Mcr-9

A "superbug" carrying mcr-9 plus a carbapenemase (e.g., NDM or KPC) leaves virtually no treatment options.

An mcr-9 positive, bla KPC-positive K. pneumoniae causing a bloodstream infection.

Like mcr-1, the rise of mcr-9 is likely linked to agriculture. In many countries, colistin has been used liberally as a growth promoter in livestock. This overuse creates a massive reservoir of resistant bacteria in the food chain. You eat the chicken, the chicken’s E. coli transfers the mcr-9 plasmid to your gut bacteria—and the cycle continues. A "superbug" carrying mcr-9 plus a carbapenemase (e

That safety net began fraying in 2015 with the discovery of mcr-1 (mobile colistin resistance). For the first time, scientists realized that colistin resistance wasn't just a chromosomal mutation; it was plasmid-borne, meaning it could jump between bacterial species like a computer virus.

mcr-9 is a reminder that bacteria are brilliant chemists. Just because we can’t see the resistance today doesn’t mean it isn’t there, waiting for the right moment to switch on. Like mcr-1, the rise of mcr-9 is likely

Stay vigilant. Wash your hands. And support antibiotic research.

For a clinician, a patient infected with an mcr-9 -positive organism presents a nuanced challenge. You eat the chicken, the chicken’s E

The rise of antibiotic-resistant bacteria has become a pressing concern globally, with the World Health Organization (WHO) labeling it as one of the biggest threats to human health. One of the most significant contributors to this problem is the emergence of carbapenem-resistant Enterobacteriaceae (CRE), which are bacteria that have developed resistance to carbapenems, a class of antibiotics considered the last line of defense against bacterial infections. Within this family of resistant genes, a new player has emerged: MCR-9. This article aims to provide an in-depth look at MCR-9, its origins, mechanisms of resistance, global prevalence, and the implications it poses to public health.

As of 2025, mcr-9 remains a "hidden" threat, but hidden threats have a way of becoming headlines. The time to act is before it becomes the next global pandemic of resistance.