Definition
Nosocomial comes from the Greek “nosos” = disease and “komein” = to care. A nosocomial infection is an infectious disease that occurs during or after a stay in a hospital or other in-patient medical facility. Nursing homes and homes for the elderly are also included in these facilities. One speaks of a nosocomial infection if the illness occurs at the earliest 48 hours or later after admission to the respective medical facility. Any infection that occurs before this time is called an outpatient infection, or may not be safely classified as nosocomial.
Cause
A characteristic feature of nosocomial infections is that a different germ spectrum than that of conventional outpatient germs plays a role. The main cause is therefore the stay in a place where there is an increased presence of these germs or where their growth is favored. The increased use of antibiotics in hospitals has led to many strains of bacteria developing resistance to antibiotics.
If a germ develops a resistance mechanism against one or more antibiotics, a stronger antibiotic must be used. Other “neighboring” bacteria are also aware of this, so to speak, and can then possibly develop resistance. In the meantime it is also known that many pathogens develop resistances through the use of antibiotics in animals in industrial agricultural mass animal husbandry. MRSA resistance has been best investigated.
Pathogen
The pathogens of nosocomial infections are often bacteria that naturally colonize the body in a certain defined population number and are in principle not actually harmful. They only become harmful when they migrate away from their original location or are carried away, e.g. when a stool germ gets into a skin wound on the lower abdomen or arm. If the patient has a severely weakened immune system (e.g. after organ transplantation or bone marrow transplantation), this promotes an increased susceptibility to infection.
These patients are given medication to suppress the reactions of their own immune system. Certain chemotherapies can also lead to the bone marrow no longer producing enough defence cells. If a body has been exposed to increased stress (serious diseases, operations), the immune system is anyway stressed and “busy” and may then no longer be able to fend off other germs sufficiently.
A distinction can be made between two large groups of germs: Puddle and airborne germs. Wet or puddle germs are among them: Pseudomonas, Legionella, E. coli, Proteus, Enterobacter and Anaerobes. They are called puddle germs because they are transmitted in hospitals via “wet ways”.
They are found in washbasins, respiratory tubes, inhalation devices, excessively diluted cleaning agents, rarely even in weak disinfectants. The dry or airborne germs are: S. epidermidis (coagulase negative) and Staphylococcus aureus (coagulase positive), Enterococcus spp. Candida spp.
, mycobacteria. They are transmitted differently, namely via medical personnel, not wearing protective clothing, via contaminated contact surfaces (such as bedspreads, medical equipment, bedside tables), indoor air, but above all through inadequate hand disinfection (most frequent transmission route!). Another problem group is the germs of multi-resistant pathogens, which can no longer be killed by several antibiotics.
The exact development of resistance is a complex and not yet fully understood process. However, there are certain risk factors that favour the development of multiresistance. If a patient is in hospital, nursing home or generally has a long hospital stay of more than 4 days, his risk increases compared to a patient who has only a short stay in hospital.
If a patient is ventilated with a breathing tube for more than 4-6 days, the risk of infection with multi-resistant germs also increases. The air we breathe is humid and thus favors the penetration of the “puddle germs” and requires thorough hygienic care. Open skin wounds represent an equally endangered entry point.
It is now also known that too short antiobiotic therapies or therapies with the wrong antibiotic favour the development of resistances. Patients who have chronic lung diseases are particularly at risk for the dry germs. The lung is equipped with its own defence system, which is weakened in the case of permanent or structural diseases.
The best known of the multi-resistant pathogens is MRSA in particular, as it is also frequently reported on in the media.It is a germ called Staphylococcus aureus, which as a skin germ colonizes every human being and only becomes dangerous when it colonizes wounds or develops resistance, for example. The M in MRSA stands for the antibiotic methicillin, but could just as well stand for “multi”, because it is usually resistant to many antibiotics. AERs (vancomycin-resistant enterococci) show further multi-resistance.
These are intestinal germs that are resistant to the antibiotic vancomycin. The group of ESBL (expected spectrum beta lactamase) are germs that produce a certain enzyme, beta lactamase, which for example overrides the group of penicillins. However, drugs have been developed specifically against these bacteria that inhibit this mechanism and are therefore easily controlled in some cases.
Pseudomonas aeruginosa is particularly feared among physicians, as it can cause serious diseases and is increasingly developing resistance. The aforementioned germs are rarely no longer treatable with antibiotics. In medical laboratories, certain tests can be carried out to find out to which antibiotics the respective germ is still sensitive and these can then be used as therapy if necessary.
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