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Medical Microbiology > Unit 2: Staphylo And Streptococcus > Flashcards

Unit 2: Staphylo And Streptococcus Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q 
An attenuated vaccine is composed of
A. Killed Microorganisms
B. Living microbes rendered a virulent or reduced in virulence
C. Inactivated bacterial toxins
D. Purified macromolecules
A

B. Living microbes rendered a virulent or reduced in virulence

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2
Q

Which of the following is a type of vaccine?

A. Inactivated agent B. purified macromolecule C. Attenuated agent D. All of the above

A

D. All of the above

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3
Q

Which o the following rxns is the result of a type 4 (delayed) hypersensitivity?
A. Sensitivity to pet dander
B. Runny nose triggered by pollen
C. Breathing difficulties after exposure to mold spores
D. Dermatitis in response to poison ivy

A

D. Dermatitis in response to poison ivy

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4
Q

Anaphylactic shock from an insect venom causes an IgE mediated reaction. How much time would it take for clinical signs to appear?

A

Within a few minutes to few hours

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5
Q

Rash on both arms after vacation in the woods, and then 12 cats days before that. What type of hypersensitivity?

A

Type 4

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6
Q

29 yo woman w/ lethargic, jaundiced, anemic infant at birth. Enlarged liver and spleen. Mother is RhD negative and after is RhD positive. This their second child. Example of

A

Type 2 hypersensitivity

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7
Q 
Jane w/ hay fever and rashes after every soccer practice ( allergic to grass) why type of hypersensitivity?
A. Atopic
B. Cytotoxic
C. Immune complex
D. Delayed hypersensitivity
A

A. Atopic

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8
Q

HIV infections typically cause

A

Secondary immunodeficiency

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9
Q

Autoimmunity is always a reaction to…

A

Self antigen

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10
Q

True or False: complement is responsible for some of the damage associated with hypersensitivity reaction

A

True

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11
Q

Three types of infectious reservoirs

A

Human carriers: asymptomatic individuals that can transmit to others
Nonliving reservoirs: soil, food, water and objects (fomite)
Animal resevoirs: direct contact, eating animals, bloodsucking anthropods.

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12
Q

Zoonoses

A

Diseases naturally spread from animal host to humans

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13
Q

Pathogenicity

A

Ability of a microorganism to cause disease

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14
Q

Virulence

A

Degree of pathogenicity: more virulent strains will only require a few cells to cause infection

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15
Q

Virulence factors definition and 5 types

A

Cellular components that play role in the organism’s ability to cause disease
1. Adhesion factors, 2. Bio films 3. Extracellular 4. Toxins 5. Anti phagocytic factors

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16
Q

Extracellular enzymes

A

Secreted by pathogens to dissolve structural chemicals- help pathogen maintain infection, and avoid defenses

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17
Q

Toxins

A

Harm tissues or trigger host immune responses

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18
Q

Toxemia

A

Presence of toxins in the bloodstream

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19
Q

Anti phagocytic factors

A

Allows pathogens to remain in a host for longer time (bacterial capsule and chemicals)

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20
Q

Direct contact transmission

A

Body contact, either between individuals or from different locations on one individual

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21
Q

Indirect contact transmission

A

Pathogen are spread from host to host by fomites

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22
Q

Droplet transmission

A

Spread of pathogen in droplets of mucus/ body fluids within one meter

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23
Q

Biological vector transmission

A

Transmit pathogens and serve as host for some stage of the pathogen’s life cycle (mosquitos, ticks, lice)

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24
Q

Mechanical vector transmission

A

Passively transmit pathogens present on their body to new hosts (flies, roaches and rats)

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25
Q

Airborn vehicle transmission

A

When pathogen travel more than 1 meter via an aerosol (sneezing, air- conditioning, coughing etc.)

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26
Q

Waterborne vehicle transmission

A

Fecal-oral infection, and cause of many GI diseases

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27
Q

Localized infection

A

Microbes enters body and reminds confined to a specific region or one or more anatomical areas (boil/ an acne pimple)

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28
Q

Focal infection

A

Spread from a local infection: exists within a circumscribed area (dental borne endocarditis)

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29
Q

Systemic infection

A

Infection spreads to several sites and tissue fluids usually in the bloodstream (throughout the body)

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30
Q

Secondary infection

A

Another infection by a different microbe occurring after a primary infection (primary weakens or breaks barriers, and secondary is opportunistic)

