Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Disease Mechanisms > Microbiology - Bacteria > Flashcards

Microbiology - Bacteria Flashcards

1
Q

How can bacteria be studied?

A

Light microscopy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What type of genetic material do bacteria contain?

A

DNA and RNA

Single double-stranded chromosome

Plasmids (circular DNA) in cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the main parts of a bacterium?

A

Cell membrane

Cell wall

(Capsule)

Flagellae (movement)

Pili/Fimbrae (adhesion)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How can bacteria be classified according to shape?

A

Coccus

Bacillus

Spirochaetes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How can Gram stain be used to differentiate between Gram +ve and Gram -ve cocci/bacilli?

A

Gram positive = purple

Gram negative = pink

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe the Gram +ve cell wall

A

Thick layer of peptidogycan

Outer cytoplasmic membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe the Gram -ve cell wall

A

Inner membrane

Thin peptidoglycan layer

Outer membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why is Gram staining important?

A

Leads us towards likely infecting organism

Many antibiotics work on bacterial cell wall - different antibiotics for Gram +ve and Gram -ve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Give two examples of organisms which don’t stain well with Gram stain?

A

Mycobacterium tuberculosis - waxy coat

Treponema pallidum (spirochaete causing syphilis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What do bacteria require for growth?

A

Food (any organic matter)

Moisture

Correct temperature (37C for most human pathogens)

Correct pH (around pH7.4 for most human pathogens)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How quickly can a bacterial population double its population under ideal growth conditions?

A

Every 20 minutes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the four phases of the bacterial growth curve

A

Lag phase (bacteria maturing, not ready to divide)

Log phase (binary division)

Stationary phase (growth rate = death rate)

Death phase (bacteria run out of nutrients and die)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe an aerobic bacteria

A

One which grows in the presence of air.

May grow anaerobically, but less well.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is a microaerophilic bacteria?

A

One which grows in an atmosphere with reduced oxygen concentration and enriched CO2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is an anaerobic bacteria?

A

One which can only grow in the absence of oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is an exotoxin?

A

A toxin (enzyme) produced inside the cell and exported from it.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Which sort of bacteria mainly produce endotoxins?

A

Gram +ve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is an endotoxin?

A

Part of the bacterial cell wall.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Which type of bacteria usually produce endotoxins?

A

Gram -ve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are two effects of toxins on the body?

A

Interact with immune cells causing release of cytokines

Damage to red and white blood cells causing leaky blood vessels - hypotension, affect blood clotting > sepsis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is LPS?

A

Lipopolysaccharide

It is found in the other membrane of Gram -ve bacteria and is an endotoxin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What type of bacteria form spores?

A

Gram +ve bacilli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Give two examples of bacteria that form spores.

A

Clostridium sp (e.g. C. diff)

Bacillus sp (e.g. anthrax)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are spores?

A

Inactive forms of bacteria that can survive adverse conditions for many years.

