California Patient Dies with Superbug Infection

California health officials recently reported the state’s first case of infection with a bacterial isolate carrying the MCR-1 gene, which gives pathogens resistance to last resort antibiotics and exacerbates the growing problem of antibiotic resistance.

The Centers for Disease Control and Prevention (CDC) tracks the presence of MCR-1, a plasmid-borne gene that gives bacterial pathogens resistance to the antibiotic drug, colistin. The DNA-containing MCR-1 gene also spreads easily amongst different bacteria. Researchers first detected the gene in strains of Escherichia coli in China, and have since found MCR-1 in Salmonella enterica, Klebsiella pneumonia, Enterobacter aerogenes, and Enterobacter cloacae. The earliest known US case of a MCR-1 producing bacterial isolate was identified in 2014, and CDC tracking shows that human cases of illness with bacterial isolates containing the resistance gene have been identified in New Jersey, Maryland, New York, Pennsylvania, Connecticut, and now California. Animal isolates have been found in South Carolina and Illinois.

On January 31, 2017, Los Angeles County Department of Public Health officials issued a statement notifying the public that doctors had identified an isolate of E. coli with the MCR-1 gene in a county resident who died last year; the patient died from another medical condition rather than from that E. coli infection. Officials believe the patient acquired the infection while travelling outside of the United States. In previous studies, researchers reported cases of isolates with MCR-1 in parts of Asia, Europe, and Canada. In Los Angeles, public health officials noted that they have found no evidence that the identified E. coli strain has spread in the local community. They are asking area healthcare providers to follow recommendations for infection control, testing, and reporting for patients with suspected and confirmed infections with bacterial strains containing MCR-1.

The news from California has come at the same time as a recent study published in the CDC journal Emerging Infectious Diseases highlights the link between the spread of MCR-1 in Vietnam and the extensive use of colistin in the country’s agriculture production. In their investigation, authors of the study analyzed fecal specimens from humans and chickens and discovered an adjusted prevalence of MCR-1 in 59.4% of chicken samples and in 20.6% of human samples. The researchers discovered that zoonotic transmission was contributing to the high prevalence of MCR-1 in Vietnam; human exposure to these chickens had led to MCR-1 colonization in humans.

The CDC's recommendations to help limit the spread of antibiotic resistance genes include proper hand hygiene, food and water safety precautions, and vaccinations to help prevent certain diseases. Antibiotic stewardship—the proper use of the right antibiotics for the right infections—as well as reducing antibiotic use in agricultural products, are the cornerstones of preventing the spread of drug resistant bacteria, according to studies, which continue to highlight the link between inappropriate antibiotic use and superbug infection outbreaks.