Catalase postive, gram positive cocci Flashcards
staphylococcus, Micrococcus and similar organisms
1
Q
What Gram stain result is typical for the Micrococcaceae family?
A
Gram positive.
2
Q
What shape are bacteria in the Micrococcaceae family?
A
Cocci (spherical).
3
Q
What is the catalase activity of the Micrococcaceae family?
A
Catalase positive.
4
Q
What are the oxygen requirements for most members of the Micrococcaceae family?
A
Aerobic or facultative anaerobic.
5
Q
Which two bacteria in the Micrococcaceae family are obligate anaerobes and catalase negative?
A
Staphylococcus aureus subsp. anaerobius and Staphylococcus saccharolyticus.
6
Q
Where are most Micrococcaceae family members commonly found?
A
As members of the indigenous flora.
7
Q
What Gram stain result is typical for the Staphylococcus genus?
A
Gram positive
8
Q
What is the catalase activity of the Staphylococcus genus?
A
Catalase positive.
9
Q
Are Staphylococcus bacteria motile or nonmotile?
A
Nonmotile.
10
Q
What are the oxygen requirements for the Staphylococcus genus?
A
Facultative anaerobes.
11
Q
How are species within the Staphylococcus genus initially differentiated?
A
By the coagulase test.
12
Q
What family?
Gram Stain: Positive
Shape: Cocci
Catalase: Positive
Oxygen Requirement: Aerobic or facultative anaerobic
A
Micrococcaceae Family
13
Q
What genus?
Gram Stain: Positive
Catalase: Positive
Motility: Nonmotile
Oxygen Requirement: Facultative anaerobes
A
Staphylococcus Genus
14
Q
what organism?
Characteristics:
Gram Stain: Gram-positive cocci in grape-like clusters
Catalase: Positive
Coagulase: Positive
Hemolysis: β-hemolytic
Colony Appearance: Yellow or golden colonies on blood agar
Fermentation: Ferments mannitol
A
Staphylococcus aureus
15
Q
What is the Gram stain result and typical arrangement of Staphylococcus aureus?
A
Gram-positive cocci in grape-like clusters.
16
Q
Gram-positive cocci in grape-like clusters.
what organism?
A
Staphylococcus aureus
17
Q
Is Staphylococcus aureus catalase positive or negative?
A
Catalase positive.
18
Q
Is Staphylococcus aureus coagulase positive or negative?
A
Coagulase positive.
19
Q
What type of hemolysis does Staphylococcus aureus exhibit?
A
β-hemolytic.
20
Q
What is the appearance of Staphylococcus aureus colonies on blood agar?
A
Yellow or golden colonies due to staphyloxanthin.
21
Q
The appearance of Staphylococcus aureus colonies on blood agar is Yellow or golden colonies due to
A
Staphyloxanthin
22
Q
Does Staphylococcus aureus ferment mannitol?
A
Yes, it ferments mannitol.
23
Q
Name three common habitats of Staphylococcus aureus.
A
Anterior nares, nasopharynx, and perineal area.
24
Q
Can Staphylococcus aureus colonize the skin?
A
Yes, it can colonize the skin.
25
Is Staphylococcus aureus found as a colonizer of mucosa?
Yes, it is a colonizer of mucosa.
26
How can Staphylococcus aureus from an endogenous strain be transmitted to a sterile site?
By traumatic introduction.
27
How is Staphylococcus aureus transmitted through direct contact?
Through person-to-person contact or fomites.
28
How is Staphylococcus aureus transmitted through indirect contact?
Through aerosolized particles.
29
What is the role of the polysaccharide capsule in Staphylococcus aureus?
It inhibits phagocytosis.
30
what virulence of Staphylococcus aureus allows the organism to adhere to inorganic surfaces and inhibits the penetration of antibiotics.
slime layer or biofilm
31
What immune responses are activated by peptidoglycan in Staphylococcus aureus?
Activates complement and interleukin 1 (IL-1), and acts as a chemotactic factor for the recruitment of polymorphonuclear leukocytes (PMNs)
32
what virulence factor of Staphylococcus aureus decreases the immune-mediated clearance of organisms from the site of infection.
Protein A
33
What is the significance of coagulase in Staphylococcus aureus?
It is a major virulence factor that builds an insoluble fibrin capsule.
34
what virulence factor of Staphylococcus aureus prevents the spread of infection by hydrolyzing hyaluronic acid.
