Multidrug-Resistant Organisms (MDROs): What Are They?


Multidrug-resistant organisms are bacteria that have become resistant to certain antibiotics, and these antibiotics can no longer be used to control or kill the bacteria. Antibiotics are important medicines. They help fight infections that are caused by bacteria. Bacteria that resist treatment with more than one antibiotic are called multidrug-resistant organisms (MDROs for short). Multidrug-resistant organisms are found mainly in hospitals and long-term care facilities. They often affect people who are older or very ill and can cause bad infections. Other terms used to describe this include antibiotic resistance, antibacterial resistance, and antimicrobial resistance. Please visit the Centers for Disease Control and Prevention website for a list of diseases/pathogens associated with antimicrobial resistance.


Are MDROs a new problem?

No. Penicillin resistance in Staphylococcus aureus, a common type of bacteria, was first found in the 1940s. Widespread use of antibiotics, plus the natural growth of bacteria over time, has created a number of MDROs.


What causes MDROs?

Multidrug-resistant organisms develop when antibiotics are taken longer than necessary or when they are not needed. At first, only a few bacteria may survive treatment with an antibiotic. The more often the antibiotics are used, the more likely it is that resistant bacteria will develop. These MDROs can go on to infect people.


How do MDROs spread?

Most often, MDROs spread from patient to patient on the hands of healthcare workers. They can also spread on objects such as medication cart handles, bed rails, bedside tables, IV poles, and catheters (soft tubes placed in the body), to name a few. They can also spread person-to-person through direct contact (touching oozing sores, for instance).


Will I get sick if I come in contact with a MDRO?

Not necessarily. In some cases, it is possible for the MDRO to be present on your body but not cause any illness. Such cases are called “colonization”. For example, Staphylococcus aureus is commonly found in various areas of the body including the skin and in the nose. Colonization rarely becomes an infection unless the bacteria spread to a part of the body where the bacteria are not usually found.


If you are sick, you are considered to be “infected”. Infection means that bacteria are in or on your body and causing an illness or other medical condition. Infection with a MDRO occurs most often in young children, the elderly, or in people who have an existing severe illness or a health condition such as chronic lung, heart, or kidney disease. Remember, healthy people are at low risk of infection.


What are some risk factors for MDRO infections?

In general, people who are healthy are at low risk of becoming infected. The risk of infection is increased if you have:

  • An existing severe illness
  • An underlying disease or condition such as diabetes, chronic kidney disease, or skin lesions
  • Previous prolonged use of  antibiotics
  • Invasive procedures, such as dialysis, and the use of medical devices that enter the body such as tubes used to drain urine (urinary catheters) or tubes in blood vessels used to give fluids, medicines, or nutrients (vascular catheters)
  • Repeated contact with the healthcare system such as numerous admissions to the hospital or regular dialysis visits
  • A long stay in the hospital
  • Previous colonization with a MDRO
  • If you are elderly or are on immune-suppressing medicine

What types of infections do MDROs cause?

Multidrug-resistant organisms can cause infections in almost any part of the body, including:

  • Bloodstream
  • Lungs
  • Urinary tract
  • Wounds
  • Skin
  • Surgical site

How are MDROs treated?

Multidrug-resistant organism infections are hard to treat because they do not respond to many common antibiotics, even the most powerful ones. But certain antibiotics can still help control MDROs in most people. The doctor will try to find the type of MDRO causing the illness. This can help choose the best antibiotic. Treatment with the wrong antibiotic can slow recovery and make the infection harder to cure.


What are ways to control the spread of MDROs?

Doctors are asked to only prescribe antibiotics when they are needed. The Centers for Disease Control and Prevention (CDC) recommends that if you are prescribed antibiotics, you follow the doctor's instructions.


One of the best ways to control the spread of germs or bacteria and prevent infections is to wash your hands with soap and water for at least 20 seconds. For more details on hand washing, please see Hand Washing: A Simple Way to Help Stop the Spread of Infection.


If you visit a person in a healthcare setting (such as a hospital or nursing home) you should:

  • Wash your hands on entering, and before leaving the person’s room
  • Wear disposable gloves if you expect to come in contact with body fluids (blood, urine, pus, vomit, saliva, feces, etc). Gowns should be worn if a lot of contact with body fluids is possible.

Outside of a healthcare setting, if you come in contact with a person who is infected or colonized with an MDRO, such as caring for an infected person in your home or giving first aid, the CDC recommends that:

  • Caregivers wash their hands with soap and warm water before and after physical contact with the person, and before leaving the person's home.
  • Towels used for drying hands after contact with the person should be washed before being used again.
  • Disposable gloves should be worn if contact with body fluids (blood, urine, pus, vomit, saliva, feces, etc.) is expected. Hands should be washed after removing the gloves.
  • Bed sheets should be changed and washed if they are soiled and on a regular basis (at least once a week or more often if needed).
  • The patient’s environment (hard surfaces like the floor, tables, bed) should be cleaned routinely and when soiled with body fluids. A commercial disinfectant or a solution of 1/4 cup of regular household bleach in 1 gallon of water is recommended.
  • Doctors and other health care personnel who provide care for the patient are notified that the patient is colonized/infected with a MDRO.

For more details, please refer to: Tips to Reduce Your Risk of Getting a Healthcare Associated Infection or visit the CDC, Antibiotic Resistance website.


What hospitals, long-term care facilities (nursing homes), and other healthcare facilities are doing to prevent MDROs:  Many hospitals, nursing homes, and other healthcare facilities take special safety measures to help prevent MDRO infections, including:

  • Hand washingThis is the single most important way to prevent the spread of MDROs.  Healthcare workers are taught to wash their hands with soap and warm water or use an alcohol-based hand sanitizer before and after treating each patient.  They are also taught to clean their hands after touching any surface and after removing protective clothing. 
  • Protective clothing:  Healthcare workers and visitors wear gloves, a gown if soiling of clothes is likely, and sometimes a mask when entering the room of a patient with a MDRO infection. The gown is removed, and hands are washed with soap and warm water before leaving the room.  
  • Careful use of Antibiotics:  Using antibiotics only when needed, and for the shortest time possible, helps prevent the growth of more MDROs.  
  • Private Rooms:  Patients with a MDRO infection are placed in a private room or share a room with others who have the same infection.  
  • Daily cleaning:  All patient care items, equipment, and room surfaces are properly cleaned and disinfected every day. Check lists may be used by staff to ensure all areas were cleaned. 
  • Vaccinations:  Streptococcus pneumoniae, a type of bacterium that can cause pneumonia, often can be resistant to one or more antibiotics. Vaccination against Streptococcus pneumoniae can prevent these antibiotic resistant infections.    
  • Monitoring:  Hospitals and other healthcare facilities monitor the spread of MDROs and educate caregivers on the best ways to prevent it.
Additional Information
To contact the Healthcare Associated Infections Program, please call 860-509-7995.