In this context, bacteria are in focus of attention. They are unicellular organisms without a cell nucleus. About 90% of the bacteria that are known are harmless, important commensals or even essential for humans and animals (e.g., the gut flora). During the last decades and with a dramatically increasing tendency, many different kinds of bacteria have accumulated mechanisms of resistances against antibiotics. They integrated these resistance mechanisms into their genetic fitment in such a stable way that these resistances are transferred to their next generations in order to guarantee survival.
It is the aim of the microorganisms to survive in an environment containing antibiotics. Bacterial antibiotic resistances are therefore more and more a solid genomic part in their fight for survival, a phenomenon that is now even getting “normal” for soil or water bacteria.
Additionally, bacteria are able to transfer such abilities to other bacteria, beyond the species level. This genetic exchange that favours multiresistance has lead to the often underestimated fact that bacteria are increasingly multiresistant or even totally resistant against widely used therapeutically relevant antibiotics. Bacteria are quickly and easily distributed over large distances on earth by water, wind, animals, humans, global mobility etc. so that their distribution cannot be controlled. This is the reason why, unexpectedly, multiresistant bacteria can be found everywhere e.g., in garden soil.
“Hospital infections” (nosocomial infections) means the medical point of view: in a hospital environment, certain typical bacterial species occur rather frequently: those that are normally living in and on humans. Many of them are “opportunistic pathogens” as they might cause infections in immunocompromised patients or at a wrong place of the body: not problematic for healthy humans and “normal” like on nasal mucus, they become dangerous for the weak patient.
Typical examples are Pseudomonas aeruginosa or Staphylococcus aureus. If hospitalized patients become colonized by such bacteria while the immune system is in a situation of being challenged for other reasons, antibiotics must be applied to restore health of the patients. Unfortunately, these typical opportunistic pathogens that are so abundant cause the most dramatic problems concerning multiresistances: they developed most sophisticated mechanisms to fight antibiotics.
This crisis is impossible to break off. To reduce the problem, only extreme hygiene and aseptic conditions might help. However, this is difficult in hospital processes where human contacts are constantly necessary. The expression “hospital infection” therefore describes a problem rather than the definition of certain microorganisms.