Hyaluronidase
35
what virulence factor of Staphylococcus aureus acilitates colonization on the skin surface and spreads in fat-containing areas of the body.
Lipase
36
What type of hemolysis is associated with Staphylococcus aureus?
Alpha and beta hemolysis, which cause hemolysis of red blood cells
37
What is the effect of Panton-Valentine Leukocidin (PVL) in Staphylococcus aureus?
It is toxic to white blood cells (WBCs).
38
what are the 8 virulence factors of staphylococcus aureus
polysaccharide capsule
slime layer or biofilm
peptidoglycan
protein A
coagulase
hyaluronidase
lipase
alpha and beta hemolysis
Panton-Valentine leucocidin (PVL)
39
What toxin in S. aureus Disrupts smooth muscles in blood vessels and is toxic to erythrocytes, leukocytes, hepatocytes, and platelets.
Alpha toxin
40
What toxin in S. aureus works in conjunction with alpha toxin and catalyzes the hydrolysis of membrane phospholipids, leading to cell lysis.
beta toxin
41
What toxin in S. aureus is cytolytic to erythrocytes and has nonspecific membrane toxicity to other mammalian cells.
delta toxin
42
Which toxin in Staphylococcus aureus is associated with Panton-Valentine leucocidin (PVL)?
Gamma toxin.
43
what toxin in S. aureusis resistant to hydrolysis by gastrointestinal (GI) enzymes, found in milk products, and associated with enterocolitis and toxic shock syndrome.
heat stable enterotoxin
44
What is the role of Toxic Shock Syndrome Toxin (TSST-1) in Staphylococcus aureus infections?
It acts as a superantigen leading to toxic shock syndrome.
45
What type of enzyme is the exfoliative toxin in Staphylococcus aureus and what is its effect?
It is a serine protease that splits the intracellular bridges of the epidermis.
46
What are the main toxins involved in staphylococcal food poisoning?
Staphylococcal enterotoxins A and D.
47
How is staphylococcal food poisoning typically transmitted?
Through ingestion of food contaminated by an infected food handler.
48
How soon do symptoms of staphylococcal food poisoning appear and resolve?
Symptoms appear within 2-6 hours and resolve within 8-10 hours.
49
What is the most common cause of septic arthritis in prepubertal children?
Staphylococcus aureus.
50
How does Staphylococcus aureus cause osteomyelitis and septic arthritis?
Through hematogenous spread or local introduction at a wound site.
51
A sequestered focus of osteomyelitis arising in the metaphyseal area of the long bone.
Brodie abscess
52
What is a common cause of nosocomial pneumonia?
Staphylococcus aureus.
53
How does Staphylococcus aureus pneumonia typically develop?
It usually follows aspiration of endogenous nasopharyngeal organisms.
54
What are some predisposing factors for Staphylococcus aureus pneumonia?
Measles, influenza A virus, cystic fibrosis, and immune deficiency
55
Which population is commonly affected by acute endocarditis caused by Staphylococcus aureus?
Individuals with left-sided valvular heart disease and IV drug users.
56
What is a common target of Staphylococcus aureus in IV drug users?
The tricuspid valve.
57
What type of infections are commonly associated with community-acquired Staphylococcus aureus?
Serious soft tissue infections.
58
What is a notable virulence factor associated with community-acquired MRSA (CA-MRSA)?
Panton-Valentine leucocidin (PVL).
59
What population is primarily affected by Scalded Skin Syndrome (Ritter's Disease)?
Neonates.
60
Which toxin is responsible for Scalded Skin Syndrome (Ritter's Disease)?
Exfoliative toxin
61
What is the mortality rate for Scalded Skin Syndrome in children versus adults?
Low in children but high in adults.
62
Which toxin is associated with Toxic Shock Syndrome (TSS)?
Enterotoxin F (TSST-1).
63
What is a common association with Toxic Shock Syndrome in women?
Tampon use.
64
Can Toxic Shock Syndrome occur in both sexes?
Yes, if a toxin-producing strain has caused the infection.
65
What is observed under microscopy for Staphylococcus aureus?
Numerous gram-positive cocci in clusters with polymorphonuclear cells.
66
Describe the colony characteristics of Staphylococcus aureus on sheep blood agar.
Round, smooth, white or pigmented (yellow-orange), and β-hemolytic.