They cannot replicate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Which diagnostic methods are used for bacterial infections?
Microscopy - Gram stained film Culture Detection of Antigen (e.g. urine sample) Detection of Antibody in blood (serology) Molecular methods (PCR) - organism's DNA or RNA
26
Which bacteriology tests can be returned with the same day?
Gram film PCT Serology (if not batched)
27
How long does culture and antibiotic sensitivity testing take?
48 hours
28
How long does TB culture take?
4 - 12 weeks
29
Which Gram +ve cocci grow in chains?
Streptococci spp Enterococcus sp
30
Which Gram +ve cocci produce α-haemolysis?
Strep. pneumoniae Strep. viridans
31
Describe Strep. pneumoniae, what infections does it produce?
Gram +ve Aerobic Coccus Chains α-haemolysis **Pneumonia, Meningitis**
32
Describe Strep. viridans, what infections does it produce?
Gram +ve Coccus Aerobic Chains α-haemolysis **Endocarditis**
33
Which Gram +ve cocci cause β-haemolysis?
Group A Strep (Strep. pyogenes) Group B Strep
34
Describe Strep. pyogenes, what infections does it cause?
Gram +ve Coccus Chains Aerobic β-haemolysis **Throat, skin infections**
35
What infection does Group B strep cause?
Neonatal meningitis
36
What is β-haemolysis?
Complete haemolysis
37
What is α-haemolysis?
Partial haemolysis
38
Which Gram +ve cocci, growing in chains, do not produce haemolysis?
Enterococcus sp.
39
What infection does Enterococcus sp produce?
UTI It is a gut commensal
40
Describe Enterococcus sp.
Gram +ve Coccus - chains Aerobic Non-haemolytic **Gut commensal**
41
Can Streptococcus and Enterococcus grow anaerobically?
Yes.
42
How are strains of Streptococcus and Enterococcus differentiated?
By the type of haemolysis they produce on blood agar plate.
43
Which antibiotic is usually used to treat Streptococcus pneumoniae?
Penicillin
44
Where are the Strep. viridans group normally found as commensals?
Upper Respiratory Tract Bowel Vagina
45
Which are the most pathogenic streptococci?
Group A and Group B those causing β haemolysis - caused by (exo)toxins that lyse red blood cells
46
Which infections are caused by Strep. pyogenes?
Streptococcal sore throat (tonsilitis) (with rash = scarlet fever) Skin & soft tissue infections - necrotising fasciitis Perperal sepsis - pregant and recently post natal women
47
Which antibiotics would be used to treat Group A strep infections?
Penicillin Amoxicillan
48
Which antibiotics are Enterococci usually sensitive to?
Most are sensitive to amoxicillin Most are resistant to penicillin
49
Describe the Staphylococci
Gram +ve Coccus - clusters Aerobic, but can grow anaerobically
50
How is Staph aureus distinguished from the other staphylococci?
Coagulase test. Staph. aureus - coagulase +ve
51
What type of commensals are the coagulase -ve Staphs?
Skin commensals
52
How do the coagulase negative staphs cause infections of prosthetic joints, heart valves, IV catheters? What is the difficulty with such infections?
Produce surface polysaccharide slime that allows them to stick to plastic and other artificial material. Hard to treat with antibiotics
53
Where is Staph. aureus normally found?
Nose Upper Respiratory Tract
54
What type of toxins are produced by Staph aureus?
Different strains produce different (exo)toxins. Toxic shock syndrome toxin Panton-Valentine leukocidin Enterotoxins
55
What do the terms MSSA and MRSA mean?
Meticillin-sensitive Staph. aureus - sensitive to flucloxacillin Meticillin-resistant Staph. aureus - resistant to all penicillins and cephalosporins (+ others)
56
Which infections are caused by Staph. aureus?
Commonest cause of skin, soft tissue and wound infection Commonest cause of bone & joint infection Food poisoning (enterotoxin-producing only)
57
What is the preferred antibiotic treatment of Staph. aureus (MSSA) infection?
Flucloxacillin
58
What is bacteraemia?
Bacteria in the bloodstream
59
What may occur if a patient has bacteraemia?
**Sepsis** Infection may spread elsewhere in body resulting in disseminated infection abcess formation
60
What is the commonest cause of bacteraemia?
Staph. aureus
61
Describe the Neisseria spp bacteria
Gram -ve Coccis - diplococci Aerobic
62
What infections are caused by Neisseria spp. bacteria?
Neisseria gonorrhoeae - gonorrhoea Neisseria meningitidis - meningitis
63
What are the coliforms?
Gram -ve bacilli Look like Escherichia coli (E. coli) on Gram film and when cultured on blood agar
64
How are the coliforms distinguished?
Biochemical reactions Antigenic structure of cell wall (serotyping) O antigens - cell wall H antigen - flagella
65
