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Bacte LEC > Staphylococcus: Additional > Flashcards

Staphylococcus: Additional Flashcards

1
Q

What is Staphylococcus aureus (SAU)?

A

An opportunistic pathogen responsible for numerous infections, ranging from mild to life-threatening. It is an important community-acquired pathogen with increasing drug resistance.

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2
Q

What are some virulence factors (VF) of Staphylococcus aureus?

A

Examples include enterotoxins, cytolytic toxins, protein A, and exfoliative toxins.

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3
Q

What is enterotoxin?

A

Heat-stable exotoxins that cause diarrhea and vomiting. They are categorized into groups A to E and G to J.

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4
Q

How stable are enterotoxins?

A

Stable at 100°C for 30 minutes. Reheating contaminated food does not prevent disease.

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5
Q

What are the main causes of food poisoning related to enterotoxins?

A

Mainly Enterotoxin A, B, and D.

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6
Q

What enterotoxins are associated with Toxic Shock Syndrome?

A

Enterotoxin B and C, G and I.

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7
Q

What is Staphylococcal Pseudomembranous Enterocolitis?

A

Caused by Enterotoxin B, which acts as a superantigen.

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8
Q

What is Toxic Shock Syndrome Toxin-1 (TSST-1)?

A

Previously known as Enterotoxin F, it is a chromosomal-mediated toxin causing the majority of menstruating-associated TSS and approximately 50% of non-menstruating cases.

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9
Q

What is the role of TSST-1 as a superantigen?

A

It stimulates T-cell proliferation and the production of a large number of cytokines.

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10
Q

How does TSST-1 affect endothelial cells?

A

At low concentrations, it causes leakage; at higher concentrations, it is cytotoxic to these cells.

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11
Q

How is TSST-1 absorbed in the body?

A

Absorbed through the vaginal mucosa, leading to systemic effects, particularly with tampon usage.

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12
Q

What is exfoliative toxin?

A

Also known as Epidermolytic Toxin, it has two types: Exfo Tox A and Exfo Tox B.

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13
Q

What condition is caused by exfoliative toxins?

A

Staphylococcal Scalded Skin Syndrome (SSS), also known as Ritter’s Disease, most common in newborns and children under 5 years of age.

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14
Q

What are cytolytic toxins?

A

Toxins that affect RBCs and leukocytes, including hemolysins and leukocidins.

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15
Q

What types of hemolysins does SAU produce?

A

Four types: alpha, beta, gamma, and delta.

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16
Q

What is the effect of A-hemolysin?

A

It damages platelets and macrophages, causing severe tissue damage.

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17
Q

What is B-hemolysin also known as?

A

Sphingomyelinase C or Hot-Cold Lysin, which acts on sphingomyelin in erythrocyte membranes.

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18
Q

What is the significance of gamma-hemolysin?

A

Found only in Panton-Valentine Leukocidin (PVL), it is lethal to polymorphonuclear leukocytes and suppresses phagocytosis.

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19
Q

What enzymes are produced by Staphylococcus aureus?

A

Examples include coagulase, protease, hyaluronidase, and lipase.

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20
Q

What is the role of hyaluronidase?

A

It hydrolyzes hyaluronic acid in connective tissues, allowing bacteria to spread during infection.

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21
Q

What is the function of protein A?

A

Identified in the cell wall of SAU, it binds the Fc portion of Immunoglobulin G (IgG), blocking phagocytosis and negating IgG’s protective effects.

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22
Q

What is the primary reservoir for Staphylococci in humans?

A

Human Nares

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23
Q

Where can Staphylococci colonize in the human body?

A

Vagina, pharynx, axilae, and other skin surfaces

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24
Q

Where is nasal carriage of Staphylococci common?

A

In hospitals, particularly in patients

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25
Q

What factors increase colonization of Staphylococci in patients?

A

Frequent contact with hospital workers and certain medical conditions

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26
Q

In which settings do patients commonly develop Staphylococci infections?

A

Nurseries, burn units, and after surgery or other invasive procedures

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27
Q

What are key infection control practices for Staphylococci?

A

Hand hygiene, environmental cleaning and disinfection, use of personal protective equipment

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28
Q

What was the increase in Methicillin-Resistant Staphylococcus aureus (MRSA) infections from 2011 to 2016?

A

Increased from 4.1% to 9.2%

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29
Q

How is Staphylococci transmitted?

