Health officials in Mie Prefecture and Hamamatsu have detected rare OXA-48-producing Escherichia coli ST11672 strains in patients with no recent international travel history. Whole-genome sequencing reveals these Japanese cases stem from distinct origins, highlighting the domestic spread of a high-risk multi-drug-resistant global clone.
Detection of OXA-48-Producing E. coli ST11672 in Mie and Hamamatsu
Carbapenem-resistant Enterobacterales infections are designated as category 5 all-case surveillance diseases under the infectious disease law, with carbapenemase production serving as their primary resistance mechanism. While IMP-type carbapenemase remains dominant in Japan, recent years have seen the emergence of NDM, KPC, and OXA-48 types—enzymes once characterized as overseas variants—in patients lacking any history of international travel. Authorities have now documented the first domestic detections of the ST11672 multi-locus sequence type among OXA-48-producing Escherichia coli strains across Mie Prefecture and Shizuoka Prefecture’s Hamamatsu city.
Beginning in 2023, medical institutions within Hamamatsu submitted reports for two carbapenem-resistant Enterobacterales infections caused by OXA-48 E. coli. Both affected patients reported no travel outside the country for several years prior to their diagnoses. Two years after the initial Hamamatsu notification, Mie Prefecture recorded a separate carbapenem-resistant Enterobacterales infection caused by the same organism in a patient who also had no international travel history.
Genomic Analysis and Epidemiological Independence
To investigate a potential epidemiological connection between these geographically separated occurrences, researchers conducted whole-genome sequencing on the isolates. Multilocus sequence typing confirmed that both the Hamamatsu and Mie specimens belonged to ST11672. Analysts then performed phylogenetic testing using the CFSAN SNP Pipeline 2.2 and created a phylogenetic tree via raxml-ng 1.2.2, incorporating genomic sequence data from overseas isolates for comparison.
The resulting phylogenetic tree demonstrated that the Mie and Hamamatsu strains were not closely related. Specifically, the single-nucleotide polymorphism count between the two clinical isolates measured 45. While scientific consensus lacks a fixed single-nucleotide polymorphism threshold to definitively prove direct transmission, published analyses of drug-resistant E. coli often reference cutoffs ranging up to 10 or 176 single-nucleotide polymorphisms. Furthermore, researchers must account for chronological accumulation rates when comparing isolates separated by time, with established accumulation models estimating roughly 2.7 to 4.39 single-nucleotide polymorphisms per year. Whether applying strict or relaxed thresholds, the analytical findings did not suggest direct transmission of the ST11672 strain within domestic channels.
Shared Resistance Profiles and Global Context
A closer examination of the genetic makeup revealed notable overlaps and distinctions in antimicrobial resistance genes. Both the Hamamatsu and Mie isolates shared the blaOXA-48 gene alongside the blaCTX-M-15 extended-spectrum beta-lactamase gene, as well as specific mutations in gyrA, parC, and parE that confer resistance to quinolones. However, the genetic profile diverged regarding additional resistance markers: blaOXA-1 and aac(6′)-Ib-cr were detected exclusively in the Hamamatsu isolate.
Although detailed analytical reports on ST11672 remain scarce, the lineage represents a single-locus variant of ST131—a widely recognized multi-drug-resistant high-risk clone—that carries the blaOXA-48 gene. European health authorities previously documented ST11672 isolates recovered in Denmark, France, and the Netherlands between 2020 and 2023. Data from the EnteroBase E. coli repository show that among registered ST11672 entries spanning 2020 to 2025, geographic distribution extends across Europe, the United States, Australia, and Vietnam. Analysis of publicly available whole-genome sequences from 31 such strains indicates that the majority harbor blaOXA-48 and blaCTX-M-15.
Simultaneous Bacterial Concerns in Municipal Waters
In Framingham, routine water quality testing detected elevated levels of E. coli at Waushakum Beach, prompting local authorities to close the swimming area. The advisory took effect on Tuesday, August 4, following high bacteria counts identified during scheduled monitoring.
Health officials emphasize that swallowing contaminated water poses direct health risks, potentially triggering symptoms such as nausea, diarrhea, stomach cramps, and vomiting. Vulnerable populations, including young children, older adults, and individuals with compromised immune systems, face heightened risks of severe illness. Waushakum Beach remains one of three municipal swimming venues in Framingham, alongside Saxonville Beach and Learned Pond Beach. The closure will stay enforced until follow-up testing confirms that water conditions meet established state safety standards.
- Hospital Intervention Reduces Stillbirths and Newborn Deaths in Sub-Saharan Africa
- Good vs. Bad Cholesterol: Differences, Risks, and New Medical Guidelines
- Shift Supervisor Job at CVS Health – Bristol, Rhode Island (news-usa.today)
- 5 Foods a Gut Health Expert Never Eats (Even Salads!) (world-today-journal.com)
