4细菌的感染,诊断,防治,消毒,灭菌.pptxVIP

Bacterial InfectionKey WordsNormal flora Opportunistic pathogenPathogenic bacteria (virulent bacteria)DysbacteriosisExotoxins EndotoxinsSeparation Culture of bacteriaBacteriemiaSepticemiaPyemiaToxemiaEndotoxemiaCarrier Colony Toxoids AntitoxinNot all bacteria cause diseaseNormal flora – The normal flora are bacteria which are found in or on our bodies on a semi-permanent basis without causing disease. There are more bacteria living in or on our bodies, than we have cells of our own. A human body contains around 1013?cells. The human body is home to around 1014 bacteria. One fourth of fecal weight is made of bacteria!The normal flora are particularly important in the large intestine.?Normal flora are also found in the?nose, mouth, throat, skin.Opportunistic bacteria – can be part of the normal flora but not pathogenic for normal persons, cause disease only in immunocompromised persons, or under specific conditions.Pathogenic bacteria (virulent bacteria) – Normally not members of the normal flora, have mechanisms to promote their own growth in the expense of host’s tissue or organ’s functionThe normal flora protect us from disease by:1. Competing with invaders for space and nutrients.2. Producing compounds (bacteriocins) which kill other bacteria.3. Lowering the pH so that other bacteria cant grow.In addition to the above ways of protecting us from disease our normal flora help us in other ways. Of course, there is a down side as well...The Good SideProduce vitamins we are unable to produce such as vitamin B12.Boost our immune system — Germ free animals (born and raised in a germ free plastic tent) are very susceptible to disease when removed from the germ free environment because their immune system is underdeveloped.Help digest food.The Bad SideIf the normal flora escape from their normal location, they can cause disease. For example,?Escherichia coli, commonly found in the intestine, can cause urinary tract infections if introduced into the bladder.Immunosuppressi