EXERCISE 5. Закончите следующие предложения:

1.Streptococci are less virulent than …

2.Viruses are sometimes more dangerous than …

3.One strain of staphylococcus is easier found in gumboils than …

4.Spores are more resistant to destruction than …

5.Bacteria are often more dangerous than …

6.Inflammation may be more protective than …

7.Infection may be often the initial cause of the disease than …

The body provides a home for a great number of the smallest organisms – microorganisms. Most of them are harmless but some take part in dental diseases. There are three different groups of microorganisms: fungi, bacteria and viruses. They may be of different kinds, both harmless and more or less dangerous.

Bacteriaare subdivided into groups according to their shape bacilli, cocci, spirochetes, spores.

Bacilli are rod – shaped bacteria. For example, lactobacillus is found in decayed teeth.

Cocciare round bacteria.

Streptococci are berry – shaped bacteria which grow in twisted chains. They are associated with different diseases. Hemolytic streptococci (called hemolytic because bacteria cause hemolysis) are responsible for such conditions as “strep” throat, tonsillitis.

Streptococci viridians (viridians means “green” and these bacteria produce a green color on the growth medium) are less virulent (poisonous) than the hemolytic form and cause infections in teeth.

Staphylococci are bacteria which grow in small clusters like grapes. One strain of staphylococcus may be found in gumboils.

There are also spiral bacteria (spirochetes) found in acute necrotizing ulcerative gingivitis.

Some bacteria can exist in the form of spores. Spores can survive extremes of temperature and live for years until conditions become more favorable again. They are highly resistant to destruction.

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