The Centers for Disease Control and Prevention (CDC) recently announced
that their investigators have identified a strain of Escherichia coli
with the colistin-resistance gene mcr-1
in a Connecticut child, in what is now the fourth patient in the United States to test positive for an isolate with mcr-1
Researchers in China were the first to discover Enterobacteriaceae with the mcr-1
gene in samples in 2015, and similar strains
have since been found in other parts of Asia, Africa, Europe, South America, and North America. Those findings have heightened worldwide concerns over the potential emergence of pan-resistant pathogens, which could one day have resistance to all antibiotics, and health experts have since tracked closely the spread of the mcr-1
gene. The World Health Organization considers antibiotic resistance
in bacteria to be one of the biggest threats to global health today, and calls out the use of antibiotic medications as a contributing factor to the rise of stronger, more virulent pathogens. The growth of antibiotic-resistant diseases has led to longer hospital stays, higher medical costs, and deadlier infections around the world.
The Pathogen Detection System at the National Center for Biotechnology Information in Bethesda, Maryland identified this most recent–and America’s fourth confirmed–case of E. coli
with the mcr-1
gene. The isolate came from a sample taken from a 2-year-old girl in Connecticut who returned to the United States in June after a two-week visit with friends and relatives in the Caribbean. On June 12 and two days before returning to the United States, the child became ill with a fever and bloody diarrhea. After a primary care provider visit, the child began a course of the aminoglycoside antibiotic paromomycin, and additionally had a brief emergency department visit while she was ill.
June 16 cultures from stool samples taken during her screening came up positive for E. coli
O157 with a plasmid blaCMY-2
gene, which while conferring resistance to third generation cephalosporins also showed the isolate remains susceptible to carbapenems, along with the mcr-1
gene. Follow up cultures from June 24 and July 1 were negative for E. coli
Researchers have yet to pinpoint the source of E. coli
O157 in the case of this child. Interviews with the patient’s parents and healthcare providers show no prior history of hospital visits or surgery. During her travels, the young child ate chicken and goat meat from a live animal market, which she did not personally visit. She also stayed in a home with a pet dog and cat.
Due to their high risk of coming in contact with mcr-1
, the child’s parents and healthcare providers who took part in her diapering and bathing during her illness were screened for the presence of bacteria with the gene via perirectal swabs. Samples from all six of the child’s household contacts, as well as environmental samples taken from around their home, did not show the presence of mcr-1
, and family members are not believed to have been colonized by the bacteria.
Along with preventing the spread of drug-resistant infections between people, the global healthcare community is also tracking how the genes that confer antibiotic resistance are shared between bacterial species. “In regard to the case in Connecticut, it is not that surprising given that we know the mcr-1
gene is out there,” Barry Kreiswirth, PhD, of the Public Health Research Institute Center at Rutgers University told Contagion
. “Identifying strains that carry this gene is not going to be that uncommon.”
According to the CDC, at least 2 million people in the United States each year are infected with bacteria that are resistant to antibiotics, and these infections lead to about 23,000 deaths annually. The CDC says that the best form of protection against these infections
is prevention, and hand hygiene, staying up-to-date on vaccinations, and safe food handling are some of the best steps to take to avoid so-called “superbugs.”
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