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Microbiology FPP > Bacteriology > Flashcards

Bacteriology Flashcards

1
Q

What are the capsulated bacteria

A

YES Some Nasty Killers Have Pretty Big Capsules

Yersinia pestis
Escherichia coli
Salmonella typhi
Streptococcus pneumoniae
Neisseria menigitidis
Klebsiella pneumoniae
Haemophilus influenzas
Pseudomonas aeruginosa
Bacillus anthracis and Bordetella pertussis
Crypococcus neoformans

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2
Q

Give 3 characteristics of the bacteria cell

A

Prokaryotic
Non membrane organelle
DNA is circular

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3
Q

What’s the cell wall of bacteria made of

A

Peptidoglycan

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4
Q

What is peptidoglycan

A

Repeating disaccharide with amino acid in a side chain extending from each disaccharide

This results in a stable cross linked structure

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5
Q

Function of the bacterial cell wall

A

•Maintains cell osmotic pressure in hypotonic environment
•contributes to sensitivity to certain antimicrobial agents (penicillin) and the immune system (antibodies, phagocytes)
•determines reactivity to Gram stain

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6
Q

What’s the size of a bacteria

A

0.2-5Mm

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7
Q

Describe the ribosomes of bacteria

A

70s (50s+30s)
The 2 subunits are targets for different antibiotics

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8
Q

What inhibits the formation of 50s ribosomal subunit in bacteria

A

Erythromycin

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9
Q

What drugs target the 50s ribosomal subunit of bacteria

A

Macrolides
Clindamycin
Chloramphenicol

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10
Q

What drugs target the 30s ribosomal subunit of bacteria

A

Aminoglycosides
Tetracycline

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11
Q

What is a protoplast

A

If peptidoglycan is digested away from the cell, gram positive cells lose their cell walls and become protoplasts.

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12
Q

Give 2 characteristics of the cell wall of a gram + bacteria

A

Thick peptidoglycan (60-90% of cell wall)
Contains Tachoic acid

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13
Q

What three things are present in gram- bacteria but absent in gram+ bacteria

A

Outer membrane
Periplasmic space
Lipopolysaccharide (endotoxin)

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14
Q

What’s the function of the techoic acid

A

( polysaccharide, antigenic) Important for serologic identification of some bacteria

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15
Q

Characteristics of the cell wall in a gram- bacteria

A

•Very thin peptidoglycan
•No techoic acid
•A unique outer cell membrane
•Periplasmic space
•Lipopolysacharide (endotoxin)

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16
Q

Function of the outer cell membrane in gram- bacteria

A

◦excludes all hydrophobic molecules (•This protects the bacteria from the action of bile salts and toxins of the gut)
◦contain narrow, restrictive protein channels called porins which permits passage of low molecular weight hydrophilic molecules.
◦Large antibiotic molecules penetrate the outer membrane slowly (antibiotic resistance)

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17
Q

Where is the periplasmic space found

A

between the cytoplasmic membrane and the outer membrane

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18
Q

What does the Periplasmic space contain in gram- bacteria

A

contains digestive enzymes and other transport proteins

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19
Q

What does the lipopolysaccharide in the gram- bacteria contain

A

•polysaccharide O antigens used in typing gram negatives (easiest target for the humoral response of the host)
• lipid A or endotoxin. Endotoxin can trigger fever and septic shock in gram negative infections

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20
Q

What does endotoxin trigger in gram- bacterial infections

A

fever and septic shock

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21
Q

What’s the function of Lipopolysaccharide found on the gram- bacteria

A

LPS also protects the cell from phagocytosis, penicillins and the antibacterial enzyme lysozyme

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22
Q

What are the flagella built of

A

Flagella are built of proteins and are strongly antigenic.

