Study highlights resistance genes in Shiga toxin-producing E coli

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Whole-genome sequencing of Shiga toxin-producing Escherichia coli (STEC) from human fecal samples found that nearly 15% harbored antimicrobial resistance (AMR) genes, English researchers reported today in the Journal of Antimicrobial Therapy.

For the study, researchers with the UK Health Security Agency extracted and sequenced DNA from fecal specimens from patients in England with suspected gastrointestinal infections, which are tested for a range of gastrointestinal pathogens. They focused on STEC O157:H7, the most frequently detected STEC serotype in the United Kingdom, and used long-read sequencing to describe the occurrence and frequency of AMR determinants in STEC O157:H7 isolates.

E coli
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Overall, 216 (14.7%) of 1,473 STEC O157:H7 isolates had at least one AMR determinant, although the proportion of isolates exhibiting AMR varied by sublineage. The highest proportions of AMR determinants were detected in sublineages Ib (28/64, 43.7%), I/II (18/51, 35.3%), and IIc (122/440, 27.7%).

In all seven sublineages, the most commonly detected AMR genes conferred resistance to aminoglycosides (11.7%), tetracyclines (11.3%), sulphonamides (11.7%), and beta-lactams (8.8%). AMR genes conferring resistance to fluoroquinolones, macrolides, and third-generation cephalosporins were rarely detected, and no carbapenemase genes were detected.

The study authors say that the proportion of STEC O157:H7 isolates in England harboring resistance to at least one class of antibiotics has decreased over the last two decades, dropping from 20% in previous studies to 14.7% in this study, a finding they suggest might be related to more regulated use of antibiotics in UK livestock. In addition, they note that the strains associated with travel outside the United Kingdom were more likely to harbor resistance genes.

They say implementing long-read sequencing into routine surveillance will enable public health officials to monitor the emergence and spread of drug-resistant enteric pathogens.

"Monitoring AMR in gastrointestinal pathogens may provide an early warning of emerging risks to public health regarding the clinical management and empirical treatment of infectious diseases," they wrote.

Quick takes: El Nino public health threat assessment, more chikungunya vaccine trial results, Florida dengue case

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  • The World Health Organization (WHO) recently posted an update on public health threats related to the June onset of the El Nino climate pattern, which is predicted to last at least until the end of the year. It said the highest risk is due to malnutrition from food insecurity and diarrheal illnesses, especially in drought-affected areas, factors that could contribute to population displacement. The next-highest risk is cholera and other diarrheal diseases due to water contamination from flooding or water scarcity in drought-affected areas, especially in East Africa. Other threats in the high-risk category include other waterborne illnesses, foodborne disease, malaria, arbovirus diseases, other vector-borne diseases, rodent-borne diseases, and vaccine-preventable diseases.
  • Bavarian Nordic yesterday reported more promising phase 3 clinical trial results for its candidate chikungunya vaccine, this time in adolescents and adults ages 12 to 65 years old. The trial enrolled more than 3,200 people who were randomized to receive a single dose of the virus-like particle vaccine or a placebo. In results 22 days after immunization, the vaccine was highly immunogenic, prompting a strong response in 98% of recipients, with neutralizing antibody titers above the study targets. Also, 86% had neutralizing antibodies at the predefined seroprotection level 6 months after vaccination. In June, the company reported similar promising findings in older people. Company officials project regulatory submission in 2024.
  • In its latest weekly mosquito-borne illness update the Florida Department of Health reported another local dengue case, raising the total to six for the year. Like the others, the patient is from Miami-Dade County. Florida eliminated dengue transmission in the 1930s, but has reported sporadic local cases due to introductions related to international travel. In 2022, it reported 68 local dengue cases, mainly from Miami-Dade County.

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