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.
The extent and prevalence of CRKP within the environment is currently unknown. The mortality rate is also unknown but is suspected to be within a range of 12.5% to as high as 44%.
The likelihood of an epidemic or pandemic in the future remains uncertain.
Over the past 10 years, a progressive increase in CRKP has been seen worldwide; however, this new emerging nosocomial pathogen is probably best known for an outbreak in Israel that began around 2006 within the healthcare system there.
In the USA, it was first described in North Carolina in 1996; since then CRKP has been identified in 41 states; and is recovered routinely in certain hospitals in New York and New Jersey. It is now the most common CRE species encountered within the United States.