Exam 2 Lecture 11 Flashcards
Staphylococci
1
Q
As of 2014, the Staphylococci genus consists of __ species and __ sub-species
A
47; 23
2
Q
Staphylococci is a gram-___ cocci
A
Positive
3
Q
Staphylococci are arranged as: (4 shapes)
A
singles, pairs, tetrads, clusters
4
Q
Why are there so many different arrangements of Staphylococci?
A
They can divide in multiple perpendicular planes. This can lead to cluster formation
5
Q
What is the DNA G/C content of Staphylococci?
A
27-41%
6
Q
True or false: Staphylococci are motile and are capable of forming spores.
A
False: they are non-motile and non-spore forming.
7
Q
What is an example of spore forming bacteria?
A
Clostridium and Bacillus species
8
Q
True or false: all staphylococci are coagulase positive
A
False: they are all catalase positive
9
Q
What is special about all Staphylococci being catalase positive?
A
This allows us to differentiate Staph from all other gram positive cocci.
10
Q
What does catalase do?
A
Catalase is an enzyme that detoxifies reactive oxygen species (ROS) by reducing hydrogen peroxide to water and oxygen.
11
Q
How do you perform a catalase test?
A
Add 3% hydrogen peroxide to a culture/suspended cells. Observe for bubbling.
12
Q
Signs of a positive catalase test
A
Bubbling
13
Q
Signs of a negative catalase test. What species would this indicate?
A
No bubbling; may indicate Streptococci or Enterococci
14
Q
What are two Staphylococci phenotypes on blood agar?
A
- Pigment production: S. aureus produces gold-colored colonies, S. epidermis produces white-colored colonies
- Hemolysis (S. aureus does beta and S. epidermidis does gamma)
15
Q
S. aureus hemolysis
A
Beta hemolysis
16
Q
S. epidermidis hemolysis
A
Gamma (none)
17
Q
What is coagulase?
A
Bacterial protein that causes clotting of blood plasma
18
Q
How do you perform the coagulase test?
A
Mix bacteria with rabbit plasma on glass slide or in tube, look for clumping/clot formation
19
Q
True or false: S. aureus is the most medically important CoPS.
A
True; all other CoPS species usually infect animals
20
Q
Staphylococci are ____ ____, but only S. aureus can perform ____ fermentation.
A
Facultative anaerobes; mannitol
21
Q
Acidic fermentation products
A
energy and lactic acid
22
Q
True or false: Majority of CoNS can ferment mannitol
A
False, they cannot
23
Q
What are some characteristics of Mannitol Salt Agar?
A
- Selective and differential medium
- Contains essential nutrients and mannitol
- High salt concentration (7.5% NaCl)
- Contains phenol red (pH indicator)
24
Q
True or false: on a mannitol salt agar plate, S. aureus will indicate a yellow to red color change.
A
False: red to yellow
25
True or false: on a mannitol salt agar plate, S. epidermis will not indicate a color change and the plate will stay red
True
26
What makes Staphylococci "hardy"?
1. Halotolerant
2. Wide temp (10-45ºC) and pH(4.0 - 9.0) ranges
3. growth with low water activity
27
Halotolerant
Can grow under high concentration of salt
28
Where do reactive oxygen species come from?
Can be self generated by aerobic respiration or they can come from immune cells
29
Where can you find coagulase in Staphylococci?
Surface bound or extracellularly
30
What does surface bound coagulase do?
Cleaves fibrinogen, resulting in fibrin precipitating out of solution to form clot
31
What does extracellular coagulase do?
Binds prothrombin, cleaves fibrinogen, fibrin precipitates out
32
When S. aureus ferments ____, this results in the production of ___ ___, which will change the __ indicator from red to yellow color
mannitol; lactic acid; pH
33
What are some rapid diagnostic methods for differentiating S. aureus?
1. Molecular (PCR to amplify genes inherent to Staph genome)
| 2. Proteomics (ex. mass spectrometry to look at mass/charge ratio of ionized proteins)
34
What gives S. aureus colonies their characteristic gold color?
