B1.2 Staphylococcus aureus Flashcards
1
Q
What is the coagulase status of Staphylococcus aureus?
A
True coagulase-positive
2
Q
Which species of staphylococci is the most virulent?
A
Staphylococcus aureus.
3
Q
On which media does Staphylococcus aureus grow well?
A
Nutrient Agar (NA) and Tryptic Soy Broth (TSB).
4
Q
Describe the appearance of Staphylococcus aureus colonies on solid media
A
Round, smooth, opaque, and butyrous
5
Q
What is the appearance of Staphylococcus aureus colonies on Blood Agar Plate (BAP)?
A
Golden yellow color and β-hemolytic
6
Q
What salt concentration is used to cultivate Staphylococcus aureus, and what does this indicate?
A
7.5 to 10% NaCl; indicates halophilic nature
7
Q
What infections is Staphylococcus aureus responsible for?
A
Skin, wound, and deep tissue infections
8
Q
What type of teichoic acid is present in the cell wall of Staphylococcus aureus?
A
Ribitol teichoic acid.
9
Q
Virulence Factors related to staphylococcus aureus
A
Antigenic Structures
Enzymes
Toxins
10
Q
Antigenic Structures present in S. aureus
A
Teichoic Acid
Peptidoglycan
Protein A
Clumping Factor
Capsular Polysaccharide
11
Q
What is the role of peptidoglycan in Staphylococcus aureus?
A
Protects from lysis and aids in adherence
12
Q
What is the unique group-specific antigen in Staphylococcus aureus?
A
Protein A.
13
Q
Prevents antibody-mediated phagocytosis by competing for the Fc portion of antibodies
A
Protein A
14
Q
Causes clumping of staphylococci in the presence of plasma
A
clumping factor
15
Q
What is the role of capsular polysaccharide in Staphylococcus aureus?
A
Protects from phagocytosis
16
Q
ENZYMES present in S. aureus
A
COAGULASE (STAPHYLOCOAGULASE)
HYALURONIDASE (SPREADING FACTOR)
STAPHYLOKINASE (FIBRINOLYSIN)
LIPASE (Fat-splitting Enzyme)
DEOXYRIBONUCLEASE (DNASE) and PHOSPHATASE
PROTEASE
GELATINASE
β-LACTAMASE
17
Q
Coagulates fibrinogen in plasma to promote fibrin layer formation around abscesses.
A
coagulase (staphylocoagulase)
18
Q
Name the two types of coagulase in Staphylococcus aureus
A
Cell-bound (clumping factor) and unbound (free) coagulase
19
Q
bound to the cell wall and clots human, rabbit or pig plasma
A
Cell-bound Coagulase or Clumping Factor
20
Q
extracellular enzymes not bound to the cell wall and cause clot formation when bacterial cells are incubated with plasma
A
Unbound or Free Coagulase
21
Q
Hydrolyzes hyaluronic acid, permitting the spread of infection
A
hyaluronidase
22
Q
Dissolves fibrin clots (fibrinolysin)
A
staphylokinase
23
Q
Acts on lipids on the skin surface, aiding in the formation of furuncles, carbuncles, and boils
produced by both coagulase (+) and coagulase (-) staphylococci
A
lipase
24
Q
Lowers viscosity of exudates and destroys DNA
A
DNase and phosphatase
25
Which enzyme in Staphylococcus aureus breaks down β-lactam drugs
β-Lactamase
26
TOXINS in S. aureus
CYTOLYTIC TOXINS
ENTEROTOXINS
TOXIC SHOCK SYNDROME TOXIN-1(TSST-1)
EXFOLIATIVE TOXIN
27
CYTOLYTIC TOXINS examples
Hemolysins and Leukocidins
28
4 Types Hemolysins and the leukocidin found in S. aureus
α-Hemolysin
β-Hemolysin (Sphingomyelinase C)
δ-Hemolysin
γ-Hemolysin
Staphylococcal Leukocidin/ Panton-Valentine leukocidin
29
Which hemolysin in Staphylococcus aureus causes severe tissue damage
α-Hemolysin
30
Act as heat-stable exotoxins causing food poisoning
enterotoxins
31
Which toxin is associated with Toxic Shock Syndrome in Staphylococcus aureus?
