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Infectious Disease Unit 1 > Bacterial Structures > Flashcards

Bacterial Structures Flashcards

1
Q

Peptidoglycan function and chemical composition

A
  • provides rigid support, protects against osmotic pressure

- made of sugar backbone with peptide side chains cross-linked by transpeptidase

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2
Q

Cell wall function and chemical composition

A
  • major surface antigen
  • peptidoglycan for support
  • Lipoteichoic acid induces TNF and IL-1
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3
Q

Outer membrane function and chemical composition

A

present in gram negatives

  • site of endotoxin (lipopolysaccharide [LPS])
  • major surface antigen
  • Lipid A induces TNF adn IL-1
  • O polysaccharide is the antigen
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4
Q

Plasma membrane function and chemical composition

A
  • site of oxidative and transport enzymes

- made of phospholipid bilayer

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5
Q

Ribosome function and chemical composition

A
  • Protein synthesis

- Made of 50S and 30S subunits

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6
Q

Periplasm function and chemical composition

A
  • space between cytoplasmic membrane and outer membrane in gram negative bacteria
  • Contains many hydrolytic enzymes, including beta-lactamases
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7
Q

Pilus/fimbria function and chemical composition

A
  • mediate adherence of bacteria to cell surface; sex pilus forms attachment between 2 bacteria during conjugation
  • made of glycoprotein
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8
Q

flagellum function and chemical composition

A
  • motility

- made of protein

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9
Q

Spore function and chemical composition

A
  • resistant to dehydration, heat, and chemicals

- made of keratin-like coat; dipicolinic acid; peptidoglycan

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10
Q

Plasmid function and chemical composition

A
  • contains variety of genes for antibiotic resistance, enzymes, and toxins
  • comprised of DNA
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11
Q

Capsule function and chemical composition

A
  • protects against phagocytosis

- comprised of organized, discrete polysaccharide layer (except Bacillus anthracis, which contains D-glutamate)

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12
Q

Glycocalyx function and chemical composition

A
  • mediates adherence to surface, esp foreign surfaces (e.g. indwelling catheters)
  • comprised of loose network of polysaccharides
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13
Q

characteristics unique to gram positive bacterial structure

A

lipoteichoic acid

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14
Q

features common to both gram positive and gram negative bacterial

A 
Flagellum
Pilus
Capsule
cell wall
peptidoglycan
cytoplasmic membrane
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15
Q

features unique to gram negative bacterial structure

A 
porin
endotoxin/LPS (outer membrane)
Periplasmic space (Beta lactamase location)
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16
Q

Bugs that don’t gram stain well

A
  • Treponema- too thin to be visualized
  • Mycobacteria (high lipid content; mycolic acids in cell wall detected by carbolfuschin in acid-fast stain)
  • Mycoplasma (no cell wall)
  • Legionella pneumophilia (primarily intracellular)
  • Rickettsia (intracellular parasite)
  • Chlamydia (intracellular parsite; lacks classic peptidoglycan because of low muramic acid)

“These Microbes May Lack Real Color”

17
Q

How to visualize Tremponemes

A

Not Gram stain – too thin to be visualized

- Dark-field microscopy and fluorescent antibody staining

18
Q

How to visualize Legionella

A

NOT Gram stain since primarily intracellular – Silver stain

19
Q

For what bugs is Giemsa stain used

A

Chlamydia, Borrelia, Rickettsia, Trypanosomes, Plasmodium

“Certain Bugs Really TRY my Patience”

20
Q

for what bugs is PAS stain used

A
  • Periodic acid-Schiff
  • Stains glycogen, mucopolysaccharides; used to diagnose Whipple disease (Tropheryma whipplei)

“PASs the sugar”

21
Q

For what bugs is Ziehl-Neelsen stain used

A
  • Carbol fuscin

- Acid fast bacteria (Nocardia, Mycobacteria), protozoa (Cryptosporidium oocysts)

22
Q

alternative to Ziehl Neelsen stain

A

auramine-rhodamine stain for screening–inexpensive, more sensitive but less specific

23
Q

for what bugs is India ink used

A

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

24
Q

for what bugs is Silver stain used

A

Fungi (e.g. Pneumocystis), Legionella, Helicobacter pylori

25
Q

Obligate Intracellular bugs

A

Rickettsia, CHlamydia, COxiella
- rely on host ATP
“Stay inside (cells) when it is Really CHilly and COld”

26
Q

Facultative Intracellular bugs

A

Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francisella, Legionella, Yersinia pestis

“Some Nasty Bugs May Live FacultativeLY”

27
Q

Encapsulated Bacteria examples

A

Streptococcus pneumoniae, Haemophilus influenzae type B, Neisseria meningitidis, Escherichia coli, Salmonella, Klebsiella pneumoniae, Gropu B strep

“SHiNE SKis”

  • capsules serve as antiphagocytic virulence factor
  • Capsule + protein conjugate serves as antigen in vaccines
28
Q

How does body deal with encapsulated bacteria

A

opsonized by spleen. Asplenics have decreased opsonizing ability and thus increased risk for severe infections

  • give S. pneumo, H flu, N meningiditid vaccines
29
Q

Encapsulated bacteria vaccines

A

some vaccines with polysaccharide capsule antigens are -conjugated to a carrier protein, enhancing immunogenicity by promoting T cell activation and subsequent class switching

  • Polysaccharide antigen alone can’t be presented to T cells
30
Q

Conjugate vaccine examples

A

Examples

  • Pneumococcal vaccine: PCV (pneumococcal conjugate vaccine, ie. Prevnar); PPSV (pneumococcal polysaccharide vaccine with no conjugated protein– Pneumovax)
  • H influenzae type B (conjugate vaccine)
  • Meningococcal vaccine (conjugate)
31
Q

Urease positive organisms

A 
Cryptococcus
H. pylori
Proteus
Ureaplasma
Nocardia
Klebsiella
S. epidermidis
S. saprophyticus

“CHuck Norriss hates PUNKSS”

32
Q

Catalase positive organisms

A

Nocardia, Pseudomonas, Listeria, Aspergillus, Candida, E. coli, Staphylococci, Serratia

“Cats Need PLACESS to hide”

33
Q

Catalase function

A
  • degrades H2O2 into H2O and bubbles of O2 before it can be converted to microbicidal products by enzyme myeloperoxidase
  • Ppl with chronic granulomatous disease (NADPH oxidase deficient) have recurrent infections with catalase + organisms
34
Q

Pigment producing organisms

A
  • Actinomyces israelii = yellow “sulfur” granules composed of filaments of bacteria
  • S. aureus = yellow/Gold (AU- Gold)
  • Pseudomonas aeruginosa= blue-green pigment
  • Serratia marcescens = red pigment (think red maraschino cherries)

Infectious Disease Unit 1 (19 decks)

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