Unit 3: Cocci

Question 1

When bacteria are plated onto blood agar, how do alpha, beta, and gamma colonies appear?

Answer 1

alpha - dark green (incomplete blood lysis)beta - clear colony (complete lysis)gamma - no change (non-hemolytic)

Question 2

How do you tell if a bacteria is catalase positive?

Answer 2

Drop hydrogen peroxide and fizzing will occur

Question 3

Lancefield typing is based on what bacterial feature?

Answer 3

carbohydrate composition of bacterial cell walls

Question 4

When bacterial growth is inhibited by bacitracin antibiotic (Bacitracin Testing), what does it indicate?

Answer 4

The culture is streptococcus pyogenes (Group A is bacitracin sensitive!)

Question 5

Describe what a positive CAMP test indicates

Answer 5

Group B strep

Question 6

What cocci are gram positive and which are gram negative?

Answer 6

Gram positive: staphylococcus and streptococcus

Grame negative: Neisseria

Question 7

How do you differentiate staphylococcus from streptococcus if they’re both gram positive?

Answer 7

Staphylococcus is catalase positive

Streptococcus is catalase negative

Question 8

What are the 3 kinds of Staph? How do you differentiate the 3?

Answer 8

Staph aureus, staph epidermis, s. saprophyticus

S. aureus is coagulase positive, create gold colonies, beta hemolytic and susceptible to bacteriophages whereas the other 2 are coagulase negative and non hemolytic (gamma).

Question 9

What are the two alpha hemolytic streptococcus

Answer 9

strep pneumoniae and strep viridans

Question 10

What are the two beta hemolytic streptococcus

Answer 10

strep pyogenes (group A)
strep agalactiae (group B)

Question 11

What differentiates Streptococcus group A from Group B?

Answer 11

Strep Group A (pyogenes) is bacitracin sensitive

Strep Group B (agalactiae) is bacitracin resistant

Question 12

What are the gamma hemolytic streptococcus

Answer 12

Strep fecalis (enterococcus fecalis / Group D) Peptostreptococcus

Question 13

What differentiates N. meningitides from N. gonorrhoeae?

Answer 13

N. meningitides has CAPSULE, ferments MALTOSE on chocolate agar

N. gonorrhoeae has NO CAPSULE, NO MALTOSE

They do share these characteristics: gram negative, diplococci, oxidase positive

Question 14

What shape does streptococci take on under microscope?

Answer 14

Chain of circles

Question 15

What shape does staphylococcus take on?

Answer 15

clusters of circles

Question 16

How does neisseria appear under microscope?

Answer 16

diplococci

Question 17

What bacteria has pili, releases several pyrogenic toxins, has streptolysin O (very antigenic), is penicillin and erythromycin sensitive. Located in pharynx and skin?

Answer 17

Group A Streptococci Strep pyogenes

Question 18

This bacteria is bacitracin resistant, has a capsule, located in genital tract and transmitted at birth. What is it and what should be given to a pregnant woman during delivery to prevent infection?

Answer 18

Group B Strep (strep agalactiae)

Must give penicillin 18 hours after rupture of membranes if labor hasn’t started to prevent ascending infection of uterus

Question 19

This is a gram positive, alpha hemolytic diplococci that has a polysaccharide capsule, usually resides in the throat and is becoming more penicillin resistant

Answer 19

Strep pneumonia

Question 20

This resides in the normal flora of the colon, causes abdominal abscesses, UTIs, endocarditis, and is sometimes penicillin resistant (use aminoglycosides)

Answer 20

Enterococcus fecalis

Streptococcus fecalis

Question 21

This resides in the mouth and female genital tract, has extracellular polysaccharides, and alpha hemolytic and gram positive

Answer 21

Strep viridans

Question 22

Found in mouth flora, respiratory tract, female genital tract and bowel. Found in abcesses with complex mix of organisms (not the primary pathogen). Non hemolytic

Answer 22

Peptostreptococcus

Question 23

What do you use to treat MRSA?

Answer 23

Vancomycin

Question 24

Found in the nose and skin. Transmitted by direct contact or indirect fomite contact. Has a Protein a, Capsule and several toxins. Resistant to penicillin and methicillin

Answer 24

Staph aureus

Question 25

Normally found in skin and mucous membrane, but attaches to nylon and plastic, infecting IVs, and antibiotics don't eliminate the infection. Catalase positive and coagulase negative.

Answer 25

Staph epidermis

Question 26

Usually causes UTIs, catalase positive, coagulase negative, nonhemolytic

Answer 26

Staph saprophyticus

Question 27

There exists a vaccine and can be treated with penicillin. Carried in respiratory tract. Endotoxin in membrane and has capsule

Answer 27

Neisseria meningitides

Question 28

Has no capsule, has a pili, found inside neutrophils , sexual or neonatal transmission. Treated with ceftriaxone and doxycycline (penicillin resistant)

Answer 28

N. gonorrhoeae

Question 29

If someone has a lesion that is sterile when swabbed, has rheumatic fever, chorea, or nephritis, what type of bacterial infection might they have had and recovered from prior to these new conditions?

Answer 29

Streptococcal infection