Toxic Shock Syndrome Toxin-1 (TSST-1).
32
What does exfoliative toxin cause in Staphylococcus aureus infections
Staphylococcal Scalded Skin Syndrome (Ritter's disease) and bullous impetigo
33
damage RBC, platelets and macrophages and cause severe tissue damage
Predominant hemolysin
α-Hemolysin
34
acts on sphingomyelin in the plasma membrane of RBC
β-Hemolysin (Sphingomyelinase C)
35
aka“hot-cold” lysine : enhanced hemolytic activity on incubation at 37° C (heat labile) and subsequent exposure to cold (4° C)
β-Hemolysin (Sphingomyelinase C)
36
exhibited in the CAMP test
lethal and dermonecrotic
β-Hemolysin (Sphingomyelinase C)
37
less toxic to cells than either α-hemolysin or β-hemolysin
produced by all S. aureus strain that cause RBC injury in culture and produce edematous lesions
δ-Hemolysin
38
associated with Panton-Valentine leukocidin (PVL)
γ-Hemolysin
39
exotoxin lethal to polymorphonuclear leukocytes
Pore forming exotoxin that suppress phagocytosis and associated with severe cutaneous infections and necrotizing pneumonia
associated with community-acquired staphylococcal infections
Staphylococcal Leukocidin/ Panton-Valentine leukocidin
40
heat-stable exotoxin: 100° C for 30 minutes
resistant to hydrolysis by gastric and jejunal enzymes
act as neurotoxins that stimulate vomiting through the vagus nerve
ENTEROTOXINS
41
Enterotoxins are produced by _____% of S. aureus isolates
30% to 50%
42
Enterotoxins A, B, and D causes
Staphylococcal food poisoning
43
Enterotoxins B and C and sometimes G and I causes
TSS
44
Enterotoxin B causes
Staphylococcal Pseudomembranous Enterocolitis (contaminated milk products)
45
TOXIC SHOCK SYNDROME TOXIN-1(TSST-1) is also known as
ENTEROTOXIN F or PYROGENIC EXOTOXIN C
46
menstruating-associated TSS= TSS associated with tampon use
chromosomal-mediated toxin
SUPERANTIGEN stimulating T-cell proliferation and production of a large amount of cytokines
TOXIC SHOCK SYNDROME TOXIN-1(TSST-1)
47
TOXIC SHOCK SYNDROME TOXIN-1(TSST-1) low concentrations=
higher concentrations=
low concentrations= leakage by endothelial cells;
higher concentrations= cytotoxic
48
EXFOLIATIVE TOXIN aka
EPIDERMOLYTIC TOXIN A and B or EXFOLIATIN
serotypes A and B
49
Serine protease that divides the intrcellular bridges of the epidermis and causes excessive sloughing of the epidermis (stratum granulosum)
causes STAPHYLOCOCCAL SCALDED SKIN SYNDROME referred to as RITTER’S DISEASE
implicated in BULLOUS IMPETIGO
EXFOLIATIVE TOXIN
50
RELATED INFECTIONS AND DISEASES S. aureus
Cutaneous Infections
Toxic Shock Syndrome
Food Poisoning
Staphylococcal Bacteremia
Staphylococcal Osteomyelitis
Staphylococcal Pneumonia
Septic Arthritis
Acute Bacterial Endocarditis
UTI
51
Cutaneous Infections caused by S. aureus
Folliculitis
Furuncles (Boils)
Carbuncles
Bullous Impetigo
Scalded Skin Syndrome
Toxic Epidermal Necrolysis (TEN)
52
mild inflammation of a hair follicle or oil gland; infected area is raised and red
Folliculitis
53
focal suppurative lesions which has resulted from an infection (folliculitis) that extend into subcutaneous tissue; large, raised, superficial abscesses
Furuncles (Boils)
54
larger, more invasive lesions develop from multiple furuncles, which can progress into deeper tissues; present with fever and chills, indicating systemic infection
Carbuncles
55
larger pustules surrounded by a small zone of erythema
highly contagious infection that spread by direct contact, fomites, or autoinoculation
Bullous Impetigo
56
superficial cutaneous infection commonly seen in newborns and young children characterized by the formation of encrusted pustules surrounded by red border
Impetigo
57
