corynebacteria棒状杆菌

1、Bacterial Flora in Human Oral CavityMade byLuan Yijun, Zhang Yanhui, Liu Junying, Li Na, Xuxia, Liu Song, Wang Ge, Zhang Tianqi, Ying Wanggui,Li Shengfeng1.Normal flora in human oral cavity2.Several dental diseases caused by bacteria3.What can we do to prevent dental diseaseThe human mouth is home t

2、o more than 500 species of bacteria. Oral bacteria include streptococci, lactobacilli, staphylococci and corynebacteria(棒状杆菌), with a great number of anaerobes, especially bacteroides(类杆菌). Normal flora changes with ageAt birth the oral cavity is sterileIt rapidly becomes colonized from the environm

3、ent Streptococcus salivarius is dominant and may make up 98% of the total oral flora until the appearance of the teeth (6 - 9 months in humans) The eruption of the teeth during the first year leads to colonization by S. mutans（变形链球菌） and S. sanguis ,they will persist as long as teeth remain Other st

4、rains of streptococci adhere strongly to the gums（牙龈） and cheeks but not to the teeth The creation of the gingival crevice（齿龈裂缝） area increases the habitat for the variety of anaerobic species found Bacteroides and spirochetes colonize around puberty Functions of normal floraoccupy available coloniz

5、ation sites contribute to host nutritioncontribute to immunityexert microbial antagonism against heterogenous speciesSince some of these bacteria are parasites or opportunistic pathogens, if they invade tissues not normally accessible to them, characteristic diseases result back Dental Plaque （牙菌斑）（

6、牙菌斑）Dental Caries （龋齿龋齿）Periodontal Disease （牙周病牙周病）Dental Plaquematerial adhering to the teeth, consists of bacterial cells (60-70% the volume of the plaque), salivary polymers, and bacterial extracellular products Streptococcus sanguis and Streptococcus mutans a weak attachment of the streptococca

7、l cells to salivary glycoproteins a pellicle on the surface of the teeth a stronger attachment ( glycosyl transferase, an enzyme on the cell surface of Streptococcus mutans, is apparently involved in initial attachment of the bacterial cells to the tooth surface and ) conversion of Sucrose (蔗糖）to de

8、xtran（右旋糖酐） and levan（左旋糖酐） polymers form the extracellular matrix of plaqueMechanism backDental Cariesthe destruction of the enamel（釉质）, dentin（牙质）or cementum（牙骨质） of teeth due to bacterial activities Streptococcus mutans, Lactobacilli， Actinomyces（放线菌）, and various proteolytic bacteria Physiologic

9、al and Biochemical Properties of Streptococcus mutans a regular component of the normal oral flora of humans contains the enzyme glycosyl transferase produces lactic acid, produces more lactic acid and is more acid-tolerant than most other streptococci stores polysaccharides made from dietary sugars

10、, can be utilized as reserve carbon and energy sources for production of lactic acid backPeriodontal Diseasebacterial infections that affect the supporting structures of the teeth (gingiva, cementum（牙骨质）, periodontal membrane and alveolar bone)Actinomyces, streptococci, spirochetes and Bacteroides The mechanisms of tissue destruction in periodontal disease are not clearly defined but hydrolytic enzymes, endotoxins, and other toxic bacterial metabolites seem to be involved backHow to prevent dental