Resistant ‘Nightmare Bacteria’ Increase Fivefold in Southeastern U.S.

Wired – by MARYN MCKENNA

There’s worrisome news here in the southeastern U.S., buried in a journal that is favorite reading only for superbug geeks like me. The rate at which hospitals are recognizing cases of CRE — the form of antibiotic resistance that is so serious the CDC dubbed it a “nightmare” — rose five times over between 2008 and 2012.  

Within that bad news, there are two especially troubling points. First, the hospitals where this resistance factor was identified were what is called “community” hospitals, that is, not academic referral centers. That’s an important distinction, because academic medical centers tend to be where the most cutting-edge care is performed, and where the sickest people are. As a result, they are where last-resort antibiotics are used the most, and therefore where resistance is most likely to emerge. That CRE was found so widely not in academic centers, but rather in community hospitals, is a signal that it is probably moving through what medicine calls “the community,” which is to say, anywhere outside healthcare. Or, you know, everyday life.

A second concern is that the authors of the study, which is in Infection Control and Hospital Epidemiology, assume that their finding is an underestimate of the actual problem.

A little background first on CRE. (Archive of posts on it is here.) The acronym stands for “carbapenem-resistant Enterobacteriaceae.” Enterobacteriaceae are a large family of bacteria that normally are carted around in your guts without causing illness. When they escape, though — for instance, during ICU treatment — they are a common cause of serious hospital-acquired infections. “Carbapenems” are a small group of very powerful antibiotics that are viewed as drugs of last resort, which work against infections that have become resistant to most other antibiotics. The acronym CRE indicates a group of resistant organisms that go by other acronyms — NDM, OXA, VIM and KPC, for instance — and that have been spreading across the globe for more than 10 years.

CREs are serious stuff: In studies, half or more of those who develop infections die.(A reader asked about references for this; I have added some at the end of the post.)There are only a few antibiotics — sometimes one, sometimes two, depending on the organism — that work against them at all, and those drugs have significant problems and side effects. Broadly speaking, the emergence of CREs brings us several steps closer to the end of the antibiotic era.

For reasons that no one has ever been able to explain, one of the CRE organisms — KPC, or Klebsiella pneumoniae resistant to carbapenems — seems to have emerged in North Carolina; it was first noted in a set of bacterial samples that a hospital in that state sent to the CDC in 1996. So it’s resonant that this study was conducted by researchers in North Carolina; it reveals how far that organism and others have spread.

About the study: It relies on data tendered to the Duke Infection Control Outreach Network by 25 community hospitals in North Carolina, South Carolina, Virginia and Georgia. The hospitals ranged in size from 100 to 657 beds, so some of them were truly small community institutions. The data was collected between January 2008 and December 2012, so as a snapshot of what is happened in the US with regard to CRE, it is pretty timely.

Out of the 25 hospitals, 16 identified 305 patients carrying or infected with CRE:

• 59 percent had identifiable infections; 41 percent were colonized, that is, carrying the bacteria asymptomatically.
• 34 percent of the cases became evident while the patient was in the hospital (hospital-onset healthcare associated) and 60 percent after patients had returned home (community-onset hospital-associated)
• of the cases that were diagnosed after someone had left an acute-care hospital, 56 percent were associated with nursing homes.

The key trend is here: In 2008, the rate of CRE detection was 0.26 cases per 100,000 patient days; in 2012, it was 1.4 per 100,000 patient-days.

Those may seem like small numbers. Here is what the authors say:

…rates of CRE, while still infrequent, are increasing dramatically in community hospitals, where the majority of Americans receive their healthcare. We believe this increase is attributable to growing reservoirs and transmission of CRE and improvement in detection. Overall, we believe the estimates from study hospitals are underestimates of the true incidence in these hospitals. This point underscores the fact that these organisms are increasingly important and relevant in all areas of healthcare, including small community hospitals.

The study is worth reading as well for an extended discussion of the challenges of CRE detection, including the pace at which new laboratory standards for detecting these organisms are being adopted (or not). Overall, though, it is a worrisome indicator that highly resistant organisms may be outpacing our ability to detect or to treat them.

Cite: Thaden JT, Lewis SS, Hazen KC et al. Rising Rates of Carbapenem-Resistant Enterobacteriaceae in Community Hospitals: A Mixed-Methods Review of Epidemiology and Microbiology Practices in a Network of Community Hospitals in the Southeastern United States.  Infection Control and Hospital Epidemiology, Vol. 35, No. 8 (August 2014), pp. 978-983. DOI: 10.1086/677157

Update: here are some references for the mortality rate for CRE infection:

• 2013: The Centers for Disease Control and Prevention’s 2013 “threat report” on antimicrobial resistance, from which this page is abstracted.
• 2012: Ben-David D et al., “Outcome of carbapenem resistant Klebsiella pneumoniae bloodstream infections,” Clinical Microbiology and Infection
• 2011: Mathers AJ et al., “Molecular Dissection of an Outbreak of Carbapenem-Resistant Enterobacteriaceae Reveals Intergenus KPC Carbapenemase Transmission through a Promiscuous Plasmid,” mBio
• 2009: Daikos GL et al., “Prospective observational study of the impact of VIM-1 metallo-beta-lactamase on the outcome of patients with Klebsiella pneumoniae bloodstream infections,” Antimicrobial Agents and Chemotherapy
• 2009: Borer A et al., “Attributable mortality rate for carbapenem-resistant Klebsiella pneumoniae bacteremia,” Infection Control and Hospital Epidemiology
• 2008: Patel G et al, “Outcomes of carbapenem-resistant Klebsiella pneumoniae infection and the impact of antimicrobial and adjunctive therapies,” Infection Control and Hospital Epidemiology

http://www.wired.com/2014/07/cre-fivefold/