Staphyloxanthin (carotenoid pigment)
35
True or false: staphyloxanthin is mainly a pigment and does not have a major function
False: is also a virulence factor
36
In S. aureus, __-hemolysin is secreted and forms pores in erythrocytes, resulting in __-hemolysis
alpha; beta
37
What can S. aureus colonize on the human body?
Skin and mucosa of asymptomatic individuals; anterior nares; hand; perineum; pharynx
38
True or false: If you are a nasal carrier of S. aureus, you have a negligibly higher chance of having S. aureus colonizing other sites of the body.
False: being a carrier significantly increases chance
39
What are the three nasal carriage patterns in healthy individuals?
1. non-carriage
2. intermittent
3. persistent
40
What does MSCRAMM stand for?
Microbial Surface Components Recognizing Adhesive Matrix Molecules
41
What does SERAM stand for?
Secretable Expanded Repertoire Adhesive Molecule
42
What are some examples of S. aureus MSCRAMM?
Fibronectin binding protein; Protein A
43
What are some examples of S. aureus SERAM?
Extracellular adherence protein (Eap); extracellular matrix binding protein (Emp); Coagulase (Coa)
44
What role do teichoic acids play in S. aureus?
It is a cell wall component that mediates host cell adherence
45
What does S. aureus Protein A bind to?
1. von Willebrand factor (vWF), which helps to stick platelets together and adhere to the walls of blood vessels at the site of a wound
2. Fc portion of antibodies
46
What does S. aureus Eap bind to in the host?
fibrinogen and fibronectin
47
S. aureus has 4 virulence factors, which are:
1. Adhesins
2. Invasins
3. Immune evasion
4. Miscellaneous toxins (pyogenic)
48
What are the two major classes of S. aureus adhesins?
1. MSCRAMM
| 2. SERAM
49
Examples of S. aureus invasins
1. Cytolytic toxins (pore forming)
| 2. Exoenzymes (spreading)
50
What is the overall function of invasins?
they are extracellular proteins that lyse cells and promote spread
51
S. aureus produces a ____ called __-_____ that lyses erythrocytes and other mammalian cells, which allows for __ hemolysis to occur.
cytolytic toxin; alpha-hemolysin; beta
52
Examples of S. aureus exoenzymes
hyaluronidase, collagenase, staphylokinase (fibrinolysin), lipase
53
Why does S. aureus produce exoenzymes?
Allows spreading from one site of infection to another (i.e. S. aureus translocates through the activity of exoenzymes)
54
An S. aureus cytotoxin called ___-___ _____ lyses neutrophils and macrophages.
Panton-Valentine Leukocidin
55
Why is it beneficial for S. aureus to be able to lyse host cells?
These cells contain nutrients needed for bacterial growth and replication
56
Hemolysins and PVL bind to ___ ___ ____ and ____, allowing a channel to form within the host cell membrane.
host membrane receptor; oligomerize
57
How does pore formation lead to cell lysis?
Allows the release of cations like Na+, Ca++, K+ in and out of the cell, changing the osmotic pressure of the host cell, causing lysis
58
Which S. aureus adhesins also serve as factors of immune evasion?
```
A. Fibronectin binding protein
B. Protein A
C. Coagulase
D. Eap
E. Collagen binding protein (Cna)
```
B and D
59
How does Protein A function in immune evasion?
Binds to Fc portion of antibodies that serves as a disguise, so host immune cells cannot differentiate pathogen from self
60
How does Eap function in immune evasion?
Impairs T-cell and neutrophil recruitment, preventing a larger immune response from occurring
61
S. aureus may also be coated with ___ ___ ___ that helps prevent recognition by immune cells.
Polysaccharide capsule coats
62
```
Which of the following S. aureus pyogenic toxins are superantigens?
