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Microbiology Exam 3 > Chapter 19: Objectives > Flashcards

Chapter 19: Objectives Flashcards

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1
Q

Contrast the virulence of Staphylococcus aureus with that of Staphylococcus epidermidis in humans.

A
  • S. aureus protein A positive, S. epidermidis protein A negative
  • S. Aureus coagulase positive, S. epidermidis negative
  • S. aureus slime layer positive, S. epidermidis positive
  • S. Aureus catalase positive, S. epidermidis positive
  • S. aureus hyaluronidase positive, S. epidermidis hyaluronidase negative
  • S. aureus staphylokinase positive, S. epidermidis staphylokinase negative
  • S. aureus lipase positive, S. epidermidis lipase positive
  • S, aureus β-lactamase positive, S. epidermidis negative
  • S. aureus toxins positive, S. epidermidis negative
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2
Q

Discuss the structural features, enzymes, and toxins of Staphylococcus that enable it to be pathogenic.

A
  • Protein A
  • Coagulase
  • Slime layer
  • Hyaluronidase
  • Staphylokinase
  • Lipases
  • β - lactamase
  • Cytolytic toxins
  • Exfoliative toxins
  • Enterotoxins
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3
Q

Protein A (staphylococcus structural defense against phagocytosis; antiphagocytic)

A

Coats the cell surface; interferes with humoral immune responses

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4
Q

Bound coagulase (staphylococcus structural defense against phagocytosis; antiphagocytic)

A
  • Converts fibrinogen into fibrin molecules
  • Fibrin clots hide the bacteria from phagocytic cells
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5
Q

Slime layers (staphylococcus structural defense against phagocytosis; antiphagocytic)

A

Capsules:
- Inhibit leukocyte chemotaxis and phagocytosis
- Facilitate attachment of Staphylococcus to surfaces

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6
Q

Enzymes (staphylococcus)

A
  • Secreted by the pathogen
  • Dissolve structural chemicals in the body
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7
Q

Cell free coagulase (Staphylococcus enzymes)

A

Triggers blood clotting

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8
Q

Hyaluronidase (staphylococcus enzymes)

A
  • Breaks down hyaluronic acid
  • Enables the bacteria to spread between cells
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9
Q

Staphylokinase (staphylococcus enzymes)

A
  • Dissolves fibrin threads in blood clots
  • Allows Staphylococcus Aureus to free itself from clots
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10
Q

Lipases (Staphylococcus enzymes)

A
  • Digest lipids
  • Allow Staphylococcus to grow in skin and in oil glands
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11
Q

β-lactamase (Staphylococcus enzymes)

A
  • Breaks down penicillin
  • Allows bacteria to survive treatment with β- lactam antimicrobial drugs
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12
Q

Toxins (Staphylococcus)

A

Chemicals that harm tissues or trigger host immune responses that cause damage
- Cytolytic toxins
- Exfoliative toxins
- Toxic- shock syndrome toxin
- Enterotoxins

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13
Q

Toxemia (staphylococcus toxins)

A

Refers to toxins in the bloodstream that are carried beyond the site of infection

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14
Q

Cytolytic toxins (staphylococcus toxins)

A
  • Alpha, beta, gama, delta, and leukocidin
  • Disrupts the cytoplasmic membrane of a variety of cells
  • Leukocidin can lyse leukocytes specifically
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15
Q

Exfoliative toxins (staphylococcus toxins)

A
  • Cause skin cells to separate and slough off
  • Exfoliative toxin causes reddened patches of the epidermis to slough off
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16
Q

Toxic-shock syndrome toxin (staphylococcus toxins)

A

Causes toxic shock syndrome

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17
Q

Enterotoxins (staphylococcus toxins)

A
  • A, B, C, D, and E
  • Stimulate symptoms associated with food poisoning
  • Are heat stable, active at 100℃ for up to 30 minutes
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18
Q

What are the three categories of Staphylococcus diseases?

