Bacteriology - Basics

Question 1

Which cell membrane structure is unique to gram-positive organisms?

Answer 1

Teichoic acid

Question 2

Which molecule, unique to the bacterial cell wall, provides rigid support and resistance against osmotic pressure?

Answer 2

Peptidoglycan

Question 3

Which heat-stable lipopolysaccharide (LPS) is found in the cell wall of gram-negative bacteria?

Answer 3

Endotoxin

Question 4

Which is the only gram-positive organism with LPS-lipid A?

Answer 4

Listeria monocytogenes

Question 5

Name five important systemic effects of endotoxin (particularly, lipid A):

Answer 5

1. ↑Interleukin (IL)-1 → fever
2. ↑ Tissue necrosis factor (TNF) → hemorrhagic tissue death
3. ↑ Nitric oxide → hypotension and shock
4. Activation of alternate complement pathway →↑ C3a (edema) and C5a (polymorphonuclear [PMN] chemotaxis)
5. Activation of factor XII → coagulation cascade → DIC

Question 6

Which has a higher toxicity, endotoxins or exotoxins?

Answer 6

Exotoxins: fatal dose on the order of 1 μg (vs hundreds of micrograms for endotoxins)

Question 7

Name the mechanism of DNA transfer characterized by the following statements:

DNA is taken up directly from the environment by competent cells

Answer 7

Transformation (can occur in eukaryotic cells, too) Medically important natural transformers: HHSNG: “Here, Have Some New Genes”: H. pylori, H. influenzae, S. pneumoniae, N. gonorrhoea

Question 8

Name the mechanism of DNA transfer characterized by the following statements:

Plasmid or chromosomal DNA transferred from one bacterium to another via cell-to-cell contact

Answer 8

Conjugation

Question 9

Name the mechanism of DNA transfer characterized by the following statements:

DNA transferred by a virus from one cell to another; can be generalized or specialized

Answer 9

Transduction

Question 10

Name the mechanism of DNA transfer characterized by the following statements:

DNA segments able to excise and reincorporate into different locations

Answer 10

Transposons

Question 11

Name the bacterium whose exotoxin has the following effects:

Superantigen that induces IL-1 and IL-2 synthesis in toxic shock syndrome; also leads to food poisoning

Answer 11

Staphylococcus aureus

Question 12

Name the bacterium whose exotoxin has the following effects:

α-Toxin is a lecithinase → gas gangrene

Answer 12

Clostridium perfringens

Question 13

Name the bacterium whose exotoxin has the following effects:

Prevents the release of the neurotransmitter (NT) glycine from Renshaw cells in spinal cord → paralysis

Answer 13

Clostridium tetani

Question 14

Name the bacterium whose exotoxin has the following effects:

↑ Adenylate cyclase by adenosine diphosphate (ADP) ribosylation → whooping cough

Answer 14

Bordetella pertussis

Question 15

Name the bacterium whose exotoxin has the following effects:

Exotoxin encoded by β-prophage; α subunit → inactivates elongation factor 2 (EF-2) halting protein synthesis; β subunit → permits entry into cardiac and neural tissue

Answer 15

Corynebacterium diphtherias

Question 16

Name the bacterium whose exotoxin has the following effects:

Erythrogenic superantigen → rash in scarlet fever

Answer 16

Streptococcus pyogenes

Question 17

Name the bacterium whose exotoxin has the following effects:

Prevents release of acetylcholine (ACh) → central nervous system (CNS) paralysis; spores in canned food and honey, construction sites

Answer 17

Clostridium botulinum

Question 18

Name the bacterium whose exotoxin has the following effects:

Heat-stable toxin ↑ guanylate cyclase; heat-labile toxin ↑ adenylate cyclase by ADP ribosylation of G protein → watery diarrhea

Answer 18

Escherichia coli

Question 19

Name the bacterium whose exotoxin has the following effects:

Inactivates the 60S ribosome → kills intestinal cells

Answer 19

Shigella dysenteriae

Question 20

Name the bacterium whose exotoxin has the following effects:

Permanent ADP ribosylation of G protein →↑ adenylate cyclase →↑ Cl- and H2OO in gut → voluminous stools

Answer 20

Vibrio cholerae

Question 21

Name the bacterium whose exotoxin has the following effects:

Exotoxin A inhibits protein synthesis by blocking EF-2

Answer 21

Pseudomonas

Question 22

Which virulence factor allows organisms to colonize mucosal surfaces?

Answer 22

IgA protease (eg, S. pneumoniae and H. influenzae)

Question 23

Name the bacterial structure associated with each antigenic classification given below:

K-antigen

Answer 23

Capsule (related to virulence of the bacteria)

K = Kapsule

Question 24

Name the bacterial structure associated with each antigenic classification given below:

O-antigen

Answer 24

Outer portion of the polysaccharide of endotoxin

O = Outer

Question 25

Name the bacterial structure associated with each antigenic classification given below:

H-antigen

Answer 25

Flagella (seen in motile species)

Question 26

Name the key virulence f actor(s) associated with each of the following organisms:

Group A streptococcus

Answer 26

M-protein, streptokinase, and hyaluronidase

Question 27

Name the key virulence f actor(s) associated with each of the following organisms:

Staphylococcus aureus

Answer 27

Protein A (prevents complement fixation and phagocytosis), penicillinase, and hyaluronidase

Question 28

Name the key virulence f actor(s) associated with each of the following organisms:

Streptococcus viridans

Answer 28

Extracellular dextran → helps bind to heart valves

Question 29

Name the key virulence f actor(s) associated with each of the following organisms:

Yersinia pestis

Answer 29

F1 capsular antigen (antiphagocytic) and protease (degrades clots)

Question 30

Name the key virulence f actor(s) associated with each of the following organisms:

Haemophilus influenzae

Answer 30

Capsule: six types (a-f) and IgA protease

Question 31

Name the key virulence f actor(s) associated with each of the following organisms:

Borrelia

Answer 31

Antigenic variation

Question 32

Name the key virulence f actor(s) associated with each of the following organisms:

Mycobacterium tuberculosis

Answer 32

Mycosides (cord factor, wax D, and sulfatides)