VMCB 122 > STREP N STAPH > Flashcards

STREP N STAPH Flashcards

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1
Q

Both staph and strep are round or coccoid in shape. What is the difference between the two?

A

Staphylococcus = grape like clusters

Streptococcus = arranged in chains

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2
Q

How are Gram positive bacteria identified?

A

based on their possession of the enzyme catalase OR ability to hemolyze culture medium

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3
Q

What family does Staphylococcus belong to?

A

Micrococcaceae

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4
Q

What is the oxygen tolerance of Staphylococcus?

A

Aerobic or facultative anaerobic

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5
Q

What are some important pathogens of Staphylococcus that are coagulase-positive

A

S. aureus

S. pseudintermedius

S. hyicus

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6
Q

Low virulence Staphylococci lack what enzyme?

A

Coagulase

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7
Q

What class of staph and strep can the catalase test identify?

A

catalase positive staphylococci and

catalase negative streptococci

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8
Q

What is the usual habitat for staphylococcus?

A

On the skin of animals and humans

Mucous membranes of the: respiratory tract, urogenital tract, transients of digestive tract

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9
Q

When do Staphylococci infections occur?

A

They are opportunistic so when there are breaks in the skin, weakened immunity, poor hygiene or disrupted flora

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10
Q

What are staphylococci resistant to?

A

Drying, heat, high salt conc

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11
Q

Give some examples of Coagulase negative Staphylococci? Mention at least 2

A

S. epidermidis
S. saprophticus
S. sciuri
S. lentus
S. gallinarum
S. chromogenes

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12
Q

What is coagulase even?

A

Converts fibrinogen to fibrin to clot plasma

Helps the bacteria evade detection and phagocytosis

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13
Q

The coagulase test is used to differentiate what specific species?

A

Highly pathogenic S. aureus from less pathogenic staph species

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14
Q

What are the two kinds of coagulase tests?

A

Slide test and Tube test

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15
Q

What does the slide test test for?

A

bound coagulase (clumping factor)

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16
Q

What is the positive indicator for the slide test?

A

clumping seen in seconds

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17
Q

What does the tube test test for?

A

free coagulase (secreted enzyme)

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18
Q

What is the positive indicator for the tube test?

A

Clot or gel formation

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19
Q

What are the 3 kinds of virulence factors that staphylococcus employs?

A

Structural and compositional VFs

Enzyme VFs

Toxin VFs

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20
Q

What is a Protein A VF?

A

Binds to the Fc moiety of IgG and exerts anti-opsonin

Basically it is strongly antiphagocytic

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20
Q

What is a clumping factor VF?

A

Bound coagulase that causes plasma to clump

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21
Q

How does teichoic acid and peptidoglycan work as VFs?

A

It inhibits the inflammatory response

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22
Q

How does carotenoid pigments such as staphyloxanthin work as VFs?

A

It can act as antioxidant to neutralize harmful (Reactive Oxygen Species) produce by immune cells during infection

