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.
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
NDM-1 is an abbreviated way to write New Delhi metallo-beta-lactamase, which
is the name given to a new (discovered in 2009) enzyme that is able to be
produced by several genera of bacteria that render the bacteria resistant to
many antibiotics in common use around the world. This enzyme belongs to a group
of enzymes (beta-lactamases) that are capable of breaking the chemical bonds of
a beta-lactam ring, which composes an important part of many antibiotics such as
drugs of the penicillin, cephalosporin, and carbapenem groups. Most of the
beta-lactamase enzymes are effective on some or most of the older antibiotics
like penicillins and cephalosporins. NDM-1, however, is effective on both the
old and newer antibiotics (carbapenems such as imipenem) that contain a
Klebsiella were the first bacteria identified (in 2009) to
produce NDM-1 in a patient that traveled from India to England with an infection
that did not respond to many antibiotics. The organism was resistant to beta-lactams and, after the organism's genetic and antibiotic resistance mechanisms
were studied, NDM-1 and its genetic source were discovered. The genetic source
was a plasmid termed "blaNDM-1," and since that discovery, other bacterial genera
have been found to have blaNDM-1 integrated into other plasmids or into the
bacterial chromosome, thus allowing the bacteria to produce NDM-1.
effective against almost all antibiotics with beta-lactam rings, is not
effective in producing antibiotic resistance against other types of antibiotics
such as fluoroquinolones (for example, ciprofloxacin [Cipro] and levofloxacin
aminoglycosides (for example, gentamicin [Garamycin] and streptomycin [Streptomycin]). Unfortunately, most
of the strains of bacteria that have NDM-1 also have either plasmid or
chromosomal resistance against these (and other) antibiotics. The term
"superbug" is often used loosely to describe organisms resistant to usually two
or more antibiotics. Because bacteria that contain NDM-1 are often resistant to
almost every antibiotic, bacteria with NDM-1 have been termed a superbug;
some investigators consider these bacteria to represent the most dangerous
superbug of all that have developed so far.
Although newly discovered in 2009
and most likely because of genetic transfer of plasmids or other chromosomal
segments, NDM-1 has been found in at least four different genera of
gram-negative bacteria (Klebsiella, Escherichia, Enterobacter, and
Acinetobacter). In addition, people in India, Pakistan, England, Canada, Sweden,
Australia, Japan, and the U.S. have been found to be infected with bacterial
strains that produce NDM-1. Researchers speculate that the extremely fast spread
of NDM-1 may be due to patients seeking medical care outside of their home
country (for example, visitors or travelers from India); others suggest the
widespread and uncontrolled use of antibiotics favors the survival of NDM-1-containing bacterial strains. Another possible reason for fast spread is that
Escherichia coli (E. coli), part of the normal bacteria found in the human
intestine, readily exchanges plasmids; in fact, the first identified patient
infected with Klebsiella containing NDM-1 was subsequently found to have an E.
coli strain, isolated from the feces, capable of producing NDM-1.
What Are Symptoms and Signs of a Person Infected With Bacteria Carrying NDM-1?
The major sign or symptom that a person is infected with bacteria carrying
NDM-1 is failure of antibiotic treatments (oral or IV) to improve the patient's
condition, especially if the patient is infected with a gram-negative bacterial
type and is being treated with an antibiotic that contains a beta-lactam ring
structure. In addition, if the person has gone to another country (for example,
India) for elective surgery or was recently treated with antibiotics for an
infection and has returned to the U.S. or another industrialized country with the
infection, caregivers should be suspicious that a bacteria producing NDM-1 may
be causing the infection. Currently, these are the major clues to suggest
infection with NDM-1.