With the pipeline for new antibiotics weak and underfunded, vaccines are seen as a potential tool for preventing the infections that drive antibiotic use and resistance.
The strain of Shigella sonnei is non-susceptible to several classes of antibiotics, and health officials say it's likely to spread.
Montana's H1N2v case was reported in a patient who had attended an agricultural fair.
Of 300 cases recorded since April, 106 have been in the US, with the rest in Europe.
The study authors suggest the strain's resistance to ceftriaxone is likely being driven by bystander resistance resulting from the use of ceftriaxone for treatment of gonorrhea.
Officials have received a growing number of reports of XDR Shigella, which is highly transmissible and resistant to commonly recommended antibiotics, in adults.
There have been 221 confirmed Shigella sonnei infections and 37 possible cases from the EU, UK, and US.
The emergence of multidrug-resistant strains of the enteric pathogen is challenging clinicians and public health officials.
A report yesterday from the United Kingdom's Health Security Agency (HSA) shows sexually transmitted Shigella infections are rising again in England after falling during the COVID-19 pandemic.
A study yesterday in The Lancet Infectious Diseases describes an ongoing outbreak of sexually transmitted, extensively drug-resistant (XDR) Shigella sonnei in the United Kingdom.