A

Direct contact with unwashed, contaminated hands and contact with inanimate objects (fomites)

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30
Q

What is decolonization in the context of Staphylococci?

A

A process to reduce colonization for specific populations

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31
Q

What are Staphylococci?

A

Catalase (+), gram (+) cocci; spherical cells (0.5 to 1.5 um) that appear singly, in pairs, and in clusters.

Greek: staphle - bunches of grapes.

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32
Q

What is the family classification of Staphylococci?

A

Member of the family ‘Staphylococcaceae’.

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33
Q

What are the characteristics of Staphylococci?

A

Nonmotile, non-spore forming, and aerobic or facultatively anaerobic; few strains are obligate anaerobes.

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34
Q

What is the colony appearance of Staphylococci?

A

Medium size (4-8mm) colonies after 18-24hr incubation; cream-colored, white, or rarely light gold, and ‘buttery looking’.

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35
Q

What are Small Colony Variants (SCV)?

A

Rare strains that are fastidious, requiring CO2, Hemin, or menadione for growth; colonies are 1/10 size of wild-type strain even after 48hrs of incubation.

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36
Q

What is the clinical significance of Staphylococci?

A

Common isolates in the clinical laboratory, responsible for numerous suppurative infections; normal inhabitants of the skin and mucus membranes of humans and other animals.

37
Q

How are Staphylococci initially differentiated?

A

By the ‘coagulase test’.

38
Q

What does a positive coagulase test indicate?

A

A clot formed in a tube containing plasma caused by ‘staphylocoagulase’.

Example of Coag (+): S. Aureus, S. Intermedius, S. pseudintermedius, S. Hyicus, S. Delphini, S. Lutrae, S. Agnetis, and some strains of S. Schleiferi.

39
Q

What is the clumping factor?

A

Causes bacterial cells to agglutinate in plasma; basis for ‘slide coag (+)’; considered an obsolete test.

40
Q

What is the purpose of the Tube Coag Test?

A

Only used for definitive testing.

41
Q

What assays provide presumptive identification of S. Aureus?

A

Rapid latex and Hemagglutination assays.

42
Q

What is the most clinically significant species of Staphylococci?

A

S. Aureus (SAU).

43
Q

What infections are caused by S. Aureus?

A

Causes various cutaneous infections and purulent abscesses, including impetigo and cellulitis.

Impetigo and Cellulitis: superficial skin and soft tissue infection.

44
Q

What are carbuncles?

A

Cutaneous infections that can progress to deeper abscesses, producing bacteremia and septicemia.

45
Q

What toxin-induced diseases are caused by S. Aureus?

A

Common cause of infective endocarditis and diseases such as food poisoning, ‘Scalded Skin Syndrome’ (SSS) and ‘Toxic Shock Syndrome’ (TSS).

46
Q

What are Coagulase-negative Staphylococci (CoNS)?

A

Includes S. Epidermidis, S. Saprophyticus, S. Lugdunensis, and S. Haemolyticus.

47
Q

What infections does S. Epidermidis cause?

A

Causes healthcare-acquired or nosocomial infections.

48
Q

What is the association of S. Saprophyticus?

A

Mainly associated with UTIs in young women sex workers.

49
Q

What infections are linked to S. Haemolyticus?

A

Recovered from wounds, septicemia, UTI, and native valve infection.

50
Q

What is the significance of S. Lugdunensis?

A

Like S. Aureus, it is slide coag (+) and needs tube coag test for differentiation; can be an aggressive pathogen associated with catheter-related bacteremia and endocarditis.

51
Q

What are the types of Micrococci?

A

Catalase (+), coagulase (-), gram (+) cocci found in the environment and as members of indigenous skin microbiota.

52
Q

How are Micrococci differentiated from CoNS?

A

Easily differentiated; they produce a yellow pigment.

53
Q

What are other cat (+), gram (+) cocci recovered from humans?

A

Includes ‘Rothia mucilaginosa’ and ‘Alloiococcus otitis’.

54
Q

What factors determine SAU infections?

A
  1. Virulence factor
  2. Size of the infectious dose
  3. Status of the host’s immune system
55
Q

How are SAU infections initiated?

A

When a breach of the skin or mucosal barrier allows staphylococci access to adjoining tissues or the bloodstream.