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31
Q

Fulminating infection

A

Multiplying with great intensity, acute with incredibly quick pathogenesis

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32
Q

Nosocomial infection

A

Hospital acquired

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33
Q

Overt infection

A

Symptomatic

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34
Q

Pyogenic infection

A

Pus producing

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35
Q

Zoonosis

A

Infection cause by pathogen normally found in animals but naturally transmissible to humans

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36
Q

Latent infection

A

A dormant state. Microbe can periodically become active and produce a recurrent disease

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37
Q

Four types of health-care associated infections

A

Exogenous, endogenous, iatrogenic, superinfections

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38
Q

Exogenous infection

A

Pathogenous acquired from the health care environment

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39
Q

Endogenous

A

Pathogen arises from normal microbiota of patient introduced to new area

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40
Q

Iatrogenic infection

A

Infection resulting from modern medical procedure

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41
Q

Super infection

A

Use of antimicrobial drugs inhibit some resident microbiota allowing other microbes to thrive and overproduce

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42
Q

Staphylococcus aureus habitat

A

Human host normal flora, human carrier normal flora, fomite or environment

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43
Q

Staphylococcus aureus disease state

A

Enters via barrier breach, pyogenic, either due to direct organism effect or toxin mediated

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44
Q

Predisposition to Staphylococcus aureus infection includes:

A

Poor hygiene/ nutrition, tissue injury, other primary infection, diabetes, immunodeficiency

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45
Q

Staphylococcus aureus pathogenic factors

A
  1. Phagocytic avoidance structures
  2. Production of enzymes
  3. Production of toxins
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46
Q

Staphylococcus aureus protein A

A

Binds to IgG and inhibits opsonization and the complement cascade

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47
Q

Staphylococcus aureus bound coagulase

A

Converts fibrinogen into fibrin molecules, and clots hide the bacterial from phagocytic cells (vegetation in endocarditis)

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48
Q

Staphylococcus aureus polysaccharide slime layers

A

Inhibits chemotaxis of immune system, and facilitates staph attachment to surfaces

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49
Q

Staphylococcus aureus virulence factors- antiphagocytic

A

Protein A, bound coagulase/ cell-free coagulase, polysaccharide slime layers (capsules)

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50
Q

Staphylococcus aureus enzymatic virulence factors

A

Hylauronidase, staphylokinase, lipases, penicillinase (beta-lactamase)

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51
Q

Staphylococcus aureus hylarunoidase

A

Breaks down hyaluronic acid, enabling spread between cells

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52
Q

Staphylococcus aureus staphylokinasae

A

Dissolves fibrin threads in blood clots, allowing Staphylococcus aureus to free itself from clots and spread to other areas

53
Q

Staphylococcus aureus lipases

A

Digests oils to remove protective layers and enhance colonization on skin and in cutaneous oil glands

54
Q

5 Staphylococcus aureus toxins

A
  1. Cytolytic toxins a, b and c
  2. Leukocidin
  3. Exfoliate or epidermolytic toxins
  4. Toxic-shock syndrome toxin
  5. Enterotoxins
55
Q

Staphylococcus aureus cytolytic toxins

A

Disrupt the cytoplasmic membrane of cells

56
Q

Staphylococcus aureus leukocidin (Panton-Valentine toxin)

A

Can lyse leukocytes specifically

57
Q

Staphylococcus aureus toxic-shock syndrome toxin

A

Causes TSS, induces fever, vomiting, shock, systemic organ damage (superantigen)

58
Q

Staphylococcus aureus Enterotoxin

A

Causes gastroenteritis; stimulating intestinal muscle contractions, nausea, intense/ violent vomiting and diarrhea

59
Q

Localized cutaneous Staphylococcus aureus infections

A

Impetigo: bubble-like swelling that can break and peel away- much bumpier than strep A caused impetigo

  1. Folliculitis: hair follicle
  2. Furuncle: boil, follicle proceeded to abscess or pustule
  3. Carbuncle- larger and deeper lesion created by aggregation and interconnection of a cluster furuncles
60
Q

Staphylococcus aureus Dissemination

A

When the infection spreads throughout the body to case systemic disease

  1. Bacteremia
  2. Osteomyelitis (infection of bone growthplate)
  3. Endocarditis
61
Q

Staphylococcus aureus toxin mediated disease

A
  1. Food intoxication- enterotoxin for GI distress
  2. Staphylococcal scalded skin syndrome: toxin induces bright red rash, blisters, and desquamation of the epidermis (schluffing off)- no scarring
  3. Toxic shock syndrome: toxemia of super-antigen leading to shock and organ failure
62
Q

Treatment of Staphylococcus aureus

A

95% are beta-lactam resistant, and antimicrobial sensitivity testing is vital. Abscesses have to be surgically perforated (or irrigated and drained for deeper wounds- invasive and lengthy therapy)

