In the Journals

Colistin resistance detected in US for second time

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July 11, 2016

A second patient in the United States has been detected with colistin resistance.

Researchers from the SENTRY antimicrobial surveillance program wrote in a letter to the editor of Antimicrobial Agents and Chemotherapy that the colistin-resistant mcr-1 gene was discovered in an Escherichia coli isolate collected in New York in May 2015.

That predates by almost a year an E. coli culture taken in April from a woman in Pennsylvania that also was found to harbor the mcr-1 gene — the first time resistance to the last-resort antibiotic was detected in a U.S. patient.

The discoveries come amid heightened concern over antimicrobial resistance and growing fears that the plasmid-borne mcr-1 gene will jump to a bacteria species that is resistant to most antibiotics.

Mariana Castanheira, PhD, director for molecular and microbiology at JMI Laboratories, and colleagues reported the most recent finding of mcr-1. They tested 13,526 E. coli and 7,480 Klebsiella pneumoniae isolates collected from 183 hospitals in 2014 and 2015, including 113 hospitals in North America, 46 in Europe, 15 in the Asia-Pacific region, and nine in Latin America. They found that 1.9% of the isolates (n = 390) were resistant to colistin, including 19 — all E. coli — that harbored the mcr-1 gene. Those isolates came from Germany (n = 5), Italy (n = 4), Spain (n = 3), Belgium (n = 1), Brazil (n = 1), Hong Kong (n = 1), Malaysia (n = 1), Poland (n = 1), Russia (n = 1), and the U.S. (n = 1).

Eight of the positive isolates were associated with bloodstream infections, five with skin and skin structure infections, three with urinary tract infections, two with respiratory tract infections and one with an intra-abdominal infection.

Although the prevalence of mcr-1 among E. coli was elevated, very low rates were observed by the overall population surveyed by the SENTRY program, which is coordinated by Castanheira and colleagues. All of the isolates carrying mcr-1 were susceptible to various antimicrobial classes.

Castanheira and colleagues, however, concluded “the prospect of a mobile gene encoding resistance to colistin evolving among isolates resistant to most clinically available antimicrobial agents is threatening for the therapy of serious infection.” – by Gerard Gallagher

Disclosure: JMI Labs received research and educational grants from numerous drug companies during 2014 and 2015, and some of its employees work for several of those companies as advisers or consultants.