• gastroenterology
• sexual networks
• gay men

Sexually transmitted enteric infections in men who have sex with men (MSM) can be caused by viruses (eg, hepatitis A), bacteria (eg, Shigella) and protozoa (eg, Giardia) and can cause hepatitis, proctocolitis and enteritis.1 Enteric infections in MSM occur in sporadic outbreaks related to sexual networks involving transmission of other STIs, geosocial app use for meeting sexual partners and chemsex (high-risk sexual behaviour and recreational drug use, including injecting drug use).1 2 Shigella is a Gram-negative bacteria closely related to Escherichia coli causing a self-limiting diarrhoea illness caused by four subtypes (S. dysenteriae, S. flexneri, S. boydii and S. sonnei). Sexually transmitted S. flexneri in MSM has been shown to be associated with significant morbidity.3 S. flexneri and S. sonnei outbreaks in MSM have shown decreasing susceptibility and resistance to azithromycin and ciprofloxacin: antimicrobials should only be used in severe diarrhoea with sepsis.4 5 We aimed to describe cases of S. flexneri and S. sonnei in MSM between 2016 and 2019 in our open access sexual health clinic in Brighton, UK, which sees 4500 MSM attendances/year with high rates of HIV and STIs.3

There were 33 cases of shigellosis in MSM with a median age of 38 years (IQR 34–47); 11/33 (33%) reported recent chemsex use; the mean number of sexual partners in the previous 3 months was 6; 42% were HIV positive; and 7/19 (37%) HIV-negative MSM were using HIV pre-exposure prophylaxis. Fifteen (45%) were found to have S. sonnei, 5/33 (15%) have S. flexneri (two cases were type IIA, and in the remaining three, typing was unavailable), and 13/33 (39%) were DNA-PCR positive but culture negative and so were not identifiable. Fourteen (42%) were diagnosed with at least one STI (gonorrhoea, 21%; chlamydia, 12%; syphilis, 3%; hepatitis C, 3%; campylobacter, 3%; and giardia, 6%). MSM with S. flexneri were more likely to be HIV positive than those with S. sonnei (p<0.05) (table 1). Antimicrobial sensitivities were available only in 11/15 cases of S. sonnei (fully sensitive, 9%; resistant to ciprofloxacin, 9%; resistant to azithromycin, 36%; and resistant to ciprofloxacin and azithromycin, 45%). Seven (21%) MSM were treated presumptively on the day of presentation with intramuscular ceftriaxone 2 g for 1–3 days followed by oral ciprofloxacin. No MSM with ciprofloxacin resistance received ciprofloxacin; the remaining 26/33 (78%) did not receive antimicrobial treatment and their diarrhoea resolved.

In this small single-centre study of sexually transmitted shigellosis in MSM, we have shown that S. flexneri is more frequently seen in HIV-positive MSM, and similar to other data, shigellosis is associated with chemsex, and resistance to both azithromycin and ciprofloxacin is common in S. sonnei.1 2 Antimicrobial treatment is unnecessary in most cases of shigellosis and empirical treatment with ciprofloxacin and azithromycin should be avoided: locally, we use ceftriaxone 2 g intramuscularly daily until antimicrobial sensitivity is known: ceftriaxone resistance has been reported at low levels in MSM.4 The increasing use of PCR culture-independent diagnostic tests makes it more difficult to identify cases and clusters within sexual networks in MSM of multidrug-resistant shigellosis: clinicians and microbiologists should be vigilant when managing MSM with diarrhoea to prevent large outbreaks of highly resistant shigellosis.