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Microbiology Exam 3 > CH. 21 AND 22 > Flashcards

CH. 21 AND 22 Flashcards

1
Q

What does Staphylococcus aureus look like on a gram stain?

A

Irregular grape-like clusters, gram + cocci

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2
Q

What is special about S. aureus colonies?

A

Can survive for months on surfaces

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3
Q

What are some of the virulence factors of S. aureus?

A
  • Vigorous inflammatory response
  • Protein that blocks chemotaxis of neutrophils
  • Secretes toxins to kill phagocytes
  • Resistant to opsonization
  • Can survive within phagosome
  • Lysozyme resistant
  • Can work as a superantigen
  • Often able to evade adaptive immune system completely
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4
Q

What is folliculitis and what causes it?

A

Infection of hair follicles that look like pimples, usually caused by S. aureus

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5
Q

How can folliculitis progress?

A

Folliculitis → furuncle (boil) → carbuncle (hard, deep round inflammation of tissue under the skin)

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6
Q

What is impetigo?

A

Non-bullous impetigo - staph infection (mainly S. aureus, sometimes S. pyogenes), isolated pustules that become crusted; Bullous impetigo - caused by toxin A from staph, causes localized exfoliation of skin

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7
Q

What is MRSA?

A

Methicillin resistant S. aureus

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8
Q

What does Streptococcus pyogenes look like on a gram stain?

A

Gram + cocci chains

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9
Q

What are hemolysins?

A

Lyse RBCs (alpha, beta, or gamma)

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10
Q

What do the different types of hemolysis look like?

A
  • Alpha-hemolysis - partial breakdown, greenish discoloration
  • Beta-hemolysis - complete breakdown, clear
  • Gamma-hemolysis - no breakdown
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11
Q

What type of hemolysis does group A strep have?

A

Beta hemolytic

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12
Q

What are streptolysins?

A

Lyse RBCs and are toxic to neutrophils

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13
Q

What does the M protein on Strep do?

A

Prevents activation of complement, helps evade phagocytosis, kills neutrophils, helps adherence

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14
Q

What is special about the S. pyogenes capsule?

A

Hyaluronic capsule - evades immune system by resembling connective tissue, body makes few ABs against it

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15
Q

What 3 substances help S. pyogenes liquefy pus to promote invasion?

A
  • Streptokinases
  • Hyaluronidase
  • Deoxyribonucleases
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16
Q

Is necrotizing fasciitis caused by just one thing?

A

No, is caused by multiple agents

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17
Q

What is the major thing at work in necrotizing fasciitis?

A

Exotoxin A acts as a superantigen causing extreme inflammation

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18
Q

Pseudomonas is a grape-smelling opportunistic pathogen in patients with what particular conditions?

A
  • Pseudomonas dermatitis
  • Otitis externa
  • Burn wound infections
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19
Q

Is conjunctivitis caused by just one agent?

A

No, a lot of pathogens can cause it

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20
Q

What is the greatest cause of blindness in the world?

21
Q

Why does trachoma cause blindness?

A

Repeated infection can cause trichiasis (in-turning of eyelashes), which abrade the cornea, causing scarring and blindness

22
Q

Know the acronyms CNS, PNS, CSF

A
  • Central nervous system
  • Peripheral nervous system
  • Cerebrospinal fluid
23
Q

What is the blood-brain barrier, and why is it important?

A

Restricts certain substances from passing into the brain from the blood

24
Q

What is meningitis?

A

Inflammation of meninges

25
What is encephalitis?
Inflammation of the brain
26
What are some causative agents of meningitis?
* Viral * Bacterial * Fungi * Protozoa
27
What are the symptoms of bacterial meningitis?
* Fever * Headache * Stiff neck * Nausea and vomiting * Convulsions and coma
28
What do all the bacterial causes of meningitis have in common?
All bacterial causes are capsular
29
What are the 3 main causes of bacterial meningitis?
* H. influenza (aerobic gram -) * Neisseria meningitides (aerobic gram -) * Streptococcus pneumoniae (gram + diplococcus)
30
How do you diagnose bacterial meningitis?
* Spinal tap to get CSF sample * Gram stain * CSF culture * Latex agglutination tests
31
What else causes meningitis?
Listeria monocytogenes (gram + rod)
32
What causes tetanus?
Clostridium tetani
33
What does C. tetani look like?
Obligate anaerobe, endospore forming, gram + bacilli
34
How does tetanospasmin work?
Potent neurotoxin released upon death and lysis of growing bacteria, enters CNS via peripheral nerves or blood
35
What is opisthotonos?
Spasms of back muscles causes bowing backwards
36
What is usually the first sign of tetanus?
Lockjaw
37
Is tetanus an infection or an intoxication?
Intoxication
38
Why does tetanus cause death?
Spasms of respiratory muscles
39
How do people get tetanus?
Common in soil contaminated with feces and enters via deep wound
40
What causes botulism?
Clostridium botulinum
41
How does C. botulinum work?
Anaerobic environments will start to create botulinum toxin which blocks the release of acetylcholine
42
How does botulism kill you?
Paralysis → respiratory and cardiac failure
43
Why don’t we feed honey to babies?
C. botulinum spores can be found in honey which babies are susceptible to due to underdeveloped immune system
44
How do you treat botulism and tetanus?
* Tetanus: DTap vaccine, Tetanus immune globulin (TIG) if wound looks problematic, Debridement, Supportive care * Botulism: Most cooking will destroy C. botulinum, Nitriles added to food to prevent bacteria growth, Infants: BabyBIG, Supportive care
45
What are some commercial uses for botox?
* For chronic headaches * Muscle contractions in cerebral palsy, parkinson’s and MS * Prevent scar formation * Eye twitching, crossed eyes, and excessive sweating * Wrinkles
46
What is special about Mycobacterium leprae?
Only bacterium that grows in the PNS
47
Why has leprosy been so stigmatized?
Not much was known about its cause and transmission and severe disfigurement caused fear and social exclusion
48
Can leprosy kill you?
Death occurs from complications like TB, not from the bacteria itself
49
Can you grow M. leprae?
Cannot be grown on artificial media but can grow in armadillos or footpads of nude mice

Microbiology Exam 3 (3 decks)

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