A. Toxic Shock Syndrome Toxin (TSST)
B. Exfoliative toxins (ETA and ETB)
C. Staphylococcal Enterotoxins
D. none of these
```
A and C
63
S. aureus exfoliative toxins function
serine protease that cleaves desmosomes, causing desquamation
64
Superantigens promote non-specific binding of ___ ___ __ to _-__ ___ in the absence of processed antigen
MHC Class II; T-cell receptor
65
Superantigens cause _-__ activation and proliferation, which can cause massive ____ production.
T-cell; cytokine
66
What kinds of cutaneous infections can S. aureus cause?
folliculitis, non-bullous impetigo, furuncle, carbuncle
67
How can a furuncle spread to become a carbuncle?
S. aureus may secrete exoenzymes to spread to surrounding, uninfected tissue and worsen the infection
68
Abscesses are characterized as:
warm, pus-filled, painful pockets
69
Folliculitis is characterized by: (3 things)
1. superficial infection of hair follicles or glands
2. clusters of small red bumps
3. pus-filled blisters
70
Non-bullous impetigo is characterized by:
1. superficial skin infection
2. bubble-like epidermal swelling
3. vesicles or pustules that rupture and leave a honey-colored crust
4. primarily occurs in young children
71
Name 5 systemic S. aureus infections
1. Bacteremia
2. Septic arthritis
3. Infective endocarditis
4. Osteomyelitis
5. Pneumonia
72
True or false: bacteremia cause by S. aureus often has high mortality rates, but incidence decreases with age.
False; incidence increases with age
73
Symptoms of bacteremia
Fever, chills, weakness, fast respiration, rapid heart rate
74
What is S. aureus induced septic arthritis and what are some symptoms?
infection of joint cavity causing inflammation; symptoms include swollen joint, pain, fever, chills
75
True or false: S. aureus induced Septic arthritis may cause hematogenous seeding of vascular synovial membrane
True
76
Infective endocarditis causes ~____ cases per year, and some risk factors include:
40,000; IV drug abuse, pacemakers, congenital heart disease
77
Osteomyelitis
infection of bone or bone marrow
78
____ is the most common cause of pathogen-induced bone destruction and is predominantly found in ____.
Osteomyelitis; children
79
Osteomyelitis is ___ in origin and ____ in nature.
hematogenous; acute
80
Osteomyelitis commonly colonizes the ____ of the long bone.
metaphysis, which is a highly vascularized area of long bones where the growth plate is located
81
Osteomyelitis usually causes:
Abscesses, inflammation, remodeling, necrosis (bone becomes brittle)
82
What are 2 factors of S. aureus that detoxify ROS?
1. Catalase
| 2. Staphyloxanthin (antioxidant that protexts against O2-, H2O2, HOCl)
83
What are 4 factors of S. aureus that lyse immune cells and/or inhibit cell recruitment/migration?
1. Hemolysins
2. Panton-Valentine Leukocidin
3. Chemotaxis Inhibiting Protein (CHIP)
4. Eap
84
S. aureus-induced pneumonia causes ~____ cases per year and is usually ____ or ____-acquired.
70,000; community; hospital
85
Necrotizing pneumonia has a ___ mortality rate and is often caused by __ ____-___ S. aureus and preceded by ____
high; PV leukocidin-producing; influenza
86
What are 4 toxigenic S. aureus infections?
1. Staphylococcal Scalded Skin Syndrome (SSSS)
2. Bullous impetigo
3. Toxic Shock Syndrome (TSS)
4. Staphylococcal Food Poisoning
87
What is Staphylococcal Scalded Skin Syndrome, and what is it caused by?
fluid accumulated and blistering skin often accompanied by desquamation; caused by exfoliative toxins ETA and ETB
88
We have multiple layers of skin that are connected via _____. S. aureus ____ ___ are serine proteases that cleave ______ _, causing desquamation.
desmosomes; exfoliative toxins; desmogelin 1
89
Desquamation
epidermal-dermal separation
90
Bullous Impetigo is a localized form of ____ and is characterized by:
SSSS; fluid-filled vesicles and flaccid blisters (bullae)
91
What is Toxic Shock Syndrome?
multisystem inflammatory response
92
In menstrual TSS, S. aureus multiples rapidly when _____, and favorable conditions will stimulate the production of ____.
