**4.6 Water**

To drink and to use waters contaminated with stool or sewage leakages is very important because they may cause infections such as typhoid, dysentery, cholera. In contaminated water, typhoid germ may exist together with intestinal bacteria. However, number of these bacteria is very less in general and it is impossible to obtain. On the other hand, commensal bacteria such as coliform bacteria, Streptococcus faecalis and Clostridium perfringens (welchii) are always obtained in contaminated water easily. Such water containing these bacteria means that the water was contaminated with the stool an this may contain typhoid germ. Coliform bacteria shows the contamination with the stool with the safest manner. The most important of them is Escherichia coli which is main commensal bacteria of the intestine. Existence of spore forming anaerobe bacteria in the absence of other bacteria shows an old contamination with the stool.

Colifrom bacteria also exists in water contaminated with stool of various animals. But they are less. More bacteria are present in the water contaminated with sewage water. It is important to detect the bacteria count in the water to determine the level of the contamination.

Detection of alive bacteria count gives information about quantity and type of organic substances. The trial is performed both at 37°C and 22°C. Bacteria which mix from human and animal origin organic substances reproduce at 37°C in particular. Those which reproduce in lower temperature are saprophyte bacteria that mix from the soil and plants or exist in the water normally.
