A new multi-drug resistant clone of Escherichia coli — ST1193 — has emerged in multiple US cities, according to research published in Clinical Infectious Diseases.
The isolate is associated with adults age <40, and comprises one quarter of fluoroquinolone-resistant clinical E coli urine isolates.
Antibiotic resistance is a rising global problem, with urinary tract infections caused by E coli being one major reason for the use of antibiotics, primarily fluoroquinolones (FQ). A multicenter surveillance study collected 6349 E coli isolates from 4 geographically diverse cities in the United States from 2016 to 2017 to determine any clonal expansion evident in FQ-resistant E coli.
Isolates were obtained from urine (96%), blood (3.5%), or wounds (0.5%). Susceptibility of the isolates to 12 antibiotics from 8 drug classes was tested and FQ-resistant isolates were further tested for clonal identity using a single-nucleotide polymorphism (SNP)-based clonotyping test (7-SNP test) and fumC/fimH sequence typing.
In total, 20.7% of all E coli isolates were FQ-resistant. The most prevalent clonal group identified across sites was H30 (per-site mean, 45.4%), followed by ST1193 (per-site mean, 23.2%). Together, these two groups accounted for an average of 68.6% of FQ-resistant isolates per site. While the overall prevalence of H30 did not change significantly from 2016 to 2017, the prevalence of ST1193 increased from 18.4% in 2016 to 25.9% in 2017 (P <.001). The clone ST1193 was resistant to multiple drugs tested: fluoroquinolones (100%), trimethoprim/sulfamethoxazole (55%), and tetracycline (53%). After multivariable adjustment, it remained highly associated with younger adults (<40) compared with H30 (odds ratio [OR], 4.3; P =.007).
The study results establish the widespread occurrence of ST1193 across the United States and highlight its importance as a growing contributor to FQ resistance. The ST1193 clone has also been reported in Europe and Asia, indicating that it is likely a pandemic clonal group similar to the H30 clone. Investigators believe that ST1193 emerged earlier than H30 and that its expansion may still be ongoing. Also, in contrast to H30, ST1193 targets younger patients and is less likely to be isolated from blood, although further investigation is needed. They concluded that “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.”
Tchesnokova VL, Rechkina E, Larson L, et al. Rapid and extensive expansion in the U.S. of a new multidrug-resistant Escherichia coli clonal group, sequence type ST1193. [published online June 29 2018]. Clin Infect Dis. doi:10.1093/cid/ciy525