV anti-pseudomonal therapy × 6 weeks; anti-pseudomonal agents: piperacillin-tazobactam, ceftazidime, cefepime, meropenem, ciprofloxacin, amikacin; combination therapy for life-threatening infections.

Burkholderia pseudomallei / Melioidosis: tropical non-fermenter, endemic in Northeast India, Odisha, Tamil Nadu; risk factor: diabetes; mimics TB/typhoid ('great mimicker'); multiple organ abscesses (liver, lung); intrinsically resistant to gentamicin; treat: IV ceftazidime or meropenem (intensive phase, 10–14 days) → TMP-SMX + doxycycline (eradication phase, 3–6 months); suspect when gentamicin fails in a febrile diabetic with multi-organ involvement from an endemic area.

REFLECT

The student in the hook with the duodenal ulcer has an older brother whose ulcer recurred twice when treated with PPI alone (without eradication). This illustrates a principle with broad applicability: treating the consequence without treating the cause leads to recurrence. H. pylori eradication permanently removes the driving force behind the ulcer, reducing recurrence from ~80% per year (with PPI alone) to ~5% per year. Reflect on this 'treat the cause, not just the consequence' principle — how does it apply to other infections in this cluster? How does it differ from the situation in melioidosis, where the eradication phase oral antibiotic course (3–6 months) prevents relapse from dormant intracellular organisms? In both cases, the immediate symptomatic treatment is only part of the story — the long-term outcome is determined by whether the physician thinks ahead to treat the underlying bacterial cause completely.