“Study shows US emergence of multidrug-resistant E coli clone”
“A new study in Clinical Infectious Diseases describes the emergence of a new multidrug-resistant Escherichia coli clone in the United States.
In a multicenter surveillance study conducted at nine sites in four US cities (Seattle, Los Angeles, Minneapolis, and New York) in 2016-2017, researchers collected 6,349 consecutive clinical E coliisolates from urine, blood, or wounds and tested them for susceptibility to antibiotics and production of extended-spectrum beta-lactamase (ESBL) production. They performed additional analysis on fluoroquinolone-resistant (FQ-R) E coli isolates to determine clonal identity and resistance mechanisms. They were looking to gain further insight into hospital reports of the occurrence of FQ-R E coli belonging to the clonal group ST1193.
Of the 6,349 E coli isolates, 1,314 (20.7%) were FQ-R and represented 45 clonal groups overall. At each site, the most prevalent clonal group among FQ-R isolates was ST131 H30 (per-site mean, 45.4%), which emerged in the late 1990s and has become the most prevalent worldwide pandemic clonal group of multidrug-resistant E coli. The second most prevalent was ST1193 (23.2%). But while the prevalence of H30 did not change between 2016 and 2017, either overall (45.8% in 2016 vs. 46.1% in 2017) or at any single site, the prevalence of ST1193 increased both overall (18.4% in 2016 vs. 25.9% in 2017) and at six sites. In addition, at four sites that provided data on 2011 FQ-R isolates, ST1193 exhibited a seven-fold overall prevalence increase (3.4% in 2011 to 23.4% in 2016-2017).
In addition to being FQ-R, the ST1193 isolates were often co-resistant to trimethoprim-sulfamethoxazole and tetracycline, but unlike ST131 H30 remain susceptible to most beta-lactam antibiotics. The researchers also found that ST1193 E coli appears to target younger patients and is less likely to be isolated from blood.
The authors say the findings, along with reports of ST1193 being isolated in hospitals in Europe and Asia, suggest that ST1193 is likely to be a pandemic clonal group similar to H30. They conclude, “Discovery of the basis for the global expansion of ST1193 could provide insights into how successful clonal groups of multidrug-resistant E. coli emerge and what interventions could limit their spread.”