bullous exfoliative dermatitis that occurs primarily in newborns and previously healthy young children
Scalded Skin Syndrome
58
localized skin lesion SSS:
few blisters,
pemphigus neonatorum,
Ritter disease
59
generalized form of SSS:
cutaneous erythema, profuse peeling of the epidermis
60
clinical manifestation with multiple causes; symptoms are due to hypersensitivity reaction
Toxic Epidermal Necrolysis (TEN)
61
rare but potentially fatal, multisystem disease characterized by sudden onset of fever, chills, vomiting, diarrhea, muscle aches, and rash, which can quickly progress to hypotension and shock
Toxic Shock Syndrome
62
Food Poisoning caused by
Enterotoxins A (78%), D (38%), and B (10%)
63
intoxication resulting from ingestion of a toxin formed outside the body
symptoms appear rapidly (2 to 8 hours after ingestion) and resolve within 24 to 48 hours: nausea, vomiting, abdominal pain, and severe cramping, diarrhea
Food Poisoning
64
perfuse and watery diarrhea due to water and electrolyte loss
FOOD POISONING
65
* Food won’t appear or taste tainted
* Death: Intoxication rather than infection
* Reheating the food – kills the bacteria, but not
inactivate the heat stable toxin
FOOD POISONING
66
ENTEROCOLITIS caused by
Enterotoxin A and (leukocidins) LukE
and LukP
67
leads to secondary pneumonia and endocarditis observed among IV drug users
Staphylococcal Bacteremia
68
secondary to bacteremia
Staphylococcal Osteomyelitis
69
secondary to influenza virus infection
multiple abscesses and focal lesions in the pulmonary parenchyma
Staphylococcal Pneumonia
70
frequent in children and occur in patients with a history of rheumatoid arthritis or IV drug abuse
Septic Arthritis
71
JOINT INFECTIONS/SEPTIC ARTHRITIS found in
Both Adults and Neonates/Children
S. aureus
S. agalactiae
S. pyogenes
Enterobacteriaceae
72
JOINT INFECTIONS/SEPTIC ARTHRITIS found in
Neonates/Children
only
H. influenzae type b (Hib)
Kingella kingae
73
JOINT INFECTIONS/SEPTIC ARTHRITIS found in
Sexually Active
N. gonorrhoea
74
Specimen of choice for testing S. aureus
Pus,
Purulent Fluids,
Sputum,
Urine,
Blood
75
Gram Stain results of S. aureus
Gram(+) cocci in irregular clusters
76
Culture Media used for S. aureus
BAP, PEA, MSA, CNA, Chapman Stone Agar, Vogel-Johnson Medium
Columbia Colistin–Nalidixic acid (CNA)
MSA and PEA
CHROM Agar
77
media used for purulent exudates
Columbia Colistin–Nalidixic acid (CNA)
78
Media used for heavily contaminated specimen
MSA and PEA
79
Media used for selective-differential for MRSA
CHROM Agar
80
Biochemical Tests used for S. aureus
Catalase Test
Coagulase Test
Mannitol Fermentaion Test
Growth on Tellurite Glycine Agar
Polymyxin B Sensitivity
Lysostaphin Sensitivity Test (2ug/ml)
Voges-Proskauer (VP) Test
Deoxyribonuclease (Dnase) Test
Pyrrolidonyl Arylamidase (PYR) Test
Rapid Methods of Identification
Molecular Methods
81
What reagent is used in the aerobic catalase test?
3% H2O2
82
What reagent is used in the anaerobic catalase test?
15% H2O2
83
What is the catalase reaction result for Staphylococcus?
Catalase positive
84
What is the catalase reaction result for Streptococcus?
Catalase negative
85
best single criterion of recognition and pathogenicity of S. aureus
Coagulase Test
86
What reagent is used in the coagulase test?
Rabbit plasma with EDTA
87
Methods for coagulase test
Slide Method
Tube Method
88
rapid screening test
detects cell-bound coagulase or clumping factor
Other Slide Coagualse Positive: S. lugdunensis and S. schleiferi
Slide Method
89
sensitive but definitive; confirm all slide negative results
detects extracellular or free coagulase
Tube Method
90
What does the slide coagulase test detect?
