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Flashcards in lecture 3 - microbe-host interactions Deck (44):
1

what is the strongest non-covalent bond in nature?
-what is this

biotin and avidin

-biotin --> essential dietary nutrient
-avidin --> binding protein, antibacterial defence mechanism. Egg whites are rich with this

2

what do microbes need?

host, food, protection from predators and competitors

**normal flora and microbs

3

what is Normal Microbita and what relationship is this?

-collection of bacteria, archaea, and eukaryotic microbes usually colonizing our bodies
-mutual relationship

4

define colonization and how this occurs

- ability of a microbe to stay affixed to a body surface and replicate
-Adhesins (stick to the right place)
-environmental factors
-susceptibility to pathogens

5

infection

A condition in which pathogenic microbes penetrate host defences, enter tissues and multiply

*just because you come in contact with pathogen ("infected") doesn't mean you have disease - if body has ability to fight off pathogen, disease process will not occur

6

infectious disease

disruption of tissue or organ (pathologic state) caused by microbes or their products

7

pathogen

-Any bacterium, virus, fungus, protozoan, or worm (helminth) that causes disease

-Parasitic relationship with its host

-Causes disease in a susceptible individual

8

what do the type and severity of infection depend on? 5 factors.

1. Dose (infectious)
2. Condition of the host (immunocomprimised)
3.Location in/on the host’s body: the “Portal of entry” – how does the pathogen get into your body
4. Genetic makeup of host and pathogen: the survival of the pathogen relies on the genetic make up of it and the environment
6.Host immune response

9

pathogenicity

an organism’s potential to cause infection or disease

10

true pathogens

-Their lifestyle depends on infecting the host
-Attack healthy people
-Infection made worse by a weak or immature immune system

Salmonella Typhi = typhoid fever

11

opportunistic pathogen

-Only cause disease when given opportunity

-breakdown in immune system or immature immunity

Pneumocystis jirovecii = fungal infection of lungs in AIDS patients

12

latent state

organism is within host but cannot be detected by culture

ex) Herpes virus

Rickettsia prowazekii

13

ecological parasites

pathogenic

Parasite is any organism that colonizes and harms its host

ectoparasite cause harm to outside of body
ex) Trichophyton rubric
"athletes foot"

endoparasite cause harm within body
ex) Wuchereria bancrofti
"elephantitis"

14

invasive pathogens

-enter and live inside host, aids in avoiding competition

small membrane-enclosed vacuoles
ex) Salmonella, Coxiella, Legionella

inside cytoplasm
ex) Shigella, Listeria

15

sign

any objective evidence of disease as noted by an observer

16

symptom

the subjective evidence of disease as sensed by the patient

17

syndrome

when a disease can be identified or defined by a certain complex of signs and symptoms

18

what are the 5 stages of infection. Order from start to finish

1. incubation period
2. prodromal phase
3.illness phase
4. decline
5. convalescence

19

incubation period

time after the microbe first infects a host but before the first signs of disease

20

prodromal phase

short period of vague symptoms and malaise; can serve as a warning of more symptoms to come but may not be noticed

21

illness phase

Typical symptoms and signs of the disease appear and fever may be present
*microbe greatly out numbers immune response

22

decline

Symptoms begin to subside; fever resolves.

*immune response outnumbers microbe

23

convalescence

period after symptoms disappear and patient recovers
*immune response greatly outnumbers microbe

24

what are the 5 patterns of infection

1. localized
2. systemic
3. focal
4. mixed
5. primary - secondary

25

necrosis

accumulated damage leads to cell death and tissue death

26

localized infection

-Pathogen(s) stay localized
-The most common type of infection

27

systemic infection

-Spread to several sites and tissues
-Usually move via bloodstream

Ex: viral infections
HIV, chickenpox

Ex: Salmonella enterica serovar Typhi
-causes Typhoid fever
-Invade intestinal epithelium, spreads to macrophage, can become resident in gall bladder

28

focal infection

-Infectious agent leaves a local infection
-Carried to other tissues
*pathogen itself stays localized but disease manifests in other areas

