The mammal organisms carry on their surfaces and in their tissues cohorts of microorganisms of various nature. There is a balance of interests and profits between the host and microbial inhabitants. The bacteria and fungi behave like comensals, colonizers, dormants, however, under certain, mostly unknown, conditions may evoke reaction of the host. This process is damaging both for the host and microbes. Large surgical trauma and allograft itself, as well as, immunosuppression create favorable conditions for imbalance between inhabiting microorganism and the recipient. The host flora and that transplanted with the organ graft become activated. Active combating of the proliferating bacteria with antibiotics becomes necessary. Our knowledge of the bacterial flora of the so called “sterile” tissues remains rudimentary. There is still a great deal of prejudice on the sterility of deep tissues e.g. muscles, fat tissue, etc. This review cumulates pertinent literature data on the microorganisms-host interactions. Our own findings on colonization of arteries and adjacent tissues are discussed in the context of atherosclerosis and grafting.

Keywords: Bacteria, Fungi, Organs, Infection