Read and learn the following words and word combinations;
1. .harmless[`hRmlqs] безвредный
2. dangerous [`deinGqrqs] опасный
3. subdivide [`sAbdi`vaid] подразделять
4. shape [Seip] очертание, форма
5. decayed teeth [di`ckeid `tJT] гнилые (испорченные) зубы
6. chain[Cein] цепь
7. cluster[`klAstq] гроздь
8. strain[strein] штамм
9. gumboil[`gAmbOil] флюс
10. acute [q`kjHt] острый
11. gingivitis [`GinGi`vaitis] воспаление десен
12. exist [ig`zist] существовать
13. survive[sq`vaiv] выживать
14. resistant[ri`zistqnt] резистентный, устойчивый
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, spirochaetes, 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 assocaated with different diseases. Hemolytic streptococci (called hemilytic because bacteria cause hemilysis) are responsible for such conditions as “strep” throat, tonsilitis.
Streptococci viridans (viridans means “green” and these bacteria produce a green colour 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 (spirochaetes) 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 favourable again. They are highly resistant to destruction.