A
  • Noninvasive (food poisoning)
  • Cutaneous (various skin conditions)
  • Systemic (Variety of infections when bacteria invade deeper tissues)
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19
Q

Describe the symptoms of staphylococcus food poisoning

A

Consumed bacteria do not continue to produce disease/ toxins, so the course of the disease is rapid usually lasting 24 hours or less.
- Nausea
- Severe vomiting
- Diarrhea
- Headache
- Sweating
- Abdominal pain

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20
Q

List the six pyogenic lesions caused by Staphylococcus aureus.

A

Cutaneous: various skin conditions
- Scaled skin syndrome
- Impetigo
- Folliculitis
- Sty
- Furuncle
- Carbuncle

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21
Q

Describe scaled skin syndrome

A
  • Caused by S. aureus
  • Exfoliative toxin causes reddened patches of the epidermis to slough off
  • Blisters contain clear fluid lacking bacteria or WBC
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22
Q

Describe impetigo

A
  • 80% caused by S. aureus
  • Reddened patches of skin become pus filled vesicles that eventually crust over
  • Generally affects children
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23
Q

Describe folliculitis

A
  • Infection of a hair follicle in which the base of the follicle becomes red, swollen, and pus filled
  • Staphylococcus aureus (cutaneous lesion)
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24
Q

Describe sty

A
  • When the infection of a hair follicle occurs at the base of the eyelid
  • Staphylococcus aureus (cutaneous lesion)
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25
Q

Describe furuncle

A
  • A large, painful raised nodular extension of folliculitis into surrounding tissue
  • Staphylococcus aureus (cutaneous lesion)
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26
Q

Describe carbuncle

A

When several furuncles coalesce, it extends deeper into the tissues, triggering fever and chills.

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27
Q

What are five systemic and potentially fatal diseases caused by Staphylococcus

A
  • Staphylococcal toxic shock syndrome
  • Bacteremia
  • Endocarditis
  • Pneumonia
  • Osteomyelitis
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28
Q

Describe staphylococcal toxic shock syndrome

A
  • Occurs when TSS toxin is absorbed through the blood
  • Life-threatening, occurs when the body is not getting enough blood flow. Lack of blood flow means the cells and organs do not get enough oxygen and nutrients to function properly
  • Characterized by fever, vomiting, red rash, low blood pressure, loss of sheets of skin
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29
Q

Describe bacteremia

A
  • Presence of bacteria in blood
  • Systemic disease caused by staphylococcus
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30
Q

Describe endocarditis

A
  • Present in the lining of the heart
  • Systemic disease caused by staphylococcus
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31
Q

Describe pneumonia

A
  • An inflammation of lungs where alveoli and bronchioles become filled with fluid
  • Systemic disease caused by staphylococcus
32
Q

Describe osteomyelitis

A
  • Bacteria invades the bones causing inflammation of bone marrow and surrounding bone
  • Systemic disease caused by staphylococcus
33
Q

If gram positive bacteria in grapelike arrangements, and are able to clot blood:

A

They are coagulase positive Staphylococcus aureus

34
Q

Discuss the history of Staphylococcal resistance to antimicrobial drugs

A
  • Only 5% of strains are susceptible to penicillin
  • Methicillin, a semisynthetic form of penicillin, which is not inactivated by β-lactamase, is the drug of choice for staphylococcus infections
  • Methicillin-resistant S. aureus (MRSA) is resistant to common antimicrobial drugs, including penicillin, macrolides, aminoglycosides, and cephalosporin; vancomycin is used to to treat MRSA infections
  • Vancomycin-resistant S. aureus arose (VRSA)
35
Q

Describe classification of streptococcal strains

A
  • Gram-positive cocci, facultative anaerobes
  • Arranged in pairs or chains
  • Catalase negative (H2O2 catalase test negative)
  • Classified on:
  • Antigens
  • Type of hemolysis (alpha, beta, gamma)
  • Cell arrangement
  • Physiological properties
  • Often categorized based on Lancefield classification: divided into serotypes based on bacteria’s antigens including serotypes A through H and K through V
36
Q

Hemolysis zone of Streptococcus pyogenes

A

Beta

37
Q

Hemolysis zone of Streptococcus pneumoniae

A

Alpha

38
Q

Hemolysis zone of Enterococcus faecalis

A

Gamma

39
Q

Describe two structures in Streptococcus pyogenes that enable this organism to survive the body’s defenses.

