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Microbiology > 3.10 > Flashcards

3.10 Flashcards

1
Q

Typical Bacteria

• Gram stain differentiation

A

§ Reflects a fundamental differentiation based on
permeability, presence or absence of outer membrane
and cell wall thickness

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2
Q

• Cellular morphology

§ 4 typical cell types

A 
v Gram (+) rods
v Gram (+) cocci
v Gram (-) rods
v Gram (-) cocci
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3
Q

• Gram positive rods have more in common with

(1) than with gram negative rods

A

gram positive cocci

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4
Q

Ø Gram positive cocci (2)

A
  • Staphylococci

* Streptococci

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5
Q

• Staphylococci (3)
types (3)
found in?

A

§ S. aureus; S. saprophyticus; S. epidermidis
§ Found in many body sites; primarily skin infections &
wounds; carbuncles; abscesses; leading to life
threatening deep tissue infections: osteomyelitis,
endocarditis
§ Severe intoxications; Food poisoning

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6
Q

Streptococci (4)

A 
§ Alpha or beta hemolysis
   v Alpha: S. pneumoniae
   v Beta: Groups A-T; Group A most prevalent in human
disease
§ Oxygen-tolerant anaerobes
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7
Q

Gram negative cocci (2)

A
  • Neisseria meningitidis

* Neisseria gonorrhea

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8
Q

Gram positive rods (2)

A
  • Non-Spore-forming aerobic rods

* Spore-forming rods

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9
Q

Non-Spore-forming aerobic rods

A

§ Corynebacterium diphtheriae and related diphtheroids

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10
Q

Spore-forming rods (3)

A

§ Aerobic: Bacillus anthracis (anthrax)
§ Anaerobic: Clostridium species
v C. botulinum; C. tetani; C. perfringens; C. difficile

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11
Q

Ø Gram negative rods

• Enteric bacteria (3)

A

§ Enterobacteriaceae (facultative anaerobes)
v Escherichia coli; Salmonella spp.; Shigella spp.;
Yersinia spp. (pestis; pseudotuberculosis)
§ Vibrio cholerae; Campylobacter jejuni; Helicobacter pylori

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12
Q

Significant non-enteric Gm- rods: (5)

A 
§ Pseudomonas aeruginosa
§ Haemophilus influenzae
§ Bordetella pertussis
§ Brucella abortus
§ Legionella pneumophila
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13
Q

Gram negative rods (contin.)
• Strictly anaerobic Gm- rods
§ Bacteroides fragilis (4)

A

ü Most common organism in the human intestine.
ü Can cause serious disease when deposited into deep tissues.
(abscesses)
ü Can be also be found in gingival pockets
ü Very stinky

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14
Q

Acid-fast bacteria

A

• Mycobacterium tuberculosis; M. leprae

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15
Q

Spirochetes (4)

A
  • Treponema pallidum (syphilis)
  • Leptospira spp. (hemorrhagic fever)
  • Borrelia recurrentis (relapsing fever)
  • Borrelia burgdorferi (Lyme disease)
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16
Q

Strictly intracellular bacteria (5)

A
  • Chlamydia trachomatis (most common STD)
  • Chlamydia pneumoniae
  • Rickettsiae (Rocky mountain spotted fever)
  • Ehrlichia (arthropod borne)
  • Coxiella burnetti (Q fever)
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17
Q

staphyle =

A

cluster of grapes

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18
Q

coccus =

A

sphere

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19
Q

aureus =

A

golden colonies

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20
Q

Staphylococcus

Characteristics: (3)

A

Gram+ cocci, catalase+

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21
Q

o2?

staphylococcus aureus

A 
O2 can
be used (faculative anaerobe)
22
Q

Ø catalase

A

Reduces the potential of phagocytes to kill

23
Q

Ø coagulase (2)

A

The tissue-invasive potential of staphylococcal infections is directly
proportional to coagulase production (S.aureus; not in other Staph. species).
• coagulase binds prothrombin: fibrinogen is cleaved anti-phagocytic fibrin coating

24
Q

clumping factor

A

fibrinogen-binding protein: cell surface proteins that bind to foreign
materials (like sutures) and to extracellular matrix.

25
Q

Ø protein A

A

Anti-phagocytic, competes with neutrophils for Fc portion of opsonizing IgGs
(on cell surface of S.aureus but not on other staphylococcal strains)

26
Q

Ø leukocidin

A

secretion: inhibits phagocytosis by granulocytes by forming pores in
phagosomal membranes, and kills phagocytes. Major factor in pus formation.

