Bacterial Structure and Stains

Question 1

Peptidoglycan

Answer 1

A sugar backbone with peptide side chains crosslinked by transpeptidase that gives rigid support, protects against osmotic pressure

Question 2

Cell wall/cell membrane

Answer 2

Made of peptidoglycan for support, lipoteichoic acid induces TNF and IL-1; major surface antigen - Gram positive

Question 3

Outer membranes

Answer 3

Lipid A induces TNF and IL-1, O polysaccharide is the antigen; major surface antigen - gram negative and site of endotoxin (LPS)

Question 4

Plasma membrane

Answer 4

Lipoprotein bilayer that is the site of oxidative and transport enzymes

Question 5

Ribosome

Answer 5

50S and 30S subunits for protein synthesis

Question 6

Periplasm

Answer 6

Space between the cytoplasmic membrane and outer membrane in gram negative bacteria that contains many hydrolytic enzymes (including B-lactamase)

Question 7

Capsule

Answer 7

Polysaccharide (except Bacillus anthracis that contains d-glutamate) that protects against phagocytosis

Question 8

Pilus/Fimbria

Answer 8

Glycoproteins that mediate adherence of bacteria to cell surface and sex pilus forms attachment between 2 bacteria during conjugation

Question 9

Flagellum

Answer 9

Protein for motility

Question 10

Spore

Answer 10

Kertain-like coat, dipicolinic acid, peptidoglycan that allows bacteria to become resistant to dehydration, heat, and chemicals

Question 11

Plasmid

Answer 11

DNA that contains a variety of genes for antibiotic resistance, enzymes and toxins

Question 12

Glycocalyx

Answer 12

Polysaccharide that mediates adherence to surfaces especially foreign surfaces

Question 13

Giemsa stains

Answer 13

Chlamydia, Borrelia, Rickettsiae, Trypanosomes, Plasmodium (Certain Bugs Really Try my Patients)

Question 14

PAS

Answer 14

Stains glycogens (PASs the sugar), mucopolysaccharides, used to dx Wipple’s disease (Tropheryma whipplei)

Question 15

Ziehl-Neelsen (carbol fuchsin)

Answer 15

Acid fast organisms (Nocardia, Mycobacterium)

Question 16

India Ink

Answer 16

Cryptococcus neoformans (mucicarmine can also be used to stain the thick polysaccharide capsule cell)

Question 17

Silver Stain

Answer 17

Fungi (Pneumocystis), Legionella, Helicobacter pylori

Question 18

Bugs that don’t stain well and why (These Rascals May Microscopically Lack Color)

Answer 18

Treponema (too thin to be visualized) - use dark field microscopy and fluorscent Ab staining
Rickettsia - intracellular parasite
Mycobacteria - high lipid content in cell wall detected by carbolfuchsin in acid fast stains
Mycoplasma - no cell wall
Legionella pneumophila - intracellular (silver stain)
Chlamydia - intracellular parasite

Question 19

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

Answer 19

H. flu

Question 20

Thayer-Martin (or VPN) media - Vancomycin (inhibits gram-positive), Polymyxin (inhibits gram negative except ______) and Nystatin (inhibits fungi)

Answer 20

N. gonorrhoeae

N. meningitidis

Question 21

Bordet-Gengou agar

Answer 21

B. pertussis (Bordet for Bordetella)

Question 22

Tellurite plate, Loffler’s media

Answer 22

C. diphtheriae

Question 23

Lowenstein-Jensen agar

Answer 23

M. tuberculosis

Question 24

Eaton’s agar

Answer 24

M. pneuomniae

Question 25

Pink colonies on MacConkey’s agar

Answer 25

Fermentation produces acid, turning colonies pink

Lactose-fermenting enterics

Question 26

Eosin-methylene blue (EMB) with green metallic sheen

Answer 26

E. coli

Question 27

Charcoal yeast extract agar buffered with cysteine and iron

Answer 27

Legionella

Question 28

Sabouraud’s agar

Answer 28

Fungi (Sab’s a fun-gi)