2 Gram-Positive Bacteria

Question 1

What are identifying characteristics of Streptococcus pneumoniae (by staining and microscopy or microbiology lab tests)?

Answer 1

Gram positive diplococci, alpha-hemolytic, sensitive to optochin (autolytic compound), and produce a large polysaccharide capsule

Question 2

What can cause a patient’s fever to break on day 4 of an infection?

Answer 2

Presence of IgM antibodies

Question 3

What bacterium is the most common cause of meningitis (called green-cap meningitis)?

Answer 3

Streptococcus pneumoniae

Question 4

What causes the green color in green-cap meningitis?

Answer 4

The green color is due to the oxidation state of iron in damaged tissues. This iron comes from the myeloperoxidase (MPO) reaction with tissues.

Question 5

All Gram-positive bacteria capsules are made of polysaccharides, except:
What kind of capsule does this bacterium have?

Answer 5

Bacillus anthracis - poly D-glutamic acid capsule

Question 6

T/F

Antibodies to the capsule will be protective against a Gram positive bacterium.

Answer 6

False. Capsules may or may not be immunogenic, and antibodies against the capsules may or may not be protective.

Question 7

In the case presentation, what were the symptoms seen with the 17-year-old male infected with Streptococcus pneumoniae?

Answer 7

• Suddenly developed shaking chills
• Violent cough with blood-tinged sputum
• Significant chest pain
• High fever (104)

Question 8

What other DNA may a Gram positive bacterium have besides a haploid chromosome?

Answer 8

Episomes (plasmids & bacteriophages), transposons, and pathogenicity islands (a few virulence factor genes that likely used to be bacteriophage or transposon)

Question 9

What is the purpose of a capsule?

Answer 9

It is often negatively charged to repel the negatively charged surface of phagocytic host cells, &/or it mimics self.

Question 10

What is the dominant virulence factor of Streptococcus pneumoniae?

Answer 10

Capsule

Question 11

What are the components of a Gram positive cell wall?

Answer 11

Lipotechoic/techoic acid
No outer membrane
Thick peptidoglycan
    *75% cross-bridged peptidoglycan
    *Some have O-acetylation

Question 12

What is the significance of O-acetylated peptidoglycan?

Answer 12

Highly inflammatory!
Difficult for humans to degrade
Collects in joints and causes arthritis (from inflammation)

Question 13

What are fimbriae?

Answer 13

Proteins, techoic acids, or lipotechoic acids that create a fuzz layer on the surface of bacteria. They are important for adhesion to host tissues &/or antiphagocytic activity &/or facilitation of nutrient uptake

Question 14

1) What are flagellae?

2) What types are there?

Answer 14

1) Polymers of flagellin proteins. Motor made up of a ring structure, a curved hook, and the filament.
2) Peritrichous - flagella surrounding the bacterium
Polar flagella - flagella on the ends

Question 15

T/F

Pathogenic cocci have flagella.

Answer 15

False.

Pathogenic cocci do NOT have flagella

Question 16

What are spores?

Answer 16

They are inert structures that are heat and dryness resistant and form when environmental conditions are hostile. When favorable conditions return, they regenerate into vegetative cells. Spore coats contain dipicolonic acid (derivative of lysine) and Ca2+

Question 17

What bacteria form spores?

Answer 17

Bacillus (aerobic) and Clostridium (anaerobic)

Question 18

What are protoplasts?

Answer 18

The structure generated when G+ bacteria are treated with enzymes to remove the cell wall. (A cell wall cannot be regenerated)

Question 19

What are poly-beta-hydroxyl-butyric acid granules?

Answer 19

Energy storage granules that are seen in some bacteria upon staining

Question 20

What do spores look like in stained preparation?

Answer 20

Clostridium tetani spores - tennis racquet appearance (rod with round end and clear zone in middle of rounding)
Bacillus spores - clear zone in rod (spore does not take up dye well)

Question 21

What bacteria have O-acetylated peptidoglycan?

Answer 21

Mainly streptococci and Neisseria

- Rheumatic fever (arthritis, carditis, neurologic autoimmune disease)
- Post-gonococcal arthritis

Question 22

What are examples of fimbrae in specific bacteria staph a. and strep pyogenes?

Answer 22

Streptococcus pyogenes - M protein

Staphylococcus aureus - ribitol teichoic acid

Question 23

What organism is a gram + diplococcus, alpha hemolytic, and optician sensitive?

Answer 23

Streptococcus pneumonia

Question 24

Which bacteria has a hyaluronic acid capsule?

Answer 24

Streptococcus pyogenes