Bacteria as causes of diseases Flashcards
What is the resolving power of the naked eye
100 micrometers
What is the resolving power of a light microscope
0.2 micrometer
Nomenclature of bacteria
Genus followed by species name
e.g. Staphylococcus (genus) aureus (species)
Define pathogen
Organism that causes disease
Define commensals
Organism which colonises the host but causes no disease in normal circumstances
Define Opportunist Pathogen
Microbe that only causes disease if host defences are compromised
Define Virulence/Pathogenicity
The degree to which a given organism is pathogenic
Define asymptomatic carriage
When a pathogen is carried harmlessly at a tissue site where it causes no disease
What does Trypanosoma Gambiense cause
Sleeping sickness
What do entamoeba histolytic cause
Amoebic dysentery
What are trypanosomes and entamoeba examples of
Eukaryotic cells
What does Borrellia recurrent cause
recurring fever
What does Borrellia Burgdorferi cause
Lyme disease
What does treponema palladium cause
Syphillis
What are Borrellia and Treponema palladium
Spiral bacteria
What does rotavirus cause
Vomiting and Diarrhea
What areas are open to bacteria
ALL mucosal surfaces Skin Beginning of urethra Kidneys Colon Mouth Eyes Anus
Are the lungs prone to bacterial colonisation
No, they should be sterile
What two shapes are most bacteria found in
Round (cocci)
Rod-shaped (bacilli)
How do gam stains help identify bacteria
Divides them into either gram positive or negative bacteria
How do we know what bacteria is gram positive
Stains purple
How do we know what bacteria is gram negative
Stains pink
What are two cocci gram positive bacteria called
diplococcus
What is a vibrio
Curved rod
What is a spirochaete
A spiral rod
Examples of spiral rods
Borrellia and Treponema palladium
Describe the structure of a bacteria
In order:
- Inner membrane
- Outer membrane
- Cell wall
- Capsule
- —— - Single chromosome of circular double stranded DNA free floating
- Pilli projecting from outermsmbrane into area (leg-like projections)
What bacteria has a double membrane
Gram negative
What bacteria has a single membrane
Gram positive
role of pilli
Used to attach to the host
Role of capsule
Protect from immune system/complement system
Difficult for immune system to recognise bacteria
Structure of a gram positive bacteria envelope
- Single cytoplasmic membrane
- Layer of peptidoglycan attached to outer part of cytoplasmic membrane
- Capsule
What binds the peptidoglycan layer to the membrane of a gram positive bacteria
Lipoteichoic acid
Structure of gram negative envelope
- Inner membrane
- THIINNER peptidoglycan sheet
- Lipoproteins
- Outer membrane
- A lipopolysaccharide layer (Endotoxin)
- Capsule
What are the spaces found between the lipoproteins called
Periplasmic space
What is the role of the lipopolysaccharide layer
It is a PAMP so can trigger immune response
Temperature range for bacteria survival
between -80 and 80 degrees
Temperature range for spores
120 degrees
pH of bacterial environment
<4
above 9
Define desiccation
Process of extracting moisture
Desiccation survival time for bacteria
2hrs - 3months
What lightwave can some bacteria survive
UV
What bacteria can survive radiation
Radmococcus by surviving on uranium
Doubling time for most viruses
1 hour
What environment allows microbes to double faster
Broth or media
How long does it take to diagnose conditions caused by mycobacterium
6-8 weeks (a LOT longer than other viruses and bacteria)
Describe the growth curve of bacteria
- Lag (slow growth - bacteria getting used to the environment and changing metabolic pathways and producing nutrients)
- Exponential (rapid increase in colony numbers)
- Stationary (nutrients run out and competition increases + toxic compounds produced)
What is an ENDOTOXIN
Component of the outer membrane of bacteria (lipopolysaccharide)
Define an EXOTOXIN
Secreted proteins of gram positive and gram negative bacteria
Consequence of an endotoxic shock
Inflammation response
Example of an exotoxin
Protein
Example of an endotoxin
Lipopolysaccharide
Exotoxin vs Endotoxin (specific or non-specific action)
Exotoxin - Specific
Endotoxin - Non-specific
How does heat effect exotoxins vs endotoxins
Exotoxins - inactivate
Endotoxins - not effected
Extent to how well exotoxins and endotoxins work as an antigen
Exotoxin - strong
Endotoxin - weak
What bacteria produces exotoxins
Gram Positive
Gram Negative
What bacteria produces Endotoxins
Gram Negative (LPS)
Can we use an endotoxin as a toxoid
No
Can we use an exotoxin as a toxoid
Yes
Three ways DNA can mutate
Base substitution
Deletion
Insertion
How many base pairs does bacterial chromosome consist of
2-4 x 10^3 Kb
Other than bacterial chromosome, where else is DNA found
Bacterial plasmids
How many bases are found in plasmid DNA
10-60Kb
What are Plasma DNA
Autonomously repeated packets of DNA that are shared between different bacteria (needed for adaptations - e.g. resistance)
How are plasmids shared between different types of bacteria
- Tra locus contains pilin and regulatory genes which form pili
- Conjugation is initiated by a signal the relaxes enzyme creates nick in one of the strands of the conjugative plasmid.
- Nicked strand is unwound
- Strand is replicated
Why is a plasmid called an episome
It can integrate itself on bacterial chromosome by homologous recombination
Why can some of the host’s genes be donated to the recipient
Because plasmids may have replicated genes from host’s DNA
What three ways are genes spread between bacteria
- Transformation via plasmids
- Transduction via Bacteriaphages
- Conjugation via sex pilus
What are bacteriophages and how do they spread DNA between bacteria
- Viruses that infect bacteria
2. Spread DNA as they jump from one bacteria to the next
What is an obligate intracellular bacteria
Parasites that can’t reproduce outside their host cell
Three obligate intracellular bacteria
- Rickettsia
- Chlamydia
- Coxiella
How do we distinguish between enterobacteriacae and other forms of bacteria
Add lactose fermenter solution to agar plate (should be able to ferment them)
Name three types of enterobacteriacae
- E. coli
- Klebsiella
- Enterobacter
- Citrobacter
What can cause problems when trying to detect lactose-fermenting bacteria
- Some are late-lactose fermenters
How do we detect late-lactose fermenters
Positive ONPG test
Two examples of late-lactose fermentors
Serratia
Citrobacter
5 examples of lactose non-fermentors
- Salmonella
- Shigella
- Yesrinia
- Proteus
- Pseudomonas Aeruginosa
Name an anaerobic gram negative bacteria
Bacteroides (B. fragilis)
What are coliform
rod-shaped gram-negative non-spore bacteria
What are Vibrio bacteria
Gram negative, curved-rod shaped
What type of bacteria is Helicobacter
Vibrio
What type of bacteria is salmonella
Coliform
How can motility help distinguish bacteria
We can see motility patterns showing up on the agar
How can we detect if Proteus mirabilis is present on a petri dish
Concentric circles formed by swimming
What type of bacteria is Proteus
Coliforms
Role of the oxidase test
Tests if micro-organisms contain cytochrome oxidase or indophenol oxidase
What is a redox indicator
an indicator which undergoes a definite color change at a specific electrode potential.
Give an example of a redox indicator used in the oxidase test
TMPD
When oxidised state, what colour is TMPD
Dark blue or maroon
What does the oxidised state mean
Organism is able to use oxygen as terminal electron acceptor
