Enteric infections in MSM treatment guidelines

Sexual transmission of enteric pathogens such as hepatitis A, shigella, salmonella, campylobacter and giardia in MSM have been well described.
Exposure of these organisms can be through direct oral-anal contact (rimming), or indirectly through  digital contact or fisting and sexual contact (such as oral sex and anal sex) .
MSM  presenting with lower gastrointestinal symptoms are often concerned about an STI and proctitis due to an STI is sometimes difficult to differentiate from gastroenteritis.
As in the general population, viral infections such as norovirus and rotavirus are the most common causes of acute gastroenteritis.
In MSM presenting with gastrointestinal symptoms consider whether there have been recent community outbreaks of hepatitis A and shigella.

Hepatitis A and shigella are both notifiable to the Victorian Department of Health.

The differential diagnosis of a MSM presenting with symptoms of acute gastroenteritis are:

• Bacterial infections such as salmonella, shigella,  campylobacter, toxin-producing E. coli and Entamoeba histolytica.
• Viral infections including hepatitis A
• Parasitic infections such as giardia and helminths (threadworm) can also cause gastrointestinal symptoms.

Investigations are not always necessary, particularly with mild GI symptoms, but the clinician should have a low threshold to investigate MSM due to the possibility of shigella.

Stool micro, culture and sensitivities (with PCR) should be performed where enteritis is suspected.  It is often prudent to perform anal swabs as certain STIs such as LGV can cause lower abdominal symptoms including abdominal pain and rectal bleeding.

Hepatitis A vaccination is advisable in all MSM.
Enteric infections are usually self-limiting.
Rehydration and symptomatic treatment is the mainstay of therapy.
Antibiotic therapy should be tailored to antimicrobial susceptibility results when available
For mild to moderate symptoms, , empirical antibiotics are not recommended due to the high rates of resistance, particularly to ciprofloxacin and azithromycin.
Where shigella is suspected and empirical therapy is required, seek advice from the local infectious diseases department or reference laboratory as rates of antibiotic resistance changes by region and over time.

The following antibiotics have been used for suspected shigella enteritis while waiting for antibiotic confirmation:

• Ciprofloxacin 500mg bd for 3 days
• Azithromycin 500mg daily for 3 days
• Trimethoprim-co-trimoxazole 160/800mg bd for 5 days.

Further advice and follow-up

• Patients should avoid sex for 7 days after symptoms resolve.
• Testing asymptomatic sexual partners for enteric infections is not recommended, however a symptomatic sexual partner should seek advice from the local sexual health centre.