67
what organism has Round, smooth, white or pigmented (yellow-orange), and β-hemolytic in SBA
Staphylococcus aureus
68
What is the purpose of using phenylethyl alcohol (PEA) or Columbia colistin-nalidixic acid (CAN) agar in the cultivation of Staphylococcus aureus?
To inhibit the growth of gram-negative bacteria.
69
How does mannitol salt agar differentiate Staphylococcus aureus from other staphylococci?
S. aureus ferments mannitol, leading to yellow colonies due to the pH indicator phenol red.
70
What does the CHROMagar medium indicate when mauve-colored colonies are observed?
The presence of MRSA (methicillin-resistant Staphylococcus aureus).
71
What is the purpose of the coagulase test in the laboratory diagnosis of Staphylococcus aureus?
To separate S. aureus from other coagulase-negative staphylococci.
72
What indicates a positive result in the bound coagulase (clumping factor) test?
Clumping observed in the rapid slide test.
73
What indicates a positive result in the extracellular coagulase (free coagulase) test?
Formation of a clot 1-4 hours after inoculation in the tube coagulase test.
74
what lab diagnosis detects bound coagulase or clumping factor.
slide test
75
What indicates a positive result in the slide coagulase test?
Macroscopic clumping in 10 seconds or less.
76
Confirmatory test of slide test
tube test
77
What does the tube coagulase test detect?
The tube test detects free coagulase.
78
What indicates a positive result in the tube coagulase test?
formation of a clot of any size.
79
How should the tube coagulase test be handled if no clot is observed after 4 hours?
Incubate at room temperature overnight and check again for clot formation.
80
What is the purpose of the catalase test in differentiating bacterial species?
t differentiates catalase-positive micrococcal and staphylococcal species from catalase-negative streptococcal species.
81
What indicates a positive catalase test?
Copious bubbles are produced when hydrogen peroxide is added.
82
What are antibodies to teichoic acid used to detect in serodiagnosis?
They are used to detect long-standing or deep-seated staphylococcal infections such as osteomyelitis.
83
What components are targeted in serodiagnostic tests for Staphylococcus aureus?
Staphylococcal toxins and other staphylococcal proteins, such as Protein A.
84
Are coagulase-negative staphylococci considered normal flora in humans and animals?
Yes, coagulase-negative staphylococci are normal flora in humans and animals.
85
What are some predisposing factors for infections caused by coagulase-negative staphylococci?
Predisposing factors include catheterization, prosthetic device implants, and immunosuppressive therapy.
86
What are the most common species of coagulase-negative staphylococci isolated in clinical settings?
The most common species isolated are Staphylococcus epidermidis and Staphylococcus saprophyticus.
87
What type of colonies does Staphylococcus epidermidis produce on blood agar?
It produces whitish, non-hemolytic colonies on blood agar.
88
SBA: It produces whitish, non-hemolytic colonies on blood agar.
Staphylococcus epidermidis
89
How does Staphylococcus epidermidis differ from Staphylococcus aureus in terms of coagulase production?
Staphylococcus epidermidis is coagulase-negative, whereas Staphylococcus aureus is coagulase-positive.
90
What is the sensitivity of Staphylococcus epidermidis to novobiocin?
Staphylococcus epidermidis is novobiocin sensitive.
91
Where is Staphylococcus epidermidis commonly found in the human body?
skin and mucous membranes
92
What are the primary modes of transmission for Staphylococcus epidermidis infections?
Infections are often endogenous, arising from the patient’s own flora, particularly after implantation of medical devices, and can also be transmitted through direct contact.
93
What is a distinguishing feature of Staphylococcus epidermidis colonies compared to other staphylococci?
Staphylococcus epidermidis colonies are whitish and non-hemolytic on blood agar, and it is sensitive to novobiocin
94
what are the virulence factors of S. epidermidis
Polysaccharide capsule
Slime layer or biofilm
Peptidoglycan
Delta toxin
95
True or false:
Staphylococcus epidermidis is less virulent than Staphylococcus aureus.
True
96
What is the most commonly encountered CoNS
Staphylococcus epidermidis
97
In what settings is Staphylococcus epidermidis most commonly encountered?
It is most commonly encountered in healthcare settings, associated with medical procedures and practices.
98
What type of infections is Staphylococcus epidermidis commonly associated with in patients with medical devices?
