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

Basic bacteriology Flashcards

(85 cards)

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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
What is the morphology of a coccus?
Circular
26
Name the two main gram-positive cocci.
Staphylococcus and streptococcus.
27
Name the main gram-negative coccus.
Neisseria
28
What is the morphology of a bacillus?
Rod
29
Which gram-positive bacilli is acid fast?
Mycobacterium
30
Name the 3 classes of gram-negative bacilli.
Enterics Respiratory Zoonotic
31
Which bacteria displays branching filamentous morphology?
Actinomyces Nocardia
32
Name the two pleomorphic bacteria.
Rickettsiae | Chlamydiae
33
Name the 3 spiral bacteria.
The spirochetes: Borrelia Leptospira Treponema
34
What bacteria does not gram stain. Why?
Mycoplasma (lacks a cell wall)
35
Name the two bacteria with unusual cell membranes/walls. What is unusual about them?
Mycoplasma (contains sterols, no cell wall) | Mycobacteria (contains my colic acid, high lipid content)
36
What 6 bugs do not gram stain well? What is the mnemonic for remembering?
``` 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
How is legionella detected?
Silver stain
38
Name the 5 bug stains.
``` Giemsa PAS (periodic acid-Schiff) Ziehl-Neelsen (carbol fuchsin) India ink Silver stain ```
39
What 5 bugs are detected by giemsa? What is the mnemonic?
``` Certain Bugs Really TRY my Patience Chlamydia Borrelia Rickettsiae Trypanosomes Plasmodium ```
40
What bug is detected by periodic acid-Schiff stain? What chemical is this stain specific for?
``` Tropheryma whipplei (Whipple disease) Glycogen (mnemonic: PASs the sugar) ```
41
What two bugs does Ziehl-Neelsen stain detect?
Acid fast bugs: Nocardia Mycobacterium
42
What bug is stained by India ink?
Cryptococcus neoformans
43
What class of bug is stained by silver stain? What two bugs are also stained by silver stain that are not in this class?
Fungi (e.g. pneumocystis) Legionella Helicobacter pylori
44
Name the growth media for H. influenza.
Chocolate agar with factors V (NAD+) and X (hematin)
45
Name the growth media for N. gonorrhoeae and N. meningitides.
Thayer-Martin media (vancomycin, polymyxin, and nystatin) | Mnemonic: Use your VPN client to connect to Neisseria
46
Name the growth media for B. pertussis.
Bordet-Gengou (potato) agar. | Mnemonic: Bordet for BORDETella
47
Name the growth media for C. diphtheria.
Tellurite agar | Loffler medium
48
Name the growth media for M. tuberculosis.
Lowenstein-Jensen agar
49
Name the growth media for M. pneumonia.
``` Eaton agar (requires cholesterol) Mnemonic: Eatin' cholesterol Makes PNEU fat. ```
50
Name the growth media for Lactose-fermenting enterics.
``` MacConkey agar (pink colonies) Eosin-methylene blue agar (E.coli makes green colonies) ```
51
Name the growth media for fungi.
Sabouraud agar | Mnemonic: SAB's a FUN GUY!
52
What is an obligate aerobe?
Use an O2 dependent system to generate ATP.
53
Name the 3 major obligate aerobes.
Nocardia Pseudomonas aeruginosa MycoBacterium tuberculosis Mnemonic: Nagging Pests Must Breathe
54
What is an obligate anaerobe?
Bugs that die in the presence of O2.
55
What causes obligate anaerobes to be sensitive to O2?
They lack catalase and/or superoxide dismutase and are susceptible to oxidative damage.
56
Name the 3 major obligate anaerobes.
Clostridium Bacteroides Actinomyces Mnemonic: Anaerobes Can't Breath Air
57
What class of antibiotic is ineffective against anaerobes? Why?
Aminoglycosides (require O2 to enter bacterial cell) | Mnemonic: AminO2glycosides
58
Name the 2 major obligate intracellular bugs.
Rickettsia Chlamydia Mnemonic: Stay inside (cells) when it is Really Cold
59
Name the 8 facultative intracellular bugs.
``` Salmonella Neisseria Brucella Mycobacterium Listeria Francisella Legionella Yersinia pestis Mnemonic: Some Nasty Bugs May Live FacultativeLY ```
60
Name the 6 major encapsulated bacteria.
``` Steptococcus pneumoniae Haemophilus Influenzae type B Neisseria meningitidis Escherichia coli Salmonella Klebsiella pneumoniae group B Strep Mnemonic: SHINE SKiS ```
61
Name the 7 major catalase positive bugs.
``` Pseudomonas Listeria Aspergillus Candida E. coli S. aureus Serratia Mnemonic: You need PLACESS for your CATs ```
62
Name the 8 major urease-positive bugs.
``` Cryptococcus H. pylori Proteus Ureaplasma Nocardia Klebsiella S. epidermidis S. saprophyticus Mnemonic: CHuck Norris hates PUNKSS ```
63
Name the 4 major pigment producing bacteria.
``` 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
What is the purpose of bacterial virulence factors?
Promote evasion of host immune response
65
What bug expresses Protein A? What does it do?
S. aureus | Binds Fc region of IgG, preventing opsonization and phagocytosis.
66
What 3 bugs express IgA protease? What does it do?
``` S. pneumoniae H. influenzae type B Neisseria Mnemonic: SHiN Enzyme cleaves IgA in order to colonize respiratory mucosa. ```
67
What bug expresses M protein? What does it do?
Group A streptococci | Prevents phagocytosis
68
Name the 3 diseases typical of exotoxin.
Tetanus Botulism Diptheria
69
Name the 2 diseases typical of endotoxin.
Meningococcemia | Sepsis by gram-negative rods
70
Name the toxin associated with corynebacterium diphtheria. What does it do?
Diptheria toxin (inactivates elongation factor 2)
71
Name the toxin associated with Pseudomonas aeruginosa. What does it do?
Exotoxin (inactivates elongation factor 2)
72
Name the toxin associated with Shigella app. What does it do?
Shiga toxin (inactivates 60S ribosome)
73
Name the toxin associated with enterohemorrhagic E. coli (EHEC) including 0157:H7 strain. What does it do?
Siga-like toxin (inactivates 60S ribosome)
74
Name the two toxins associated with enterotoxigenic E. coli. What molecule does each over-activate? What is the physiological consequence?
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
What toxin is associated with bacillus anthraces? What does it do?
Edema factor (causes characteristic edematous borders of black eschar in cutaneous anthrax)
76
What toxin is associated with vibrio cholera? What does it cause?
Cholera toxin (causes "rice water" diarrhea)
77
What toxin is associated with bordetella pertussis? What does it do?
Pertussis toxin (paralyzes cilia causing whoop)
78
What toxin is associated with clostridium tetani? What does it cause?
Tetanospasmin (causes lockjaw by cleaving SNARE proteins, preventing inhibitory neurotransmitter release)
79
What toxin is associated with clostridium botulinum? What does it cause?
Botulinum toxin (causes flaccid paralysis/floppy baby by cleaving SNARE proteins, preventing stimulatory neurotransmitter release)
80
What toxin is associated with clostridium perfringens? What does it cause?
Alpha toxin (causes gas gangrene and hemolysis)
81
What two toxins are associated with streptococcus pyogenes? What does it cause?
``` Streptolysin O (lyses RBCs contributing to beta-hemolysis) Exotoxin A (toxic shock syndrome causing fever, rash, shock) ```
82
What toxin is associated with staphylococcus aureus? What does it cause?
Toxic shock syondrome toxin TSST-1 ( causes fever, rash, shock)
83
What is endotoxin?
LPS found in outer membrane of gram-negative bacteria (both cocci and rods)
84
Name the 9 features of endotoxin.
``` Edema Nitric oxide DIC/Death Outer membrane (located) TNF-alpha O-antigen eXtremely heat stable IL-1 Neutrophil chemotaxis Mnemonic: ENDOTOXIN ```
85
What 5 bacterial toxins are encoded in a lysogenic phage?
``` 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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