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Gram Positive Staphlococci Flashcards

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1
Q

What are the other names for drug-resistant strains of Staphylococcus aureus?

A

MRSA and VRSA

MRSA stands for Methicillin-Resistant Staphylococcus aureus, while VRSA stands for Vancomycin-Resistant Staphylococcus aureus.

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2
Q

What is the shape and arrangement of Staphylococcus aureus?

A

Cocci and irregular, grapelike (‘staph’)

The term ‘staph’ refers to the cluster formation characteristic of this bacterium.

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3
Q

What is the Gram status of Staphylococcus aureus?

A

Positive

This indicates that the bacterium retains the crystal violet stain used in the Gram staining procedure.

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4
Q

What structural features does Staphylococcus aureus have?

A

May have capsules, no flagella, no endospores

Capsules can help in evading the immune response, while the absence of flagella and endospores is typical for this genus.

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5
Q

What is the colony morphology of Staphylococcus aureus?

A

Large, round, yellowish, opaque; can look ‘sticky’

This morphology helps in identifying Staphylococcus aureus in laboratory settings.

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6
Q

What is the optimum temperature for Staphylococcus aureus growth?

A

37°C

This temperature is typical for human pathogens as it matches the human body temperature.

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7
Q

What are the oxygen requirements of Staphylococcus aureus?

A

Facultative anaerobe

This means it can grow in both the presence and absence of oxygen.

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8
Q

Is Staphylococcus aureus tough? True or False?

A

True

It can withstand high salt, extremes in pH, and high temperatures.

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9
Q

What percentage of Staphylococcus aureus strains have penicillinase?

A

95%

This enzyme makes them resistant to penicillin and ampicillin.

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10
Q

What type of hemolysis is caused by Staphylococcus aureus?

A

Beta-hemolysis

This is primarily caused by alpha-toxin and beta-toxin.

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11
Q

Fill in the blank: Staphylococcus aureus can withstand _______.

A

high salt, extremes in PH, and high temperatures

This characteristic is significant for its survival in various environments.

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12
Q

What toxins are associated with the hemolysis caused by Staphylococcus aureus?

A
  • Alpha-toxin
  • Beta-toxin

These toxins contribute to its pathogenicity and ability to lyse red blood cells.

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13
Q

Where is S. aureus commonly found?

A

Present in most environments frequented by humans, including fomites

Fomites are inanimate objects or surfaces that can carry infectious agents.

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14
Q

What percentage of healthy adults carry S. aureus?

A

20-60%

Carriage is mostly in the anterior nares, skin, nasopharynx, and intestine.

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15
Q

How is S. aureus transmitted?

A

Touch, fomites, medical equipment

These methods of transmission highlight the importance of hygiene and sanitation.

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16
Q

Is S. aureus an opportunistic or true pathogen?

A

Opportunistic

It can cause infections under certain conditions, such as poor hygiene and nutrition.

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17
Q

What factors can lead to S. aureus infections?

A

Poor hygiene, nutrition, tissue injury, preexisting primary infection, diabetes, immunodeficiency

These conditions increase susceptibility to infection.

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18
Q

Fill in the blank: S. aureus is present in _____ environments frequented by humans.

A

[most]

This includes various surfaces and objects that people frequently come into contact with.

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19
Q

What is coagulase?

A

An enzyme that coagulates blood plasma

Coagulase is a key virulence factor of Staphylococcus aureus.

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20
Q

What is the function of hyaluronidase?

A

Digests connective tissue of the host

Hyaluronidase facilitates the spread of bacteria through tissues.

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21
Q

What does lipase do?

A

Digests oils, allowing bacteria to more easily colonize the skin

Lipase enhances the ability of bacteria to thrive on skin.

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22
Q

What is penicillinase?

A

An enzyme that inactivates penicillin, rendering the bacterium resistant

This enzyme contributes to antibiotic resistance in bacteria.

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23
Q

What are hemolysins?

A

Toxins that lyse red blood cells

Hemolysins can be classified into alpha, beta, gamma, and delta types.

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24
Q

What is leukocidin?

A

A toxin that lyses neutrophils and macrophages

Leukocidin helps bacteria evade the immune response.

