Gram (+) and Gram (-) Cocci I Flashcards
1
Q
Factors that enable an organism to cause disease
A
Virulence factors
2
Q
Adhesins/cell surface factors and secreted enzymes/toxins are examples of
A
Virulence factors
3
Q
What are the three major genera of Gram (+) Cocci?
A
Staphylococci, streptococci, and enterococci
4
Q
Gram-stains blue and the cells are in clusters like a bunch of grapes
A
Staphylococci
5
Q
Are hardy bacteria, i.e. they are resistant to heat and drying
A
Staphylococci
6
Q
Staphylococci persist on
A
Formites
7
Q
Staphylococci are classified as
A
Factultative anaerobes
8
Q
All pathogenic staphylococci are
A
Catalase (+)
9
Q
Unlike streptococci, Staphylococci are
A
Catalase (+)
10
Q
The catalase test is a quick method to distinguish between
A
Staphylococci and streptococci
11
Q
The major pathogen of the staphylococci
A
S. aureus
12
Q
S. aureus stands out from the other staphylococci because it is
A
Coagulase positive
13
Q
All other pathogenic strains of staphylococci are
-Ex: S. epidermis and S. saprophyticus
A
Coagulase negative
14
Q
Shows “Golden” colonies on agar
A
Staphylococcus aureus
15
Q
Normal flora of the anterior nares in 1/3 of people
-most common bacterial human pathogen
A
S. aureus
16
Q
What are the two cytotoxins of S. aureus?
A
Hemolysins and PVL (leukocidin)
17
Q
What are the three superantigen toxins of S. aureus?
A
TSST-1, enterotoxin, and exfoliatin
18
Q
What are the three invasins of S. aureus?
A
Staphylokinase, Collagenase, and Lipase
19
Q
What are the three cell surface virulence factors of S. aureus?
A
Protein A. Capsule, and Adhesisn
20
Q
Has an anti-opsoin effect by binding the Fc region of antibodies
A
Protein A
21
Q
Facilitate attachment to host cells/connective tissue
A
Adhesins
22
Q
S. aureus cytotoxin that lyses erythrocytes
A
Hemolysins (ex: a-Toxin)
23
Q
S. aureus cytotoxin that lyses PMNs
A
Panton-Valentine Leukocidin (PVL)
24
Q
Target mammalian cell membranes
A
S. aureus cytotoxins
25
Enzymes that facilitate penetration through extracellular tissue, eg. staphylokinase, hyaluronidase, lipase, DNase
"Spreading factors"/invasins
26
An example of enterotoxins is
Food poisoning
27
Skalded skin syndrome is an example of
Exfoliatin
28
Carriage rate for healthy adults is 20-30
S. Aureus
29
A very common hospital associated infection (facilitated by ability to persist on fomites)
S. aureus
30
Tissue injury, diabetes, immunodeficiency, and pre-existing primary infections are predisposition factors to
S. aureus infection
31
What are the 4 Skin and Soft Tissue Infections (SSTIs) that are common with S. aureus infection?
1. ) Furuncles
2. ) Carbuncles
3. ) Impetigo
4. ) Cellulitis
32
Small pus-filled local infections
Furuncles
33
Larger skin abcesses
Carbuncles
34
Spreading, crusted skin infection
Impetigo
35
Deep skin infection
Cellulitis
36
Infections of other tissues, potentially from metastasis of superficial infections can be seen with
S. aureus infection
37
In children, S. aureus is the most common cause of
Osteomyelitis (bone infection)
38
Can also cause a septic joint/septic arthritis
S. aureus
39
Often follows viral influenza infections, especially in hospitalized patients
-Manifestation of S. aureus
Pneumonia
40
A clinical manifestation of S. aureus that is frequently associated with IV drug abuse.
Acute endocarditis
41
Rapid onset of vegetation on valve that can embolize to other tissue including lungs or brain
Acute endocarditis
42
A clinical manifestation of S. aureus that results in a high fever, hypotension, rash, and multi-organ failure
Toxic Shock Syndrome fro TSST-1
43
With an S. aureus infection, you can get "food poisoning: or gastroenteritis from
Enterotoxins
44
Presents as acute onset of GI distress with characteristic projectile vomitting
Food poisoning from enterotoxins
45
Exfoliatin toxin induced bright red flush, blisters (bullae) causing bullous impetigo, then desquamation of the epidermis
-also a form of S. aureus infection
Scalded Skin Syndrome
46
Most common clinical presentation of staphylococcal infections is
Skin and Soft Tissue Infections (SSTIs)
47
By 1955, almot all S. aureus was resistant to penicillins due to the enzymes
Penicillinase/B-lactamase
48
Penicillin modified with bulky side groups that prevented binding of penicillinase was developed to bipass
S. aureus drug resistance to penicillin
49
What is the name of a common anti-staphylococcal "penicilinase-resistant" penicillin used in the clinic
Methicillin
50
S. aureus acquired a new gene mecA that encodes for PBP2A, this lead to
Methicillin Resistant S. aureus (MRSA)
51
Initially, MRSA emerged in hospitals. Hospital strains tend to be resistant to additonal antibiotics such as
Tetracycline and clindamycin
52
Usually absent/less virulent in hospital MRSA
PVL genes
53
Community strains of MRSA tend to be susceptible to a broader range of antibiotics. They are generally more virulent due to production of
Toxins
-PVL genes usually present
54
Currently >95% of S. aureus isolates are
Penicillin resistant
55
What percentage of S. aureus isolates are methicillin resistant?
