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USMLE Step 1 First Aid (2014) Microbiology > Basic bacteriology > Flashcards

Basic bacteriology Flashcards

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1
Q

What is the function of peptidoglycan?

A

Gives rigid support, protects against osmotic pressure

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2
Q

What is the chemical composition of peptidoglycan?

A

Sugar backbone with peptide side chains cross-linked by transpeptidase.

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3
Q

What is the function of cell walls / cell membranes of gram positive bacteria?

A

Major surface antigen.

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4
Q

What is the chemical composition of cell wall / cell membrane of gram positive bacteria?

A

Peptidoglycan for support. Lipoteichoic acid induces TNF and IL-1.

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5
Q

What is the function of the outer membrane of gram negative bacteria?

A

Site of endotoxin (lipopolysaccharide), major surface antigen.

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6
Q

What is the chemical composition of the outer membrane of gram negative bacteria?

A

Lipid A (induces TNF and IL-1), and O polysaccharide (antigen).

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7
Q

What is the function of the plasma membrane?

A

Site of oxidative and transport enzymes.

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8
Q

What is the chemical composition of the plasma membrane?

A

Phospholipid bilayer.

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9
Q

What is the function of the ribosome?

A

Protein synthesis.

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10
Q

What is the chemical composition of the ribosome?

A

50s and 30s subunits.

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11
Q

What is periplasm?

A

Space between cytoplasmic membrane and outer membrane in gram-negative bacteria.

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12
Q

What is contained within the periplasm?

A

Hydrolytic enzymes including beta-lactamases.

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13
Q

What is the function of the capsule?

A

Protects against phagocytosis.

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14
Q

What is the capsule composed of?

A

Polysaccharide.

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15
Q

What is the function of the pilus/fimbria?

A

Adherence of bacteria to cell surface.

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16
Q

What is the pilus/fimbria composed of?

A

Glycoprotein

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17
Q

What is the function of the flagellum?

A

Mobility

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18
Q

What is the composition of the flagellum?

A

Protein

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19
Q

What is the function of a bacterial spore?

A

Resistant to dehydration, heat, and chemicals.

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20
Q

What is the chemical composition of a bacterial spore?

A

Keratin-like coat, dipicolinic acid, peptidoglycan.

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21
Q

What is the function of a plasmid?

A

Contains genes for antibiotic resistance, enzymes, and toxins.

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22
Q

What is the chemical composition of a plasmid?

A

DNA

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23
Q

What is the function of a glycocalyx?

A

Adherence of bacteria to surfaces, especially foreign surfaces (e.g. catheters).

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24
Q

What is the chemical composition of a glycocalyx?

A

Polysaccharide.

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25
Q

What is the morphology of a coccus?

A

Circular

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26
Q

Name the two main gram-positive cocci.

A

Staphylococcus and streptococcus.

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27
Q

Name the main gram-negative coccus.

A

Neisseria

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28
Q

What is the morphology of a bacillus?

A

Rod

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29
Q

Which gram-positive bacilli is acid fast?

A

Mycobacterium

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30
Q

Name the 3 classes of gram-negative bacilli.

A

Enterics
Respiratory
Zoonotic

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31
Q

Which bacteria displays branching filamentous morphology?

A

Actinomyces Nocardia

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32
Q

Name the two pleomorphic bacteria.

A

Rickettsiae

Chlamydiae

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33
Q

Name the 3 spiral bacteria.

A

The spirochetes:
Borrelia
Leptospira
Treponema

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34
Q

What bacteria does not gram stain. Why?

A

Mycoplasma (lacks a cell wall)

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35
Q

Name the two bacteria with unusual cell membranes/walls. What is unusual about them?

A

Mycoplasma (contains sterols, no cell wall)

Mycobacteria (contains my colic acid, high lipid content)

36
Q

What 6 bugs do not gram stain well? What is the mnemonic for remembering?

A 
These Microbes May Lack Real Color
Treponema (too thin to be visualized)
Mycobacteria (high lipid content)
Mycoplasma (no cell wall)
Legionella pneumophila (intracellular)
Rickettsia (intracellular)
Chlamydia (intracellular)
37
Q

How is legionella detected?

A

Silver stain

38
Q

Name the 5 bug stains.

