Intro to Infectious Disease

Question 1

Basis for gram staining

Answer 1

• differentiate bacteria by chemical and physical properities of cells walls via detection of peptidoglycan
• gram-positive = blue on gram stain
• gram-negative = pink on gram stain

Question 2

4 basic divisions of bacteria

Answer 2

• Gram-positive
  
  • cocci
  • rods
• Gram-negative
  
  • cocci
  • rods

Question 3

Important gram-positive cocci

Answer 3

• Staph Aureus → catalase + / pairs & clusters / coagulase +
  
  • BAD!!!
• Staph other → pairs & clusters /coagulase -
  
  • not as bad
• Strep → catalase - / pairs & chains

Question 4

Important gram-negative cocci

Answer 4

• Neisseria
• Moraxella

Question 5

Important gram-negative rods

Answer 5

• E. Coli, Pseudomonas → divide into Lactose-fermenters +/-
• UTI, Abd, nosocomial

Question 6

Important gram-positive rods

Answer 6

• Listeria
• Clostridium

Question 7

Important non-staining bacteria

Answer 7

• Gram (+): M. tuberculosis
• No cell wall: Mycoplasma, Chlamydia
• Gram (-) but too small: Rickettsia, Spirochetes (Syphilis)
• Gram (-) : Legionella

Question 8

Lactose-fermenting bacteria

Answer 8

• E coli
• Klebsiella
• Enterobacter
• Citrobacter

Question 9

NonLactose-fermenting bacteria

Answer 9

• Pseudomonas aeruginosa
  
  • Oxidase (+), strict aerobe
• Salmonella
• Shigella

Question 10

“Four questions” in the evaluation of patient w/presumed infectious disease

Answer 10

• First, find out chief complaint: Fever, MS change, cough, diarrhea, rash, ↑/↓ WBC, low BP, etc.
• 1) Is it infection?
• 2) Where is it?
• 3) What are the bugs at this site?
• 4) What are the drugs?

Question 11

Gram-positive vs. Gram-negative bacterios

Answer 11

• Gram-positive (blue on gram stain)
  
  • Teichoic acid
  • Thick PG Cell wall
  • (accessible outer PG)
• Gram-negative (pink on gram stain)
  
  • LPS
  • Thin PG Cell wall
  • (PG covered by membrane [porins])

Question 12

Common syndromes associated w/S. auresu

Answer 12

• Localized infection (boils, cellulitis)
• Disseminated infection
  
  • blood, heart, joints, metastatic

Question 13

Common syndromes associated w/coagulase-negative staph.

Answer 13

• infection @ prosthetics
• Where is the plastic?
• Where is the metal?

Question 14

Common syndromes associated with Group A Step

Answer 14

• Group A strep = S. pyogenes
• Bacteremia, Sepsis
• Rheumatic fever
• Acute IE
• Pneumonia/empyema
• TSS
• Necrotizing fasciitis

Question 15

Syndromes associatied w/gram-negative cocci

Answer 15

• gonorrhea
• meningitis
• pneumonia

Question 16

Syndromes associatied w/gram-negative rods

Answer 16

• UTI
• Abdominal infections
• nosocomial infections

Question 17

Syndromes associatied w/gram-positive cocci

Answer 17

• Cellulitis
• endocarditis
• abscess

Question 18

Syndromes associatied w/gram-positive rods

Answer 18

• Meningitis
• fasciitis

Question 19

Evidence of infection in Hx

Answer 19

• -Acute (±)
• Susceptible host
• Ill Contact
• Travel

Question 20

Evidence of infection in PE

Answer 20

• -Fever (±)
• -Inflammation (±)
• • Pus
• -Focal/source

Question 21

Evidence of infection in Labs

Answer 21

• -­ WBC (left shift; toxic granulations)
• -­ CRP, ESR
• • Imaging
• • Pyuria