Author – Brandi Limbago, PhD
You’ve likely seen the news over the last couple of weeks warning people about “The [so-called] New Superbug NDM-1,” a newly discovered gene that makes bacteria resistant to last-resort antibiotics called beta-lactams or carbapenems. NDM stands for New Delhi Metallo-beta-lactamase, and in this case the NDM gene rendered antibiotics useless in three cases of infection with carbapenem-resistant Enterobacteriaceae (CRE). CDC discovered NDM-1 in the United States this year and reported it through the MMWR in June. Is it concerning? Absolutely; and we are working closely with healthcare providers and health departments to stop transmission of these bacteria.
That said, I’d like to point out that the story shouldn’t be solely about these bacteria being new or imported from other countries; the story should be about the whole group of CRE and untreatable infections they cause. In reality, these are not the first CRE cases we’ve seen in the United States. Not even close. NDM-1 is actually just one type of CRE and represents a larger antibiotic resistance issue that we already have, right now, in this country. CDC has been working with partners to prevent a type of CRE known as KPCs (carbapenemase-producing Klebsiella pneumonia). The KPC gene also makes Enterobacteriaceae bacteria resistant to beta-lactam/carbapenem antibiotics, just in a different way than NDM-1. KPCs have been reported in about 35 states and are associated with high mortality – 40 percent in one report. It may be in the other 15 states as well, but has not been reported to CDC. So, let’s not wait for NDM-1 in order to take action.
What exactly is happening with these Enterobacteriaceae? They are Gram-negative bacteria that normally live in our intestines. When not held in check by our body’s normal defenses, these same bacteria can cause serious infections, especially in hospitalized patients with medical devices such as catheters or ventilators. These infections are typically treated with beta-lactams, but when a resistance gene such as NDM-1 or KPC get into the bacteria, the result is a multi-drug resistant organism (MDRO) that can be very difficult to treat.
The good news is that we know strategies to prevent transmission of CRE infections, but more needs to be done. CDC issued guidance in 2009 about CRE transmission prevention, regardless of whether they’re NDM- or KPC-producers. We also have several guidelines on MDRO and other healthcare-associated infection prevention. The challenge now is motivating the healthcare community to take action, including using antibiotics wisely, following transmission prevention guidelines, and implementing overall infection prevention recommendations.
So while I think that all the attention to NDM-1 has raised awareness about the broader CRE problem, which is good, we need providers to take the recommended steps towards prevention. Patients’ lives could depend on it.