Ch. 23 Flashcards
1
Q
Most microorganisms are ___.
A
Benign
2
Q
Humans are colonized by ___ at birth.
A
Microorganisms
3
Q
Microorganisms usually found associated with human ___ ___.
A
Body tissue
4
Q
Pathogens -
A
Microbial parasites
5
Q
Pathogenicity -
A
The ability of a parasite to inflict damage on the host (cause disease)
6
Q
Virulence -
A
Measure of pathogenicity (attachment structures, enzymes, toxins)
7
Q
Opportunistic pathogen -
A
Causes disease only in the absence of normal host resistance
8
Q
Infection -
A
Situation in which a microorganism is established and growing in a host, whether or not the host is harmed
9
Q
Disease -
A
Damage or injury to the host that impairs host function
10
Q
___ provide a favorable environment for the growth of many microorganisms.
A
Animals
11
Q
Infections frequently begin at sites in the animals ___ ___.
A
Mucous membranes
12
Q
The ___ surface varies greatly in chemical composition and moisture content.
A
Skin
13
Q
Skin
Three microenvironments:
A
- dry skin
- moist skin
- sebaceous skin
14
Q
Dry skin:
A
Forearms and palms of hands
15
Q
Moist skin:
A
Inside of nostrils, armpits, umbilicus
16
Q
Sebaceous skin
A
Side of the nose, back of scalp, upper chest and back
17
Q
Skin microflora examined by molecular ___ methods.
A
Ecology
18
Q
Skin microflora examined by molecular ecology methods.
How many phyla detected?
A
19
19
Q
Each microenvironment shows a unique ___.
A
Microbiota
20
Q
The skin microflora
Composition is influenced by:
A
- environmental factors
- host factors
21
Q
The ___ ___ is a complex, heterogeneous microbial habitat.
A
Oral cavity
22
Q
Saliva contains ___ enzymes.
A
Antimicrobial
23
Q
High concentrations of nutrients near surfaces in the mouth promote what?
A
Localized microbial growth
24
Q
The ___ consists of a mineral matrix surrounding living tissue.
A
Tooth
25
Enamel -
Mineral matrix in teeth
26
Dentin and pulp -
Living tissue in teeth
27
How do bacteria colonize tooth surfaces?
Bacteria colonize tooth surfaces by first attaching to acidic glycoproteins there by saliva.
28
___ analysis of human microflora shows a complex microbial community.
Metagenomic
29
Human microflora
- most microorganisms are facultatively aerobic
- some are obligately anaerobic
- some are obligately aerobic
30
The human gastrointestinal (GI) tract consists of:
Stomach, small intestine, and large intestine
31
What is the GI tract responsible for?
Digestion of food, absorption of nutrients, and production of nutrients by the indigenous microbial flora
32
The GI tract contains how many microbial cells?
10^13-10^14
33
Microbial populations in different areas of the GI tract are influenced by...
Diet and the physical conditions in the area
34
The ___ of the stomach and the duodenum of the small intestine prevents many organisms from colonizing the GI tract.
Acidity
35
Functions and products of intestinal flora.
Compounds produced include:
- vitamins
- gas, organic acids, and odor
- enzymes
36
A restricted group of organisms colonizes the upper ___ ___.
Respiratory tract
37
Examples of organisms that colonize the upper respiratory tract:
Staphylococci, steptococci, diphtheroid, bacilli, and gram-negative cocci
38
Staphylococcus aureus and Streptococcus pneumoniae can be found in the __ of some healthy individuals.
Nasopharynx
39
The lower respiratory tract lacks microflora in ___individuals.
Healthy
40
Upper respiratory tract:
- sinuses
- nasopharynx
- pharynx
- oral cavity
- larynx
41
Lower respiratory tract:
- trachea
- bronchi
- lungs
42
The ___ is typically sterile in both males and females.
Bladder
43
Urogenital tract
Altered conditions (such as change in pH) can cause potential pathogens in the urethra (such as ___ ___ and ___ ___) to multiply and become pathogenic.
Escherichia coli and Proteus mirabillis
44
E. coli and P. mirabilis frequently cause what in women?
Urinary tract infection
45
The ___ of the adult female is weakly acidic and contains significant amounts of glycogen.
Vagina
46
___ ___, a resident organism in the vagina, ferments the glycogen, producing lactic acid.
Lactobacillus acidophilus
47
___ ___ maintains a local acidic environment.
Lactic acid
48
What are pregnant women tested for?
Group B Strep
49
Virulence can be estimated from experimental studies of the ___.