The ROS are toxic to the bacteria

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23
Q

What are MSCRAMMs

A

Microbial Surface Components Recognizing Adhesive Matrix Molecules

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24
What is the function of MSCRAMMs?
They are adhesins that can **bind to host molecules** so it can coat the cell with it. Host molecules have antigens that immune cells recognize as non-foreign material and so don't phagocytose it.
25
What is Clumping factor A (ClfA)?
A surface protein that facilitates adhesion to fibrinogen to clump bacteria Fibrin clots can hide the bacteria
26
What is the mechanism of Protein A?
Protein A on the surface of S. aureus freely binds to the Fc region of antibodies to avoid phagocytosis They can also release protein A and have it attach to the Fc of B-cells to cause cell death
27
Why is teichoic acid important?
So that the staph can **adhere and colonize** the mucosal surface
28
Which serotypes of S. aureus have capsules that cause most infections?
Serotype 5 and 7
29
What is the function of coagulase as a VF?
It clots plasma to protect bacteria
30
What is the function of Hyaluronidase as a VF?
It breaks down hyaluronic acid to let bacteria move between cells to spread to other tissues
31
What is the function of staphylokinase?
To dissolve blood clots formed from coagulase
32
What is the function of lipase as a VF?
Digest lipids to allow staph to grow on skin surface and oil glands
33
What is the function of B-lactamases as a VF?
Breaks down penicillin to help bacteria survive treatment
34
What does hemolysin do as a VF?
it lyses RBCs (hemolysis) (Alpha, Beta, Gamma)
35
What do leukocidins do as a VF?
kill leukocytes (as in -cide)
36
Which Staph species produces Leukocidins?
S. aureus S. pseudintermedius
37
What do Exfoliative toxins do as a VF?
It causes **epidermal damage via exfoliation of necrotic tissue** and causes greasy pig disease
38
Which staph species produces exfoliative toxins?
S. hyicus
39
What do enterotoxins cause?
Food poisoning
40
Which staph species is known for producing enterotoxins?
S. aureus
41
What does toxic shock syndrome toxin (TSST-1) do as a VF?
Causes systemic inflammation
42
When culturing on blood agar, what is the expected effect of hemolysin?
Area of clearing or zone of hemolysis
43
Are all staph species capable of producing hemolytic zones?
Not all, **only the coagulase positive staph** give rise to colonies with hemolytic zones
44
What are the 3 types of hemolysis and how do they differ?
Alpha = incomplete or partial (green or brown appearance) Beta = complete hemolysis Gamma = no hemolysis
45
What is the name of Leukocidin that S. aureus produces?
Panton-Valentine leukocidin
46
What is the other name for exfoliative toxin?
Dermonecrotoxin
47
Which Enterotoxin is mostly associated with disease?
Enterotoxin A
48
Which Enterotoxin is found in contaminated milk?
Enterotoxin C and D
49
Which Enterotoxin causes staphylococcal pseudomembranous enterocolitis?
Enterotoxin B
50
Why are enterotoxins so troublesome to destroy?
Because they need to be destroyed at 100C for 80 mins
51
How does the TSST work?
It can **induce *lymphokine* production** and **result in tissue damage**
52
What is the pathogenesis of staphylococcus?
They primarily act as opportunistic pathogens
53
What are the predisposing conditions that lead to infection of S. aureus?
Skin injuries Respiratory infections Reduced host resistance Immunosuppression Disrupted flora
54
What are the 3 categories of diseases caused by staphylococci?
Non-invasive diseases Cutaneous diseases Systemic diseases
55
What is a non-invasive disease from staphylococci?
Via food poisoning from eating enterotoxin-contaminated food
56
What is a cutaneous disease from staphylococci?
Various skin conditions including **scalded skin**, impetigo, folliculitis
57
What is a systemic disease from staphylococci?
Toxic shock, bacteremia, endocarditis, pneumonia
58
Which staphylococci can cause infections in humans? Give at least 2
S. aureus S. epidermidis S. saprophyticus S. haemolyticus S. hominis
59
What kind of diseases can we expect from staphylococcus?
Cutaneous infections Deep infections Food poisoning Exfoliative disease such as Staphylococcal scalded skin syndrome (Skin) Toxic shock syndrome
60
What does S. aureus cause in cows?
**Contagious mastitis** which is the inflammation of the udder and invades the mammary glands
61
What does S. aureus cause in avians?
**Bumblefoot** which is a pyogranulomatous process of subcutaneous tissue of foot that can infect joints
62
What does S. hyicus cause in pigs?
Greasy pig disease or exudative epidermitis
63
What does S. intermedius cause in dogs and cats?
Pyoderma and otitis externa
64
What is the optimum temperature of staphylococci?
35-37 C
65
What kind of media is best for staphylococci?
Non-enriched media and bacteriological media
66
What colors do S. aureus colonies have?
Gray to deep golden yellow colonies
67
What colors are S. epidermidis colonies?
gray to white
68
Staphylococcus grows in the presence of what compound?
7-10% NaCl
69
What is the selective medium that isolates staphylococci?
MSA
70
In nutrient agar, what do S. aureus and S. epidermidis colonies look like?
S. aureus = golden yellow S. epidermidis = white
71
What is the shape of staphylococci colonies?
Round and large
72
What causes the golden color of S. aureus?
Carotenoid pigments that occur with or without beta hemolysis
73
What is the expected appearance of S. aureus when cultured on MSA?
Yellow colonies with yellow medium
74
What is the expected appearance of S. epidermidis when cultured on MSA?
Pink colonies with pink medium
75
What is Baird Parker Medium?
A medium containing tellurite
76
What happens when you culture S. aureus on BPM?
It reduces tellurite to for black shiny colonies
77
Are the halos surrounding the colonies of staph on BMP a form of hemolysis?
No because theres no blood to lyse on BMP, instead its probably due to lipase
78
What is Purple Agar Base?
A medium containing **bromocresol purple (a pH indicator) and 1% maltose**
79
What is the function of PAB?
It **differentiates S. aureus from S. pseudintermedius** because both are coagulase positive
80
What happens when S. aureus is cultured on PAB?
It rapidly ferments maltose and produces acid and yellow colonies can be observed
81
What happens when S. pseudintermedius is cultured on PAB?
Slow or less acid and colonies remain purple
82
What is MRSA?
Methicillin-resistant S. aureus
83
What is it about MRSA that lets it resist methicillin?
It has a mutation that lets it resist B-lactam antibiotics
84
What causes the resistance to B-lactam antibiotics?
A mecA gene that encodes an altered penicillin-binding protein (PBP2a) which has a low affinity to B-lactam antibiotics
85
What are some examples of B-lactam antibiotics?
methicillin penicillin cephalosporins carbapenems
86
How is staphylococci diagnosed sa lab?
observing gram-stained smears of samples cultivating them in blood agar conducting biochemical tests Phage typing since some S. aureus strains are susceptible
87
How do we treat staphylococci infections?
**Antibiotics** such as methicillin, oxacillin, cefazolin, cephalotin
88
What are second choice antibiotics for treatment of staph infections?
**Lincosamides** like *clindamycin* **Glycopeptides** like *vancomycin* and *teicoplanin*
89
What is the usual habitat of streptococcus and enterococcus?
Mucous membrane and respiratory tract = streptococcus Intestinal tract = enterococcus On decaying matter
90
What are the 3 members of the Streptococci family?
Streptococcus Enterococcus Peptoniphilus
91
What are some members of Enterococcus?
E. faecalis E. faecium
92
What are some members of Peptoniphilus?
P. indolicus
93
What methods/test are used to differentiate streptococci?
Types of hemolysis Lancefield grouping Biochemical testing
94
Which streptococci are A-hemolytic?
S. pneumoniae Viridans streptococcus
95
Which streptococci are Beta-hemolytic?
S. pyogenes S. agalactiae
96
Which streptococci are G-hemolytic?
E. faecalis
97
What is the lancefield grouping scheme?
It is a categorization method that **categorizes B-hemolytic streptococci based on antigens** on their cell wall
98
How is S. pneumoniae serotyped via the Lancefield grouping scheme?
via their capsules
99
How is S. pyogenes serotyped via the Lancefield grouping scheme?
via M proteins
100
How many groups does the lancefield grouping scheme have?
20 groups
101
Who created the Lancefield grouping scheme?
Rebecca Lancefield
102
What is the Lancefield group of S. pyogenes
A
103
What does S. pyogenes cause in humans, rodents, and dairy cattle?
**Pharyngotonsilitis** Pyoderma Erysipelas Puerperal fever **Rheumatic fever** Glomerulonephritis (mastitis)
104
What Lancefield group does S. agalactiae belong to?
B
105
What does S. agalactiae cause in dairy cattle?
Neonatal infections
106
What does S. equi spp. equi cause in horses?
Strangles or severe infection of URT
107
What does S. dysgalactiae cause in dairy cattle?
Acute, severe mastitis
108
What do all Group E, Strep species cause in swine?
**Cervical lymphadenitis** or Swine strangles Also **jowl abscesses**
109
What does S. bovis cause in cattle?
Cattle bloat
110
What are the main virulence factors for streptococci?
M protein and hyaluronidase
111
What does M. protein do?
A cell wall antigen that has anti-phagocytic property
112
What is the difference between Streptolysin O and S?
Streptolysin O is antigenic meaning it is oxygen labile Streptolysin S is non-antigenic meaning it is oxygen stable They both lyse cells
113
What is the function of erythrogenic toxins?
They cause rashes in scarlet fever But they **release large amounts of cytokines** causing *pyrogenicity (fever) and lethal shock*
114
What is the specific disease that S. pyogenes causes?
Necrotizing fasciitis
115
What causes Streptococcal mastitis?
S. agalactiae (for contagious mastitis) S. dysgalactiae (for environmental mastitis) S. uberis
116
What does S. equi subsp. equi cause?
Strangles or rhinopharyngitis
117
What are the clinical presentations of Strangles?
**Snotty nose** (thick yellow-white) **Enlarged lymph nodes** under jaw
118
How is strangles transmitted?
Contact with nasal discharge
119
What happens if strangles is prolonged?
**Metastatic abscess** - "bastard" strangles Purpura hemorrhagica **Guturral pouch** empyema
120
How do you treat strangles?
Penicillin
121
What is the most common associations of Streptococcus suis?
Meningitis, arthritis, and septicemia Mostly MENINGITIS
122
What are the most notable members of the Enterococcus species?
E. faecalis
123
What are the selective media that facilitiates Streptococci growth?
**Crystal violet blood agar** - for S. pyogenes and inhibition of S. aureus **PNF medium** - Contains polymyxin B sulphate, neomycin sulphate, and fusidic acid - allows good growth of S. pyogenes
124
What is the Edwards medium used for?
**Selects for streptococci** and **indicates aesculin hydrolysis** (darkening of colonies and medium)
125
Which Strep species demonstrates aesculin hydrolysis?
E. faecalis
126
How do you treat streptococcal pharyngitis?
Oral penicillin V or amoxicillin
127
How do you treat patients who are allergic to penicillin?
**Cephalosporin or macrolides**
128
How do you treat severe streptococcal infections?
Penicillin + clindamycin (**protein synthesis inhibitors**) Clindamycin needed cuz severe na
VMCB 122
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