Staph Aureus Flashcards
(69 cards)
1
Q
Primary reservoir of staph aureus
A
Naress
2
Q
plate that is selective for Staphylococcus and Differential for S. aureus
A
Mannitol Salt Agar
3
Q
what does CoNS mean
A
Coagulase negative staphylococcus
4
Q
what’s a coag pos staph
A
staph aureus
5
Q
what’s a coag neg staph
A
could be staph epi or staph sapro or unknown
6
Q
Mode of transmission for staph aureus
A
breach in the skin
7
Q
what are the 3 super antigen toxins that staph aureus is associated with?
A
enterotoxins, exfoliative toxins, and TSST
8
Q
staph aureus most important structural cellular component
A
protein A
9
Q
what enzymes are associated with staph aureus
A
coagulase, hyaluronidase, lipase, penicillinase
10
Q
SUPERANTIGENS cause a release in CYTOKINES which cause what for the patient?
A
fever and hypotensive shock
11
Q
what symptoms is enterotoxin A associated with
A
food poisoning
12
Q
what is enterotoxin C and D associated with?
A
contaminated milk products
13
Q
what is enterotoxin B associated with?
A
pseudomembranous enterocolitis
14
Q
how is TSST-1 absorbed?
A
through vaginal mucosa surfaces
15
Q
Chromosomal-mediated toxin
A
TSST-1 (Superantigen)
16
Q
Associated with super absorbent Tampons on Sterile packing after surgical procedures
A
TSST-1 (Superantigen)
17
Q
Toxic Shock Syndrome causes these symptoms
A
high fever, hypotension and shock
18
Q
this virulence factor is associated with Ritters disease. what toxin is this?
A
Exfoliative toxin
19
Q
(SSSS) Scalded skin sydrome or Ritters disease is associated with what bacteria?
A
Staph aureus
20
Q
(SSSS) Scalded skin sydrome or Ritters disease is mainly seen in what type of patients
A
children
21
Q
morphology of staph sp on BAP is what
A
creamy, white, or, rarely, light gold; Buttery looking
22
Q
how is staph appeared on a stain
A
singles, in pairs, and in clusters often
referred to as “bunches of grapes
23
Q
what Staph sp. produce b hemolysis
A
S. aureus
24
Q
STAPH SP can be either Aerobic or facultative anaerobe. true or false
A
true
25
the most important test in differentiating staph from strep
catalase
26
important test used to classify Staph species
coagulase
27
Coagulase is an Enzyme that converts fibrinogen to what?
fibrin; clots plasma
28
human pathogen; coagulase pos staphylococcus
Staph aureus
29
S. epidermidis and S. saprophyticus are coagulase pos or neg
neg (CoNS)
30
this bug is mainly related to hospital-acquired infections
S. epidermidis
31
causes urinary tract infections (UTIs) in young, sexually active females
S. saprophyticus
32
Extracellular proteins that are toxic for many cells: RBCs, WBCs,
fibroblasts, macrophages and platelets. ex: Hemolysins and Leukocidins
Cytolytic Toxins
33
S. aureus produces four hemolysins. what are they?
alpha beta delta and gamma
34
this hemolysin lyses RBCs and damages platelets and tissues
α-hemolysin (alpha)
35
this hemolysin shows enhanced activity by acting on the
sphingomyelin of RBC membranes, causing lysis.
β-hemolysin (beta)
36
this hemolysin causes injury to cells and leukocytes but is less
lethal
δ-hemolysin (delta)
37
this hemolysin binds with P-V Leukocidin
-hemolysin (gamma)
38
an enzyme in staph that's Very diagnostic but importance in virulence is NOT COMPLETELY UNDERSTOOD
Coagulase Enzyme
39
an enzyme in staph that Hydrolyzes the hyaluronic
acid present in connective tissues, helping spread of infection
Hyaluronidase Enzyme -(SPREADING FACTOR)
40
an enzyme in staph that Breakdown of the fats and oil created by the sebaceous glands on skin surfaces
Lipase Enzyme
41
an enzyme in staph that hydrolyzes the β-lactam ring of penicillin making penicillin –resistant staphylococci.
Penicillinase Enzyme– (β-lactamase specific for penicillin)
42
Binds the Fc portion of antibodies to avoid phagocytosis
Protein A
43
this cellular component binds to the fc portion of immunoglobulin and assists in blocking phagocytosis
Protein A
44
Abscess is filled with pus and
surrounded by necrotic tissues and damaged leukocytes
SUPPURATIVE
45
a painful inflammation of the skin and subcutaneous tissue
Furuncle (boil)
46
Boils that have multiple lesions and progress into deeper tissues
Carbuncles
47
infection caused by staph aureus with localized skin infection with pus filled vesicles
Impetigo
48
infection caused by staph aureus; destruction of bones; Most common cause in Adults
Osteomyelitis
49
This syndrome is caused by Staphylococcal Exfoliative Toxin; its and extensive exfoliative dermatitis that occurs primarily in newborns and previously healthy young children. NO ACTIVE ORGANISM AT THE SITE
SSSS (Staphylococcal Scalded skin syndrome), or
Ritter’s disease
50
occurs primarily in newborns and previously healthy young children; highly contagious; BLISTERS HAVE ACTIVE BACTERIA PRESENT (not toxin mediated destruction)
Bullous exfoliative dermatitis
51
Extreme cases can of Toxic Shock Syndrome (TSS) can lead to
Disseminated intravascular coagulation (DIC), hypotension and shock.