27
Q

digestive enzymes

A

digestive enzymes proteases, DNase, nuclease, lipases

hyaluronidase (spreading factor: digests extracellular matrix)

28
Q

staphylokinase

A

converts plasminogen to plasmin, increasing invasion by digesting
fibrin clots and cleaves C3b and IgG to inhibit phagocytosis

29
Q

β-lactamase

A

Enzymatic digestion of penicillins (90% strains have plasmid-based antibiotic resistance)

30
Q

α-, β-, γ-, and δ-toxins are all

A

hemolysins: lyse erythrocytes (lab phenomenon)

31
Q

§ α-hemolysins (pores) are (4)

A

hemolytic, leukocytic, destroy skin, cause smooth muscle paralysis

32
Q

§ β-hemolysins are cytolytic sphingomyelinases that destroy —

A

nerves

33
Q

§ γ-hemolysins lyse like related — on neutrophil lysosomal membranes

A

leukocidin

34
Q

Empyema:

A

Empyema: Collection of pus in a naturallyexisting anatomical cavity (e.g. lungs)

35
Q

pyogenic infections:

A

pus-forming (massive amounts of neutrophils and other leukocytes are
lysed by bacterial factors (e.g. leukocidin) and release their lysosomal
contents in attempting phagocytic killing of the staphylococci).

36
Q

Invasive pus-forming infections (4)

A

FOLLICULITIES
FURNUNCLES
CARBUNCLES
(SYSTEMIC) BACTEMIA FEVER

37
Q

superangtigens- overrides the

A

specificity of the t cell response

38
Q

Ø enterotoxins Heat-stable (cooking doesnt help!) toxins A, B, C1, C3, D, E are super-Aglike: cause of

A

gastrointestinal upset typical of food poisoning
(Vomiting may be induced by inflammatory reaction of subepithelial macrophages to
toxins with a resulting change in vascular permeability)

39
Q

Toxic Shock Syndrome Toxin TSST:

A

mass activation of T cells leads to large

production of inflammatory cytokines (heat and protease-resistant TSST-1; chromosomal gene)

40
Q

exfoliative toxin

A

{heat-stable, chromosomal), B (heat-labile, plasmid) : SSSS

staphylococcal scalded-skin syndrome

41
Q

TSS: Toxic Shock Syndrome

A

Increased oxygenation of vagina by tampons, and

foreign surface adhesion, caused massive growth

42
Q

SSSS: Staphylococcal Scalded Skin Syndrome

A

Ø exfoliative toxins A, B cause loss of layers of the skin in SSSS
Nester 04 Fig. Murray05 Fig.22-5
Neutralizing A

43
Q

Nosocomial Staphylococci a

A

surgery, implant & instrument risk

44
Q

Nosocomial (hospital instruments and
implants) infections
(often coagulase-negative S.epidermidis)

A
45
Q

Endocarditis:
• acute: —% S.aureus
• if artificial heart valves: —% S.epidermidi

A

60

80

46
Q

S.epidermidis:

A

dental extraction risk

47
Q 
most frequent causes of bacterial arthritis by age 
oeganism: staphylococcus aureus 
neonates
2 mo-2 ye 
30-10 yr 
adult
A

10-125%
25-50%
25-50%
25-75%

48
Q

Gram+ cocci, aerobic / facultatively anaerobic
coagulase+ catalase+
Epidemiology (4)

A 
skin + mucosa +aerosols
surface survival
(hospital instruments, implants)
nosocomial
(hospitalacquired)
high temperature
(40ºC) and salt resistant
49
Q

β-lactamase (plasmid): >—% penicillin resistant

A

90

50
Q

penicillin-binding protein 2a (chromosomal): causes — Resistance

A

Methicillin

51
Q

–% of hospital strains are MRSA; –% of community strains are MRSA
What can you do in case of (Enterococcus-derived) VRSA ? nothing

A

50

20

52
Q

Coagulase─ : Other Staphylococci like S.epidermidis or S.saprophyticus (2)

A
  • Thick cell wall, slime capsule, (S.saprophyticus: urease secretion → acute cystitis
  • Opportunistic hospital pathogens (instruments, catheters, heart valves)

Microbiology (42 decks)

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