Emergence of a New STI: Drug-Resistant Shigella
A gut pathogen that leads to diarrhea and vomiting is evolving into a serious and challenging sexually transmitted infection (STI).
Each year in the United States, approximately 450,000 individuals are diagnosed with shigellosis, which has the potential to result in dysentery.
Traditionally, this highly contagious bacteria has been transmitted primarily through contaminated food and water, especially during travel, and is commonly seen in young children at daycare centers.
However, since around the early 2000s, Shigella has started to be recognized as a sexually transmitted infection.
While anyone can contract Shigella, it’s particularly noted as being more prevalent in certain communities among gay, bisexual, and other men who have sex with men (GBMSM).
Several strains that circulate within these groups have developed resistance to multiple antibiotics, with some nearing the status of being untreatable.
A recent report from the US CDC indicates that extensive drug-resistant (XDR) variants of Shigella have increased significantly from 2011 to 2023.
In 2011, none of the samples were resistant to five common antibiotics; by 2023, this figure rose to 8.5 percent.
Notably, the majority of these drug-resistant infections were found in adult men, many of whom hadn’t traveled abroad recently.
Molecular biologist Shangxin Yang noted that at the University of California, Los Angeles (UCLA), they’re now observing about one case of extensively drug-resistant Shigella each month, compared to just one case throughout the entire year in 2022.
Yang remarked, “It’s almost like an explosion of this pathogen in the community,” indicating the seriousness of the situation.
Sexually transmissible shigellosis was initially identified in 1974, but at that time, it accounted for a small fraction of cases.
Recent findings, however, suggest that sexual contact is becoming an increasingly significant mode of transmission.
This information is somewhat challenging to confirm, as patients and healthcare providers might not fully understand that Shigella can be sexually spread, and sexual histories might not always be documented.
According to the CDC, data shows that over one-third of patients with extensive drug-resistant shigellosis were hospitalized, with nearly half of those with known HIV status also living with HIV.
Epidemiologist Naeemah Logan mentioned that this pattern of XDR Shigella strains among vulnerable populations is concerning and is not confined to the United States; rather, it fits within a broader global trend.
In a corresponding study from the University of Cambridge, geneticist Kate Baker reported a similar rise in the United Kingdom.
Baker highlighted that many men who have sex with men are unaware of the heightened risks associated with sexually transmitted Shigella.
She noted, “This disease has shifted from being somewhat treatable with standard medications to nearly untreatable over the past decade.”
The UK Health Security Agency (UKHSA) warned that while most Shigella cases may resolve independently, more severe cases necessitate treatment, which is becoming increasingly limited.
Forecasts suggest that by 2025, 86 percent of Shigella sonnei samples and 94 percent of Shigella flexneri samples examined by UKHSA will exhibit antibiotic resistance, particularly among sexual networks in England.
Previous research indicated that up to a third of patients with sexually transmitted Shigella faced hospitalization for an average of four to five days.
Baker asserted that this issue involves multiple overlapping variants all rapidly gaining resistance to standard treatments, stressing that treatment for sexually contracted Shigella may differ from those contracted through travel.
No clear reasons explain why this distinction exists. Still, Baker’s study pointed to a phenomenon referred to as ‘bystander resistance’, suggesting that antibiotics intended for one type of infection could inadvertently foster resistance in other pathogens.
Alicia Calvo-Villamañán from the Gulbenkian Institute in Portugal pointed out an interesting correlation: when UK treatment guidelines ceased recommending azithromycin for gonorrhea, the emergence of resistance in Shigella decreased. This doesn’t imply a direct causative relationship, but it raises questions about how treating other STIs may influence drug-resistant Shigella infections, which are often overlooked in STI screenings.
The California Department of Public Health emphasizes that the best preventive measure against Shigella during sexual activity is to avoid contact with anyone who has experienced diarrhea within the last two weeks.
They also recommend using protection during oral and anal sex and ensuring cleanliness before and after sexual activities.
If someone suspects a Shigella infection, they should seek testing and treatment promptly.
Consultant in sexual health Daniel Richardson highlighted the need for clinicians to inquire about sexual transmission in dysentery cases and provide appropriate advice, emphasizing that sexually transmitted Shigella tends to have higher antimicrobial resistance than other types, warranting checks for additional sexually transmitted infections.