Where are the coliforms often found?
Gut commensal
66
Name some gut commensal coliforms.
E. coli (most strains) Klebsiella spp Enterobacter spp Proteus spp
67
Name some gut pathogens
Salmonella spp Shigella spp Verotoxin producting E. Coli - VTEC - O157, O104
68
Which antibiotic is the first line treatment for infections caused by coliforms?
Gentamicin
69
Why do patients with coliform sepsis because unwell very rapidly?
Endotoxin is released from Gram -ve cell wall when the bacteria die
70
Which Gram -ve bacilli are strict aerobes?
Pseudomonas aeruginosa Legionella pneumophilia (Legionnaire's disease)
71
Which Gram -ve bacilli are spiral or curved?
Vibrio cholera Campylobacter spp Helicobacter pylori
72
Which Gram -ve (cocco)bacillus is the most common cause of chest infection?
Haemophilus influenzae
73
Which bacteria are strict anaerobes?
Clostridium spp Bacteroides spp
74
Describe Clostridium spp bacteria
Gram +ve Anaerobic Bacillus Normal bowel flora - found in faeces & soil Produces spore Produce exotoxins
75
Which anaerobic Gram +ve bacteria is associated with antibiotic diarrhoea, especially in the elderly?
Clostridium difficile
76
Which Gram +ve anaerobic bacteria causes gas gangrene, a severe soft tissue infection following wound contamination?
Clostridium perfringens
77
Which Gram +ve anaerobic bacteria causes tetanus?
Clostridium tetani
78
Describe Bacteroides spp
Gram -ve Anaerobic Bacillus Normal bowel flora, normally non-pathogenic, cause infection in sterile sites such as peritoneum and biliary tract
79
What is the first line treatment for infections caused by anaerobic bacteria?
Metronidazole
80
What is the first line treatment for infections caused by coliforms?
Gentamicin
81
How are mycobacteria classified by staining?
Acid Fast Bacilli (AFB) Acid-Alcohol Fast Bacilli (AAFB)
82
Give two examples of spirochaetes
Treponema pallidum - syphilis Borrelia burgdoferi - Lyme disease
83
Do spirochaetes stain with Gram stain?
No
84
How do you choose an antibiotic?
Site of infection - likely organisms Orally or IV Allergies Local guidelines
85
Which antibiotics are less likely to cause C. diff infection?
Narrow spectrum
86
Why are antibiotics sometimes given in combination?
Cover a broad range of organisms Prevent development of resistance Synergistic effect
87
How do antibiotics work?
Attacking bacterial cell wall Attacking bacterial ribosome Acting on bacterial DNA
88
Which antibiotics act on bacterial cell wall?
Penicillins Cephalosporins Glycopeptides
89
Name four antibiotics in the penicillin group. On which part of the bacteria do they act?
Penicillin Flucloxacillin Amoxicillin Co-amoxiclav **Bacterial cell wall**
90
Name a cephalosporin On which part of the bacteria does it act?
Ceftriaxone ## Footnote **Bacterial cell wall**
91
Name a glycopeptide antibiotic. On which part of the bacteria does it act?
Vancomycin ## Footnote **Bacterial cell wall**
92
Which penicillins can be used to treat Gram +ve organisms?
Penicillin (IV, oral) Flucloxacillin (IV, oral)
93
Which penicillins can be used to treat Gram -ve organisms?
Penicillin Amoxicillin Co-amoxiclav
94
Which antibiotics inhibit protein synthesis?
Macrolides Tetracyclines Aminoglycosides
95
Name three macrolide antibiotics. On which part of the bacteria do they act?
Clarythromycin Azithromycin Erythromycin **Inhibit protein synthesis**
96
Name a tetracycline antibiotic. On which part of the bacteria does it act?
Doxyclycline ## Footnote **Inhibits protein synthesis**
97
Name an aminoglycoside. On which part of the bacteria does it act?
Gentamicin ## Footnote **Inhibits protein synthesis**
98
Which antibiotics act on bacterial DNA?
Metronidazole Trimethoprim (+ sulphonamide = co-trimoxazole) Fluoroquinolones (Ciproflaxacin)
99
How does genetic variation in bacteria result?
Mutation Gene transfer
100
What are the three mechanisms of gene transfer in bacteria?
Transformation Conjugation Transduction
101
How are genes transferred through transformation?
DNA released by dead bacteria is taken up by living bacteria and incorporated into either plasmids or the bacterial chromosome
102
How are genes transferred through conjugation?
Bacterial sex Sex pilus transfers plasma DNA from one bacteria to another
103
How are genes transferred through transduction?
Viruses that infect bacteria transfer bits of DNA from one bacterium to another
104
What aspects of antibiotic therapy lead to resistance?
Unecessary antibiotics Sub-therapeutic dosing Exposure to low concentrations of antibiotic in environment

Disease Mechanisms (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions