LAB S19 Flashcards
(117 cards)
1
Q
gram staining of staphylococcus
A
positive
2
Q
diameter of staphylococcus
A
0.5- 1.5 um
3
Q
arrangement of staphylococci
A
grape-like clusters
3
Q
arrangement of staphylococci
A
grape-like clusters
4
Q
specimen obtained for pyogenic infections
A
pus
5
Q
specimen obtained from septicemia
A
blood
6
Q
specimen obtained from meningitis
A
CSF
7
Q
specimen obtained from resporatory infections
A
sputum
8
Q
specimen obtained from UTI
A
urine
9
Q
specimen obtained from suspected carriers
A
nasal swab
10
Q
direct smear is prepared from climical material such as
A
CSF or pus
11
Q
the direct smears should aldo be examined for the presence of:
A
imflammatory cells
12
Q
2 routine culture media for staphylococcus
A
- Blood Agar Medium
2. Mannitol Salt Agae
13
Q
enriched medium that supports the growth of staphylococci and permits observation of the pattern of hemolysis of blood
A
blood agar medium
14
Q
both a selective and differential medium for staphylococci
A
Mannitol Salt Agar
15
Q
selective component of agar
A
7.5% NaCl
16
Q
7.5% NaCl inhibits the growth of other organisms except halotolerant species like:
A
staphylococcus
enterococcus
17
Q
the differential component of MSA
A
mannitol
18
Q
mannitol fermentation results in acids which is indicated by
A
phenol red to yellow
19
Q
approximate formula of per liter MSA
A
Pancreatic digest of casein (5g) peptic digest of animal tissue (5g) beef extract (1g) NaCl (75g) D-mannitol (10g) Phenol red (25mg) Agar (15g)
20
Q
incubation of MSA and BAM for colonial characterization
A
35-37C
24- 48 hrs
21
Q
usual size of staphylococcal colonies
A
medium to large (1-2 mm)
22
Q
usual color of staphylococcal colonies
A
off-white or gray
23
Q
usual surface of staphylococcal colonies
A
smooth
24
usual elevation of staphylococcal colonies
slightly raised, low convex
25
usual density of staphylococcal colonies
opaque
26
usual comsistency of staphylococcal colonies
butyrous
27
usual size of S. aureus
large (4-6mm diameter)
28
color of some strains of S. aureus
creamy yellow or yellow-orange
29
golden yellow pigment produced by some strains of S. aureus
lipochrome
30
hemolytic property of S. aureus which is apparent after prolonged incubation
B- hemolysis
31
usual size of S. epidermidis
small to medium
32
usual density of S. epidermidis
opaque
33
usual color of S. epidermidis
gray-white
34
hemolytic property of S. epidermidis
non-hemolytic
35
staphylococcus which may have slimee producing strains that adhere to agar surface
S. epidermidis
36
usual size of S. saprophyticus
large
37
usual margin of S. saprophyticus
entire
38
usual surface of S. saprophyticus
very glossy, smooth
39
usual density of S. saprophyticus
opaque
40
usual consistency of S. saprophyticus
butyrous
41
usual elevation of S. saprophyticus
convex
42
color of S. saprophyticus colonies
usually white but can be yellow or orange
43
MSA with yellow discoloration and yellow colonies
S. aureus or S. saprophyticus
44
MSA with no color change and red colonies
S. epidermidis
45
Three identification tests of Staphylococcus
1. catalase test
2. coagulase test
3. novobiocin test
46
test that distinguishes gram positive cocci: staphylococci and streptococci
catalase test
47
staphylococcus is catalase:?
positive
48
streptococcus is catalase?
negative
49
principle of catalase test
ability of staphylococcus to produce catalase enzyme, whoch decomposes hydrogen peroxid into water and oxygen
50
the evolution of oxygen in the catalase test resulting into rapid bubble formation is referred to as:
effervescence
51
it is better to use staphylococci from this agar medium for catalase test
MSA
52
procedure for slide catalase test
add 1 drop of 3% hydrogen peroxide
53
procedure for tube catalase test
add 2-3 ml of 3% hydrogen peroxide to 18-24 hr culture slant
54
how long to wait before observing catalase test result
20-30 secs
55
single most reliable characteristic for identifying S. aureus
coagulase test
56
principle of coagulase test
S. aureus produces coagulase, which bind plasma fibrinogen causing plasma to clot
57
the culture for coagulase test should be taken from this medium
BAM
58
medium for both sliide and tube coagulase
commercially produced lyophilized rabbit plasma with EDTA
59
why rabbit plasma
high amlunts of coagulase reacting factor
60
why not human plasma
contains variable amounts of CRF and contain staphylococcal antibodies
61
why not citrated plasma
some bacteria like enterococci can utiloze citrate and yield positive result
62
screening test for S. aureus
slide coagulase test
63
principle of slide coagulase test
bound coagulase in cell wall of most S. aureus or clumping factors convert fibrinogen into fibrin
64
bound coagulase causes:
rapid cell agglutination
65
human coagulase negative species that can be slide coagulase positive
S. lugdunensis
| S. schleiferi
66
procedure of slide coagulase test
emulsify colony in 2 saline circles
drop plasma in one and water in the other
rock slide 5-10 secs
67
positive result of slide coagulase test
white precipitates or clumping within 10-15 seconds of mixing
68
positive for slide coagulase =
S. aureus
69
negative for slide coagulase test:
confirm with tube coagulase test
70
confirmatory test for S. aureus
tube coagulase test
71
principle of tube coagulase test
free coagulase secreted extracellularly by all strains of S. aureus react with CRF, which react with fibrinogen to form fibrin
72
positive result of tube coagulase test:
clotting of plasma
73
positive for tube coagulase test
S. aureus
74
negative for tube coagulase test
S. epidermidis or S. saprophyticus
| proceed to novobiocin test
75
procedure for tube coagulase test
pipet 0.5 ml plasma to test tube
transfer colony and emulsify until milky
incubate for 4 hrs in water bath
76
if tube coagulase test is negative after 4 hours of incubation?
read again after 18-24 hours at room temperature
77
why should tube coagulase negative result be read again after putting in room temperature?
some strains produce staphylokinase on prolonged incubation causing dissolution of the clot
78
one of the methods to distinguish between coagulase negative staphylococci: S. epidermidis and S. saprophyticus
novobiocin test
79
significant staphylococcus in urinary tract infections
S. saprophyticus
80
important agent involved in several infectious processes
S. epidermidis
81
concentration of novobiocin disc
5 ug
82
less than 12 mm ZOI in novobiocin
resistant = S. saprophyticus
83
greater than 16 mm ZOI
susceptible- S. epidermidis
84
5 additional culture media for isolation of staphylococcus species
1. Columbia CNA agar
2. Phenylethyl Alcohol (PEA) agar
3. Vogel-Johnson (VJ) agar
4. Chapman stone agar
5. Baird-Parker agar
85
contains sheep blood, colistin, and nalidixic acid
Columbia CNA agar
86
purpose of sheep blood in Columbia CNA agar
supports fastidious bacteria
| allows hemolytic reactions
87
purpose of colistin and nalidixic acid in Columbia CNA agar
selective for G+ and inhibits G-
88
formula per liter of Columbia CNA agar
```
pancreatic digest of casein (12g)
peptic digest of animal tissue (5g)
yeast extract (3g)
beef extract (3g)
corn starch (1g)
NaCl (5g)
Agar (13.5g)
colistin (10mg)
nalidixic acid (10mg)
```
89
contains sheep blood but cannot be used for determining hemolytic reactions
phenylethyl alcohol (PEA) agar
90
components of PEA agar that inhibits G- bacteria
B-phenylethyl alcohol
91
formula per liter of PEA agar
```
pancreatic digest of casein (15g)
papic digest of soybean meal (5g)
NaCl (5g)
B-PEA (2.5 g)
Agar (15 g)
```
92
agar which inhibits all nonstaphylococcal organisms
Vogel Johnson agar
93
selectivity of VJ agar is due to these three components
potassium tellurite
lithium chloride
glycine
94
principle of VJ agar
tellurite is reduced by S. aureus into metallic tellurium = black or gray colonies
mannitol degraded to acid = phenol red turned to yellow
95
approximate per liter formula of VJ agar
```
tryptone (10g)
yeast extract (5g)
mannitol (10g)
dipotassium phosphate (5g)
lithium chloride (5g)
glycine (10g)
agar (15g)
phenol red (25mg)
```
96
agar containing high salt content, gelatin, ammonium sulfate, mannitol and bromcresol purple
Chapman stone agar
97
selective component of chapman stone agar
5.5% salt content
98
allows detection of hydrolysis in chapman stone agar, characterized by clear zone around colonies
ammonium sulfate
99
differential component of chapamn stone agar
mannitol and bromcresol purple
100
yellow colonies surrounded by clear halo in chapman stone agar
S. aureus
101
nonpigmented colonies with or without colonies
S. epidermidis
102
approximate per liter formula of chapman stone agar
```
yeast extract (2.5g)
pancreatic digest of casein (10g)
gelatin (30g)
D-mannitol (10g)
NaCl (55 g)
Ammonium sulfate (75g)
dipotassium phosphate (5g)
agar (15g)
```
103
Also has inhibitory action for nonstaphylococcal organisms but incorporates sodium pyruvate and egg yolk
Baird Parker Agar
104
3 selective components of Baird Parker agar
tellurite, lithium chloride, glycine
105
stimulates growth of S. aureus im Baird Parker Agar without destroying selectivity
Sodium pyruvate
106
function of egg yolk in Baird-Parker agar
demonstrate:
proteolysis by lecithinase
lipolysis by lipase
through clear zones in the agar
107
colonial characteristic of S. aureus in Baird parker agar
black, shiny, convex, 1-5 mm with narrow white edge
108
colonial characteristic of S. epidermidis in Baird Parker Agar
black, shiny, irregular shape with opaque zone around colonies after 24 hrs
109
2 additional identification tests for S. aureus
DNase test
| thermostable endonucelase test
110
principle of DNase test
detects DNase which depolymerizes DNA into nucleotides
111
method of DNase test
inoculate DNA agar plate (streak or spot)
incubate 35 C for 24-48 hrs
flood with 1N HCl (precipitates DNA)
112
positive DNase reaction
clear area surrounding growth
113
positive for DNase test
S. aureus
114
eliminates the need for 1N HCl
methyl green or toluidine blue
115
method for thermostable nuclease test
3mm holes are cut into DNase test agar by cork borer
wells are filled with 24 hr broth culture boiled in water bath for 15 minutes
plate incubated overnight at 35C
116
positive thermostable nuclease test
pink zone = S. aureus
