Multi-drug resistant organisms (MDROs)

What are MDROs?

MDROs are bacteria that show resistance to several classes of antibiotics. Clinically relevant MDROs are mainly vancomycin-resistant enterococci (VRE), methicilin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Gram-negative pathogens (MRGN). MRGN is a collective term for various Gram-negative bacteria (mainly Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa or Acinetobacter baumannii). A distinction is made between resistance to three (3MRGN) or four (4MRGN) different antibiotic classes.

Infections with MDROs

MDROs are usually the resistant variants of the bacterial species that are part of the normal flora of the human body. S. aureus is often found on the skin and in the nasopharynx. Enterococci and the Gram-negative bacteria in question belong to the intestinal flora. They are facultative pathogens and initially not dangerous in their natural habitat. However, if they get into the urinary tract, wounds or the bloodstream, they can cause infections. Resistant bacteria basically cause the same infections as the corresponding antibiotic-sensitive bacteria. The more resistance there is, the more difficult it is to treat the infections, as there are fewer treatment options. Therefore, the primary goal is to avoid such infections. Often, patients are diagnosed with MDRO colonisation without having an infection. The resistant bacteria are temporarily or permanently part of the skin or intestinal flora. Patients colonised with MDROs have an increased risk of developing a nosocomial infection with MDROs.

Hygiene measures for MDROs

Hygiene measures in the case of the occurrence of antibiotic-resistant bacteria have two different goals: On the one hand, an infection of the MDRO carrier itself must be prevented. On the other hand, a transmission to other patients, especially to risk groups, should be avoided. In this context, basic hygiene and especially hand disinfection is crucial and a prerequisite for the effectiveness of any further measures. Whether hygiene measures are necessary that go beyond basic hygiene (e.g. isolation of the patient and protective clothing for the staff) depends on the individual and facility-related risk factors and on the pathogen itself. An underlying risk analysis must take into account the pathogen's transmission route and the risk profile of the patient population being treated.


1 KRINKO (2018) Hygienemaßnahmen zur Prävention der Infektion durch Enterokokken mit speziellen Antibiotikaresistenzen. Bundesgesundheitsbl 61:1310–1361.

2 KRINKO (2014) Empfehlungen zur Prävention und Kontrolle von Methicillinresistenten Staphylococcus aureus-Stämmen (MRSA) in medizinischen und pflegerischen Einrichtungen. Bundesgesundheitsbl 57:696–732.

3 KRINKO (2012) Hygienemaßnahmen bei Infektionen oder Besiedlung mit multiresistenten gramnegativen Stäbchen. Bundesgesundheitsbl 55:1311–1354.

Knowledge Database

The A-to-Z database provides information on each pathogen, the most common infections that it triggers, its main transmission paths and recommendations on disinfection. In the glossary, you will find explanations of infection control terms. Search now!

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