52
What is Toxic Shock Syndrome (TSS) caused by?
TSST-1
53
what disease do these toxins from staph aureus cause? Enterotoxin A, B, D (A and D most common)
Food Poisoning (Rapid Onset)
54
how fast do symtoms appear after ingesting food? and how long do they last?
appear 2-8 hours; gone in 24-48
55
what are some symptoms of food poisoning
Nausea, vomiting, abdominal pain, and cramping (no diarrhea)
56
Cultural Characteristics of Staph aureus
Round, smooth, white, creamy colonies ;; Can exhibit yellow pigment (only with extended incubation)
57
does staph aureus ferment mannitol?
yes, the color is yellow on a mannitol salt agar
58
enterotoxin(THAT CAUSE FOOD POISONING A,B,D) are heat liable or stable ?
heat stable for up to 100°C/30 min, MILD REHEATING WILL NOT KILL ENTEROTOXIN
59
Describe two common characteristics shared by most Staphylococcus species, as observed through Gram staining and catalase testing
Most Staphylococcus species are GRAM POS COCCI, meaning they appear as purple spherical bacteria under a microscope after Gram staining due to their thick peptidoglycan layer. They are also CATALASE POSITIVE, which means they produce the enzyme catalase that breaks down hydrogen peroxide into water and oxygen, resulting in bubbling when hydrogen peroxide is added to a colony.
60
Explain the fundamental difference between coagulase-positive and coagulase-negative staphylococci and name the most significant human pathogen in the coagulase-positive group.
Coagulase-positive staphylococci produce the enzyme coagulase, which clots plasma by converting fibrinogen to fibrin, while coagulase-negative staphylococci do not produce this enzyme. The most significant human pathogen among the coagulase-positive staphylococci is Staphylococcus aureus.
61
Name three important virulence factors produced by Staphylococcus aureus and briefly explain how each contributes to the bacterium's pathogenicity.
Three important virulence factors of Staphylococcus aureus include Protein A, which binds to the Fc portion of antibodies, inhibiting phagocytosis; coagulase, an enzyme that clots plasma and may help evade the immune system; and enterotoxins, which are heat-stable toxins that can cause food poisoning by acting as superantigens in the gastrointestinal tract.
62
Describe the pathogenesis of Staphylococcal Scalded Skin Syndrome (SSSS). Is the active bacteria typically found at the site of skin sloughing?
Staphylococcal Scalded Skin Syndrome (SSSS) is caused by exfoliative toxins (Exfoliatin A and B) produced by certain strains of Staphylococcus aureus. These toxins act as superantigens and cause the separation of the epidermal layer of the skin. Interestingly, the active Staphylococcus aureus bacteria are typically not found at the site of skin sloughing; the disease is toxin-mediated from a distant infection site.
63
Explain why Staphylococcus aureus food poisoning has a rapid onset of symptoms. Name at least two enterotoxins commonly associated with this condition.
Staphylococcus aureus food poisoning has a rapid onset of symptoms (2-8 hours) because the illness is caused by the ingestion of pre-formed, heat-stable enterotoxins present in contaminated food, rather than requiring bacterial growth and toxin production within the host. Common enterotoxins associated with this condition include Enterotoxin A and Enterotoxin D.
64
What are the key differences in colony morphology and hemolytic activity on Sheep Blood Agar (SBA) that can help differentiate Staphylococcus aureus from typical CoNS?
On Sheep Blood Agar (SBA), Staphylococcus aureus typically forms round, smooth, creamy white to light gold colonies and often exhibits beta-hemolysis, characterized by a clear zone of complete red blood cell lysis surrounding the colonies. Coagulase-negative staphylococci (CoNS) generally produce small- to medium-sized, nonhemolytic (gamma-hemolysis) or weakly hemolytic colonies that are gray to white.
65
Describe how the Microdase test and bacitracin susceptibility can be used to differentiate Micrococcus species from Staphylococcus species.
Micrococcus species are typically Microdase positive, meaning they produce oxidase enzymes that can oxidize a chromogenic reducing agent on the Microdase disk, resulting in a blue or purple color change. In contrast, most Staphylococcus species are Microdase negative. Additionally, Micrococcus luteus is susceptible to bacitracin, while most CoNS are resistant.
66
Explain the significance of the mecA gene in staphylococcal infections and name the antibiotic typically used in the laboratory to detect methicillin resistance in Staphylococcus aureus.
The mecA gene is significant because it encodes for a modified penicillin-binding protein (PBP2a) that has a low affinity for beta-lactam antibiotics, including methicillin, conferring methicillin resistance to staphylococci. In the laboratory, oxacillin is generally used as a surrogate marker to detect methicillin resistance in Staphylococcus aureus.
67
A gene found in methicillin-resistant staphylococci that encodes for a modified penicillin-binding protein (PBP2a) with low affinity for beta-lactam antibiotics.
mecA gene
68
A class of antigens that cause non-specific activation of T-cells, resulting in an excessive release of cytokines and potentially leading to toxic shock.
Superantigen
69
A molecule produced by a pathogen that contributes to its ability to cause disease.
Virulence factor
