Ch. 12

Question 1

What color are gram positive bacteria?

Answer 1

purple, have a single, thick membrane, retain a purple color when stained with crystal violet dye

Question 2

What color are gram negative bacteria?

Answer 2

red, double cell membranes

Question 3

free-floating bacteria

Answer 3

planktonic bacteria

Question 4

attached bacteria

Answer 4

bacteria that can attach to surfaces and to one another; communities of attached bacteria are described as living in a biofilm; once it attaches, it activates a whole different set of gene that give it different characteristics

Question 5

biofilm

Answer 5

a living film containing well organized community of microorganisms that grows on a surface; can exist on any solid surface that is exposed to a bacteria-containing fluid; biofilms thrive in dental unit water and suction lines

Question 6

lifecycle of biofilm

Answer 6

1. Attachment: bacteria attach to surface
2. Growth: The attached bacteria releases substances that attract other free-floating bacteria to join the biofilm community, secrete a film known as extracellular slime layer; helps keep bacteria attached to the surface and acts as a protective shield for bacteria; the bacteria multiply rapidly and grow away from surface to form 3d mushroom shaped mature biofilms that attach to a surface at a narrow base; movement of the fluid surrounding the mature biofilms results in extensions that stream from main body of biofilm.
3. Detachment: clumps of the main biofilm break off and are carried away by the fluid surrounding the biofilm; these detached clumps can attach to other portions of a surface and form new bacterial colonies.

Question 7

5 phases in formation of biofilm

Answer 7

Phase 1= acquired pellicle coats tooth surface
Phase 2= initial colonizers attach to the acquired pellicle
Phase 3= additional bacteria coaggregate with initial colonizers
Phase 4= formation of extracellular slime layer and microcolony
Phase 5= mature biofilm characterized

Question 8

acquired pellicle

Answer 8

within minutes after cleaning the tooth surface, this forms, and is composed of glycoproteins (mucins) and antibodies.
the purpose of it is to protect the enamel from acidic activity. it also alters the charge and energy of the tooth surface, facilitating bacterial adhesion. “double sided tape”

Question 9

fimbriae

Answer 9

the hair like structures on some bacteria that enable them to attach rapidly upon contact with tooth surface

Question 10

bacterial blooms

Answer 10

periods when specific species or groups of species grow at rapidly accelerated rates.

Question 11

microcolony

Answer 11

bacteria attach to a surface and to each other. each microcolony is a tiny independent community containing thousands of compatible bacteria. the environmental conditions among several microcolonies may include differences in oxygen concentration, pH, and temperature. the bacterial diversity helps ensure the survivability of the plaque biofilm in widely varying oral conditions.

Question 12

extracellular slime layer

Answer 12

dense protective barrier that surrounds the bacterial microcolonies, acts like a shield from antibiotics, antimicrobials, and immune system

Question 13

fluid forces

Answer 13

the fluid forces of saliva surrounding the biofilm influence the shape of the plaque biofilm, as well as the spatial arrangement of the bacteria inside, these fluid forces result in the development of extensions from the main body of the biofilm and can break free and be swallowed, expectorated, or form new biofilm colonies in other areas of the mouth. fluid forces also result in cell-to-cell collisions of the bacteria within the biofilm. bacterial cell collisions lead to a more rapid spread of genes among the bacteria than there would be if there were no fluid forces acting on the biofilm. rapid transfer of genes may result in enhanced bacterial virulence and antimicrobial resistance. They are constantly evolving!

Question 14

fluid channels

Answer 14

as biofilm forms, a series of fluid channels are formed that penetrate the extracellular slime layer, these fluid channels direct fluids in and around the biofilm bringing nutrients and oxygen to bacteria and carrying bacterial waste products away. the fluids contain everything from saliva to any beverages consumed.