-In toxemia, the infection remains localized, but toxins spread to other tissues

Unusual cases: Streptococcal pharyngitis
Bacteria in throat (“Strep throat”)
Antibodies against bacterial cell wall also attack other tissues, such as heart and joints

29

mixed infection

-Multiple species contribute to infection

Example: dog bite
all sorts of different bacteria enter the wound

Can be called “polymicrobial” disease

30

primary - secondary infection

-Successive
-Can occur due to weakened immunity
-Localized or systemic
-having one infection predisposes you to contracting another

Example:
Child scratches chickenpox (primary)
Then gets a localized Staphylococcus aureus infection (secondary)

31

what does "getting sick" from microbes depend on?

verdant, amount, and immunity

32

what weakens host defence and increases susceptibility?

-age (young and old)
-genetic and acquired immune alterations
-sugery/ organ transplants
-underlying disease
-chemo/ immunosuppressants
-stress (physical/ emotional)
-other infections

33

what are the 5 steps in pathogenesis?

-finding portal of entry (depends on virulence)
-attaching firmly (virulent factor)
-surviving host defences
-causing damage (disease) (infection)
-exiting host

34

what are the main portals of entry?

-usually same regions that harvest normal flora
Skin * most common cutaneous or membranous
GI tract
Respiratory tract
Urogenital tract
Endogenous biota

35

how to microbes attach to host?

Fimbriae
Capsules
Surface proteins
Viral spikes

36

how do microbes survive host mechanisms?

Avoiding phagocytosis (WBC)
Avoiding death inside phagocyte
-ex) salmonella avoids being digested by macrophages even though it is “caught
Absence of specific immunity

IMMUNE

37

how do microbes cause disease?

Direct damage
Toxins and/or
enzymes

Indirect damage
Inducing
inappropriate,
excessive host
response (over-reactive immune response)

38

how do microbes leave host

Portals of exit
Respiratory tract,
salivary glands
Skin cells
Fecal matter
Urogenital tract
Blood

39

what is the portal of entry for the greatest number of pathogens?
-what type of microbes?

respiratory portal

Examples: Streptococcal sore throat, Meningitis, Diphtheria, Whooping cough, Influenza, Measles, Mumps, Rubella, Chickenpox, Common cold, Bacteria and fungi causing pneumonia, TB


-Upper resp. tract infection (URI)
-lower resp. tract infection (LRI)
*LRI leading cause of infectious disease (tb, flu)

40

how do microbes enter through GI tract?

-Pathogens contained in food, drink, and other ingested substances

-can be adapted to survive digestive enzymes and pH changes; most are killed in stomach

examples: Salmonella, Shigella, Vibrio, certain strains of Escherichia coli, Poliovirus, Hepatitis A virus, Echovirus, Rotavirus, Entamoeba histolytica, Giardia lamblia

41

how do pathogens enter through skin and mucous membranes?
-examples
-what is the bodies reaction?

-Unbroken = a very tough barrier
-Nicks, abrasions, punctures weaken this line of defence

examples:
Skin
Staphylococcus aureus
Streptococcus pyogenes

Eye (mucous membrane)
Haemophilus aegyptius
Neisseria gonorrhoeae

defence: Antigen presenting cell
-alert immune resposne

42

how do pathogens enter through urogenital portal?

STI's - account for 4% of all infections
-enter skin or mucosa of penis, external genitalia, vagina, cervix, and urethra
-Some can penetrate an unbroken surface
not always STI
ex) Uropathogenic E. coli - cause UTI
"opportunistic pathogen"

43

how do microbes cause infection in pregnancy and birth?

-cross placenta (syphilis spirochete, HIV)
-perinatally when the child is contaminated by the birth canal

*herpes is deadly to new borns

44

how do pathogens exit their host

-A parasite must have a means to leave and transmit infection again

-Usually the same door they came in by

The mechanism of exit greatly influences spread in the human population

ex) flu enters through rest. and exits