Sexually transmitted enteric infections (STEIs) in men who have sex with men (MSM) have been documented since the 1960s, but their importance is increasingly evident in the modern diagnostic era. The spread of multiplex molecular tests has improved recognition of these infections, which often fall between the categories of foodborne and sexually transmitted diseases. This blurred classification complicates surveillance and response, while the global rise of antimicrobial resistance (AMR) highlights the urgency of timely diagnosis, targeted therapy, and effective prevention strategies. 

STEIs include bacterial (Shigella, Campylobacter, diarrheagenic Eschericia coli, Salmonella), protozoal (Giardia, Entamoeba histolytica, Cryptosporidium), and viral pathogens such as hepatitis A. Transmission occurs mainly through oral–anal sexual practices, with outbreaks reported across North America, Europe, and Asia. Although foodborne and zoonotic exposures remain important, endemic sexual transmission disproportionately affects MSM, driving recurrent outbreaks and sustained community transmission. 

Traditional stool culture and microscopy remain important, but nucleic acid amplification tests and multiplex polymerase chain reaction (PCR) panels have transformed detection. These assays offer rapid, sensitive identification of multiple pathogens within hours, supporting better patient management and antimicrobial stewardship. However, reflexive culture remains necessary to enable strain typing, track outbreaks, and determine resistance profiles. 

Shigella and Campylobacter are of particular concern due to their low infectious dose, ease of person-to-person spread, and escalating drug resistance. Extensively drug-resistant (XDR) strains resistant to fluoroquinolones, macrolides, and third-generation cephalosporins have now been detected in multiple regions. 

Diarrheagenic Escherichia coli (Enteroaggregative-, Enteropathogenic-  and Shiga toxin–producing- Escherichia coli) are common in MSM, frequently detected in both symptomatic and asymptomatic carriers. While many infections are self-limiting, certain strains can cause prolonged diarrhea or serious complications. 

Salmonella is less commonly sexually transmitted but remains relevant for invasive typhoidal strains and immunocompromised individuals. 

Protozoa such as Giardia and E. histolytica continue to cause both asymptomatic carriage and outbreaks, with amebic liver abscesses representing a severe complication. 

Emerging challenges. Rising AMR in STEIs, especially Shigella and Campylobacter, threatens effective therapy. Sexual networks and international travel accelerate the spread of resistant strains across continents. Preventive strategies such as human immunodeficiency  virus (HIV) pre-exposure prophylaxis (PrEP) and doxycycline post-exposure prophylaxis (doxy-PEP) may alter STEIs epidemiology, but their impact is still uncertain. Behavioral and social factors—including group sex, chemsex, and sex-on-premises venues—play a key role in shaping transmission networks. 

Clinical and public health implications. STEIs often present as nonspecific gastroenteritis or proctitis, making sexual history-taking critical for appropriate testing and counseling. Empiric therapy is complicated by resistance, and local susceptibility data should guide choices. Beyond individual care, community-level education and better integration of sexually transmitted infections and enteric disease surveillance are essential to reduce transmission. Yet awareness remains low among both MSM and healthcare providers, underscoring the need for improved knowledge and practice. 

Future directions. Priorities include defining the true population burden of STEIs, strengthening AMR surveillance, and tailoring interventions to sexual networks. Advances in genomic epidemiology, host–pathogen interaction studies, and behavioral research will be critical for guiding prevention and treatment. Bridging the siloed domains of sexual health and enteric disease, while engaging affected communities, will be central to reducing morbidity and preserving treatment effectiveness. 

Reference 

Newman, K.L., Snoeyenbos Newman, G., Cannon, C.A., Fang, F.C. Sexually transmitted enteric infections in men who have sex with men. Clin Microbiol Rev (2025). https://doi.org/10.1128/cmr.00075-23