63
Q

Staphylococcus epidermis location and common diseases

A

Produces slime layer so commonly infects plastic/ artificial units (IV lines, catheters, prosthetic heart valves)

64
Q

Staphylococcus saprophyticus characteristic and diseases

A

Sensitive to a wide range of antibiotics, and common cause of urinary infection in sexually active young women

65
Q

Gram stain of Staphylococcus aureus

A

Gram positive

66
Q

Catalase activity of Staphylococcus aureus

A

Catalase positive

67
Q

Staphylococcus aureus blood agar pattern

A

B-hemolysis

68
Q

Staphylococcus aureus mannitol fermentation?

A

Ferments mannitol

69
Q

Staphylococcus aureus coagulase activity?

A

Coagulase positive

70
Q

Staphylococcus aureus DNAase activity?

A

DNAase positive

71
Q

Staphylococcus aureus: novobiocin sensitivity?

A

Yes, novobiocin sensitive

72
Q

Staphylococcus epidermidis gram stain

A

Gram positive cocci

73
Q

Staphylococcus epidermidis catalase activity?

A

Catalase positive

74
Q

Staphylococcus epidermidis Blood agar pattern

A

Non-hemolytic

75
Q

Staphylococcus epidermidis mannitol fermentation?

A

Does not ferment mannitol

76
Q

Staphylococcus epidermidis coagulase activity?

A

Coagulase negative

77
Q

Staphylococcus epidermidis novobiocin sensitivity

A

Novobiocin sensitive

78
Q

Staphylococcus saprophyticus gram stain

A

Gram positive cocci

79
Q

Staphylococcus saprophyticus catalase activity

A

Catalase positive

80
Q

Staphylococcus saprophyticus blood agar pattern

A

Non-hemolytic

81
Q

Staphylococcus saprophyticus mannitol fermentation

A

Does not ferment mannitol

82
Q

Staphylococcus saprophyticus coagulase activity

A

Coagulase negative

83
Q

Staphylococcus saprophyticus DNAase activity

A

DNAase negative

84
Q

Staphylococcus saprophyticus Novobiocin sensitivity

A

Novobiocin RESISTANT

85
Q

Streptococcus pyogenic virulence factors

A

M protein, streptokinase, hyaluronidase, streptolysins, Erythrogenic toxin

86
Q

Streptococcus pyogenes M protein

A

Destabilizes complement and evade phagocytosis

87
Q

Streptococcus pyogenes streptokinase

A

Lysis of fibrin- blood clots. Aids in spreading

88
Q

Streptococcus pyogenes hyaluronidase

A

Facilitates the spread of streptococcus through tissue by breaking down hyaluronic acid

89
Q

Streptococcus pyogenes streptolysins

A

Lyse red blood cells, leukocyte, platelets, other cells (cytolysins) causing cell and tissue injury

90
Q

Streptolysins S

A

Alters membrane permeability and lysis RBC, leukocytes and other cells

91
Q

Streptolysins O

A

Forms membrane penetrating channels (porin) leading to membrane defects and cell lysis (losing cytoplasmic content)
— Cardiotoxic
— Antigenic during strep throat infections, but not during skin infections.

92
Q

Erythrogenic toxin (Streptococcus pyogenes)

A

Act as super antigen- cardiotoxic, can suppress antibody response: results in rash seen in scarlet fever

93
Q

Streptococcus pyogenes impetigo

A

Crusted, flatter and flakey, school-age epidemics; highly contagious

94
Q

Streptococcus pyogenes erysipelas

A

Pathogen (through skin) that enters through a break in the skin and eventually spreads through dermis and subcutaneous tissues: can remain superficial or become systemic (VERY red and inflamed)

95
Q

Streptococcal pharyngitis

A

Inflammation and white spots. If untreated can create severe sequelae

96
Q

Rheumatic fever (Streptococcus pyogenes)

A

—Follows overt or subclinical pharyngitis
— Carditis, joints, blood vessels and subcutaneous tissues
— chronic progressive damage to heart valves/ muscles
— autoimmune response against heart antigen

97
Q

Streptococcus pyogenes scarlet fever

A

Streptococcus pyogenes strain carrying a prophage, coding for Erythrogenic toxin: chest rash across whole body; typically due to untreated pharyngitis

98
Q

Streptococcus pyogenes acute glomerulonephritis

A

Follows either cutaneous or pharyngeal infections (common in children)antigen-antibody complexes deposit in the glomerulus- impairs kidney filtration