65%
56
What is the first line of treatment for MRSA infections?
Vancomycin
57
Relatively uncommon but growing in importance
Vancomycin Intermediate and Vancomycin Resistant S. aureus (VISA nd VRSA)
58
A lipopeptide that can be used for VISA and VRSA treatment
Daptomycin
59
An oxazolidone that can be used for VISA and VRSA treatment
Linezolid
60
A cephaolosporin with affinity for PBP2a used to treat VISA an VRSA
Ceftaroline
61
What are two examples of coagulase negative staphylococci?
S. epidermidis and S. saprophyticus
62
Major component of normal skin flora
-seen in wound infections through broken skin
S. epidermidis
63
Produces cell surface polysaccharide “slime” that adheres to bioprosthetic materials and acts as a barrier to antibiotics
-Less virulent
S. epidermidis
64
Frequently involved in nosocomial and opportunistic infections
–Catheters or Medical Devices, IV lines
S. epidermis
65
Most strains of S epidermidis are highly resistant to
Penicillins and methicillins
66
Normal in vaginal flora
-infections include UTI and cystitis in women
S. saprophyticus
67
S. saprophyticus is distinguished from other CoNS and S. aureus by its natural resistance to
Novobiocin
68
S. saprophyticus is sensitive to
Penicillin G
69
Gram-positive spherical/ovoid cocci arranged in long chains; commonly in pairs
Streptococcus
70
A distinguishing feature of Streptococcus is that they are
Catalase (-)
71
Most parasitic forms of Streptococcus are
-require an enriched media
Fastidious
72
Streptococcus are sensitive to drying and heat and aerobically they are considered to be
Aerotolerant anaerobes
73
The classification of streptococci is based on
Hemolysis pattern on blood agar and cell wall antigen
74
Complete erythrocyte destruction resulting in YELLOW zone of clearance around colony
Beta-hemolysis
75
Partial destruction of hemoglobin, agar below/around colony appears GREEN/BROWN
Alpha-hemolysis
76
No hemolysis, hemoglobin remains red around colony
Gamma-hemolysis
77
Serological classification based on an antigenic cell wall polysaccharide called C-substance
Streptococcus Lancefield groups
78
Reaction with specific antisera tested in a slide agglutination assay. Common Lancefield groups are
A, B, D and none
79
Streptococci pyogenes is called
Group A Streptococci (GAS)
80
What are the 4 virulence factors of GAS?
M-potein, streptolysin O and S, Streptococcal Pyrogenic Exotoxins (SPE) A, B, C, and the enzyme streptokinase
81
Lyse red blood cells
-ASO titers
Streptolysin O and S
82
Essential for GAS infection
-highly variable antigenic
M-protein
83
What are the three major clinical manifestations of GAS infection?
1. ) Streptococcal pharyngitis
2. ) Streptococcal skin infections
3. ) Streptococcal toxic shock syndrome
84
Also known as “strep throat”: purulent inflammation in the pharynx.
-Can be associated with scarlet fever, a toxin mediated skin rash
Streptococcal pharyngitis
85
Impetigo or erysipelas which could lead to cellulitis or more severe necrotizing fasciitis
Streptococcal skin infections
86
Superantigen pyrogenic exotoxin (SPE) mediated shock and multi-organ failure
Streptococcal toxic shock syndrome
87
What is an example of post-infection sequelae of GAS infections?
-antibody mediated
Acute Rheumatic Fever (ARF)
88
Occurs within 2-3 weeks following pharyngitis due to antibodies that also recognize cardiac myocytes
Acute Rheumatic Fever
89
Can occur 1-2 weeks after pharyngitis or a skin infection
Acute Post-Streptococcal Clomerulonephritis (APSGN)
90
What are three symptoms of APSGN?
Hematouria, oliguria, proteinuria
91
Inhabits throat, nasopharynx, occasionally skin in humans
S. pyogenes
92
S. pyogenes can be transmitted by
Contact, droplets, and food
93
The portal of entry for S. pyogenes is generally the
Skin or pharynx
94
Children are the predominant group affected for cutaneous and throat infections. In fact, ~30% of all bacterial pharyngitis in children due to
GAS
95
Group B Streptococci (GBS) is called
S. agalactiae
96
Makes up the normal flora of female reproductive tract
-Colonization can be intermittent, transient, or persistent
S. agalactiae (GBS)
97
S. agalactiae is the leading cause of
Neonatal sepsis, meningitis, or pneumonia
98
Pregnant women are routinely screened at 35-37 weeks for
GBS colonization
99
Distinguishing Group A Streptococci from Group B Streptococci is based upon
Bacitracin Sensitivity
100
Beta-hemolytic sensitive to Bacitracin
GAS