56
Q

What is the normal defense mechanism against SAU infections?

A

Individuals with a healthy immune system can combat the infection more easily than those with impaired immune systems.

57
Q

What happens once initial barriers are crossed in SAU infections?

A

It activates the host’s acute inflammatory response, leading to the proliferation and activation of polymorphonuclear cells.

58
Q

What is a focal lesion in the context of SAU infections?

A

Production of toxins and enzymes.

59
Q

What type of infections are caused by SAU?

A

Suppurative infections (discharge or pus).

60
Q

What is an abscess in SAU infections?

A

An abscess is filled with pus and surrounded by necrotic tissues and damaged leukocytes.

61
Q

What are benign skin infections caused by SAU?

A

Folliculitis, furuncles, and bullous impetigo.

62
Q

What are opportunistic infections in SAU infections?

A

Infections that occur from previous skin infections such as cuts, burns, and surgical incisions.

63
Q

What is folliculitis?

A

Relatively mild inflammation of a hair follicle or oil gland; infected area is raised and red.

64
Q

What are furuncles?

A

Large, raised, superficial abscesses that are an extension of folliculitis.

65
Q

What are carbuncles?

A

Large, more invasive lesions that develop from multiple furuncles, can progress into deeper tissues; present with fever and chills.

66
Q

How does bullous impetigo differ from nonbullous impetigo?

A

Staphylococcal pustules are larger and surrounded by a small zone of erythema.

67
Q

What is impetigo?

A

A highly contagious infection easily spread by direct contact, fomites, or auto inoculation.

68
Q

What can increase colonization of SAU?

A

Blocked hair follicles, sebaceous glands, and sweat glands.

69
Q

How can SAU infections be misidentified?

A

They can be misidentified as insect or spider bites.

70
Q

Who is particularly predisposed to developing staphylococcal infections?

A

Immunocompromised individuals, particularly those undergoing chemotherapy.

71
Q

What is Scalded Skin Syndrome (SSS)?

A

A bullous exfoliative dermatitis primarily in newborns and previously healthy young children.

72
Q

What causes Scalded Skin Syndrome?

A

Staphylococcal exfoliative or epidermolytic toxin; present at a lesion distant from the site of exfoliation.

73
Q

What is the mortality rate of Scalded Skin Syndrome in children and adults?

A

Low (0%-7%) in children; can be 50% in adults.

74
Q

What is another name for Scalded Skin Syndrome?

A

Ritter’s Disease.

75
Q

What characterizes Scalded Skin Syndrome?

A

Cutaneous erythema followed by profuse peeling of the epidermal layer of the skin.

76
Q

What is the healing time for Scalded Skin Syndrome?

A

Complete healing occurs after around 10 days.

77
Q

What must Scalded Skin Syndrome be differentiated from?

A

Toxic Epidermal Necrolysis (TEN).

78
Q

What is Toxic Shock Syndrome?

A

A rare but potentially fatal multisystem disease; localized infection.

79
Q

What are the symptoms of Toxic Shock Syndrome?

A

Sudden onset of fever, chills, vomiting, diarrhea, muscle aches, and rash.

80
Q

When was Toxic Shock Syndrome first described?

A

In 1978, associated with women using highly absorbent tampons.

81
Q

What are the two categories of Toxic Shock Syndrome?

A

Menstruating-Associated and Nonmenstruating-Associated.

82
Q

What is the source of contamination in Staphylococcal Food Poisoning?

A

Infected food handler.

83
Q

What are the symptoms of Staphylococcal Food Poisoning?

A

Gastrointestinal disturbances appearing rapidly at 2-8 hours and resolving within 24-48 hours.

84
Q

What is Staphylococcal Bacteremia?

A

Observed among intravenous drug users; contaminated needles or from a focal lesion.

85
Q

What can local SAU infections progress to?

A

Bacteremia leading to secondary pneumonia, endocarditis, or bone infection.

86
Q

What is Staphylococcal Pneumonia?

A

Occurs secondary to influenza virus infection; characterized by multiple abscesses and focal lesions.

87
Q

What are the symptoms of Staphylococcal Osteomyelitis?

A

Fever, chills, swelling, and pain.

88
Q

What is Septic Arthritis?

A

SAU infection in children; history of rheumatoid arthritis, diabetes mellitus, or recent joint surgery.

Bacte LEC (51 decks)

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