Review

Question 1

Media:

Tryptic soy agar with 5% sheep blood. Allows differentiation of hemolysis.

Answer 1

SBA (sheep blood agar)

-for most nonfastidious bacteria

Question 2

Media:

Chocolate agar is used for the isolation of fastidious organisms including ___________ and ____________.

Answer 2

Haemophilus and Neisseria

-supplies X (hemin) and V (NAD) factors. Incubate in 5% CO2

Question 3

CNA agar is used for the isolation of…

Answer 3

Gram-positive cocci (GPC), especially from wound and stool culture

Question 4

Examples of alpha-hemolytic on SBA

Answer 4

Streptococcus pneumoniae, viridans
streptococci, some enterococci

Question 5

Examples of beta-hemolytic on SBA

Answer 5

Group A strep, group B strep, Listeria
monocytogenes

Question 6

Example of gamma (nonhemolytic)

Answer 6

some enterococci

Question 7

Causes suppurative cutaneous infections, toxic shock
syndrome, food
poisoning

Answer 7

S. aureus

Question 8

Coagulase pos.
Ferments mannitol
(yellow colonies on
mannitol salt agar).
Usually DNase & thermonuclease pos.

Answer 8

S. aureus

Question 9

S. aureus:

85%–90%
resistant to ________

Answer 9

penicillin

Question 10

S. aureus:

most are _______-hemolytic (small zone)

Answer 10

beta

Question 11

Coagulase-negative
staphylococci (CNS):

neg. Grow
on mannitol salt agar
but don’t ferment
mannitol. Sensitive to ___________

Answer 11

Novobiocin

Question 12

UTI in young sexu-
ally active females, urethritis & prosta-
titis in males

GPC, usually in
clusters

Answer 12

S. saprophyticus

Question 13

Coagulase neg. Resistant
to novobiocin. May
ferment mannitol.

Answer 13

S. saprophyticus

-Novobiocin only
performed when CNS
isolated from urine of
female.

Question 14

Usually nonpathogenic. Found in environment &
on skin, mucous
membranes,
oropharynx

Large GPC in
pairs, tetrads
(predominant
arrangement),
clusters

Answer 14

Micrococcus

Question 15

Often pigmented
(bright yellow,
orange, pink, tan).
High-domed
colonies.

Answer 15

Micrococcus

Question 16

Key characteristics of Micrococcus

Answer 16

Catalase pos. Coagulase
neg. Oxidative.
Microdase (modified
oxidase) pos. Susceptible to bacitracin. Resistant to furazolidone & lysostaphin.

Question 17

Not commonly iso-
lated. Must differenti-
ate from staph.
Usually only grow
aerobically.

Answer 17

Micrococcus

Question 18

enterococci are __________ for catalase.

Answer 18

neg

Question 19

Mannitol salt agar (MSA):

What color is pos?
example of pos?

Answer 19

turns yellow (from pink)

S. aureus pos

Question 20

Mannitol salt agar (MSA):

7.5% salt inhibits most organisms
other than _______

Answer 20

Staph.

Question 21

Causes 90% of
strep infections.
Strep sore throat,
rheumatic fever,
glomerulonephritis,
scarlet fever (scar-
latina), erysipelas,
puerperal sepsis,
impetigo

Answer 21

Group A streptococci
(GAS)

most common is S. pyogenes.***

Question 22

Enterococcus:

Hydrolyzes esculin.
Grows in 6.5% NaCl
broth. PYR _____

Answer 22

pos

Question 23

Streptococcus
pneumoniae:

Bile solubility ______
Sensitive to ___________

Answer 23

pos

optochin

Question 24

Normal in upper
respiratory tract
of some. Most
common cause
of community-
acquired pneumo-
nia. Major cause
of otitis media***,
meningitis in
adults. Infects
sinuses, eyes

Answer 24

Streptococcus
pneumoniae

Question 25

Viridans streptococci:

Resistant to _________.
Bile solubility _____.

Answer 25

optochin

neg

Question 26

Normal in oral,
respiratory, GI mucosa. Opportunistic
pathogens. Frequent cause of
subacute bacterial
endocarditis.
Gingivitis & dental
caries (cavities)

Answer 26

Viridans streptococci

Question 27

Optochin disk:

What is susceptible?

What is resistant?

Answer 27

S. pneumoniaesusceptible.
Viridans strep resistant

Question 28

what is pos for bile solubility?

Answer 28

S. pneumoniaepos