Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

USMLE Microbiology > Introduction > Flashcards

Introduction Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

What is the purpose of peptidoglycan?

A

Gives rigid support and protects against osmotic pressure

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

What is the purpose of the capsule?

A

To protect against phagocytosis and T cell mediated immune responses

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

What is the structure of glycocalyx?

A

Polysaccharide

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

What is the function of glycocalyx?

A

Mediates adherence to surfaces (especially foreign surfaces)

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

What kind of bacteria contain an outer membrane?

A

Gram negative

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

What are spores made out of?

A

Keratin-like coat, dipicolinic acid

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

Describe the role of the outer membrane (present in gram negatives)

A
  • It is made out of lipopolysaccharide which is a major surface antigen
  • Lipid A induces TNF and IL-1
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Wat type of bacteria contain lipoteichoic acid?

A

Gram positives

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

What kind of bacteria contain thinner peptidoglycan cell walls?

A

Gram negatives

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

What kind of bacteria contain a larger periplasmic space?

A

Gram negatives

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

What does the periplasmic space contain?

A

Contains enzymes necessary for bacterial virulence such as lipases, Beta lactamases, phosphatases and proteases (can inhibit penicillin)

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

What structure can cause the release of TNF-alpha from macrophages? (causing toxic shock)

A

Lipopolysaccharide endotoxins on outer membranes of gram negatives

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

What bacteria does not contain a cell wall? What do they contian instead?

A

Mycoplasma (gram positive organism)

- instead contain sterols

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

What is unique about the cell wall of mycobacteria?

A
  • Contains mycolic acid and has a high lipid content
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a gram stain made from?

A
  • Crystal Violet and iodine cause a dark purple/blue colour in gram positives
  • Safranin acts as a counter stain (causes gram negatives to stain pink)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What organisms cannot be identified via gram staining?

A
  • Treponema
  • Rickettsia
  • Mycobacteria
  • Mycoplasma
  • Legionella pneumophila
  • Chlamydia

These Rascals May Microscopically Lack Colour

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

Why can mycoplasma not be gram stained?

A

No cell wall

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

Why can mycobacteria not be gram stained?

A

The cell wall has a high lipid content (requires acid-fast stain)

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

What are mycobacteria visulaized with?

A

Acid-fast staining

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

Why can Treponema not be gram stained?

A

Too thin

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

Why can Rickettsia, Legionella pneumophila and Chlamydia not be visualised with gram staining?

A

They are all intracellular organisms (Chlamydia also lacks muramic acid in its cell wall)

22
Q

How are treponemes visualised?

A

Darkfield microscopy and fluorescent antibody staining

23
Q

What is legionella visualised with?

A

Silver stain (or immunofluorescent staining)

24
Q

What organisms can be visualised with immunofluorescent staining?

A

Intracellular parasites (Rickettsia, legionella pneumophila and chlamydia)

25
Q

What can a Giemsa stain be used to visualise?

A
  • Borrelia
  • Plasmodium
  • Trypansomes
  • Chlamydia
26
Q

What can PAS (periodic acid Schiff) be used to identify?

And what does it stain specifically?

A
  • Tropheryma whippelii (cause of Whipple’s disease)

- Stains glycogen, mucopolysaccharides

27
Q

What does the Ziehl-Neelsen visualise?

A

Acid-fast organisms (such as mycobacteria e.g TB)

28
Q

What can the India ink stain be used to visualise?

A

Cryptococcus neoformans (mucicarmine can also be used to stain the thick polysaccharide capsule red)

29
Q

What can the silver stain be used to visualise?

A
  • Fungi

- Legionella

30
Q

What media is used to grow haemophilus influenzae?

A

Chocolate agar with factors V (NAD+) and X (hematin)

31
Q

What media is used to grow Neisseria gonorrhoeae?

A
  • Thayer-Martin media

- aka VPN media (Vancomycin, Polymyxin and Nystatin)

32
Q

What type of organisms turn pink on MacConkey’s agar?

A

Lactose-fermenting enterics (e.g E. coli)

33
Q

What other than MacConkey’s agar can E. coli be grown on?

A

Eosin-methylene blue (EMB) agar (grows as blue/black colonies with metallic sheen)

34
Q

What media is legionella grown on?

A

Charcoal yeast extract agar buffered with cysteine and iron

35
Q

What medium are fungi grown on?

A

Subouraund’s agar

36
Q

What are examples of obligate aerobes? (organisms which require O2 to generate ATP)

A
  • Nocardia
  • Pseudomonas aeruginosa
  • Mycobacterium tuberculosis
  • Bacillus
    Nagging Pests Must Breathe
37
Q

Where can psedomonas aeruginosa be found?

A
  • Burn wounds
  • Nosocomial pneumonia
  • Pneumonias in cystic fibrosis patients
38
Q

Where can M. tuberculosis commonly reactivate? (e.g after immune compromise or TNF-alpha inhibitor use)

A

The apices

39
Q

What are examples of obligate anaerobes?

A
  • Clostridium
  • Bacteroides
  • Actinomyces
    Can’t Breathe Air
40
Q

What enzyme do obligate anaerobes lack?

A

Catalase and/or superoxide dismutase

- Makes them susceptible to oxidative damage

41
Q

Where can anaerobes be found as normal flora?

A

GI tract (foul-smelling)

42
Q

Why are aminoglycosides ineffective against anaerobes?

A

They require O2 to enter into the bacterial cell

43
Q

What are examples of obligate intracellular organisms?

A
  • Rickettsia
  • Chlamydia
    Stay inside cells when its Really Cold
44
Q

What are examples of facultative intracellular organisms?

A
  • Salmonella
  • Neisseria
  • Bruccella
  • Mycobacterium
  • Listeria
  • Francisella
  • Legionella
  • Yersinia pestis
    Some Nasty Bugs May Live FaculativeLY
45
Q

What are examples of encapsulated bacteria?

A
  • Streptococcus pneumoniae
  • H. influenza type B
  • Neisseria Meningitidis
  • Salmonella
  • Klebsiella pneumoniae
  • Group B strep
    SHiN SKis
46
Q

What is a positive quellung reaction?

A

If encapsulated bug is present the capsule swells when specific anticapsular antisera are added

47
Q

What does catalase degrade?

A

H2O2 (hydrogen peroxide)

48
Q

What organisms are catalase positive?

A
  • Staph aureus
  • Serratia
  • Pseudomonas
  • Actinomyces
  • Candida
  • E. coli
    you need SSPACE for your cats
49
Q

What kind of miccrobes are patients with chronic granulomatous disease vulnerabe to?

A

Catalase positive organisms as they reley on H2O2 to fight infection (they have a NADPH oxidase deficiency)

50
Q

What disease does Borrelia cause?

A

Lyme’s disease

USMLE Microbiology (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions