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► Med 11 - USMLE 1 > Micro Basic > Flashcards

Flashcards in Micro Basic Deck (71):
1

Peptidoglycans
Composition
Function

Sugar backbone with peptide side chains cross linked by transpeptidase
Support. Protects against osmotic pressure

2

Lipoteichoic acid
Where is it?
What does it do?

Cell wall of Gram+
Induces TNF and IL1

3

LPS
AKA
Location
What is it?
Components

Endotoxin
Outer membrane of Gram-
Major Surface Ag
Lipid A (induces TNF and IL1)
O polysaccharide is the antigen

4

Periplasm
What is it?
What kind of organisms
What does it contain

Space between cytoplasmic membrane outer membrane
Gram-
Hydrolytic enzymes include β lactamase

5

Capsule
Made from...
Function

Polysaccharides (except in Bacillus anthracis which contains D-glutamate)
Protects against phagocytosis

6

Pilus/Fimbria
Composition
Function

Glycoprotein
Mediates adherence of bacteria to cell surface. Sex pilus for conjugation

7

Flagellum
Composition
Function

Protein
Motility

8

Spore
Composition
Function

Keratin-like coat, Dipicolinic acid, Peptidoglycan
Resistance to heat, chemicals, dehydration

9

Glycocalyx
Composition
Function

Polysaccharide
Mediates adherence to surfaces (especially foreign surfaces)

10

Outer layer composition in Gram+ vs Gram- bacteria

+
Inside to outside:
Cytoplasmic membrane, Peptidoglycan (cell wall), Capsule
Pilus, Flagellum, Lipoteichoic acid (lipids + teichoic acids)
-:
Cytoplasmic membrane, Perplasm, Peptidoglycan, Endotoxin (LPS), Capsule
Pilus, Flagellum

11

Outer layers of Mycoplasma

Membrane contains sterols and have no cell walls

12

Cell wall of Mycobacteria

Contains mycolic acid with high lipid content

13

Bugs that do not gram stain?

"These Rascals May Microscopically Lack Color"
Treponema (too thin), Rickettsia (intracellular), Mycobacteria (high lipid content in cell wall), Mycoplasma (no cell wall), Legionella pneumophila (intracellular), Chlamydia (intracellular and lacks muramic acid in cell wall)

14

Giemsa Stains for what organisms

"Certain Bugs Really Try my Patience"
Chlamydia, Borrelia, Rickettsiae, Trypanosomes, Plasmodium

15

PAS
Name
What does it stain?
Use

Periodic Acid Schiff Base
"PASs the sugar"
Glycogen, Mucopolysaccharides
Diagnoses Whipple's Disease (Tropheryma Whipplei)

16

Ziehl-Neelsen Stain
Name
Organisms

Carbol Fuchsin
Acid Fast organisms (Nocardia, Mycobacterium)

17

India Ink

Cryptococcus neoformans
Mucicarmine can also be used to stain thick polysaccharide capsule red

18

Silver Stain

Fungi, Legionella, Helicobacter pylori

19

Culture Requirements for H. influenzae

Chocolate agar with factor V (NAD) and X (hematin)

20

Culture Requirements for N gonorrhoeae and N meningitidis

Thayer-Martin (or VPN) media
Vancomycin (inhibits Gram+ organisms), Polymyxin (inhibit Gram- organisms except Neisseria), Nystatin (inhibits fungi)

21

Culture Requirements for B pertussis

"Bordet for Bordetella)
Bordet-Gengou (potato) agar

22

Culture Requirements for C diphtheriae

Tellurite plate, Loffler's media

23

Culture Requirements for M tuberculosis

Lowenstein Jensen agar

24

Culture Requirements for M pneumoniae

Eton's agar

25

Culture Requirements for lactose fermenting enterics

Pink colonies on MacConkey's agar (fermentation produces acid, turning colonies pink)
E coli is also grown on eosin-methylene blue (EMB) agar as colonies with green metallic sheen

26

Culture Requirements for Legionella

Charcoal yeast extract on agar buffered with cysteine and iron

27

Culture Requirements for Fungi

"Sab's a Fun Guy"
Sabouraud's agar

28

Obligate Aerobes

"Nagging Pests Must Breathe"
Nocardia, Pseudomonas aeruginosa (can use nitrates in anaerobic environment), Mycobacterium tuberculosis, and Bacillus

29

Obligate Anaerobes
Name
Weakness
Gross
Culture?
What doe they produce?
Where are they normally?
What antibiotics don't work on them?

"Anaerobes Can't Breathe Air"
Clostridium, Bacteroides, Actinomyces
Lack Catalase and/or SOD and are thus susceptible to oxidative damage
Foul smelling because of short chain fatty acids
Difficult to culture
Produce gas (CO2, H2) in tissue
Normal GI flora
Aminoglycosides ineffective because they need O2 to enter cell

30

Obligate intracellular bugs

"Stay inside when its Really Cold"
Rickettsia, Chlamydia
Can't make their own ATP

31

Facultative Intracellular bugs

"Some Nasty Bugs May Live FacultativeLY"
Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francissela, Legionella, Yersinia pestis

32

Encapsulated Bacteria
Purpose of capsule
Test
Examples
Who is especially at risk?

Antiphagocytic virulence factor that can serve as an antigen in vaccines
Quellung Positive (Swelling = Swellung)
"SHiNE SKiS"
Streptococcus pneumoniae, Haemophilus influenzae B, Neisseria meningitidies, E coli, Salmonella, Klebsiella pneumoniae, group B Strep
Asplenics. Give S pneumoniae, H influenzae, and N meningitidis vaccines

33

Catalase+ organisms
Function of catalase
Who is at risk?
Examples

Degrades H2O2 before it can become microbicidal
People with chronic granulomatous disease (NADPH oxidase deficiency) because they degrade the limited H2O2
"PLACESS for your CATs"
Pseudomonas, Listeria, Aspergillus, Candida, E coli, S aureus, Serratia

34

Problem with polysaccharide capsule antigens?
How is ti solved?

T cells not activated because polysaccharides cannot be presented
Conjugate to a protein to promote T cell activation and class switching

35

Pneumovax

Polysaccharide vaccine w/o conjugated protein against pneumococcus

36

Prevnar

Conjugated Polysaccharide vaccine against pneumococcus

37

H influenzae Type B Vaccine

Conjugated vaccine

38

Meningococcal Vaccine

Conjugated vaccine

39

Urease+ bugs

"CHuck norris hates PUNKSS"
Cryptococcus, H pylori, Proteus, Ureaplasma, Nocardia, Klebsiella, S epidermidis, S saprophyticus

40

Pigment producing bacteria

Actinomyces israelii - yellow sulfur granules (israel has yellow sand)
S aureus - yellow pigment
Pseudomonas aeruginosa - blue-green (like arugula)
Serratia marcescens - red pigment (red maraschino cherries)

41

Protein A
Function
Organisms

Binds Fc of Ig to prevent opsonization and phagocytosis
S aureus

42

IgA protease
Function
Organisms
Organ susceptible

Cleaves IgA
"SHiN"
S pneumoniae, H influenzae B, Neisseria
Respiratory mucosa

43

M Protein
Function
Organisms

Prevents phagocytosis
GAS

44

Exotoxin
Source
Secreted from cells?
Composition
Location of gene
Tox

Gram+ and Gram-
Secreted from cells
Polypeptide
Plasmid or Bacteriophage
Highly toxicity

45

Exotoxin
Antigenicity
Vaccines
Stability
Examples

Induces high titer Abs called antitoxins
Toxoids used as vaccines
Destroyed rapidly at 60 degrees (except for Staphylococcal enterotoxin)
Tetanus, Botulism, Diphtheria

46

Endotoxin
Source
Secreted from cells?
Composition
Location of gene
Tox

Outer cell membrane of most Gram-
Not secreted
Lipopolysacharide (structural part of bacteria released when lysed)
Bacterial chromosome
Low toxicity

47

Endotoxin
Clinical effects
MoA
Antigenicity
Vaccines
Stability
Examples

Fever, Shock
Induces TNF and IL1
Poorly antigenic
No toxoids formed and no vaccine available
Staple at 100 degrees C for 1 hour
Meningococcemia, Sepsis by Gram- rods

48

Corynebacterium diphtheriae
Kind of toxin produced?
Name of toxin?
MoA of toxin
Manifestation

Exotoxin
Diphtheria toxin
ADP ribosylating A-B toxin: Inactivates Elongation Factor (EF2) thus inhibiting protein synthesis
Pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck)

49

Pseudomonas aeruginosa
Kind of toxin produced?
Name of toxin?
MoA of toxin
Manifestation

Exotoxin
Exotoxin A
ADP ribosylating A-B toxin: Inactivates Elongation Factor (EF2) thus inhibiting protein synthesis
Host cell death

50

ADP ribosylating A-B toxin
Names
MoA

Diphtheria toxin, Exotoxin A, Heat Labile, Cholera toxin, Pertussis toxin
B (binding) component binds host cell surface receptor enabling endocytosis; A (active) component attaches to ADP-ribosyl to disrupt host cell proteins

51

Shigella Spp
Kind of toxin produced?
Name of toxin?
MoA of toxin
Manifestation

Exotoxin
Shiga Toxin (ST)
Inactivates 60S ribosome by removing adenine from rRNA inhibiting protein synthesis
GI mucosal damage --> dysentery. Enhances release of cytokines --> HUS

52

Enterohemorrhagic E coli (EHEC)
Strain
Kind of toxin produced?
Name of toxin?
MoA of toxin
Manifestation

O157:H7
Exotoxin
Shiga-Like Toxin (SLT)
Inactivates 60S ribosome by removing adenine from rRNA
Enhances release of cytokines --> HUS
Does not invade host cells

53

Enterotoxigenic E coli
Kind of toxin produced?
Name of toxin?
MoA of toxin
Manifestation

Exotoxin
Heat-Labile Toxin (LT) and Heat-Stable Toxin (HS)
HL (ADP ribosylating A-B toxin): Overactivates AC --> ↑cAMP --> ↑Cl secretion in gut and water efflux
HS: Overactivates GC --> ↑cGMP --> ↓ resorption of NaCl and water in the gut
Watery diarrhea
"Labile in Air --> AC"
"Stable in Ground --> GC"

54

Bacillus Anthracis
Kind of toxin produced?
Name of toxin?
MoA of toxin
Manifestation

Exotoxin
Edema Factor
Mimics AC and increases cAMP
Responsible for characteristic edematous borders of black eschar in cutaneous anthrax

55

Vibrio cholerae
Kind of toxin produced?
Name of toxin?
MoA of toxin
Manifestation

Exotoxin
Cholera toxin
ADP ribosylating A-B toxin: Permanently activates Gs --> Overactivates AC --> ↑cAMP --> ↑Cl secretion in gut and water efflux
Rice water diarrhea

56

Bordetella pertusis
Kind of toxin produced?
Name of toxin?
MoA of toxin
Manifestation

Exotoxin
Pertussis toxin
ADP ribosylating A-B toxin: Permanently inactivates Gi --> Overactivates AC --> ↑cAMP --> impaired phagocytosis to permit survival of microbe
Whooping cough (coughs on expiration and whoops on inspiration
100 day cough in adults

57

Clostridium tetani
Kind of toxin produced?
Name of toxin?
MoA of toxin
Manifestation

Exotoxin
Tetanospasmin
Cleaves SNARE protein required for NT release of GABA and Gly neurons (Renshaw cells in spinal cord)
Muscle rigidity, lock jaw, Risus sardonicus

58

Clostridium botulinum
Kind of toxin produced?
Name of toxin?
MoA of toxin
Manifestation
Where do they get it from?

Exotoxin
Botulinum toxin
Cleaves SNARE protein required for NT release of ACh from neurons
Flaccid paralysis, floppy baby
Honey

59

Clostridium perfringens
Kind of toxin produced?
Name of toxin?
MoA of toxin
Manifestation

Exotoxin
Alpha toxin (lecithinase)
Phospholipase that degrades tissues and cell membranes
Degradation of phospholipid C --> myonecrosis (gas gangrene) and hemolysis (double zone of hemolysis on blood agar)

60

Streptococcus Pyogenes
Kind of toxin produced?
Name of toxin?
MoA of toxin
Manifestation

Exotoxin
Streptolysin O
Degrades cell membranes
Lyses RBCs (contributes to β hemolysis and host produces ASO used to diagnose RF)

61

Staphylococcus aureus
Kind of toxin produced?
Name of toxin?
MoA of toxin
Manifestation

Exotoxin
Toxic Shock Syndrome Toxin (TSST1)
Brings together MHCII and TCR to cause release of IFNγ and IL2 --> shock
TSS: fever, rash, shock

62

Streptococcus pyogenes
Kind of toxin produced?
Name of toxin?
MoA of toxin
Manifestation

Exotoxin
Exotoxin A
Brings together MHCII and TCR to cause release of IFNγ and IL2 --> shock
TSS: fever, rash, shock

63

Endotoxin Pathway of Action

LPS --> Macs --> IL1 (fever), TNF (fever hypotension), NO (hypotension)
LPS --> complement --> C3a (hypotension, edema), C5a (neutrophil chemotactic)
LPS --> tissue factor --> coagulation cascade --> DIC

64

Endotoxin Mnemonic

"ENDOTOXIN"
Edema, NO, DIC/Death, Outer membrane, TNFα, O Ag, eXtremely heat stable, IL1, Neutrophil chemotaxis

65

Bacterial Growth Curve

Lag: metabolic activity w/o division
Log (exponential): Rapid cell division
Stationary: Nutrient depletion slows growth. Spore formation in some bacteria
Death: Prolonged nutrient depletion and buildup of waste products lead to death

66

Which antibiotics work on the log phase?

Cephalosporins and Penicillins becuase they act on peptidoglycan synthesis

67

Bacterial Transformation
Mechanism
Bacteria that can do it?

Take up DNA from surroundings
"SHiN"
S pneumoniae, H influenzae, Neisseria

68

Conjugation
F+ x F-
Hfr x F-

F+ x F-: dsDNA plasmid with genes for pilus
Hfr x F-: transfer of plasmid and chromosome genes after plasmid incorporation

69

Transposition

Segments of DNA jump from one location to another. Genes can be transferred from plasmid to chromosomes and vice versa
Flanking DNA can be transferred as well

70

Transduction
Generalized
Specialized

Packaging event: Bacterial DNA packaged into lytic phage by accident
Excision event: Flanking regions around bacterial DNA is put into a Lysogenic phage

71

Genes encoded in lysogenic phage

"ABCDE"
shigA-like toxin
Botulinum toxin, Cholera toxin, Diphtheria toxin, Erythrogenic toxin of Strep pyogenes