Question 15

coaggregation

Answer 15

is the cell-to-cell adherence of one oral bacterium to another. it is not random, each bacterial strain only has a limited set of bacteria to which they are able to adhere

Question 16

early bacterial colonizers

Answer 16

are nonpathogenic. the ability of these species to attach to the tooth surface lays the foundation for the growth of dental plaque biofilms. early colonizers include many streptococcal species, such as Stretococcus mitis and Streptococcus oralis that have the ability to attach to the tooth pellicle as well as to each other. Another early colonizer is Actinomyces viscosus. They release chemical signals that indicate to the next group of bacteria that conditions are favorable for them. many early and intermediate cant attach to tooth pellicle but have ability to coaggregate with strep species.free floating bacteria cant join until conditions are favorable

Question 17

intermediate and late colonizers

Answer 17

intermediate species=Fusobacterium nucleatum, in turn coaggregate with the last colonizers

Question 18

things to remember

Answer 18

• free floating bacteria cannot intiate perio disease
• if biofilm is adequately disrupted by daily self care and routine professional care the biofilm will always be reforming, it will start over at beginning with early colonizers

Question 19

sequence of bacterial attachment

Answer 19

acquired pellicle formation at 0 hours, bacterial adhesion, supragingival plaque at 6 hours (Actinomyces, Streptococci), plaque maturation at day 7 (Filamentous bacteria), well differentiated subgingival biofilm at 12 weeks

Question 20

bacterial attachment zones

Answer 20

the zones of subgingival bacterial attachment are the tooth surface and the epithelial lining of the perio pocket. bacteria also may attach to other bacteria that are attached to one of these surfaces.

Question 21

tooth associated plaque biofilms

Answer 21

bacteria that are attached to the tooth surface. bacteria attach to an area of tooth surface that extends from the gingival margin almost to the junctional epithelium, at the base of the pocket, subgingival bacteria appear to have the ability to invade dentinal tubes of the cementum. Filamentous microorganism, cocci, and rods including S. mitis, S. sanguis, and A. viscosus dominate tooth associated biofilms.

Question 22

tissue associated plaque biofilms

Answer 22

bacteria that adhere to the epithelium. very different from tooth associated. the layers closet to the soft tissue wall contain large numbers of spirochetes and flagellated bacteria. gram negative cocci and rods are also present. there is a predominance of species such as S. oralis, Stretococcus intermedius, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, and F. nucleatum, can invade the gingival connective tissue and be found within perio connective tissues and on the surface of the alveolar bone.

Question 23

unattached bacteria

Answer 23

in addition to the attached bacteria, the perio pocket also contains many free-floating bacteria that are not part of the biofilm.

Question 24

transmission of perio bacteria

Answer 24

bacteria in biofilm is transmissible which is the transfer of bacteria from the oral cavity of one person to another. transmission is not contagion, which means it may pass from one person to another by direct or indirect contact via substances such as inanimate objects. kissing is primary means by which saliva and bacterial contents are transmitted.

Question 25

resistance to antibiotics and antimicrobial agens

Answer 25

bacteria in biofilm are resistant to pill form antibiotics and antimicrobials. antibiotic does that kill free floating bacteria would need to be increased as much as 1500 which would kill patient, antimicrobial agents work best when used in conjunction with mechanical cleaning that removes or disrupts the dental plaque biofilm

Question 26

protective mechanisms of biofilm

Answer 26

extracellular slime layer: very dense, may prevent drugs from penetrating fully, may protect bacteria against leukocytes, may block what leukocytes release thereby damaging surrounding body tissue.

enzymes: some bacteria produce enzymes that degrade antibiotics faster than the drug can penetrate into the biofilm.

dormant bacteria: the biofilm is very think and bacteria in the deepest layers become dormant because they are cut off from nutrients, antibiotics only work on bacteria that are active and reproducing, when antibiotics are completed, the dormant active bacteria within the biofilm reactivate

Question 27

physical removal of dental plaque is essential

Answer 27

control of dental plaque biofilms is best achieved by the physical disruption such as brushing, flossing, periodontal instrumentation. it take some time for complex structure of a mature plaque biofilm to form

Question 28

socransky’s microbial complexes

Answer 28

these studies identified specific groups of bacteria: T. forsythia, P. gingivalis, and Treponema denticola that were significantly associated with periodontitis. yellow, green, and orange complexes were thought to be compatible with gingival health, orange and red thought to be the major etiologic agents of periodontal disease

Question 29

the hypotheses

Answer 29

• nonspecific plaque hypothesis
• specific plaque hypothesis
• microbial homeostasis-host response hypothesis (current perspective): it is the host response not the type of bacteria which determines whether perio destruction progresses

Question 30

commensal organisms

Answer 30

commensalism is a relationship between individuals of two species in which one species (the commensal organisms) obtains benefits from the other species without either harming or helping the host species.