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23
Q

What’s the antigen found in flagella

A

The H antigens and are important targets of protective antibody response

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24
Q

What’s another name for o antigen

A

Somatic antigen

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25
What are the differences shapes or forms flagella can be
•polar/monotrichous (single cell, restricted to the pole), • lophotrichous (a tuft at one pole) •amphitrichous: one or more flagella at both ends of the cell •peritrichous (distributed over the cell surface). •ceohalotrichous: a tuft both ends
26
How do you describe a bacteria with no flagella
Atrichous
27
Other than locomotion, what other function does the flagella have in bacteria
• Flagella can help in identifying certain types of bacteria e.g, Proteus species show a rapid 'swarming' type of growth on solid media. •Highly antigenic
28
Describe the capsule of a bacteria
A gelatinous polysaccharide and/or polypeptide outer covering •It may be firmly attached or loosely attached as a slime layer
29
What’s is a biofilm
Within the ***slime layer*** (more slimy than capsule) many cells can come together to form a biofilm, which may protect them from antibiotics and toxins
30
Functions of a capsule in bacteria
•Virulence factor, protecting bacteria from phagocytosis by immune cells(***has the most angtigenic variations)*** e.g Streptococcus pneumoniae . •Permit bacteria, to adhere to cell surfaces and structures such as medical implants, catheters and so on. •Capsules can be a source of nutrients and energy to microbes •Prevents cell from drying out (desiccation) •Polysaccharides from certain capsules is antigenic and can elicit production of protective antibodies
31
What is the point of adherence in bacteria
•Adherence is an important first step in colonization and sometimes leads to disease.
32
What is capsule made up of
Capsular antigen
33
Example of capsule being a source of nutrients and energy for bacteria
Streptococcus mutans, which ***colonizes teeth,*** ferments the sugar in the capsule and the acid byproducts contribute to tooth decay.
34
Examples of capsules that are highly antigenic
Included in vaccines •Such a vaccine is used against Hemophilus influenzae , Streptococcus pneumoniae and Neisseria meningitidis.
35
Describe the DNA of bacteria
the cytoplasm contains DNA, which is typically a single circle concentrated in a nucleoid region and not membrane bound
36
Describe how the genetic information of bacteria are Carried
Genetic information is carried in a long double stranded DNA. This is the chromosome, which comprise genes. • Genetic information may also be ***extrachromosomal, present as plasmid***
37
What are the plasmids I’m the bacteria
Small, extrachromosomal DNA circles.
38
How do plasmids replicate
•Plasmids replicate independently of the chromosome
39
What’s the function of a plasmid in a bacteria
carry genes that are not essential for cell survival but may give some advantage to an organism e.g they can carry genes for antibiotic resistance and toxin production.
40
What is a pili in bacteria
project from the cell wall but are more rigid than the flagella. •***Also called fimbriae***
41
Functions of pili In bacteria
They function in attachment to host cells (act as adhesins) •They prevent phagocytosis
42
What kind of bacteria are pili seen In more
Present in many Gram negative bacteria ◦e. g Neisseria gonorrhoea uses its fimbriae to attach to the lining of the genital tract and initiate an STD
43
What are the 2 types of pili
Somatic pili Sex pili (F pili)
44
Which pili is used for conjugation
F. Pili Sex pili act to join bacterial cells for transfer of DNA from one cell to another (bacterial conjugation)
45
Functions of fibriae (other than prevent phagocytes and for adhesion)
•Fimbriae also act as receptors for viruses that infect bacteria (bacteriophages) •Fimbriae and cell walls of Streptococcus pyogenes are coated with M protein.
46
Function of M protein in bacteria