99
Q

Streptococcal Toxic Shock Syndrome

A

Bacteria: multisystem, system to StrepTSS. Organ failure, shock, death. Usually due to wound infection instead of tampon over exposure

100
Q

Necrotizing Fasciitis (Streptococcus pyogenes)

A

Life-threatening, sepsis, edema, erythema and pain. Streptococcal myositis resembles clostridial gangrene. Toxin mediated so will not be able to cure with antibiotics

101
Q

Streptococcus pyogenes treatment

A

Penicillin IS effective. Catalase negative, bacitracin susceptible, slide agglutination (clumping)

102
Q

Streptococcus agalactiae-

A

Group B streptococcus

103
Q

Streptococcus agalactiae most common infection

A

Colonizes urogenital tract of pregnant woman and mother fails to pass protective antibodies to fetus. Invasive disease in newborns.
Early onset: neonatal bacteremia, meningitis, and pneumonia
Late-onset disease: meningitis

104
Q

Viridans group streptococci characteristics and diseases

A

— mostly a-hemolytic, some non hemolytic, lack group-specific carbohydrates, most common cause of dental carries, gingivitis and subacute bacterial endocarditis. Can also cause meningitis

105
Q

5 groups of Viridans streptococci

A 
Boris
Anginosus
Mitis 
Mutant
Salivarius
106
Q

Pneumococcal pneumonia

A

Most common disease caused by Streptococcus pneumoniae, usually requiring some predisposing condition or age factor

107
Q

Streptococcus pneumoniae sinusitis and otitis media

A

Ear and sinus infection. Sometimes occur following viral infection due to wet congested areas and compromised mucosa. Most common cause of otitis media in children under the age of 3

108
Q

Streptococcus pneumoniae bacteremia and endocarditis

A

Streptococcus pneumoniae can enter the blood through lacerations or tissue damage

109
Q

Pneumococcal meningitis

A

Incredibly severe form of meningitis, with much higher mortality rate than other causes. Partially due to damaging treatment, where additional toxins are released upon attack by antimicrobials, further progressing the disease state and irritating the brain and spinal fluid

110
Q

Streptococcus pneumoniae vs Enterococcus

A

Enterococcus distinguished by its sensitivity to bile

111
Q

Streptococcus pyogenes hemolytic pattern

A

large zone of beta-hemolysis

112
Q

Streptococcus pyogenes external components

A

C5a protease, 5-protein antigen, C-carbohydrate, capsule and fimbriae

113
Q

Streptococcus pyogenes penicillin resistant?

A

No, B-lactams are largely effective. Uncommon but possible resistant strains

114
Q

Streptococcus pyogenes bacitracin sensitivity?

A

Sensitive to bacitracin

115
Q

Group B Streptococcus (agalactiae) B-hemolytic pattern

A

Smaller zone of B-hemolysis

116
Q

Group B Streptococcus (agalactiae) bacitracin sensitivity?

A

Resistant to bacitracin

117
Q

Group B Streptococcus (agalactiae) pathogenicity?

A

Most often infects newborns (and sometimes the mother) who lacks specific antibodies

118
Q

Group B Streptococcus (agalactiae) catalase activity

A

Catalase negative

119
Q

Group B Streptococcus (agalactiae) bile esculin?

A

Bile esculin negative

120
Q

Group B Streptococcus (agalactiae) B-lactam usage?

A

penicillin, ampicillin (B-lactams) are effective (often used as a prophylactic during birth to reduce cases of newborn infections

121
Q

Streptococcus Pneumoniae B-hemolytic pattern

A

Alpha-hemolytic in aerobic conditions, B-hemolytic in anaerobic conditions! Crazy…

122
Q

Streptococcus Pneumoniae external characteristics

A

Diplococci, with capsule required for pathogenicity, bile sensitive

123
Q

Streptococcus Pneumoniae Quellung rxn

A

Confirmed with positive quellung reaction, testing for the capsule

124
Q

Enterococcus B-hemolytic pattern

A

None (gamma hemolytic)

125
Q

Enterococcus external characteristics

A

Diplococci, or in short chains, no capsule, bile insenstive

126
Q

Two species of Enterococcus that cause diseases in humans

A

Enterococcus faecalis and Enterococcus faecium. Normally found in human colon and rarely pathogenic there, but if introduced to a different body cavity.

127
Q

Enterococcus infections

A

Often healthcare-associated; wound infections, endocarditis, urinary tract infections.

128
Q

Enterococcus treatment

A

Difficult to treat, as often resistant to antimicrobials (susceptibility studies are important)

Medical Microbiology (11 decks)

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