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Bacteria and Drug Resistance


VitalsignsBacteria live in our bodies and in our environment, usually without causing any illness. When bacteria do make us sick, antibiotics are usually available to treat the illness. However, over time, bacteria develop resistance to some types of antibiotics. This means that the drugs are no longer effective at killing the bacteria and the infections become harder to treat. If bacteria are resistant to more than one type of antibiotic, they are called multidrug-resistant organisms, or MDROs.

It is possible to carry a MDRO in or on your body but not show any symptoms; this is called colonization. Symptoms of an active infection will depend on the type of organism, the site of infection, and individual risk factors.

MDROs are transmitted via direct contact with an infected person or indirect contact with contaminated objects/surfaces in the environment of an infected person. It is important to take the appropriate steps to help prevent an infection caused by a MDRO. One important thing healthcare professionals, patients, and visitors can do is practice good hand hygiene very often, including:

  • Before preparing or eating food
  • Before touching their eyes, nose, or mouth
  • Before and after changing wound dressings or bandages
  • After using the restroom
  • After blowing their nose, coughing, or sneezing
  • After touching surfaces in healthcare facilities that may be contaminated such as bed rails, bedside tables, doorknobs, remote controls, or the phone.

There are several types of MDROs:carbapenem-resistant Enterobacteriaceae (CRE), methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-intermediate or vancomycin resistant Staphylococcus aureus (VISA/VRSA), and vancomycin-resistant enterococci (VRE). Sometimes these infections can be found in the community, but more often, they are found in healthcare settings.


Carbapenem-resistant Enterobacteriaceae (CRE)
Enterobacteriaceae are a family of bacteria that include germs such as Klebsiella pneumoniae and E. coli. These bacteria can live in our environment or in our bodies and can cause a variety of infections including gastrointestinal illness, pneumonia, wound infections, or invasive infections of the blood or other body organs. Most of these bacteria can be treated with antibiotics called carbapenems. However, for carbapenem-resistant Enterobacteriaceae (CRE), the carbapenem antibiotics are no longer effective. Unfortunately, carbapenem antibiotics are often the last line of defense against infections that are resistant to other antibiotics as well.

Healthy people generally do not get CRE infections. In healthcare settings, CRE infections usually occur among patients who are receiving treatment for other conditions. Patients whose care requires devices like ventilators (breathing machines), urinary (bladder) catheters, or intravenous (vein) catheters, and patients who are taking long courses of certain antibiotics are most at risk for CRE infections.

Many healthcare facilities are increasingly aware of CRE and have instituted infection prevention measures to limit the spread of these infections. Healthcare settings should continue to follow Centers for Disease Control and Prevention (CDC) guidance for preventing the spread of CRE.


Methicillin-resistant Staphylococcus aureus (MRSA)
Staphylococcus (staph) bacteria are often found on the skin and in the nose of healthy people. These bacteria can also grow in wounds or other sites in the body, sometimes causing an infection. Methicillin-resistant Staphylococcus aureus (MRSA) is resistant to a class of antibiotics called beta-lactams, which includes methicillin as well as more common antibiotics such as oxacillin, penicillin, and amoxicillin. In the community, most MRSA infections are skin infections and may appear as red boils or pimples. More severe or potentially life-threatening MRSA infections occur most frequently among patients in healthcare settings and may initially present as symptoms such as fever and pain at the site of infection.

Like MRSA, vancomycin-intermediate Staphylococcus aureus (VISA) and vancomycin-resistant Staphylococcus aureus (VRSA) are types of staph bacteria that are resistant (or have intermediate resistance) to antibiotics. Because of their resistance to vancomycin, an antibiotic often used to treat other types of drug-resistant infections, VISA/VRSA infections can be more difficult to treat. VISA/VRSA infections may affect the skin or may get into the bloodstream, causing a more serious type of infection. VISA/VRSA infections are very rare.


Vancomycin-resistant Enterococci (VRE)
Enterococci are a group of bacteria naturally found in the intestines of humans and other animals. Vancomycin-resistant enterococci (VRE) are a group of bacteria that are resistant to vancomycin, an antibiotic commonly used to treat drug-resistant bacteria. These strains are usually found in healthcare settings where antibiotic use is common.

VRE can cause infections of the urinary tract, the bloodstream, or of wounds associated with catheters or surgical procedures. Risk factors for VRE infection include underlying illness, weakened immune system, recent abdominal surgery, urinary or venous catheter use, prolonged hospital admissions, and long-term treatment with antibiotics.


To learn more about antibiotic resistance and multidrug-resistant organisms:


Last Updated: 03-14-2013

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