chapter 5 microbiology

Question 1

whats a pathogen?

Answer 1

microorganism capable of causing disease

Question 2

what does opportunistic mean?

Answer 2

cause disease only in compormised individuals

Question 3

LD 50

Answer 3

“lethal dose” number of organisms needed to kill half the hosts cells

Question 4

ID 50

Answer 4

Infectious dose, number of organisms needed to infect half the hosts

Question 5

Communicable disease

Answer 5

spread from host to host. When a disease is highly communicable it is considered contagious

Question 6

Endemic

Answer 6

constanly present at a low level in a specific population

Question 7

Epidemic

Answer 7

occurs more frequently than usual

Question 8

pandemic

Answer 8

worldwide distribution

Question 9

stages of infectious diseases are….

Answer 9

incubation period, prodomal period, acute specific illness, recovery period.

Question 10

incubation period

Answer 10

time between acquisition of organism or toxin and the commencement of symptoms

Question 11

prodomal period

Answer 11

non specific symptoms like fever and malaise, loss of appetite

Question 12

acute specific illness

Answer 12

specific symptoms start occurring

Question 13

recovery period

Answer 13

illness stops and returns to normal

Question 14

what are the determinates of pathogenicity?

Answer 14

transmission, adherence, invasiveness and toxigenicity

Question 15

How are pathogens transmitted?

Answer 15

inhalation, ingestion, inoculation

Question 16

name the 4 important portals of entry for pathogens

Answer 16

skin, respiratory tract, gastrointestinal tract, genitourinary tract

Question 17

what are biofilms?

Answer 17

aggregates of interactive bacteria attached to a solid surface( including prosthesis). Up to 65% of human infections are associated with biofilms

Question 18

what is a quorum in biofilms?

Answer 18

sensing molecules- biofilms secrete this which tend to repulse incoming bacteria or activate the communal bacteria to seek new bodies

Question 19

sessile organisms in biofilms

Answer 19

harder to eradicate when sessile

Question 20

planktonic biofilm organisms

Answer 20

easier to eradicate

Question 21

what does collagenase and hyaluronidase to for bacteria

Answer 21

degrade intercellular substances allowing easy spread of bacteria through tissue

Question 22

what does coagulase do for bacteria?

Answer 22

accelerates formation of fibrin clot which helps protect the organisms from phagocytes

Question 23

what does immunoglobulin A protease do for bacteria?

Answer 23

kills IgA on mucosal layers

Question 24

leukocidins role for bacteria is …

Answer 24

kills neutrophilic leukocytes and macrophages

Question 25

what is pyogenic inflammation?

Answer 25

pus producing

Question 26

what is granulomatous inflammation?

Answer 26

granuloma forming

Question 27

Name some contributing factors fo toxigenicity

Answer 27

endotoxins, fever, hypotension, activation of cascade pathway for inflammation, increased phagocytic activity, increased antibody production

Question 28

Endotoxins

Answer 28

they are the cell wall of lipopolysacharides of gram negative bacteria and are not actively released from the cell. These cause fever, shock, and other general symptoms. Some biological effects are below

Question 29

fever

Answer 29

due to release of IL-1 ( interleukin 1). They act on the hypothalamic temperature regulatory centre and reset it to a higher temperature

Question 30

hypotension-

Answer 30

from release of bradykinin which decrease peripheral resistance

Question 31

exotoxins

Answer 31

highly toxic but have good antigens and induce the synthesis of protective antibodies called antitoxins

Question 32

what are exotoxins categorized into?

Answer 32

neurotoxins, enterotoxins, and miscellaneous exotoxins

Question 33

Name some neurotoxins and what they do

Answer 33

tetanus toxin-blocks the release of inhibitory transmitter which leads to sustained contractions of voluntary muscles
diptheria toxin- inhibits protein synthesis in all eukaryotic cells

botulinum toxin-blocks release of acetylcholine at the synapse , producing paralysis of both voluntary and involuntary muscles

Question 34

what do enterotoxins do?

Answer 34

increase cAMP which promotes cellular chloride ion excretion and inhibition of sodium ion absorption which leads to diarrhoea

Question 35

natural defeses of the oropharynx and intestinal tract

Answer 35

Continuous desquamation of epithelium, presence of saliva, mucous in intestine, gastric acid, bile and proteolytic enzymes, movements of tonuge and cheek and peristalsis, immune mechanisms

Question 36

Defense mechanisms of respiratory tract

Answer 36

mucous from golblet cells and mucociliary escalator, IgA in respiratory secretions, alveolar phagoytes

Question 37

Defense of genitourinary tract

Answer 37

natural mucosal desquamation, vaginal secretions and cervical mucous, flushing of urine action

Question 38

What is viraemia?

Answer 38

entry of the virus into the blood

Question 39

permissive infection

Answer 39

virus enters host and synthesizes its componets and assembles and are released. Cell usually dies

Question 40

non- permissive infection

Answer 40

transforms the host cell and integrates its DNA into the hosts genome. Cell remains alive