NDM-1 stands for New Delhi metallo-beta-lactamase, which is an enzyme produced by certain strains of bacteria that have recently acquired the genetic ability to make this compound. The enzyme is active against other compounds that contain a chemical structure known as a beta-lactam ring. Unfortunately, many antibiotics contain this ring, including the penicillins, cephalosporins, and the carbapenems.
NDM-1 infection was first identified (in 2009) in people who resided in or traveled to the India and Pakistan. Antibiotic use in India is not as restricted as it is in the United States and some researchers feel overuse of carbapenems allowed NDM-1 to develop. Others point to the advent of medical tourism as a cause of NDM-1 spread among countries. Medical tourism refers to patients who travel to a country to get medical care that is not available or is more expensive in their own country. The three first cases of NDM-1 infection in the United States were identified in June 2010 in Americans who had recently sought medical care in India. Vacation and business travel have also played a role in introducing NDM-1 bacteria into countries outside of the Indian subcontinent. Cases have now been detected in many countries, including Great Britain, Canada, Sweden, Australia, Japan, and the United States.
Cases of NDM-1 infection are usually caused by gram negative bacteria from the Enterobacteriaceae family. This family includes common bacteria like Escherichia coli (E. coli) and Klebsiella. These bacteria reside in the bowel and may spread from person to person if hands or items are contaminated with fecal material. To date, strains of Klebsiella, Escherichia, and Acinetobacter genera of bacteria are known to possess the gene for NDM-1.
What are symptoms and signs of a person infected with bacteria carrying NDM-1?
Bacteria from the Enterobacteriaceae family are the most common cause of urinary infections. They can also cause bloodstream infections (sepsis), pneumonia, or wound infections. Symptoms and signs reflect the site of the infection. Most patients will have fever and fatigue. If bacteria enter the bloodstream, patients may go into shock. Symptoms do not differ between bacteria that express NDM-1 and those that do not. However, patients who have bacteria producing NDM-1 will not respond to most conventional antibiotics and are at high risk for complications.
Centers for Disease Control and Prevention
“Detection of Enterobacteriaceae Isolates Carrying Metallo-Beta-Lactamase -— United States, 2010.” http://www.cdc.gov/mmwr/preview/
mmwrhtml/mm5924a5.htm
Centers for Disease Control and Prevention
“Guidance for Control of Infections with Carbapenem-Resistant or Carbapenemase-Producing Enterobacteriaceae in Acute Care Facilities.” http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5810a4.htm
Carbapenem-resistant Enterobacteriaceae (CRE)
The term CRE refers to carbapenem-resistant and carbapenemase-producing Enterobacteriaceae. Currently, the most common type of carbapenemase in the United States is the Klebsiella pneumoniae carbapenemase (KPC). In 2010, carbapenemases known as metallo-beta-lactamases (MBL) were first detected in the U.S.: New Delhi MBL (known as NDM-1) and Verona-Integron encoded MBL (known as VIM).
Clinical significance
K. pneumoniae can cause the disease Klebsiella pneumonia.
They cause destructive changes to human lungs inflammation and hemorrhage with cell death (necrosis) that sometimes produces a thick, bloody, mucoid sputum (currant jelly sputum). Typically these bacteria gain access after a person aspirates colonizing oropharyngeal microbes into the lower respiratory tract.
As a general rule, Klebsiella infections are mostly seen in people with a weakened immune system. Most often illness affects middle-aged and older men with debilitating diseases. This patient population is believed to have impaired respiratory host defenses, including persons with diabetes, alcoholism, malignancy, liver disease, Chronic obstructive pulmonary diseases (COPD), glucocorticoid therapy, renal failure, and certain occupational exposures (such as paper mill workers).
Many of these infections are obtained when a person is in the hospital for some other reason (a nosocomial infection).
The most common infection caused by Klebsiella bacteria outside the hospital is pneumonia, typically in the form of bronchopneumonia and also bronchitis. These patients have an increased tendency to develop lung abscess, cavitation, empyema, and pleural adhesions. It has a high death rate of about 50% even with antimicrobial therapy. The mortality rate can be nearly 100% for persons with alcoholism and bacteremia.
In addition to pneumonia, Klebsiella can also cause infections in the urinary tract, lower biliary tract, and surgical wound sites. The range of clinical diseases includes pneumonia, thrombophlebitis, urinary tract infection (UTI), cholecystitis, diarrhea, upper respiratory tract infection, wound infection, osteomyelitis, meningitis, and bacteremia and septicemia. If a person has an invasive device in their body then contamination of the device becomes a risk; for example respiratory support equipment and urinary catheters put patients at increased risk.
Also, the use of antibiotics can be a factor that increases the risk of nosocomial infection with Klebsiella bacteria. Sepsis and septic shock can follow entry of the bacteria into the blood.