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25
What do enterotoxins induce?
Nausea, vomiting, and diarrhea ## Footnote Enterotoxins are associated with food poisoning by Staphylococcus aureus.
26
What is the effect of toxic shock syndrome toxin?
Induces fever, vomiting, rash, and organ damage ## Footnote This toxin is a major factor in toxic shock syndrome.
27
What is the function of catalase?
Converts hydrogen peroxide into harmless water and bubbles ## Footnote Catalase protects bacteria from oxidative damage.
28
What is the purpose of the coagulase test?
To identify Staphylococcus aureus which produces the enzyme coagulase ## Footnote Coagulase is a virulence factor that helps in the diagnosis of S. aureus infections.
29
What does coagulase do in plasma?
Converts soluble fibrinogen to insoluble fibrin ## Footnote The fibrin coats bacterial cells, protecting them from opsonization and phagocytosis.
30
What are the two forms of coagulase produced by Staphylococcus aureus?
* Bound coagulase * Free coagulase
31
What is detected in the slide coagulase test?
Bound coagulase or clumping factor ## Footnote This test results in clumping if positive.
32
What is detected in the tube coagulase test?
Free coagulase ## Footnote This test measures the ability to form clots in a liquid medium.
33
True or False: A positive slide coagulase test shows clumps.
True
34
Fill in the blank: The coagulase test helps to identify _______.
Staphylococcus aureus
35
What is the significance of the fibrin coat produced by coagulase?
It protects bacterial cells from opsonization and phagocytosis ## Footnote This is crucial for the survival of the bacteria in the host.
36
What does MRSA stand for?
Methicillin-resistant S. aureus ## Footnote MRSA is a type of bacteria that is resistant to several antibiotics, making infections harder to treat.
37
What is the death rate for MRSA infections without bacteremia?
0.2% ## Footnote Bacteremia refers to the presence of bacteria in the blood, which significantly increases the risk of death.
38
What is the death rate for MRSA infections with bacteremia?
60% ## Footnote This highlights the severe consequences of MRSA infections that enter the bloodstream.
39
How can initial MRSA infections be confused?
They can be confused with spider bites ## Footnote It is important to learn the differences in symptoms to ensure proper treatment.
40
What is an abscess?
A tender mass filled with pus due to infection ## Footnote Abscesses are usually red, warm, and painful.
41
What is the typical treatment for abscesses caused by MRSA?
Surgically perforated and cleaned ## Footnote This involves puncturing the abscess to allow pus to drain and then cleaning the wound to prevent further infection.
42
Fill in the blank: MRSA carries multiple _______.
resistance ## Footnote This refers to MRSA's ability to resist treatment from various antibiotics.
43
What is a cutaneous abscess?
An abscess that penetrates the skin after an initial cut or abrasion ## Footnote This condition is often associated with MRSA infections.
44
What can happen if a staphylococcal abscess goes deeper?
It can go from localized to systemic
45
What are localized cutaneous infections caused by Staphylococcus aureus?
Infections that invade skin through wounds, follicles, or glands
46
What is a furuncle?
A boil; inflammation of hair follicle or sebaceous gland that progresses into abscess or pustule
47
What is a carbuncle?
A larger and deeper lesion created by aggregation and interconnection of a cluster of furuncles
48
What is impetigo?
Bubble-like swellings that can break and peel away; most common in newborns
49
What is food intoxication in the context of staphylococcal disease?
Ingestion of heat stable enterotoxins leading to gastrointestinal distress
50
What is staphylococcal scalded skin syndrome?
A toxin-induced condition causing bright red flush, blisters, then desquamation of the epidermis
51
What is toxic shock syndrome?
Toxemia leading to shock and organ failure
52
What is osteomyelitis?
An infection established in the metaphysis that leads to abscess formation. ## Footnote Osteomyelitis is often associated with systemic infections caused by bacteria.
53
What is bacteremia?
A condition where bacteria from another infected site or medical devices enter the bloodstream, potentially leading to endocarditis. ## Footnote Bacteremia can be a serious complication of infections.
54
What type of infections do coagulase-negative staphylococci, such as Staphylococcus epidermidis, commonly cause?
Healthcare-associated and opportunistic infections in immunocompromised patients. ## Footnote These infections can include endocarditis, bacteremia, and urinary tract infections.
55
Where does Staphylococcus epidermidis typically reside in the human body?
On skin and mucous membranes. ## Footnote It is part of the normal flora but can cause infections when the skin barrier is compromised.
56
