## Most Common Preceding Infection in GBS **Key Point:** Campylobacter jejuni is the single most common bacterial pathogen associated with GBS worldwide, accounting for 20–40% of antecedent infections in GBS cases. ### Epidemiology of GBS Triggers | Pathogen | Frequency | Geographic Notes | GBS Variant | |----------|-----------|------------------|-------------| | **Campylobacter jejuni** | 20–40% | Worldwide, especially in developing countries | Axonal (AMAN/AMSAN) | | Cytomegalovirus | 5–10% | Immunocompromised, post-transplant | Demyelinating | | Epstein-Barr virus | 5–10% | Younger patients | Demyelinating | | Mycoplasma pneumoniae | 5–10% | Respiratory prodrome | Demyelinating | | Zika virus | 5–15% | Emerging in endemic regions | Axonal | **High-Yield:** In India and other developing nations, Campylobacter jejuni from contaminated poultry and water is the leading identified antecedent. The patient's history of acute gastroenteritis 2 weeks prior is the classic temporal relationship (typically 1–4 weeks before neurological onset). ### Mechanism **Clinical Pearl:** Campylobacter jejuni carries lipopolysaccharides (LPS) with epitopes that cross-react with gangliosides (GM1, GD1a) on peripheral nerve axons. This molecular mimicry triggers autoimmune attack on motor axons, leading to axonal variants of GBS (AMAN). **Mnemonic:** **C-GBS** — **C**ampylobacter causes **G**BS most **C**ommonly in the community. ### Why Campylobacter Stands Out 1. Ubiquitous in poultry and water supplies 2. Causes symptomatic gastroenteritis (diarrhea) — patients recall the preceding illness 3. Strong epidemiological link in prospective studies 4. Associated with more severe, axonal phenotypes [cite:Harrison 21e Ch 446]
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