Staphylococcus epidermidis is commonly associated with infections related to the implantation of medical devices, such as bacteremia, endocarditis, and septic arthritis.
99
What appearance would you expect to see under the microscope when identifying Staphylococcus epidermidis?
Numerous gram-positive cocci in clusters.
100
SBA: Small to medium-sized, opaque, gray-white colonies; most colonies are non-hemolytic.
Staphylococcus epidermidis
101
What is the novobiocin sensitivity profile of Staphylococcus saprophyticus?
Novobiocin resistant.
102
Difference of S. epidermidis and S. saprophyticus
Novobiocin susceptibility testing
103
Virulence factor of Staphylococcus saprophyticus
Peptidoglycan
104
In which population is Staphylococcus saprophyticus a common cause of urinary tract infections?
Young, sexually active females
105
Is Staphylococcus saprophyticus commonly associated with health care-associated infections similar with S. epidermidis?
No, it is not associated with health care-associated infections
106
What is the rank of Staphylococcus saprophyticus as a cause of urinary tract infections in young females?
It is the second most common cause of UTIs, after E. coli.
107
Sheep Blood Agar; colonies are large, glossy, smooth, opaque, butyrous, convex, and usually white but can range from yellow to orange.
Staphylococcus saprophyticus
108
How is Staphylococcus saprophyticus identified using Novobiocin susceptibility testing?
S. saprophyticus is resistant to Novobiocin, whereas other coagulase-negative staphylococci are susceptible.
109
What is the significance of using a 5mg Novobiocin disk in the laboratory diagnosis of Staphylococcus saprophyticus?
It helps differentiate S. saprophyticus from other coagulase-negative staphylococci based on resistance or susceptibility to Novobiocin.
110
What is a common clinical misidentification issue with Staphylococcus intermedius?
It may be misidentified as S. aureus if only coagulase testing is performed.
111
Which coagulase-positive staphylococcus is commonly associated with skin infections in dogs?
Staphylococcus pseudintermedius.
112
What coagulase-positive staphylococci produce clumping factor and may give a positive slide coagulase test?
Staphylococcus lugdunensis and Staphylococcus schleiferi.
113
Where can Micrococcus be found as part of the normal flora?
Skin, respiratory tract, and other sites in the body.
114
What is the coagulase result for Micrococcus?
Coagulase-negative
115
What is the result of the modified oxidase test for Micrococcus?
Modified oxidase positive, showing a dark blue color within 2 minutes.
116
How is Micrococcus tested for bacitracin susceptibility?
By applying a 0.04 U bacitracin disk on sheep blood Mueller-Hinton medium and observing for a zone of inhibition.
117
What is the result of the bacitracin susceptibility test for Micrococcus?
Micrococcus is susceptible to bacitracin, showing a clear zone of inhibition.
118
How does Micrococcus respond to the furazolidone susceptibility test?
Micrococcus is resistant to furazolidone, with no zone of inhibition.
119
What reagent is used in the modified oxidase test for Micrococcus?
6% tetramethylphenylene diamine hydrochloride in dimethyl sulfoxide.
120
What percentage of Staphylococcus aureus isolates are typically resistant to penicillin?
About 85-90%.
121
What enzyme do Staphylococci produce that contributes to resistance against β-lactam antibiotics?
β-lactamase.
122
What is the term used for methicillin-resistant Staphylococcus aureus?
MRSA (Methicillin-Resistant Staphylococcus aureus) or ORSA (Oxacillin-Resistant Staphylococcus aureus)
123
Why is vancomycin used in the treatment of MRSA infections, and what is the current challenge with this treatment?
Vancomycin is used as an alternative treatment for MRSA infections, but vancomycin resistance is increasing.
124
What is the resistance characteristic of Methicillin-Resistant Staphylococcus epidermidis (MRSE)?
MRSE is resistant to methicillin and is also referred to as Oxacillin-Resistant Staphylococcus epidermidis (ORSE).
125
Cocci
Gram +
Catalase +
Coagulase +
Staphylococcus aureus
126
Cocci
Gram +
Catalase -
Steptococci
127
Cocci
Gram +
Catalase +
Coagulase -
Modified oxidase +
Bacitracin susceptibility (S)
Micrococcus
128
Cocci
Gram +
Catalase +
Coagulase -
Modified oxidase -
Bacitracin susceptibility (R)
Coagulase negative staphylococcus
