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Sexually Transmitted Enteric Infections

Sexually Transmitted Enteric Infections

Sexually Transmitted Enteric Infections

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STEIs Overview - Gut Instincts Gone Wrong

  • Definition: Infections of the gastrointestinal tract transmitted through sexual contact, distinct from classical STIs.
  • Transmission Modes: Primarily oral-anal (anilingus), digital-rectal contact; less commonly, fomites.
  • High-Risk Populations: Predominantly men who have sex with men (MSM).
  • Pathogen Spectrum: Includes:
    • Bacteria: Shigella spp., Salmonella spp., Campylobacter spp., E. coli (EHEC, EPEC).
    • Viruses: Hepatitis A, Hepatitis E, Norovirus, Rotavirus.
    • Protozoa: Giardia lamblia, Entamoeba histolytica, Cryptosporidium spp.

⭐ Many enteric STIs present with symptoms of proctitis (rectal inflammation) or proctocolitis (inflammation of rectum and colon).

Bacterial Pathogens - Proctitis Perpetrators

Presumptive Rx (acute proctitis): Ceftriaxone 500mg IM (1g if ≥150kg) + Doxycycline 100mg BD x 7d.

PathogenSxDxRx
Neisseria gonorrhoeaeRectal pain, pus, tenesmusGram-stain (GNDC), NAATsCeftriaxone 500mg IM + Doxy 100mg BDx7d
Chlamydia trachomatis (non-LGV)Mild/asymptomatic; dischargeNAATsDoxy 100mg BDx7d or Azithro 1g PO x1
Chlamydia trachomatis (LGV)Severe proctocolitis, bloody discharge, ulcersNAATs, SerologyDoxy 100mg BDx21d
Treponema pallidumAnal chancre, proctitisDark-field, SerologyBenzathine Pen G 2.4MU IM x1
Shigella spp.Bloody diarrhea, fever, tenesmusStool culture, NAATsCipro 500mg BDx3-5d or Azithro 500mg ODx3d (check resistance)
Salmonella spp.Diarrhea (±blood), feverStool culture, NAATsSupportive; Cipro if severe
Campylobacter spp.Bloody diarrhea, feverStool culture (special media), NAATsAzithro 500mg ODx3d

⭐ LGV proctocolitis mimics IBD; can cause strictures/fistulae.

Protozoal & Viral Agents - Microscopic Marauders

  • Protozoal Agents:
    • Entamoeba histolytica (Amoebiasis):
      • Bloody diarrhea, abdominal pain, liver abscess.
      • Stool microscopy (cysts/RBC-laden trophozoites), Ag tests, PCR.
      • Metronidazole/Tinidazole, then luminal agent (Paromomycin).
    • Giardia lamblia (Giardiasis):
      • Foul, fatty stools (steatorrhea), bloating. 📌 'Gay Bowel Syndrome' (historical), fatty stools.
      • Stool microscopy (cysts/trophozoites), Ag tests.
      • Metronidazole, Tinidazole, Nitazoxanide.
    • Cryptosporidium spp. (Cryptosporidiosis):
      • Watery diarrhea (severe in immunocompromised).
      • Modified acid-fast (oocysts), Ag tests.
      • Nitazoxanide (immunocompetent); HAART (HIV).
  • Viral Agents:
    • Herpes Simplex Virus (HSV) Proctitis:
      • Severe anorectal pain, tenesmus, vesicles.
      • Viral culture, PCR from lesions.
      • Acyclovir, Valacyclovir.

      ⭐ HSV proctitis: severe anorectal pain, tenesmus, radicular pain (Elsberg syndrome).

    • Cytomegalovirus (CMV) Colitis:
      • Bloody diarrhea, pain (immunocompromised, CD4 < 50).
      • Colonoscopy + biopsy (owl's eye), PCR.
      • Ganciclovir, Valganciclovir.
    • Hepatitis A Virus (HAV):
      • Jaundice, fever, nausea. Fecal-oral (sexual).
      • Anti-HAV IgM.
      • Supportive. Vaccination.

Clinical Approach & Mgmt - Gut Check & Game Plan

  • Clinical Syndromes:

    • Proctitis: Anorectal pain, tenesmus, discharge, bleeding. Affects distal 10-12 cm rectum.
    • Proctocolitis: Proctitis symptoms + bloody/mucoid diarrhea, abdominal pain, ±fever. Involves rectum & colon.
    • Enteritis: Watery diarrhea, nausea, vomiting, abdominal cramps. Primarily small bowel.
  • Diagnostic & Management Pathway:

  • Management Principles: Aim for etiologic diagnosis. Syndromic approach for severe cases or diagnostic delay. Partner notification and treatment are vital.

  • Prevention: Counsel on safe sex (condoms), hygiene. Offer Hepatitis A/B vaccination. PrEP for HIV indirectly reduces risk.

⭐ A thorough sexual history is crucial as it guides the differential diagnosis and testing for enteric STIs.

High‑Yield Points - ⚡ Biggest Takeaways

  • Sexually transmitted enteric infections are prevalent in MSM (Men who have Sex with Men).
  • Common presentations include proctitis, proctocolitis, and enteritis.
  • Key pathogens: Shigella, Salmonella, Campylobacter, LGV (C. trachomatis), N. gonorrhoeae, HSV, HPV, E. histolytica, Giardia.
  • LGV proctocolitis mimics IBD with tenesmus and bloody discharge; biopsy shows granulomas.
  • Gonococcal proctitis is often asymptomatic; diagnosed by NAAT.
  • Syphilitic proctitis may show anal chancres or condylomata lata.
  • Amebiasis and Giardiasis are common protozoal infections, treated with metronidazole.

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