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Fundamentals of Pathology > W12 - Bacterial morphology > Flashcards

W12 - Bacterial morphology Flashcards

1
Q

Bacteria in numbers

A
  1. 3 × 10^29 bacteria in the oceans
  2. 3 × 10^21stars in the universe

Bacteria in a teaspoon of soil = Humans inAfrica (1 x 109)

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2
Q

Number of bacterial species

A

Total: > 0.7 - 100 million?

In the human gut : 500 – 1000

Species causing human disease : <100

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3
Q

Methods of classifying bacteria

A

Size

Gross structure

CW structure

Differential stains

Morphology

Growth requirements

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4
Q

Size ranges

A

0.3μm - 3μm

(Virus = 0.02μm - 0.3μm)

(WBC = 7μm - 25μm)

(Plant Cell = 10μm - 100μm)

Thiomargarita namibiensis = 300,000 nm

Mycoplasma genitalium = 300 nm

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5
Q

Structural components

A

Haploid (single chromosome) DNA (circular)

DNA in nucleoid region = NOT bound in a nucleus

Ribosomes in cytoplasm

Peptidoglycan membrane
No mitochondria

No membrane bound organelles
+/- Capsule
+/- Pilli / Flagella
+/- Spore

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6
Q

CW gram -ve

A

Extra outer membrane with integral lipopolysaccharides Periplasmic space

Escherichia.coli

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7
Q

CW gram +ve

A

Thick peptidoglycan layer integral with Lipo/teichoic acid

Streptococcus pyogenes

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8
Q

CW acid fast

A

Thick layer of mycolic acids linked by arabino-galactans integral with lipoarabinomannan

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9
Q

Gram stain

A

A differential cell wall stain dividing bacteria into
Hans Christian Joachim Gram 1882
Gram positive – BLUE/PURPLE Gram negative – RED/PINK

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10
Q

Gram -ve means

A

Negative means the alcohol step damages the outer membrane and allows the BLUE/PURPLE Crystal Violet dye out.

The second Safranin/Carbol fuschin dye then stains the cell wall RED/PIN

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11
Q

Gram stain proces

A

Fix (white) → crystal violet (blue) → iodine (purple) → alcohol →carbol fushcin or safranin

at alcohol -ve is white whereas +ve is purple

at last step +ve still purple whereas -ve pink

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12
Q

Cell Wall & Acid Fast Stain

A

Acid Fast RED (Ziehl–Neelsen : ZN) or FLOURESCENT (Auramine)

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13
Q

AFB+ and AFB-

A

Fix (white) → carbol fuschin or auramine (red) → acid + alcohol → background stain

+ve stays red

-ve white from acid + alcohol

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14
Q

Gram positive cocci

A

in pairs (diplococci)

Streptococcus pneumoniae (pneumonia)

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15
Q

Non Acid Fast

A

they do NOT retain (keep fast) the Carbol Fuschin/Auramine stain on cell surface when washed with acid

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16
Q

Gram positive cocci

A

(in chains)

Streptococcus pyogenes (pharyngitis)

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17
Q

Gram positive cocci in clusters

A

Staphylococcus aureus (toxic shock syndrome)

18
Q

Gram positive rods

A

(bacillus)

Corynebacterium diphtheriae (diphtheria)
Pallisades
Chinese writing

19
Q

Gram positive rods (with spores)

A 
Clostridium tetani (tetanus) 
Clostridium perfringens (gangrene) Clostridium difficile (pseudomembranous colitis)
Bacillus anthrax (anthrax)
20
Q

Gram negative rods (bacilli)

A 
Escherichia coli (colitis) 
Salmonella typhi (typhoid fever)
21
Q

Gram negative cocci (diplococci)

A

Neisseria meningitidis (meningitis) Neisseria gonorrhoea (gonorrhoea)

22
Q

Spiral (helical) shaped

A 
Treponema pallidum (syphilis) Helicobacter pylori (stomach ulcers) 
Vibrio cholerae (cholera)
23
Q

Acid Fast Stains

A

Mycobacterium tuberculosis
Auramine
Ziehl-Neelsen

Cording colony

24
Q

Cell wall deficient

A 
Mycoplasma pneumoniae (atypical pneumonia)
No cell wall = no staining
Have only lipoprotein outer coat
25
Q

Factors affecting growth

A 
Division rate
Lag phase time 
Oxygen availability 
Carbon availability 
Temperature
pH 
Inhibitors 
Growth Factors
26
Q

Rapid growers

A 
Vibrio cholerae (a curved flagellate) Division every 20-40 minutes
= 1,073,741,824 bacteria from 1 starting cell overnight
27
Q

Slow growers

A 
Treponema pallidum (syphilis) 
Division every 30 hours
28
Q

Dormancy

A 
Mycobacterium tuberculosis (lung abscess)
Division every 18 hours (min) - 80 years?
29
Q

Obligate Aerobes

A

Require SOME oxygen to make ATP (energy/growth) Most tolerate O2( Air = 21%O2: 0.04%CO2) eg Pseudomonas aeruginosa

Some (Microaerophiles) only tolerate 5% O2 eg Helicobacter pylori

Some (Capnophiles) require CO2higher than in air (5-10%) eg. Neisseria gonorrhoeae

30
Q

Facultative Anaerobes

A

Use oxygen or fermention or anaerobic respiration eg. E.coli

31
Q

Aerotolerant Anaerobes

A

Cannot use oxygen but can tolerate it eg. Clostridium botulinum (botulism)

32
Q

Obligate Anaerobes

A

Oxygen is toxic

eg. Clostridium tetani (tetanus)

33
Q

Psychrophiles

A

extremophilic bacteria or archaea which are cold‐loving
(-20ºC to 20ºC)
eg. Campylobacter jejuni (food poisoning

34
Q

Mesophiles

A

an organism that grows best in moderate temperature, neither too hot nor too cold

(2ºC to 45ºC)
eg. Most animal pathogens

35
Q

Thermophiles

A

an organism—a type of extremophile—that thrives at relatively high temperatures

(42ºC to 80ºC) eg. Bacillus stearothermophilus (used for sterilisation strips)

36
Q

Extreme (hyper) thermophiles

A

(60ºC to 250ºC) eg. Thermus aquaticus (source of Taq for PCR)

37
Q

Campylobacter jejuni

A

(a common cause of food poisoning)

Grows between 0ºC to 45ºC.
This allows it to grow in cattle (humans 37ºC : cattle 42ºC) AND in badly prepared food IN YOUR FRIDGE!!!

Very few faecal organisms grow at 42ºC
We use this to differentially isolate Campylobacter jejuni from stool samples

38
Q

Acidophile

A

Helicobacter pylori (stomach ulcers)

39
Q

Neutrophile

A

Most human pathogens

40
Q

Alkaliphile

A

Bacillus cereus (food poisoning)

41
Q

Carbon usage

A

Bacteria with the Lac gene can ferment Lactose

42
Q

Why systemic classification?

A
  1. Shows how much is present ( + culture : shows viability) Important from normally sterile samples (blood, CSF) Quantification can give a measure of risk
  2. Pathogen confirmation Not all bacteria are pathogens (Commensals) Commensals in one host can cause disease in another
  3. Indicates treatment options Clinico-pathological manifestations are often species specific
  4. Speciation enables epidemiological study

Fundamentals of Pathology (23 decks)

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