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Microbiology > Gram positive infections: bench to bedside (word document) > Flashcards

Gram positive infections: bench to bedside (word document) Flashcards

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1
Q

What are the gram positive cocci?

A

staphylococcus, streptococcus, enterococcus

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2
Q

What are the gram positive bacilli?

A

corynbacterium, listeria

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3
Q

What are the gram stain pattern of the following aerobic gram positive cocci: staphylococcus, streptococcus, enterococcus

A

Staphylococcus – Gram positive cocci in clusters

  • Streptococcus – Gram positive cocci in pairs OR Gram positive cocci in chains
  • Enterococcus – Gram positive cocci in pairs and chains
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4
Q

What are the staphylococcal species associated with human infections?

A 
o	Staphylococcus aureus
o	Coagulase negative Staphylococcus – term used to describe a group of bacteria
•	Staphylococcus epidermidis
•	Staphylococcus saprophyticus
•	Others
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5
Q

What does the catalaze test show for the three gram positive cocci?

A

Positive = staphylococci

catalaze negative = Streptococci, Enterococci

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6
Q

How do you differnetiate between staph. aureus and both staphylococcus epidermis, and staphylococcus saprophyticus and others?

A
  • Coagulase: Enzyme converts fibrinogen ⇒ fibrin
    o Positive = Staphylococcus aureus
    o Negative = Staphylococcus epidermidis, Staphylococcus saprophyticus, others
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7
Q

What local infections does staphylococcus aureus produce?

A

o Skin and soft tissue – cellulitis, impetigo, folliculitis/furuncles/carbuncles, mastitis, necrotizing fasciitis

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8
Q

What invasive infections are produced by staphylococcus aureus?

A

o Bacteremia
o Endocarditis
o Osteomyelitis/septic arthritis

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9
Q

What toxin mediated infections - toxin producing strains of S. aureus - are produced by staphylococcus aureus?

A

o Toxic shock syndrome
o Staphylococcal scalded skin syndrome
o Food poisoning

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10
Q

For coagulase negative staphylococcus infections, what are the local and invasive infections produced?

A
  • Local infections
    o Urinary tract infection – S. saprophyticus
  • Invasive infections – associated with foreign devices (prosthetic joint, prosthetic valve)
    o Bacteremia
    o Endocarditis
    o Osteomyelitis/septic arthritis
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11
Q

What are the streptococcus species associated with human infection?

A
  • Streptococcus pneumoniae
    • Group A Streptococcus (GAS) – Streptococcus pyogenes
    • Group B Streptococcus (GBS) – Streptococcus agalactiae
    • Group C (GCS) and Group G Streptococcus (GGS)
    • Viridans group Streptococci – encompasses large group of streptococci
      that live in oropharyngeal and GI tract
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12
Q

How do you differentiate between streptococcal species?

A

hemolytic pattern on blood agar
- alpha-hemolytic: incomplete hemolysis of blood agar – zone of green
around bacterial colony on blood agar
- Streptococcus pneumonia, Viridans group streptococci
- beta-hemolytic: complete hemolysis of blood agar – zone of clear around
bacterial colony on blood agar
- GAS, GBS, GCS, GGS
- gamma-hemolytic: no hemolysis of blood agar
- Viridans group streptococci
- Lancefield group – method of grouping beta-hemolytic bacteria based on carbohydrate composition of cell walls (Group A, B, C, etc)

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13
Q

What are the local and invasive infections caused by streptococcus pneumonia?

A 
-	Local infections
o	Otitis media
o	pneumonia
-	Invasive infections
o	meningitis
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14
Q

What is Group A streptococcus also known as and what are the local, invasive, and toxic infections caused by it?

A

Group A Streptococcus (S. pyogenes): Infections
- Local infections
o Skin and soft tissue – cellulitis, impetigo, folliculitis/furuncles/carbuncles, mastitis, necrotizing fasciitis
o Tonsillopharyngitis / paratonsillar abscess / retropharyngeal abscess
- Invasive infections
o Bacteremia
o Osteomyelitis/septic arthritis
- Toxin mediated infections – toxin producing strain
o Toxic shock syndrome

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15
Q

Bacteremia - peripartum sepsis (maternal or neonatal) is caused by what type of streptococcus?

A

Group B Streptococcus (S. agalactiae): Infections
- Invasive infections
o Bacteremia – peripartum sepsis (maternal or neonatal)

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16
Q

What is the local infection caused by Group C and Group G streptococcus?

A

o Tonsillopharyngitis / paratonsillar abscess / retropharyngeal abscess

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17
Q

What are the infections caused by the viridans group streptococcus?

A

Viridans group Streptococcus: Infections
- invasive infections
o bacteremia
o endocarditis

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18
Q

What are the enterococcus species associated with human infections?

A

Enterococcal species associated with human infections

- Enterococcus faecalis
- Enterococcus faecium
19
Q

What are the local infections caused by enterococcus?