A 
Giemsa
PAS (periodic acid-Schiff)
Ziehl-Neelsen (carbol fuchsin)
India ink
Silver stain
39
Q

What 5 bugs are detected by giemsa? What is the mnemonic?

A 
Certain Bugs Really TRY my Patience
Chlamydia
Borrelia
Rickettsiae
Trypanosomes
Plasmodium
40
Q

What bug is detected by periodic acid-Schiff stain? What chemical is this stain specific for?

A 
Tropheryma whipplei (Whipple disease)
Glycogen (mnemonic: PASs the sugar)
41
Q

What two bugs does Ziehl-Neelsen stain detect?

A

Acid fast bugs:
Nocardia
Mycobacterium

42
Q

What bug is stained by India ink?

A

Cryptococcus neoformans

43
Q

What class of bug is stained by silver stain? What two bugs are also stained by silver stain that are not in this class?

A

Fungi (e.g. pneumocystis)
Legionella
Helicobacter pylori

44
Q

Name the growth media for H. influenza.

A

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

45
Q

Name the growth media for N. gonorrhoeae and N. meningitides.

A

Thayer-Martin media (vancomycin, polymyxin, and nystatin)

Mnemonic: Use your VPN client to connect to Neisseria

46
Q

Name the growth media for B. pertussis.

A

Bordet-Gengou (potato) agar.

Mnemonic: Bordet for BORDETella

47
Q

Name the growth media for C. diphtheria.

A

Tellurite agar

Loffler medium

48
Q

Name the growth media for M. tuberculosis.

A

Lowenstein-Jensen agar

49
Q

Name the growth media for M. pneumonia.

A 
Eaton agar (requires cholesterol)
Mnemonic: Eatin' cholesterol Makes PNEU fat.
50
Q

Name the growth media for Lactose-fermenting enterics.

A 
MacConkey agar (pink colonies)
Eosin-methylene blue agar (E.coli makes green colonies)
51
Q

Name the growth media for fungi.

A

Sabouraud agar

Mnemonic: SAB’s a FUN GUY!

52
Q

What is an obligate aerobe?

A

Use an O2 dependent system to generate ATP.

53
Q

Name the 3 major obligate aerobes.

A

Nocardia
Pseudomonas aeruginosa
MycoBacterium tuberculosis
Mnemonic: Nagging Pests Must Breathe

54
Q

What is an obligate anaerobe?

A

Bugs that die in the presence of O2.

55
Q

What causes obligate anaerobes to be sensitive to O2?

A

They lack catalase and/or superoxide dismutase and are susceptible to oxidative damage.

56
Q

Name the 3 major obligate anaerobes.

A

Clostridium
Bacteroides
Actinomyces
Mnemonic: Anaerobes Can’t Breath Air

57
Q

What class of antibiotic is ineffective against anaerobes? Why?

A

Aminoglycosides (require O2 to enter bacterial cell)

Mnemonic: AminO2glycosides

58
Q

Name the 2 major obligate intracellular bugs.

A

Rickettsia
Chlamydia
Mnemonic: Stay inside (cells) when it is Really Cold

59
Q

Name the 8 facultative intracellular bugs.

A 
Salmonella
Neisseria
Brucella
Mycobacterium
Listeria
Francisella
Legionella
Yersinia pestis
Mnemonic: Some Nasty Bugs May Live FacultativeLY
60
Q

Name the 6 major encapsulated bacteria.

A 
Steptococcus pneumoniae
Haemophilus Influenzae type B
Neisseria meningitidis
Escherichia coli
Salmonella
Klebsiella pneumoniae
group B Strep
Mnemonic: SHINE SKiS
61
Q

Name the 7 major catalase positive bugs.

A 
Pseudomonas
Listeria
Aspergillus
Candida
E. coli
S. aureus
Serratia
Mnemonic: You need PLACESS for your CATs
62
Q

Name the 8 major urease-positive bugs.

A 
Cryptococcus
H. pylori
Proteus
Ureaplasma
Nocardia
Klebsiella
S. epidermidis
S. saprophyticus
Mnemonic: CHuck Norris hates PUNKSS
63
Q

Name the 4 major pigment producing bacteria.

