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Microbio > Gram Positive Staphlococci > Flashcards

Gram Positive Staphlococci Flashcards

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
Q

What do enterotoxins induce?

A

Nausea, vomiting, and diarrhea

Enterotoxins are associated with food poisoning by Staphylococcus aureus.

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26
Q

What is the effect of toxic shock syndrome toxin?

A

Induces fever, vomiting, rash, and organ damage

This toxin is a major factor in toxic shock syndrome.

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27
Q

What is the function of catalase?

A

Converts hydrogen peroxide into harmless water and bubbles

Catalase protects bacteria from oxidative damage.

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28
Q

What is the purpose of the coagulase test?

A

To identify Staphylococcus aureus which produces the enzyme coagulase

Coagulase is a virulence factor that helps in the diagnosis of S. aureus infections.

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29
Q

What does coagulase do in plasma?

A

Converts soluble fibrinogen to insoluble fibrin

The fibrin coats bacterial cells, protecting them from opsonization and phagocytosis.

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30
Q

What are the two forms of coagulase produced by Staphylococcus aureus?

A
  • Bound coagulase
  • Free coagulase
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31
Q

What is detected in the slide coagulase test?

A

Bound coagulase or clumping factor

This test results in clumping if positive.

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32
Q

What is detected in the tube coagulase test?

A

Free coagulase

This test measures the ability to form clots in a liquid medium.

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33
Q

True or False: A positive slide coagulase test shows clumps.

A

True

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34
Q

Fill in the blank: The coagulase test helps to identify _______.

A

Staphylococcus aureus

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35
Q

What is the significance of the fibrin coat produced by coagulase?

A

It protects bacterial cells from opsonization and phagocytosis

This is crucial for the survival of the bacteria in the host.

36
Q

What does MRSA stand for?

A

Methicillin-resistant S. aureus

MRSA is a type of bacteria that is resistant to several antibiotics, making infections harder to treat.

37
Q

What is the death rate for MRSA infections without bacteremia?

A

0.2%

Bacteremia refers to the presence of bacteria in the blood, which significantly increases the risk of death.

38
Q

What is the death rate for MRSA infections with bacteremia?

A

60%

This highlights the severe consequences of MRSA infections that enter the bloodstream.

39
Q

How can initial MRSA infections be confused?

A

They can be confused with spider bites

It is important to learn the differences in symptoms to ensure proper treatment.

40
Q

What is an abscess?

A

A tender mass filled with pus due to infection

Abscesses are usually red, warm, and painful.

41
Q

What is the typical treatment for abscesses caused by MRSA?

A

Surgically perforated and cleaned

This involves puncturing the abscess to allow pus to drain and then cleaning the wound to prevent further infection.

42
Q

Fill in the blank: MRSA carries multiple _______.

A

resistance

This refers to MRSA’s ability to resist treatment from various antibiotics.

43
Q

What is a cutaneous abscess?

A

An abscess that penetrates the skin after an initial cut or abrasion

This condition is often associated with MRSA infections.

44
Q

What can happen if a staphylococcal abscess goes deeper?

A

It can go from localized to systemic

45
Q

What are localized cutaneous infections caused by Staphylococcus aureus?

A

Infections that invade skin through wounds, follicles, or glands

46
Q

What is a furuncle?

A

A boil; inflammation of hair follicle or sebaceous gland that progresses into abscess or pustule

47
Q

What is a carbuncle?

A

A larger and deeper lesion created by aggregation and interconnection of a cluster of furuncles

48
Q

What is impetigo?

A

Bubble-like swellings that can break and peel away; most common in newborns

49
Q

What is food intoxication in the context of staphylococcal disease?

A

Ingestion of heat stable enterotoxins leading to gastrointestinal distress

50
Q

What is staphylococcal scalded skin syndrome?

A

A toxin-induced condition causing bright red flush, blisters, then desquamation of the epidermis

51
Q

What is toxic shock syndrome?

A

Toxemia leading to shock and organ failure

52
Q

What is osteomyelitis?

A

An infection established in the metaphysis that leads to abscess formation.

Osteomyelitis is often associated with systemic infections caused by bacteria.

53
Q

What is bacteremia?

A

A condition where bacteria from another infected site or medical devices enter the bloodstream, potentially leading to endocarditis.

Bacteremia can be a serious complication of infections.

54
Q

What type of infections do coagulase-negative staphylococci, such as Staphylococcus epidermidis, commonly cause?

A

Healthcare-associated and opportunistic infections in immunocompromised patients.

These infections can include endocarditis, bacteremia, and urinary tract infections.

55
Q

Where does Staphylococcus epidermidis typically reside in the human body?

A

On skin and mucous membranes.

It is part of the normal flora but can cause infections when the skin barrier is compromised.

