A fourth case of bacterial infection harboring the mcr-1 gene has been reported in a child recently returned from a visit to the Caribbean, according to a case report published Sept. 9 in Morbidity and Mortality Weekly Report.
The mcr-1 gene, which confers resistance to the last-resort antibiotic colistin, was first reported in China and is the first plasmid-mediated colistin-resistance mechanism to be identified. Since its discovery in 2015, cases have been reported in Africa, Asia, Europe, South America, and North America.
Janice Haney Carr/CDC
This colorized scanning electron micrograph depicts a number of Escherichia coli bacteria of the strain O157:H7. This strain of E. coli is an emerging cause of foodborne illness.
In this case report, a young patient developed fever and bloody diarrhea 2 days before returning to the United States from a 2-week visit to the Caribbean. The child were treated with the paromomycin and a stool specimen was collected on June 16, with follow-up cultures on June 18 and June 23.
All revealed Escherichia coli O157 harboring mcr-1. The isolates also carried a plasmid blaCMY-2 gene, which confers resistance to third-generation cephalosporins. Stool cultures taken on June 24 and July 1 were negative for E. coli O157 (MMWR. 2016 Sep 9. http://dx.doi.org/10.15585/mmwr.mm6536e3).
Family members in close contact with the patient also were tested; all were found to be negative. Similarly, 16 environmental samples collected from the kitchen and diaper-changing area of the patient’s home were negative for mcr-1.
Researchers reported that the patient was “typically healthy,” and the child’s diet included fruit, dairy products, and meat. While on vacation in the Caribbean, the child ate meat purchased at a live animal market but did not visit the market personally. The child also had contact with a pet dog and cat.
“At this time, CDC recommends that Enterobacteriaceae isolates with a colistin or polymyxin B MIC plus or minus 4 mcg/mL be tested for the presence of mcr-1; testing is available through CDC,” wrote Dr. Amber M. Vasquez and her colleagues from the Centers for Disease Control and Prevention. “Prompt reporting of mcr-1–carrying isolates to public health officials allows for a rapid response to identify transmission and limit further spread.”