Module 4.1 Staphylococcaceae and Micrococcus Laboratory diagnosis

Question 1

Staphylococcus:

specimen to be collected for wound and other pyogenic infections

Answer 1

pus

Question 2

Staphylococcus:

specimen to be collected for septicemia

Answer 2

blood

Question 3

Staphylococcus:

specimen to be collected for meningitis

Answer 3

CSF

Question 4

Staphylococcus:

specimen to be collected for respiratory infections

Answer 4

sputum

Question 5

Staphylococcus:

speciment to be colected for UTI

Answer 5

urine

Question 6

Staphylococcus:

specimen to be collected from suspected carriers

Answer 6

nasal swab

Question 7

in direct smears, staphylococci can appear as

Answer 7

single cells, pairs, tetrads, and short chains

Question 8

the direct s,ears should also be examined for tge presence of

Answer 8

inflammatory cells

Question 9

2 routine laboratory media where Staphylococcus grow well

Answer 9

1. Blood agar medium (BAM)

2. Mannito salt agar (MSA)

Question 10

Enriched medium that supports the growth of staphylococci and permits observation of the pattern of hemolysis of blood

Answer 10

blood agar medium

Question 11

selective and differential medium for staphylococci

Answer 11

Mannitol Salt Agar

Question 12

components of MSA

Answer 12

Pancreatic digest of casein (5g)
Peptic digest of animal tissue (5g)
Beef extract (1g)
NaCl (75g)
D-mannitol (10g)
Phenol red (25mg)
Agar (15g)

Question 13

color of uninoculated MSA

Answer 13

light to medium rose red

Question 14

percentage of salt in MSA

Answer 14

7.5%

Question 15

purpose of high salt content

Answer 15

inhibits growth of other organisms except enterococcis

selectively allows growth of halotolerant staphylococci

Question 16

mannitol fermentation results in formation of

Answer 16

acids

Question 17

when acid from mannitol fermentation is formed, the phenol red indicator of the MSA agar turns to

Answer 17

yellow

Question 18

staphylococcus species if MSA agar turns to yellow

Answer 18

S. aureus

Question 19

staphylococcus species if phenol red in agar remains red

Answer 19

S. epidermidis

Question 20

incubation time and temperature of staphylococcus in agar

Answer 20

35-37 C for 24-48 hours

Question 21

colony size of staphylococcus in BAM

Answer 21

1-2 mm

Question 22

general appearance of staphylococcal colonies (color, elevation, consistency)

Answer 22

off-white or gray, opaque
slightly raised, low convex
smooth and bytrous consistency

Question 23

Colony size of some S. aureus

Answer 23

4-6 mm

Question 24

Color of some S. aureus colonies

Answer 24

creamy yellow or yellow-orange

clue: aureus means golden

Question 25

term for golden yellow pigments that S.aureus produce

Answer 25

lipochrome

Question 26

hemolytic property of S. aureus that becomes apparent after prolonged incubation

Answer 26

distinct or hazy zone of β-hemolysis around the colonies

Question 27

size of S. epidermidis colonies in BAM

Answer 27

small to medium

Question 28

color of S. epidermidis colonies in BAM

Answer 28

opaque gray white

Question 29

S. epidermidis colony characteristics in BAM

Answer 29

• non hemolytic

- sticky/ adherent to agar surface

Question 30

S. saprophyticus colony size in BAM

Answer 30

large

Question 31

color of S. saprophyticus colony in BAM

Answer 31

opaque, usually white but can be yellow or orange

Question 32

consistency of S. saprophyticus in BAM

Answer 32

very glossy, smooth, butyrous

Question 33

3 identification tests for Staphylococcus in sequential order

Answer 33

1. catalase test
2. coagulase test
3. novobiocin test

Question 34

performed in G+ cocci isolates which distinguishes staphylococci from streptococci

Answer 34

catalase test

Question 35

staphylococcis is catalase-

Answer 35

positive

Question 36

streptococci is catalase-

Answer 36

negative