Tampon is inserted; TSST-1
93
True or false: When TSST-1 is produced, it is absorbed and enters the bloodstream.
True
94
Symptoms of toxic shock syndrome
1. high fever
2. erythematous rash
3. hypotension
4. skin desquamation
95
Nonmenstrual TSS mainly occurs in ____ and is usually caused by:
women; barrier contraceptives, surgery, lesions
96
What causes Staphylococcal Food poisoning?
Staphylococcal enterotoxins, specifically SEA (80% of cases)
97
Staphylococcal enterotoxins are usually resistant to:
heat, acid, and inactivation by GI proteases
98
Staphylococcal food poisoning occurs when you ______. Symptoms start to occur __-__ after ingestion.
consume SEA (preformed toxin); 30 min-8 hours
99
Staphylococcal food poisoning causes ____ ___ in the GI tract. SEs will stimulate ___ ___ in intestines. This sends a signal via the ___ and ___ nerves to the ____ brain center. Lastly, the brain sends a signal back to the ____.
inflammatory changes; neural receptors; vagus and sympathetic; emetic; stomach
100
SFP food sources
meats, dairy products, potatoes, eggs, salads (creamy)
101
True or false: CoNS are usually white colored colonies and do not ferment mannitol.
True
102
CoNS hemolysis
None (gamma)
103
True or false: CoNS colonize skin and mucous membranes of humans and animals and therefore are significant members of human microbiota.
True
104
There are __ species categorized as CoNS, and of those, __ species colonize humans.
38; 20
105
___ is the most commonly recovered CoNS.
S. epidermidis
106
True or false: CoNS are never considered pathogenic.
False; they may become opportunistic pathogens in patients with increased risk, such as those that are immunocompromised or use medical devices.
107
CoNS has fewer ___ ___ than S. aureus
virulence factors
108
S. epidermidis has 4 main classes of virulence factors, which include:
1. adhesins
2. Accumulation factors
3. Exoenzymes
4. Immune escape
109
What do S. epidermidis adhesins attach to?
Hydrophobic surfaces (polystyrene) and host MSCRAMMs
110
S. epidermidis accumulation factors
Exopolysaccharide; accumulation-associated protein (Aap)
111
S. epidermidis exoenzymes
lipase (GehD), protease (Esp)
112
S. haemolyticus characteristics
- 2nd most common species in CoNS infections
- colonizes skin microbiome
- has virulence factors (adhesins and cytotoxins)
- highest level of antibiotic resistance among CoNS
113
What kinds of infections can S. haemolyticus cause?
native valve endocarditis, bacteremia, peritonitis, UTIs, osteomyelitis, can infect wounds/joints
114
S. saprophyticus can cause ___ mainly in young, sexually active women.
UTIs
115
S. saprophyticus colonizes the _____ and ___ tracts as well as the ____.
genitourinary and GI; perineum
116
True or false: S. saprophyticus virulence factors include adhesins and enzymes such as urease.
True
117
S. lugdunensis can cause severe infections similar to _____. It uses virulence factors such as:
S. aureus; adhesins, enzymes, cytotoxin
118
What is the primary cytotoxin that S. lugdunensis uses?
S. lugdunensis synergistic hemolysins (SLUSH)
119
What infections can S. lugdunensis cause?
skin and soft tissue, endocarditis, bacteremia, peritonitis, prosthetic joint, osteomyelitis, septic arthritis, abscess
120
True or false: Staphylococci use quorum sensing in order to regulate its virulence factor production and biofilm formation.
True
121
What are the benefits to forming biofilms?
protection against immune system and antibiotics
122
Characteristics of small colony variant Staphylococci
- slow-growth on lab media
-mutations in essential metabolic genes
resistant to different antibiotics depending on mutation