Lethal dose 50 (LD50)
50
Lethal dose 50
The amount of an agent that kills 50% of the animals in a test group
51
Highly virulent pathogens
Show little difference in the number of cells required to kill 100% of the population as compared to 50% of the population
52
Attenuation -
The decrease or loss of virulence
53
Toxicity -
Organism causes disease by means of a toxin that inhibits host cell function or kills host cells
54
Exotoxins:
Cytotoxin
Neurotoxin
Enterotoxin
55
___ can travel to sites within host not inhabited by pathogen.
Toxins
56
Invasiveness -
Ability of a pathogen to grow in host tissue at densities that inhibit host function
57
___ can cause damage without producing a toxin.
Invasiveness
58
Many pathogens use a combination of toxins, invasiveness, and other virulence factors to enhance ___.
Pathogenicity
59
Bacteria and viruses that initiate infection often adhere specifically to epithelial cells through what?
Interactions between molecules on the surfaces of the pathogen and the host cell
60
Bacterial adherence can be facilitated by:
- extracellular macromolecules that are not covalently attached to the bacterial cell surface (slime layer, capsule)
- fimbriae and pili
61
The ___ ___ of a pathogen is insufficient to cause host damage.
Initial inoculum
62
The pathogen must multiple and colonize the ___.
Tissue
63
What is most important in affecting pathogen growth?
Availability of nutrients
64
Pathogens may grow locally at the site of invasion or may...
Spread throughout the body
65
Bacteremia -
The presence of bacteria in the bloodstream
66
Septicemia -
Bloodborne systematic infection
67
Septicemia may lead to..
Massive inflammation, septic shock, and death
68
Infection requires..
Attachment to surface as well as growth
69
Attachment and growth have been well studied in the formation of ___ on tooth surfaces.
Biofilms
70
Acidic ___ from saliva form a thin film.
Glycoproteins
71
Streptococcus sobrinus and streptococcus mutans are common agents in __ __.
Tooth decay
72
Dental plaque -
Extensive growth of oral microorganisms, especially streptococci, results in a thick bacterial layer
73
As plaque continues to develop, ___ bacterial species begin to grow.
Anaerobic
74
Dental caries -
As dental plaque accumulates, the microorganisms produce high concentrations of acid, resulting in decalcification of the tooth enamel
75
Pathogens produce enzymes that:
- enhance virulence by breaking down or altering host tissue to provide access to nutrients
- protect the pathogen by interfering with normal host defense mechanisms
76
Example of enzyme that enhances virulence by breaking down or altering host tissue to provide access to nutrients?
Hyaluronidase
77
Example of enzyme that protects the pathogen by interfering with normal host defense mechanisms?
Coagulase
78
___ species encode a large number of virulence factors.
Salmonella
79
Salmonella also contains ___ plasmids.
Resistance (R plasmids)
80
Several genes that direct invasion are clustered together on the chromosome as ___ ___.
Pathogenicity islands
81
Three categories of exotoxins:
Cytotoxins
AB toxins
Superantigen toxins
82
Exotoxins -
Proteins released from the pathogen cell as it grows
83
Cytotoxins (cytolytic toxins) -
Work by degrading cytoplasmic membrane integrity, causing cell lysis and death
84
Toxins that lyse red blood cells are called ___.
Hemolysins
85
Staphylococcus alpha-toxin
Kills nucleated cells and lyses erythrocytes
86
AB toxins
- consist of two subunits, A and B
- work by binding to a host cell receptor (B subunit) and transferring damaging agent (A subunit) across the cell membrane
87
Examples of AB toxins
- diphtheria toxin
- tetanus toxin
- botulinum toxin
88
Clostridium tetani and clostridium botulinum produce AB exotoxins that affect ___ ___.
Nervous tissue
89
Botulinum toxin
Consists of several related AB toxins that are the most potent biological toxins known
90
Tetanus toxin
Also an AB protein neurotoxin
91
Enterotoxins
Exotoxins whose activity affects the small intestine
- generally cause massive secretion of fluid into the intestinal lumen, resulting in vomiting and diarrhea
92
Example of enterotoxin
Cholera toxin
93
Endotoxin
The lipopolysaccharide portion of the cell envelope of certain gram-negative bacteria, which is a toxin when solubilized
94
Endotoxins generally ___ toxic than exotoxins.
Less
95
Presence of endotoxin can be detected by the ...
Limulus amoebocyte lysate (LAL) assay
96
Hosts have innate resistance to most pathogens:
- natural host resistance
- tissue specificity
- physical and chemical barriers
