Page 175 - 84 human physiolofy part-1

The Immune System

human cells, compounds can be found that can kill specific bacterial targets while leaving the
human patient unharmed. Antibacterial agents can be successful in wiping out a bacterial
infection. The problem with antibiotics is that many strains of bacteria are growing resistant to
them. Plus, our bodies are not getting the chance to develop immunity to certain bacteria. It may
be better to use probiotics (new supplements that promote the growth of healthy and helpful
bacteria) rather than depend on antibiotics so much.

Protozoans

• The protozoans are mostly eukaryotic unicellular organisms with organelles and a nucleus.
• Malaria is the most dangerous disease caused by protozoans and is endemic in about 50%
of the populations on Earth. Two to four million people die each year from malaria, a million of
these are under the age of five. malaria is caused by one of the Plasmodium species of
mosquitoes.

Fungi

• Fungi are more like animals and humans than they are like bacteria because of their
eukaryotic cells. Though they produce large, visible colonies on old bread, molds and yeasts are
in the category of microscopic fungi. Yeasts are one-celled and reproduce by budding. Molds
exist as cell chains, called hyphae.
• Mycoses are diseases caused by fungi. Because of the similarity between human cells and
fungal cells, it has been difficult for scientists to design antibiotics that are effective against
fungi and do not harm humans. Some of the diseases caused by fungi are: tineas, vaginal
infection (candidiasis), and histoplasmosis.

Diagnosis Infectious diseases are diagnosed by laboratory techniques such as microscopy and
culture. Since many bacteria have no color, scientists have developed special staining procedures to
more accurately diagnose.

• Culture

Bacteria and fungi can be identified by growing them on plates until colonies are visible. Viruses
are cultured on eggs or live cells.

• Antibiotic sensitivity

After colonies of bacteria are grown on plates, discs are placed on the plates that contain different
antibiotics. Bacteria will not grow around the most effective antibiotic.

• Tests for viruses

Since viruses are too small to be seen with a light microscope, viral infections can be diagnosed
indirectly by their effects on cells. Some viruses cause changes to the surface of cultured cells, causing
them to stick together.

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