•M protein acts as an important virulence factor by adhering to host cells and resisting phagocytosis
47
Why can some substances pass through the thick peptidoglycan in gram+ bacteria
•Gram positive thickly meshed peptidoglycan layer ***does not block diffusion of low molecular weight compounds*** so, some substances (antibiotics, dyes, detergents), can pass through
48
Can antibiotic and chemicals pass through the gram- cell wall
No
49
Why is the dark blue color retained in gram+ bacteria
Crystal violet is trapped in the thick peptidoglycan layer
50
What is the dark blue color not retained in gram- Bacteria
The outer cell membrane of the Gram negative cell wall is partially destroyed by alcohol, so crystal violet is washed out and a counterstain can be taken
51
Virulence of bacteria depends on what certain cell structures
Pili Flagella Capsule
52
Describe the staining mechanism
•Pour ***crystal violet*** (60 secs) •Wash off with water and flood with ***Lugols iodine*** (60 secs) •Wash off with water and ***decolorise with 95% alcohol*** •Counterstain with ***safranin*** (60 secs) and wash off with water
53
Describe the gram+ staining characteristics
Cells that absorb the crystal violet and hold onto it- •they stain blue or purple or black.
54
Describe the gram- staining characteristics
If the cells do not absorb crystal violet, it is washed off by the alcohol, the cells will then absorb safranin or dilute carbol fuschin •Gram negative organisms stain pink or red
55
How do medically important bacteria produce energy
Medically important bacteria use chemical and organic compds as energy source to produce ATP
56
How do obligate intracellular organisms produce energy
not capable of metabolic pathways, so get ATP from host cells
57
How do obligate intracellular bacteria form energy
not capable of metabolic pathways, so get ATP from host cells
58
Examples of obligate intracellular bacteria
•Chlamydia, Rickettsia
59
What are the metabolic characteristics of bacteria
•Obligate aerobes •Facultative anaerobes •Microaerophilic •Obligate anaerobes
60
What are the major classes of bacteria
•Gram positive bacilli •Gram positive cocci •Gram negative bacilli •Gram negative cocci •Others
61
Which group of bacteria is the largest group
Gram negative bacilli
62
What is a gram+ cocci catalase+ bacteria
Staphylococcus
63
List out the gram+ coccus bacteria
• Staphylococcus (S Aureus is coag +ve) S. Epidermis is coag -ve • Streptococcus • Enterococcus • Strep Viridian’s (anaerobic)
64
Which gram + coccus bacteria is anaerobic
Strep Viridian’s
65
What are the gram + bacillus bacteria
•Bacillus •Listerium •Nocardia •Coryne bacteria • Actinomyces • Clostridium • Lactobacillus
66
Which gram+ bacillus bacteria is anaerobic
• Actinomyces • Clostridium • Lactobacillus
67
Which gram+ bacillus bacteria is aerobic
•Bacillus •Listerium •Nocardia •Coryne bacteria
68
What are the gram - cocci bacteria
• Moraxella • Neisseria
69
Are Moraxella and Neisseria aerobic or anaerobic
Aerobic (gram- cocci)
70
What are the gram- bacillus bacteria
• Haemophillus • Klebsiella • Proteus • Acinectobacter • Pseudomonas • Yersinia • Salmonela • Campylobacter • Enterobacter • Morganella • Bacteriodes
71
Which of the gram- bacillus bacteria is anaerobic
Bacteriodes
72
Which bacteria is too small to be seen with light the microscope
Spirochetes
73
Which bacteria is acid fast stain
Mycobacteria
74
Which bacteria is without cell wall, only cell membrane
Mycoplasma
75
What are the antigens in a bacteria
•O (somatic) antigens to classify Gram negative bacilli •O antigen, H (flagella) antigen and Vi (capsular) •Over 2000 serotypes of Salmonella •M protein classifies S. pyogenes into >80 types •Cell wall carbohydrate antigen is used to group the Streptococci
76
What does M protein classify
S. pyogenes into >80 types
77
What is Cell wall carbohydrate antigen used to classify
Streptococcus
78
What are O antigens used to classify
Gram- bacteria
79
What are the basic characteristics and identifying features of bacteria
