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Microbiology > Infectious Disease and Pathogenicity > Flashcards

Infectious Disease and Pathogenicity Flashcards

1
Q

Cocci bacteria

A

Round and spherical

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2
Q

Bacilli

A

Rod shaped

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3
Q

Monococcus

A

Single round cell

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4
Q

Diplococcus

A

Paired cells

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5
Q

Staphylococcus

A

Grouped cells

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6
Q

Streptococcus

A

Chained cells

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7
Q

Bacteria cell components

A 
Cell Wall
Flagella
Pilli/fimbriae
Nucleoid
Plasmids
Cytoplasm 
Ribosomes
Endospore 
Capsule
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8
Q

What is an endopsore?

A

Small, highly resistant, thick-walled, “resting” cells
Produced in response to environmental stressors
Formed when bacteria stops growing as environment cant support its growth

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9
Q

What are inclusion bodies?

A

Form in cytoplasm
Can be fat/iron/proteins
Protein aggregates
Site of viral multiplication

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10
Q

Gram negative bacteria

A

Outer and inner membrane

Thin layer of peptidoglycan

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11
Q

Gram positive bacteria

A

No outer membrane

Thick layer of peptidoglycan

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12
Q

What separates the outer and inner membrane in gram negative bacteria?

A

Periplasm

Smaller one in gram positive

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13
Q

Function of periplasmic space

A 
Protein oxidation
Folding 
Thin layer of peptidoglycan
Quality control
Contains enzymes involved in cell's metabolism
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14
Q

When are resistant spores formed?

A

In adverse conditions

Environmental stress e.g lack of nutrients, bad pH

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15
Q

Why do bacteria produce spores?

A

To produce a dormant and highly resistant cell to preserve the cell’s genetic material in times of extreme stress
The spores are resistant to UV/radiation/Biocides/ Gamma radiation

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16
Q

Layers of spore (innermost to outermost)

A 
Core
Inner membrane 
Germ cell wall
Cortex
Outer membrane 
Coat 
Exosporum
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17
Q

Function of exosporum?

A

adherence and biocide protection

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18
Q

Sequence of treatment

A
  1. Observance of patient- symptoms
  2. Sampling
  3. Laboratory observation and culture
  4. Identification tests
  5. Treatment e.g antibiotics
  6. Observation of population
  7. Preventing transmission
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19
Q

Definition of disease

A

A disturbance in the state of health wherin the body cannot carry out all its normal functions

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20
Q

Infectious disease definition

A

Infection caused by pathogenic micro-organisms

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21
Q

Infection definition

A

Invasion and multiplication of a pathogenic microbe within or on a host

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22
Q

Contamination

A

Presence of microbes in a location/environment

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23
Q

What is koch’s postulates?

A

4 criteria to establish a causative relationship between a microbe and disease

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24
Q

What are the 4 criterias of koch’s postulates?