A 
Actinomyces israelii (yellow granules)
Mnemonic: Israel has yellow sand
S. aureus (yellow pigment)
Mnemonic: aureus (Latin) = gold
Pseudomonas aeruginosa (blue-green pigment)
Mnemonic: a blue-green rug
Serratia marcescens (red pigment)
Mnemonic: red maraschino cherries
64
Q

What is the purpose of bacterial virulence factors?

A

Promote evasion of host immune response

65
Q

What bug expresses Protein A? What does it do?

A

S. aureus

Binds Fc region of IgG, preventing opsonization and phagocytosis.

66
Q

What 3 bugs express IgA protease? What does it do?

A 
S. pneumoniae
H. influenzae type B
Neisseria
Mnemonic: SHiN
Enzyme cleaves IgA in order to colonize respiratory mucosa.
67
Q

What bug expresses M protein? What does it do?

A

Group A streptococci

Prevents phagocytosis

68
Q

Name the 3 diseases typical of exotoxin.

A

Tetanus
Botulism
Diptheria

69
Q

Name the 2 diseases typical of endotoxin.

A

Meningococcemia

Sepsis by gram-negative rods

70
Q

Name the toxin associated with corynebacterium diphtheria. What does it do?

A

Diptheria toxin (inactivates elongation factor 2)

71
Q

Name the toxin associated with Pseudomonas aeruginosa. What does it do?

A

Exotoxin (inactivates elongation factor 2)

72
Q

Name the toxin associated with Shigella app. What does it do?

A

Shiga toxin (inactivates 60S ribosome)

73
Q

Name the toxin associated with enterohemorrhagic E. coli (EHEC) including 0157:H7 strain. What does it do?

A

Siga-like toxin (inactivates 60S ribosome)

74
Q

Name the two toxins associated with enterotoxigenic E. coli. What molecule does each over-activate? What is the physiological consequence?

A

Heat-labile toxin (increases cAMP)
Heat-stable toxin (increases cGMP)
Mnemonic: Watery diarrhea, labile in the Air (Adenylate cyclase), stable on the Ground (Guanylate cyclase)
Causes water secretion in the gut

75
Q

What toxin is associated with bacillus anthraces? What does it do?

A

Edema factor (causes characteristic edematous borders of black eschar in cutaneous anthrax)

76
Q

What toxin is associated with vibrio cholera? What does it cause?

A

Cholera toxin (causes “rice water” diarrhea)

77
Q

What toxin is associated with bordetella pertussis? What does it do?

A

Pertussis toxin (paralyzes cilia causing whoop)

78
Q

What toxin is associated with clostridium tetani? What does it cause?

A

Tetanospasmin (causes lockjaw by cleaving SNARE proteins, preventing inhibitory neurotransmitter release)

79
Q

What toxin is associated with clostridium botulinum? What does it cause?

A

Botulinum toxin (causes flaccid paralysis/floppy baby by cleaving SNARE proteins, preventing stimulatory neurotransmitter release)

80
Q

What toxin is associated with clostridium perfringens? What does it cause?

A

Alpha toxin (causes gas gangrene and hemolysis)

81
Q

What two toxins are associated with streptococcus pyogenes? What does it cause?

A 
Streptolysin O (lyses RBCs contributing to beta-hemolysis)
Exotoxin A (toxic shock syndrome causing fever, rash, shock)
82
Q

What toxin is associated with staphylococcus aureus? What does it cause?

A

Toxic shock syondrome toxin TSST-1 ( causes fever, rash, shock)

83
Q

What is endotoxin?

A

LPS found in outer membrane of gram-negative bacteria (both cocci and rods)

84
Q

Name the 9 features of endotoxin.

A 
Edema
Nitric oxide
DIC/Death
Outer membrane (located)
TNF-alpha
O-antigen
eXtremely heat stable
IL-1
Neutrophil chemotaxis
Mnemonic: ENDOTOXIN
85
Q

What 5 bacterial toxins are encoded in a lysogenic phage?

A 
ShigA-like toxin
Botulinum toxin
Cholera toxin
Diptheria toxin
Erythrogenic toxin of S. pyogenes
Mnemonic: ABCDE

USMLE Step 1 First Aid (2014) Microbiology (1 decks)

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