Cell-bound coagulase (clumping factor)
91
Which species are slide coagulase positive besides S. aureus?
S. lugdunensis and S. schleiferi
92
What does the tube coagulase test detect?
Extracellular (free) coagulase
93
Name other tube coagulase-positive species besides S. aureus
S. hyicus,
S. intermedius,
S. lutrae,
S. delphini, and
S. schleiferi subsp. coagulans
94
At what temperature should the tube coagulase test be incubated initially?
35°C–37°C
95
How long should the tube coagulase test be incubated before reading the result?
1-4 hours
96
During a coagulase test, if no clot forms after 4 hours what should you do
reincubate at room temperature for additional 20 hours
97
What is the significance of reading the tube coagulase test result within 4 hours?
To prevent false negatives due to fibrinolysin activity
98
Coagulase plasma is not suitable with
Citrate
99
These species use citrate and release calcium forming clot in the absence of coagulase causing a false positive result for Coagulase test
Pseudomonas and Enterococci
100
What medium is used for the mannitol fermentation test?
Mannitol Salt Agar (MSA)
101
S. aureus can ferment mannitol and can tolerate high salt concentrations of what percent
(7.5-10%)
102
What is the pH indicator used in the mannitol fermentation test
Phenol Red
103
What is the positive result for mannitol fermentation on MSA?
Yellow-colored colonies with a yellow halo
104
What colonies does S. aureus produce on tellurite glycine agar?
Jet-black colonies
105
What is the reaction of S. aureus to polymyxin B?
Resistant
106
What is the reaction of other staphylococci to polymyxin B?
Susceptible
107
What is the reaction of S. aureus in the lysostaphin sensitivity test?
Sensitive
108
What is the reaction of micrococci in the lysostaphin sensitivity test?
Resistant
109
What is the culture medium for the Voges-Proskauer (VP) test?
VP broth with 5% glucose
110
used to differentiate S. aureus (+) from S. intermedius (-)
Voges-Proskauer (VP) Test
111
What reagents are used in the Voges-Proskauer (VP) test?
α-naphthol and KOH
112
Name VP-positive species besides S. aureus
S. lugdunensis, S. haemolyticus, and S. schleiferi
113
What culture medium is used in the DNase test?
DNA-methyl green agar
114
What is the DNase result for S. aureus?
DNase positive
115
What substrate is used in the PYR test?
Pyroglutamyl-β-naphthylamide (PYR)
(Lpyrrolidonyl-β-naphthylamide; PYR)
116
differentiates coagulase(+) staphylococci by slide method
Pyrrolidonyl Arylamidase (PYR) Test
117
What reagent is used in the PYR test?
p-dimethylaminocinnamaldehyde
118
What is the end product of the PYR test?
L-pyrrolidone and β-naphthylamine
119
What is the positive result for the PYR test?
Cherry red color
120
Name PYR-positive species
S. lugdunensis,
S. intermedius,
S. schleiferi,
S. haemolyticus
121
Rapid Methods of Identification
Particle Agglutination Test
Staphyloslide use sensitized sheep RBC
Staphaurex
BACTiStaph
Staphylochrome
Sero-STAT
Bacto Staph Latex
Accu-Staph
Hemostaph
Staphylatex
122
plasma-coated carrier particles (latex)
plasma detects both clumping factor (with fibrinogen) and protein A in the cell wall of S. aureus (with IgG)
Staphylatex
123
What does plasma-coated carrier particles in rapid tests detect?
Clumping factor (fibrinogen) and Protein A (IgG)
124
Molecular Methods used in the detection of S. aureus
Real-time PCR
Qualitative Nucleic Acid Hybridization
Assays
125
What molecular method is used to detect MRSA and MSSA?
Real-time PCR
126
staphylococci from prepared smears in
blood cultures
identification of mecA gene
Qualitative Nucleic Acid Hybridization
Assays
127
What gene is identified by molecular methods in S. aureus?
mecA gene
128
What specimen is used for molecular testing for S. aureus?
Anterior nares swabs
129
Advantage of Qualitative Nucleic Acid Hybridization Assays
rapid detection test for MRSA