A
  1. The specific causing agent must be seen in every disease
  2. The agent must be isolated from a diseased host and grown in pure culture
  3. The specific disease must be reproduced when a pure culture of the bacteria is inoculated into a healthy susceptible host
  4. The agent must be re-isolated from the diseased host and identified as identical to the specific disease causing agent
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25
What diseases does koch's postulates work for?
Plague Anthrax Cholera Typhoid
26
When is koch's postulates less evident in?
Condition is chronic Condition has multiple causes Conditions where pathogen can't be grown outside of body (in-vitro) No suitable animal model of infection
27
What conditions would koch's postulates be less evident for?
Pneumonia Wound infections Septicaemia Urinary Tract infections
28
What is normal flora?
Micro-organisms present on body surfaces covered by epithelial cells and are exposed to the external environment
29
Where in the body is normal flora found?
Gastrointestinal tract Respiratory Tract Genitourinary tract
30
Normal flora and host cell
They live in benign symbiosis with one another
31
Examples of normal flora
E.coli found in the intestines | Staphylococcus aureus in nostrils
32
Why can't normal flora cause disease even if they are pathogenic?
They lack attachment to a suitable surface
33
When does normal flora become pathogenic?
When environment changes e.g environmental stress, hormonal levels, stress, climatic e.g MRSA
34
6 stages of disease progression
1 and 2- transmission and exposure to disease 3 and 4- Adherence and invasion 5 and 6- Colonisation and Tissue Damage
35
What does successful exposure and transmission depend on?
Number of microbes- the more the better Airborne- size, density, surface features Waterborne- density, surface features, hydrophobicity Contact- resistance to dessication, spore formation, adhesion Vectors Fomites Distribution on host: into cuts , digestive system, genitourinary system, lungs
36
What does adherence and invasion depend on?
Adherence depends on host's and microbe's features Invasion depends on breaking i surface layers or acitve procedures from microbe Chemotaxis and motility Attachment via pilli/non-fimbrial adhesions Penetrations of epithelia/cells via proteases Anti-phagocytic capsules may allow survival stopping phagocyte entering microbe Virulent bacteria can inject epithelium cells with molecules to change features of surface
37
What does colonisation and tissue damage depend on?
Growth of bacteria in host means host's responses are avoided Growth of microbe in host requires nutrients There is limited nutrient availability in the host cell Tissue damage caused by accumulation of toxins released by microbe
38
What defences does the host cell have?
1. Physical barriers (e.g sebum on skin) 2. Cellular defences (phagocytes, killer cells) 3. Inflammation 4. Complement System 5. Immunity
39
What is the result of bacteria prolonging an immune response?
Chronic infection
40
3 characteristics of a pathogen
1. Virulence 2. Pathogenicity 3. Virulence/Pathogenicity factor
41
Pathogenicity
Ability of a pathogen to produce an infectious disease in an organism
42
Virulence
Relative degree of damage caused by pathogen/ degree of pathogenicity of a pathogen
43
Virulence/Pathogenicity Factor
Microbial product/strategy that causes virulence/pathogenicity
44
Molecular determinants of pathogenicity
1. Attachment to host tissues 2. Production and delivery of various factors 3. Replication and evasion of immunity 4. Damage to host tissues
45
How do bacteria adhere to host?
Bacteria employ proteins such as adhesins which are normally found on ends of fimbriae/pilli Adhesins can consist of glycocalyx
46
What do bacteria use to penetrate host?
Enzymes (proteases) Capsules Cell wall components
47
How do bacteria damage host cells?
``` Direct damage Endotoxins Exotoxins Toxins Hypersensitivity reactions (allergies) ```
48
What do pilli/fimbriae attach to on host cell?
Host cell glycoprotein receptors
49
Role of capsules in bacteria?
Prevent phagocytes attaching Preventing phagocytosis e.g streptococcus pneumoniae
50
What enzyme is released by bacteria to get into host cell?
Proteases
51
A few enzymes released by bacteria that harm eukaryotic cells
Coagulase Collagenase Haemolysins Leukocydins
52
Which bacteria releases haemolysins?
Alpha haemolytic streptococci | Beta haemolytic streptococci
53
Difference between alpha and beta haemolytic streptococci?
Alpha- haemolysins released cause incomplete lysis of RBCs | Beta- haemolysins released cause complete lysis of RBCs
54
Which bacteria produces coagulase?
Staphylococcus aureus
55
Action of coagulase?
Causes blood to coagulate (clot) Blood clot prevents phagocytes phagocytosing bacteria Fibrinogen converted to fibrin= clot
56
What bacteria produces collagenase?
Clostridium perfringens
57
Action of collagenase?
Breaks down collagen in muscle tissue | Allowing bacteria to spread through muscle tissue
58
Action of leukocidins?
Pore forming exotoxins that kill leukocytes Cause degranulation of lysosomes within leukocytes Decreases host resistance
59
2 types of toxins released by bacteria
Endotoxins | Exotoxins
60
What bacteria are exotoxins mainly produced in?
Gram positive bacteria
61
How do exotoxins work?
Secreted by bacteria cell into surrounding medium | Mainly by gram positive bacteria
62
What are endotoxins part of?
Part of outer portion of cell wall in gram negative bacteria
63
How do endotoxins work?
Once bacteria dies and cell wall is broken down endotoxins are released

Microbiology (5 decks)

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