A RECENT study has revealed an alarming rise in multidrug-resistant Shigella sonnei in Vancouver, Canada among people experiencing homelessness (PEH).
S. sonnei is a bacterium known to cause sexually transmitted enteric infections in men who have sex with men (MSM). From 2015–2022, a total of 163 cases were reviewed, showing a dramatic shift in the population affected by these infections.
Between 2015–2020, MSM accounted for the vast majority of infections, with 45 out of 46 cases (98%) in this group. However, in the more recent period, from 2021–2022, PEH represented 77% of the cases. While a small overlap between MSM and PEH populations was noted in both periods, the primary burden of infection has shifted to individuals facing homelessness.
The study also identified an increase in the severity of Shigella infections. Severe cases, which include hospitalization, bacteremia, or death, were significantly more common in the recent period. In fact, 61% of infections in 2021–2022 were classified as severe, compared to just 14% in the historical period (2015–2020). This rise in severity may be attributed to underlying vulnerabilities in the PEH population, such as poor living conditions and limited access to healthcare.
Genomic analysis of the bacterial strains revealed a dominant clone of multidrug-resistant (MDR) S. sonnei, specifically the 3.6.1.1.2 clone (CipR.MSM5), which showed resistance to all first- and second-line antibiotics but retained susceptibility to ceftriaxone. This clone was closely associated with the more severe cases, raising concerns about the bacterium’s resistance patterns.
Overall, the study underscores a troubling shift from sexually transmitted to likely environmentally acquired S. sonnei infections, with an increase in severity and the emergence of a highly resistant strain, particularly among those experiencing homelessness. The findings highlight the need for targeted public health interventions to address these rising challenges.
Ada Enesco, EMJ
Reference
Stefanovic A et al. Increased severity of multidrug-resistant Shigella sonnei infections in people experiencing homelessness. Clin Infect Dis. 2024; DOI: 10.1093/cid/ciae575.
