Infections colonization can be defined as wound colonization referring to wound nonreplicating microorganisms when the replicating organisms of the infected wounds exist and the tissue is damaged. Infections colonization is performed by extrinsic organisms that colonize all multicellular organisms. Infections colonization presupposes the existence of extrinsic organisms either in commensal or in symbiotic relations with the host. Commensal relationship can be represented by different species of staphylococcus that live on the human skin. Symbiotic relationships are common for anaerobic bacteria that colonize mammalian colon. It is worthy of note that none of these colonizations can be considered infections.
The matter of circumstance is the only difference between infections colonization and infection. Right conditions can stimulate non-pathogenic organisms to turn to pathogenic ones. Even the most virulent organism needs certain circumstances to get an infection. There are some colonizing bacteria that prevent colonization and adhesion of pathogenic bacteria. So, it is possible to say that they are in symbiotic relationship with the host. The bacteria prevent the development of the infection and stimulate wound healing. Viridianis streptococci and corynebacteria sp. are examples of such colonizing bacteria.
It is interesting to know that staphylococcus species are harmless when they are on the skin. But when they get to a sterile space, they multiply with an amazing speed, creating a very large burden on the host. The examples of sterile spaces are the peritoneum or the joint capsule.
Any infectious disease needs a vector (or mode of transmission) and an agent. Malaria is a good example to show that. The disease is caused by such a parasite as Plasmodium falciparum. Nevertheless, the parasite is harmless till it is not transmitted by the vector. The vector in this case is Anopheles mosquito, which introduces the parasite into the blood stream. The vector may be not biological. A lot of infections are transmitted by means of the droplets that are in the airway, for instance tuberculosis and common cold.
The World Health Organization represents AIDS/HIV, malaria and TB as the most dangerous disease killers. As for diarrheal diseases and lower respiratory infections (such as different pneumonias) that are also rather dangerous, they are caused by various bacteria, parasites and viruses.
It is necessary to mention that children account for a great percentage of diarrheal and lower respiratory deaths. Among the most popular childhood diseases are poliomyelitis, measles, tetanus, pertussis and diphtheria.
Topical diseases are represented by Chagas disease, leishmaniasis, onchocerciasis, trypanosomiasis, schistosomiasis and lymphatic filariasis.
Speaking about the death ranking, it has changed from 1993 to 2002 and the results are as follows: the rank of AIDS has risen from 7th to 2nd place and the rank of Hepatitis B has fallen from 6th to 11th.