Silent infections that evade both symptoms and immune detection are reshaping the global burden of bacterial sexually transmitted diseases — and the standard clinical toolkit is struggling to keep pace. Anorectal chlamydia, gonorrhoea, and syphilis are not niche concerns; they are accelerating epidemics with distinct biological behaviors that differ meaningfully from their urogenital counterparts, demanding a rethink of how screening, treatment, and prevention are structured.
This comprehensive review in Nature Reviews Gastroenterology & Hepatology synthesizes the epidemiology, pathogenic mechanisms, diagnostic advances, and prevention landscape for anorectal bacterial STIs. A central finding is that anorectal infections are disproportionately asymptomatic — particularly in men who have sex with men — where rectal prevalence frequently surpasses urogenital rates. This asymptomatic persistence is not random: bacterial adaptation to rectal mucosal environments and a locally attenuated immune response suppress inflammatory signaling below the threshold required to generate symptoms. Molecularly, this represents genuine pathogen-host co-evolution, not simply mild disease. On the diagnostic front, nucleic acid amplification testing has dramatically improved sensitivity, yet a persistent challenge involves differentiating viable, transmissible organisms from residual non-viable genetic material — a distinction with real clinical consequences for treatment decisions and antimicrobial stewardship. Doxycycline post-exposure prophylaxis (doxy-PEP) emerges as the most clinically actionable prevention advance, with trial data showing substantial reductions in chlamydia and syphilis incidence, though implementation in varied healthcare settings remains inconsistent.
The gonorrhoea resistance trajectory is the most urgent concern embedded in this review. Neisseria gonorrhoeae has demonstrated a near-systematic ability to acquire resistance to each successive first-line antibiotic, and the rectal niche — with its distinct microbiome and immune milieu — may accelerate resistance selection. From a population health standpoint, the integration of AI-assisted screening triage and expanded point-of-care molecular diagnostics could meaningfully shift detection rates, but both remain at early implementation stages. This review is confirmatory of known epidemiological trends but genuinely advances mechanistic understanding of why anorectal sites behave differently, making it a valuable synthesis for clinicians and researchers. Its limitation is inherent to the review format: it consolidates existing evidence rather than generating new causal data.