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Microbiology HIS > Host-Pathogen interactions > Flashcards

Host-Pathogen interactions Flashcards

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Biology 101 flashcards
1
Q

Colonization?

A

A bacterium occupies and multiplies in a particular

area of the human body

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2
Q

Infection?

A

Colonization of the body by a bacterium capable of

causing disease

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3
Q

Disease?

A

Infection that produces symptoms

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4
Q

Asymptomatic carrier?

A

Infected person that do not have detectable symptoms

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5
Q

Virulence (pathogenesis)?

A

The ability of a bacterium to cause infection

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6
Q

Virulence factor?

A

Bacterial product or strategy that contributes to virulence

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7
Q

Primary pathogens?

A

Not normally associated with the host and cause infection

• E.g. Yersinia pestis (Plague), Influenza virus

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8
Q

Opportunistic pathogens?

A

Cause disease under some circumstances

• E.g. Pseudomonas aeruginosa (associated with burns)

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9
Q

Sometimes the pathogen is part of the normal flora?

A

E.g. Staphylococcus epidermidis causing catheter-related diseases

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10
Q

The normal microbial flora?

A

In healthy individuals
• The internal tissue (blood, brain, lungs, muscle etc.) are normally free of microorganisms

However
• Surface tissue (i.e. the skin and mucous membranes) are constantly colonized/infected by
various microbial species

Many members of the normal flora are either pathogens or opportunistic pathogens

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11
Q

Vaginal child-birth?

A 
Vagina-bacteria such as
• Lactobacillus spp.
• Prevotella spp.
• Sneathia spp.
• et.al.
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12
Q

Lactobacillus produce?

A

Hydrogen-peroxide
• Lactic acid
• Toxic molecules
These inhibit the growth of more pathogenic bacteria

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13
Q

Sitisms?

A 
Parasitism
Beneficial for one part but at the expense of the other
• Protozoa
• Helmints
Mutualism
Beneficial for both parts
• Normal-flora
Commensalism
Beneficial for one part but ether help or hurt the other
• Decomposers
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14
Q

The skin?

A 
The skin is not hostile to bacteria
• Dry
• Acidic
• Salty
• “Cool”
• Lytic enzymes
• Antimicrobial peptides
• Shedding
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15
Q

Resident and transient flora?

A

Resident flora
Mostly Gram-positive bacteria
• Staphylococcus epidermidis

Transient flora
Varying flora
• Alfa-hemolytic streptococci
• Spore-forming bacteria
• Intestinal-bacteria
• Gram-negative environmental-bacteria
• Yeast

Function
• Consume nutrient
• Occupies space
• Alters the pH

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16
Q

Flora of the mucous membranes?

A 
Eyes
• Normally few bacteria due to lysozyme
• Can be:
o Coagulase-negative staphylococci (KNS)
o Alfa-hemolytic streptococci

Ears
• Common skin-flora
• Intestinal-bacteria

Nose
• KNS
• Staphylococcus aureus

17
Q

Life in mouth?

A

There are lots of nutrients in saliva
• Nutrients are present at low concentrations
• Food particles and cell debris thus provide high
concentrations of nutrients near surfaces (teeth and gum)
Saliva contains
• Lysozyme (cleaves peptidoglycan)
• Lactoperoxidase
Before and after teeth
• Before: aerotolerant bugs, e.g. streptococci and lactobacilli
• After: anaerobes that usually grow as biofilm

18
Q

Dental plaque?

A

Glycoproteins from the saliva adhere to tooth surface
• To these proteins, bacterial cells can attach
o Streptococcus sanguis
o Streptococcus sobrinus
o Streptococcus mutans
As dental plaque accumulates, the bacteria produce organic acids
that decalcify the tooth enamel (caries)

19
Q

Hemolysis?

A 
Streptococci produce hemolysins
• α-hemolysis
o Results in a greenish color
• β-hemolysis
o Total-hemolysis
• γ-hemolysis
o No hemolysis
20
Q

Normalflora of the mouth?

A 
Consists of viridans streptococci (viridis, Lat. ”green)
• α-hemolytic streptococci
• Low-pathogenic
Diseases
• Plaque
• Caries
• Gingivitis
• Bacteremia
• Subacute endocarditis
21
Q

Intestinal normal-flora?

A

Bacterial life in the gut
The stomach fluids are very acidic
• Prevents entry of microorganisms into the intestinal tract
Helicobacter pylori
• May result in ulcers and gastric cancer
• Produces urease, which transforms urea → ammonium (increase in pH)

22
Q

Intestinal normal-flora?

A 
300-1000 different species
• A mass between 1.5 and 2.5 kg
• Most of them are anaerobic
The number differs between parts of gastrointestinal tract
• Most bacteria are found in colon
• Constitute 50-60 % of feces
23
Q

The function of intestinal flora?

A 
Metabolic function
• Break-down of sugar
o Cellulose
o Starch
• Break-down of protein
o Elastin
o Collagen
Vitamin-synthesis
• Vitamin K
• Vitamin B12

Protective-effect
• Protect epithelial cells
• Consume nutrients
Bacteriocine-production

24
Q

Bacterial life in the lungs?

A 
Most pathogens are trapped by secretions from the mucous membranes and expelled
The upper respiratory tract
• Staphylococcus aureus
• Streptococcus pneumoniae
The lower respiratory tract
• No resident microflora
25
Q

Life in the urogenital tracts?

A

The bladder is typically sterile but the epithelial cells of the urethra is often colonized
Anatomical differences predispose women to get urinary tract infections
• Escherichia coli
• Staphylococcus saprophyticus
• Klebsiella spp.
• Proteus mirabilis
• Enterococcus spp.

26
Q

Harmful microbial interactions?

A

E A I CG TI D

27
Q

Exposure?

A 
Bacteria mostly infects via
• Skin
• Respiratory tracts
• Gastrointestinal tracts
• Urogenital tracts
28
Q

Adherence?

A 
Adherence proteins
Slime (polysaccharides)
• Important for binding to host-cells
and other bacteria
Capsule
• Also prevents phagocytosis
Fimbriae and pili
• Adherence surface protein-structures
29
Q

Invasion?

A

Bacteria generally need access to underlying tissues
Generally a break or a wound is required
• Can be caused by toxins?

30
Q

Growth?

A 
Growth is affected by:
• Temperature
• pH
• Oxygen
• Normal flora
• Nutrients/trace elements
The bacteria must be able to handle
• Stomach acids
• Bile
• Skin secretions
• IgA (present on mucosal membranes)
31
Q

Invasiveness?

A

• The ability of an organism to grow in host-tissue in such large numbers that the pathogen
inhibits host-function

32
Q

Toxicity?

A

The ability of an organism to cause disease by means of a toxin that inhibits host-cell function
or kills host-cells

33
Q

Measuring virulence ?

A

ID50
• The dose of an agent required to infect 50 % of the animals in a test group

LD50
• The dose of an agent that kills 50 % of the animals in a test group

Microbiology HIS (18 decks)

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