CRE Bacteria Infection
(Carbapenem-Resistant Enterobacteriaceae)

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Recent news agencies have presented short but eye-brow raising comments made by the CDC about new and "dangerous" bacteria. The bacteria go by many names in the public press; "superbug 2013," "nightmare bacteria," and "dangerous bacteria" are just some of the names. Unfortunately, most news stories have only a few minutes to explain a somewhat complicated situation involving genetics, bacterial adaptation to environmental pressures, and the impact on human populations that makes the CDC researchers and many other researchers and doctors concerned. This article is designed to present readers with some further insights into these "dangerous" bacteria. The CDC name for these bacteria is CRE bacteria; the CRE stands for Carbapenem-Resistant Enterobacteriaceae.

First, what are dangerous CRE (Carbapenem-Resistant Enterobacteriaceae) bacteria? Simply stated, these bacteria are members of related bacterial genera that are commonly found almost everywhere in the world, often colonizing humans and animals (living in or on humans and animals mucosal surfaces, gastrointestinal tracts and on some areas on the skin). However, CRE possess a unique genetic makeup that allows the bacteria to make a component (an enzyme) that protect CRE bacteria from a powerful antibiotic - Carbapenem. The most notable genera that can share and even transfer this genetic trait to other members of the Enterobacteriaceae are E. coli and Klebsiella pneumoniae. Because these bacteria generate similar problems for patients (especially treatment difficulties) most investigators simply group them together and term them CRE bacteria. Similar types of components are termed KPC (Klebsiella pneumoniae carbapenemase) and NDM (New Delhi Metallo-beta-lactamase). This resistance to Carbapenem is not the only reason these bacteria are considered dangerous.

The genetics of Enterobacteriaceae are complex; many genera and strains possess genetic material that codes for resistance against many types of antibiotics; unfortunately, as a strain develops resistance to an antibiotic, not only does it become resistant to that antibiotic, the genes that confer resistance to one antibiotic become linked to each other. Consequently, as different antibiotic resistance occurs, the genetic material can become linked together thus conferring antibiotic resistance to several antibiotics in a single bacterial strain. Such bacteria that are resistant to several antibiotics are considerably more dangerous to humans they may infect than are bacteria susceptible to antibiotics.

As new antibiotics are introduced, they put survival pressure on bacteria. New antibiotics can pressure the bacteria to adapt to survive even the newest and powerful antibiotics; bacteria survive by allowing those few bacteria that develop stable resistance components that are genetically coded, to replicate, and then pass on genetic antibiotic resistance to other bacteria. Unfortunately, this new genetic ability is then again linked to other antibiotic resistant genetic material, thus resulting in "dangerous" bacterial strains that are resistant to many, if not all, antibiotics. That is the current situation for CRE bacteria. Keep in mind that there are strains of CRE bacteria that can fairly easily transfer genetic information to other bacterial strains that do not have multiple drug resistance, but may have the potential to be dangerous under certain circumstances (for example enterotoxigenic E. coli).

Currently, the outbreak of CRE bacteria is small. However, it may not remain that way. The CDC and other researchers know that many strains of Enterobacteriaceae can be deadly and difficult to treat even without being resistant to most antibiotics (for example, E. coli 0157:H7). How much damage could E. coli do to humans if it became a CRE bacterium by genetic transfer and retained its current pathogenic characteristics? Researchers and the CDC do not want to see this happen. In addition when a patient becomes infected with a CRE bacterium, the death rate is 50%, even with multiple antibiotic treatment and supportive measures. With additional pathogenic traits (easy person to person transfer, the ability to synthesize toxins like enterotoxins) added to the ability to be resistant to most, if not all antibiotics, the bacteria could devastate large populations of people. Since there are very few drug companies developing new antibiotics, the survival advantage may tip in favor of the bacterial pathogens, not to the infected people being treated with antibiotics.

Because the current CRE outbreak is small and often confined to hospital intensive care units, nursing homes, and other treatment areas where the use of new and powerful antibiotics is most frequent, the CDC has developed an attack method to keep CRE and other similar bacteria away from the general population and to reduce the "dangerous" bacteria's chances for survival and passage from these areas. The detailed method is described in the reference below and all healthcare workers are urged to participate to prevent widespread outbreaks of CRE and similar bacteria. An abbreviated version of the CDC recommendations is as follows:

Summary of Prevention (of CRE infections) Strategies for Acute and Long-Term Care Facilities (CDC 2012)

Core Measures for All Acute and Long-term Care Facilities

1. Hand Hygiene
  • Promote hand hygiene
  • Monitor hand hygiene adherence and provide feedback
  • Ensure access to hand hygiene stations


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