Bacterial Structures

Question 1

Peptidoglycan function and chemical composition

Answer 1

• provides rigid support, protects against osmotic pressure

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

Question 2

Cell wall function and chemical composition

Answer 2

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

Question 3

Outer membrane function and chemical composition

Answer 3

present in gram negatives

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

Question 4

Plasma membrane function and chemical composition

Answer 4

• site of oxidative and transport enzymes

- made of phospholipid bilayer

Question 5

Ribosome function and chemical composition

Answer 5

• Protein synthesis

- Made of 50S and 30S subunits

Question 6

Periplasm function and chemical composition

Answer 6

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

Question 7

Pilus/fimbria function and chemical composition

Answer 7

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

Question 8

flagellum function and chemical composition

Answer 8

• motility

- made of protein

Question 9

Spore function and chemical composition

Answer 9

• resistant to dehydration, heat, and chemicals

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

Question 10

Plasmid function and chemical composition

Answer 10

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

Question 11

Capsule function and chemical composition

Answer 11

• protects against phagocytosis

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

Question 12

Glycocalyx function and chemical composition

Answer 12

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

Question 13

characteristics unique to gram positive bacterial structure

Answer 13

lipoteichoic acid

Question 14

features common to both gram positive and gram negative bacterial

Answer 14

Flagellum
Pilus
Capsule
cell wall
peptidoglycan
cytoplasmic membrane

Question 15

features unique to gram negative bacterial structure

Answer 15

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

Question 16

Bugs that don’t gram stain well

Answer 16

• 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”

Question 17

How to visualize Tremponemes

Answer 17

Not Gram stain – too thin to be visualized

- Dark-field microscopy and fluorescent antibody staining

Question 18

How to visualize Legionella

Answer 18

NOT Gram stain since primarily intracellular – Silver stain

Question 19

For what bugs is Giemsa stain used

Answer 19

Chlamydia, Borrelia, Rickettsia, Trypanosomes, Plasmodium

“Certain Bugs Really TRY my Patience”

Question 20

for what bugs is PAS stain used

Answer 20

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

“PASs the sugar”

Question 21

For what bugs is Ziehl-Neelsen stain used

Answer 21

• Carbol fuscin

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

Question 22

alternative to Ziehl Neelsen stain

Answer 22

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

Question 23

for what bugs is India ink used

Answer 23

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

Question 24

for what bugs is Silver stain used

Answer 24

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

Question 25

Obligate Intracellular bugs

Answer 25

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

Question 26

Facultative Intracellular bugs

Answer 26

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

Question 27

Encapsulated Bacteria examples

Answer 27

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

Question 28

How does body deal with encapsulated bacteria

Answer 28

opsonized by spleen. Asplenics have decreased opsonizing ability and thus increased risk for severe infections - give S. pneumo, H flu, N meningiditid vaccines

Question 29

Encapsulated bacteria vaccines

Answer 29

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

Question 30

Conjugate vaccine examples

Answer 30

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)

Question 31

Urease positive organisms

Answer 31

``` Cryptococcus H. pylori Proteus Ureaplasma Nocardia Klebsiella S. epidermidis S. saprophyticus ``` "CHuck Norriss hates PUNKSS"

Question 32

Catalase positive organisms

Answer 32

Nocardia, Pseudomonas, Listeria, Aspergillus, Candida, E. coli, Staphylococci, Serratia "Cats Need PLACESS to hide"

Question 33

Catalase function

Answer 33

- 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

Question 34

Pigment producing organisms

Answer 34

- 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)