A
  • Protein M: interfers with opsonization and lysis by destabilizing complement
  • Hyaluronic acid capsule: remain hidden from phagocytic cells
40
Q

Protein M

A
  • Structural feature of Streptococcus pyogenes that enables the organism to survive the body’s defenses
  • Interferes with opsonization and lysis by destabilizing complement
41
Q

Hyaluronic acid capsule

A
  • Structural feature of Streptococcus pyogenes that enables the organism to survive the body’s defenses
  • Because hyaluronic acid is normally found in the body, white blood cells may ignore bacteria “camouflaged” by this type of capsule
42
Q

Identify four kinds of enzymes that facilitate the spread of Streptococcus pyogenes in the body

A
  • Streptokinases
  • Deoxyribonucleases
  • C5a peptidase
  • Hyaluronidase
43
Q

Identify the action of pyrogenic toxins in causing disease symptoms by Streptococcus pyogenes

A
  • Also known as Erythrogenic toxins
  • Stimulate the release of cytokines that cause fever
  • Toxin genes carried on bacteriophages
44
Q

What are treatments for Group A: streptococcus pyogenes

A

Treatment:
- Penicillin is effective
- Sensitive to erythromycin, cephalosporin, bacitracin

45
Q

What are seven diseases caused by Streptococcus pyogenes (group A) and the treatments available.

A
  • Pharyngitis (strep throat)
  • Rheumatic fever
  • Scarlet fever
  • Pyoderma
  • Erysipelas
  • Necrotizing fasciitis
  • Glomerulonephritis
    Treatment:
  • Penicillin is effective
  • Sensitive to erythromycin, cephalosporin, bacitracin
46
Q

Pharyngitis

A
  • Also known as strep throat
  • Inflammation of the pharynx
  • Purulent (pus containing) abscesses covering the tonsils
  • Group A Streptococcus: Streptococcus pyogenes
47
Q

Rheumatic fever

A
  • Complication of untreated streptococcal pharyngitis
  • Inflammation damages the heart valves and muscle
  • Autoimmune response against heart antigens
  • Damaged heart valves and achy joints
  • Group A Streptococcus: Streptococcus pyogenes
48
Q

Scarlet fever

A
  • Involve lysogenized strain of S. pyogenes (due to pyrogenic toxins)
  • Strawberry red tongue
  • Chest rash develops that spreads across the body
  • Group A Streptococcus: Streptococcus pyogenes
49
Q

Pyoderma

A

Pus-producing lesions involving lymph nodes, pain and inflammation
- Group A Streptococcus: Streptococcus pyogenes

50
Q

Prefix Pyro-

A
  • Causes fever
  • Example: Pyrogenic
51
Q

Prefix Pyo-

A
  • Produces pus
  • Pyoderma
52
Q

Erysipelas

A
  • Involves surrounding superficial lymphatic tissue and triggers pain and inflammation
  • Group A Streptococcus: Streptococcus pyogenes
53
Q

Necrotizing fasciitis

A
  • Characterized by redness, intense pain, and swelling at the site of infection
  • Bacteria digest the muscle fascia (connective tissue) and fat tissue
  • Patients develop fever, nausea, mental confusion, drop in blood pressure
  • Affected tissue must be removed completely
  • Group A Streptococcus: Streptococcus pyogenes
54
Q

Glomerulonephritis

A
  • Antibodies bound to antigens of Group A Streptococcus are not removed from circulation and instead accumulate in the glomeruli (small blood vessels) of the kidneys’ nephrons (filtering units)
  • Puffy face due to retention of fluid by damaged kidney, tea colored urine due to hematuria
  • Autoimmune disorder
  • Group A Streptococcus: Streptococcus pyogenes
55
Q

Identify the conditions under which group A Streptococcus causes disease.