56
Q

Fill in the blank: Staphylococcus epidermidis may cause _______ infections by penetrating through broken skin.

A

wound

57
Q

True or False: Staphylococcus epidermidis is primarily associated with community-acquired infections.

A

False

It is primarily linked to healthcare-associated infections.

58
Q

What is a potential complication of bacteremia?

A

Endocarditis.

Endocarditis is an infection of the inner lining of the heart, which can be life-threatening.

59
Q

What area of the bone is primarily affected in osteomyelitis?

A

Metaphysis.

This is the region where blood supply is rich, making it prone to infection.

60
Q

What is the primary origin of bacteria in cases of bacteremia?

A

From another infected site or medical devices.

61
Q

What are the key functions of the spongy bone?

A

Provides structural support and houses bone marrow.

Spongy bone is found mainly at the ends of long bones and in the interiors of others.

62
Q

List two infections caused by Staphylococcus epidermidis.

A
  • Endocarditis
  • Urinary tract infection
63
Q

What is the shape and arrangement of Staphylococcus epidermidis?

A

Cocci and irregular, grapelike (‘staph’)

Characteristic arrangement of cocci bacteria.

64
Q

What is the Gram status of Staphylococcus epidermidis?

A

Gram positive

Indicates the type of cell wall structure.

65
Q

What structural features does Staphylococcus epidermidis have?

A

May have capsules, no flagella, no endospores

Capsules can contribute to virulence.

66
Q

What is the colony morphology of Staphylococcus epidermidis?

A

White, raised

Typical appearance on culture media.

67
Q

What is the optimum temperature range for Staphylococcus epidermidis?

A

30 - 37°C

Optimal growth temperature for this bacterium.

68
Q

What are the oxygen requirements of Staphylococcus epidermidis?

A

Facultative anaerobe

Can grow in both the presence and absence of oxygen.

69
Q

Is Staphylococcus epidermidis tough and resistant to anything?

A

Yes, resistant to high salt and has natural antibiotic resistance to many antibiotics

This resistance can complicate treatment.

70
Q

Where is Staphylococcus epidermidis commonly located?

A

Human skin and nose

Normal flora of the human body.

71
Q

How is Staphylococcus epidermidis transmitted?

A

Touch, fomites, medical equipment

Common routes of transmission in healthcare settings.

72
Q

Is Staphylococcus epidermidis an opportunistic or true pathogen?

A

Opportunistic

Among the most common nosocomial infections.

73
Q

What enzyme does S. epidermidis produce to degenerate hydrogen peroxide?

A

Catalase

Catalase converts hydrogen peroxide into oxygen and water.

74
Q

What is the function of urease in S. epidermidis?

A

Converts urea into ammonium

Urease activity can influence local pH and contribute to infection processes.

75
Q

What does the Polysaccharide Intercellular Adhesin do?

A

Allows S. epidermidis to stick to biofilms

This adhesion is crucial for the formation of biofilms on medical devices.

76
Q

What are lipolytic enzymes associated with in S. epidermidis?

A

Lead to acne scars

These enzymes damage the sebaceous gland, resulting in scarring.

77
Q

What is a key characteristic that differentiates S. epidermidis from S. aureus?

A

Coagulase negative

Coagulase status is a critical factor in identifying Staphylococcus species.

78
Q

What hemolytic activity is associated with S. epidermidis?

A

Hemolysin negative

This indicates that S. epidermidis does not lyse red blood cells.

79
Q

What clinical concern is associated with S. epidermidis contamination?

A

Contamination of plastics, especially medical equipment and implants

This can lead to serious infections, particularly in immunocompromised patients.

80
Q

How can S. epidermidis migrate in the body?

A

Can migrate to heart valves

This poses a risk for endocarditis in susceptible individuals.

81
Q

What is the role of S. epidermidis in acne vulgaris?

A

Involved in the condition following initial colonization by Propionibacterium acnes

S. epidermidis exacerbates the condition through its lipolytic enzymes.

82
Q

What are biofilms?

A

Clusters of bacteria and other microbes held together by slime layers, capsules, and other molecules

Biofilms can form on various surfaces and are significant in medical and environmental contexts.

83
Q

Name two infections associated with Staphylococci biofilms.

A
  • Osteomyelitis
  • Endocarditis

Osteomyelitis is an infection of the bone, while endocarditis affects the heart’s inner lining.

84
Q

How do biofilms affect medical devices?

A

They can lead to medical device infections

Biofilms can form on catheters and prosthetic devices, complicating treatment.

85
Q

Fill in the blank: Biofilms are held together by _______.

A

[slime layers, capsules, and other molecules]

These structures provide stability and protection to the bacterial community.

Microbio (5 decks)

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