Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
Dr. Balentine received his undergraduate degree from McDaniel College in Westminster, Maryland. He attended medical school at the Philadelphia College of Osteopathic Medicine graduating in1983. He completed his internship at St. Joseph's Hospital in Philadelphia and his Emergency Medicine residency at Lincoln Medical and Mental Health Center in the Bronx, where he served as chief resident.
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
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