•Colony shape/xteristic in culture •Haemolytic patterns (α, β, non) • pigmented •Specialised structures like flagella, spores, capsule •Biochemical reactions to ascertain presence of metabolic activity •Fermentation (fermentative & non-fermentative bacilli) •Motility •oxidase reaction •Indole reaction •Urease production •Hydrogen sulphide production
80
What do you need to test the motile of a bacteria
Hanging drop test
81
What are the 3 types of hemolytic pattern in a bacteria
B-hemolysis alpha-hemolysis Gamma-hemolysis
82
What is beta hemolysis
Complete hemolysis (Clear area when bacteria is dropped)
83
What are the 2 examples of beta hemolysis
GAS- Group A Streptococci GBS- Group B streptococci
84
What is alpha hemolysis
Partial hemolysis (Greenish area where bacteria is dropped)
85
Example of alpha hemolysis
Streptococcus viridans
86
What is gamma hemolysis
No hemolysis
87
Example of gamma hemolysis
Peptostreptococcus Enterostreptococcus
88
How do you detect a bacteria
***•Culture*** •Cell free media – colonial morphology on culture media ***•Microscopy*** •Stains -Gram stain (morphology), giemsa stain ricketsia –light microscopy •Wet prep - phase contrast or dark-field microscopy •Serology •Agglutination, CFT, fluorescent antibody test, PCR etc •Antigen detection •Latex agglutination •DNA based techniques
89
How can you classify bacteria based on their oxidase reaction
Obligate aerobic Obligate anaerobic Facultative anaerobic Microarrophilic
90
Examples of bacteria that cannot be stained
Mycobacteria, including M. tuberculosis Treponema pallidum Mycoplasma pneumoniae Legionella pneumophila Chlamydiae, including C. trachomatis
91
Examples of bacteria that cannot be stained
•Rickettsiae •Mycobacteria, including M. tuberculosis •Treponema pallidum •Mycoplasma pneumoniae •Legionella pneumophila •Chlamydiae, including C. trachomatis
92
Why can’t mycobacteria be stained
Too much lipid in cell wall so dye cannot penetrate
93
What is used for mycobacteria instead of regular stain
Acid-fast stain
94
Why can’t Treponema pallidum be gram stained
It’s too thin to see
95
What’s used for treponema pallidum instead of gram stain
Dark-field microscopy or fluorescent antibody
96
Why can’t Mycoplasma pneumoniae be gram stained
No cell wall Very thin
97
What is used for Mycoplasma pneumoniae instead of gram stain
Nothing
98
Why can’t Legionella pneumophila be gram stained
Poor uptake of red counterstain
99
What’s used for Legionella pneumophila instead of normal farm stain
Prolong time of counterstain
100
Why can’t Chlamydiae, including C. trachomatis be gram stained
Intracellular; very small
101
What’s used for Chlamydiae, including C. trachomatis instead of normal gram stain
Inclusion bodies in cytoplasm
102
Why can’t Rickettsiae be gram stained
Intracellular Very small
103
What’s used for Rickettsiae instead of normal gram stain
Giemsa or other tissue stains
104
Describe the DNA based techniques
•A probe is a section of DNA that is meant to adhere to its opposite strand of DNA •PCR – DNA can be amplified and then identified • has specificity and high speed capabilities •DNA sequence of a particular component of their ribosomes •used as a tool to group bacteria together that are believed to have evolved from a common ancestor. •Their ribosomal RNA would be very similar (16s RNA)
105
How are bacteria grouped according to how dangerous they are
•Pathogens -are always likely to cause disease •Opportunistic -cause disease only when they have a special opportunity to gain entrance inside the body •Invasive -proactively create portals of entry -
106
Examples of pathogenic bacteria
Salmonella typhi, Vibrio cholerae
107
Examples of opportunistic bacteria
Bacteroides fragilis, Clostridium difficile, Pseudomonas aeruginosa
108
Examples of invasive bacteria
Salmonella enteritidis,
109
What is present in a gram- bacteria after digestion (losing peptidoglycan)
Spheroplast
110
What enzyme is found in the Periplasmic space
B-lactamase
111
What is the function of B-lactamase
Destroys B-lactams
112
Example of B-lactam drug
Penicillin
113
What has the most antigenic variations in a bacteria
Capsule

Microbiology FPP (4 decks)

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