A

Urinary tract infection

20
Q

What are the corynebacterium species associated with human infections?

A
  • C. diphtheria – covered in Toxin mediated infections
21
Q

What is the listerial species associated with human infections? and it’s infections?

A

L. monocytogenes
- Invasive infections
o Neonatal sepsis – bacteremia, meningitis, pneumonia

22
Q

What is the laboratory diagnosis of gram positive infections?

A

Specimen - pus, blood, CSF, pleural fluid, synovial fluid, urine
- gram stain and culture

23
Q

What are the principles of treatment for impetigo, and folliculitis?

A
  • Topical therapy: mupirocin, fucidic acid
24
Q

What are the principles of treatment for other infections?

A
  • localized, not extensive, not toxin mediated: po antibiotics sufficient
  • extensive localized infections, abscess, invasive, septic shock: IV abx, may need surgery for debridement of devitalized tissue
25
Q

If an abcess is present what should you do?

A

drain abscess + antibiotics

26
Q

If there is toxin mediated: septic shock, staphylococcal scalded skin syndrome, what should you do?

A
  • Supportive therapy
  • IV antibiotic
  • IVIG – when septic shock present
27
Q

If there is toxin mediated: food poisoning, what should you do?

A

– self limited illness, no treatment required

28
Q

If there is a neonatal infection, what should you do?

A

requires inpatient treatment with parenteral antibiotics

29
Q

For MSSA (methicillin susceptible S. aureus) what antibiotic should you give?

A

o penicillinase resistant penicillins – Cloxacillin (po, IV)
o First generation cephalosporins – Cephalexin (po), Cefazolin (IV)
o Clindamycin (po, IV)

30
Q

For the Streptococci – Viridans group Streptococci, GAS, GBS, GCS, GGS what antibiotic should you give?

A

o Penicillin – penicillin V (po), penicillin G (IV)

o First generation cephalosporins – Cephalexin (po), Cefazolin (IV)

31
Q

For the Streptococci – S. pneumoniae, what antibiotic should you give?

A

o 2nd and 3rd generation cephalosporins

32
Q

For the enterococci, what antibiotic should you give?

A

o ampicillin susceptible – ampicillin

o ampicillin resistant – vancomycin

33
Q

For listeria, what type of antibiotic should you give?

A

ampicillin

34
Q

for methicillin resistant S. aureus (MRSA) what should you give for antibiotics?

A
  • resistance to beta-lactam antibiotics: tested by resistance to methicillin
  • d/t mecA gene – altered PBP2a (penicillin binding protein 2a)
  • antibiotic – vancomycin, other antibiotics as indicated by susceptibility pattern
35
Q

What are hospital associated MRSA risk factors?

A
  • prolonged or multiple hospitalizations
  • multiple courses of antibiotics
  • presence of indwelling line or tracheal tube
  • contact with MRSA positive individual
36
Q

What are community associated MRSA risk factors?

A
  • athletes
  • crowded living situations – homeless shelters, jails, army
  • Aboriginal
  • Tattoos
  • IVDU
37
Q

What are the vancomycin resistant Enterococci (VRE)?

A
  • resistance to: vancomycin
  • d/t production of peptidoglycan precursors that have decreased affinity for vancomycin
  • antibiotic options limited
38
Q

What are the VRE risk factors?

A
  • prolonged or multiple hospitalizations
  • multiple courses of antibiotics
  • presence of indwelling line or tracheal tube
  • immunosuppression
39
Q

What are the prevention and control measures for skin and soft tissue infections?

A

a. Skin and soft tissue infections
- Hand washing
- Standard precautions: Wear gloves when examining skin

40
Q

What are the prevention and control measures for respiratory infections?

A
  • Hand washing

- Droplet precautions: Gloves, gown, mask for healthcare workers

41
Q

What are the prevention and control measures for patient colonized/infected with MRSA or VRE?

A
  • Nasal/groin swab to detect colonization
  • Hand washing before entering room and after exiting
  • Private room
  • Gloves, gown for HCW
  • Gloves, gown for patient when not in room
42
Q

For the gram stains, what is special about gram negative organisms?

A

Gram negative organisms (Red): higher lipid content of cell walls

  • Increased permeability to acetone (decolorizer)
  • Lose crystal violet and take up safranin
43
Q

For the gram stains, what is special about the gram positive organisms?

A

Gram positive organisms (Blue/Violet): increased number of cross-linked teichoic acid in cell wall

  • Decreased permeability to acetone
  • Retain crystal violet and take up safranin
44
Q

What is the coagulase test?

A

Coagulase: converts fibrinogen to fibrin

  • Rabbit plasma inoculated with Staphylococcal bacteria
  • Positive – serum coagulates, forms clot
  • Negative – serum remains liquid

Microbiology (13 decks)

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