Fill in the blank: Staphylococcus epidermidis may cause _______ infections by penetrating through broken skin.
wound
57
True or False: Staphylococcus epidermidis is primarily associated with community-acquired infections.
False ## Footnote It is primarily linked to healthcare-associated infections.
58
What is a potential complication of bacteremia?
Endocarditis. ## Footnote Endocarditis is an infection of the inner lining of the heart, which can be life-threatening.
59
What area of the bone is primarily affected in osteomyelitis?
Metaphysis. ## Footnote This is the region where blood supply is rich, making it prone to infection.
60
What is the primary origin of bacteria in cases of bacteremia?
From another infected site or medical devices.
61
What are the key functions of the spongy bone?
Provides structural support and houses bone marrow. ## Footnote Spongy bone is found mainly at the ends of long bones and in the interiors of others.
62
List two infections caused by Staphylococcus epidermidis.
* Endocarditis * Urinary tract infection
63
What is the shape and arrangement of Staphylococcus epidermidis?
Cocci and irregular, grapelike ('staph') ## Footnote Characteristic arrangement of cocci bacteria.
64
What is the Gram status of Staphylococcus epidermidis?
Gram positive ## Footnote Indicates the type of cell wall structure.
65
What structural features does Staphylococcus epidermidis have?
May have capsules, no flagella, no endospores ## Footnote Capsules can contribute to virulence.
66
What is the colony morphology of Staphylococcus epidermidis?
White, raised ## Footnote Typical appearance on culture media.
67
What is the optimum temperature range for Staphylococcus epidermidis?
30 - 37°C ## Footnote Optimal growth temperature for this bacterium.
68
What are the oxygen requirements of Staphylococcus epidermidis?
Facultative anaerobe ## Footnote Can grow in both the presence and absence of oxygen.
69
Is Staphylococcus epidermidis tough and resistant to anything?
Yes, resistant to high salt and has natural antibiotic resistance to many antibiotics ## Footnote This resistance can complicate treatment.
70
Where is Staphylococcus epidermidis commonly located?
Human skin and nose ## Footnote Normal flora of the human body.
71
How is Staphylococcus epidermidis transmitted?
Touch, fomites, medical equipment ## Footnote Common routes of transmission in healthcare settings.
72
Is Staphylococcus epidermidis an opportunistic or true pathogen?
Opportunistic ## Footnote Among the most common nosocomial infections.
73
What enzyme does S. epidermidis produce to degenerate hydrogen peroxide?
Catalase ## Footnote Catalase converts hydrogen peroxide into oxygen and water.
74
What is the function of urease in S. epidermidis?
Converts urea into ammonium ## Footnote Urease activity can influence local pH and contribute to infection processes.
75
What does the Polysaccharide Intercellular Adhesin do?
Allows S. epidermidis to stick to biofilms ## Footnote This adhesion is crucial for the formation of biofilms on medical devices.
76
What are lipolytic enzymes associated with in S. epidermidis?
Lead to acne scars ## Footnote These enzymes damage the sebaceous gland, resulting in scarring.
77
What is a key characteristic that differentiates S. epidermidis from S. aureus?
Coagulase negative ## Footnote Coagulase status is a critical factor in identifying Staphylococcus species.
78
What hemolytic activity is associated with S. epidermidis?
Hemolysin negative ## Footnote This indicates that S. epidermidis does not lyse red blood cells.
79
What clinical concern is associated with S. epidermidis contamination?
Contamination of plastics, especially medical equipment and implants ## Footnote This can lead to serious infections, particularly in immunocompromised patients.
80
How can S. epidermidis migrate in the body?
Can migrate to heart valves ## Footnote This poses a risk for endocarditis in susceptible individuals.
81
What is the role of S. epidermidis in acne vulgaris?
Involved in the condition following initial colonization by Propionibacterium acnes ## Footnote S. epidermidis exacerbates the condition through its lipolytic enzymes.
82
What are biofilms?
Clusters of bacteria and other microbes held together by slime layers, capsules, and other molecules ## Footnote Biofilms can form on various surfaces and are significant in medical and environmental contexts.
83
Name two infections associated with Staphylococci biofilms.
* Osteomyelitis * Endocarditis ## Footnote Osteomyelitis is an infection of the bone, while endocarditis affects the heart's inner lining.
84
How do biofilms affect medical devices?
They can lead to medical device infections ## Footnote Biofilms can form on catheters and prosthetic devices, complicating treatment.
85
Fill in the blank: Biofilms are held together by _______.
[slime layers, capsules, and other molecules] ## Footnote These structures provide stability and protection to the bacterial community.

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