A
  • Often causes diseases when normal competing microbiota are depleted
  • When adaptive immunity is impaired
  • Streptococcus is not a normal member of the microbiota of the skin Gram-positive bacteria in short chains or pairs in cutaneous specimens, can provide preliminary diagnosis of: pyoderma, erysipelas, and necrotizing fasciitis
  • Streptococci are normally in pharynx so a rapid strep test is used to identify the presence of group A streptococcal antigens
56
Q

What is a rapid strep test used to identify

A

The presence of Group A: Streptococcus pyogenes

57
Q

Discuss the epidemiology, diagnosis, treatment, and prevention of infections with Streptococcus agalactiae

A
  • often infects newborns and immunocompromised patients
  • ELISA test used to diagnosis
  • Penicillin G or ampicillin
  • Vaccination for women to protect future children
58
Q

Epidemiology of Streptococcus agalactiae

A
  • Often infects newborns without specific antibodies
  • Older immunocompromised patients also at risk
59
Q

Diagnosis of Streptococcus agalactiae

A
  • ELISA test used to identify group B streptococcus, utilizing antibodies directed against the bacteria’s distinctive cell wall polysaccharides
60
Q

Treatment of Streptococcus agalactiae

A
  • Penicillin G is the drug of choice, or ampicillin
61
Q

Prevention of Streptococcus agalactiae

A
  • Immunization of women can protect future children
62
Q

Identify the normal sites of viridans streptococci in the human body

A
  • Mouth
  • Pharynx
  • GI tract
  • Genital tract
  • Urinary tract

But are opportunistic

63
Q

List three serious diseases Viridan Streptococci cause.

A
  • Dental caries
  • Meningitis
  • Endocarditis
64
Q

Describe how the structure of Streptococcus pneumoniae affects its pathogenicity

A
  • Gram-positive cocci the mostly form pairs
  • Unpigmented, alpha-hemolytic colonies on blood agar
  • Polysaccharide capsule (required for virulence)
  • Phosphorylcholine in cell wall
  • Secretory IgA protease
  • Pneumolysin
65
Q

Streptococcus pneumoniae: Phosphorylcholine

A
  • Stimulates cells to phagocytize the bacteria
66
Q

Streptococcus pneumoniae: Secretory IgA protease

A
  • Destroys IgA
67
Q

Streptococcus pneumoniae: Pneumolysin

A
  • Binds to cholesterol in the cytoplasmic membranes of epithelial cells, producing pores that result in lysis of cells
68
Q

Streptococcus pneumococcal disease: Pneumococcal pneumonia

A
  • Bacteria multiply in the alveoli, damaging the alveolar lining , allowing fluid, RBCs and leukocytes to enter the lungs
69
Q

Streptococcus pneumococcal disease: Sinusitis and Otitis Media

A
  • Bacteria can invade sinuses and middle ear causing pus and inflammation
70
Q

Streptococcus pneumococcal disease: Bacteremia and Endocarditis

A
  • Colonize in blood and heart
  • Both in Staph and Strep
71
Q

Streptococcus pneumococcal disease: Pneumococcal meningitis

A
  • Can spread to the meninges
72
Q

Diagnosis of Streptococcus pneumococcus

A
  • Gram of sputum smears, positive
  • Confirmed with Quellung reaction - Anti-capsular antibodies cause the capsule to swell
73
Q

Quellung reaction

A
  • Used to identify pneumococci, in which anti capsular antibodies cause the capsule to swell
74
Q

Treatment of Streptococcus pneumoniae

A
  • Penicillin
75
Q

Prevention of Streptococcus pneumoniae

A
  • Vaccine made from purified capsular material

Microbiology Exam 3 (6 decks)

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