Bacterial basics

Question 1

Gram positive

Answer 1

• thick peptidoglycan cell wall
  
  • NAG NAM sugar polymer repeats
    
    • linked by peptide side chain
      
      • linked by penicillin binding protein (PBPs)

Question 2

Gram negative

Answer 2

• thin cell wall
• outermmebrane and cytoplasmic membrane
  
  • periplasmic space
• ​contains lipopolysaccharides
• Porins

Question 3

Gram positive bacilli

Answer 3

• Corynebacterium
• Clostridium
• Listeria
• Bacillus anthracis

Question 4

Beta hemolytic strep

Answer 4

• pyogenes (Group A)
• agalactiae (Group B)
• ruptures the RBC (zone of clear on blood agar)

Question 5

Gamma hemolytic strep

Answer 5

• no affect on blood agar
• Enterococcus
  
  • ​E. faecalis
  • E. faecium

Question 6

Alpha hemolytic strep

Answer 6

• S. pneumoniae
• S. viridans
• oxidation of iron in the hgb = green area on blood agar

Question 7

Gram negative cocci

Answer 7

• Neisseria species
• N. meningitidis = glucose and maltose +
• N. gonorrhoeae = glucose +

Question 8

Facultative bacteria

Answer 8

• survive with or without oxygen

Question 9

Facultative anaerobes

Answer 9

• use oxygen if it is available
• can also create energy without oxygen

Question 10

Microaerophiles

Answer 10

• require oxygen for energy but only like small amounts
• atmospheric concentrations of oxygen = 21% = toxic

Question 11

Aerotolerant anaerobes

Answer 11

• do not use oxygen but are not harmed by it

Question 12

Obligate or Strict Anaerobes

Answer 12

• harmed by the presence of oxygen

Question 13

Bacterial Replication Requires

Answer 13

• lots of deoxynucleotides
• essential cofactor in DNA synthesis
  
  • tetrahydrofolate
    
    • the precursor to this is targeted by abx that inhibit folate synthesis

Question 14

MIC

Answer 14

• measure the minimum concentration of abx that is able to suppress growth of the bacteria

Question 15

MBC

Answer 15

• measures the minimum concentration of an abx that kills the bacterial isolate

Question 16

Kirby-Bauer Method

Answer 16

• discs on the agar plate
• method for testing for antimicrobial susceptibility
• larger disc = lower MIC = increased susceptibility

Question 17

E-test/ Epsilometer Test

Answer 17

• agar diffusion method of testing bacteria susceptibility
• rectangular strip on agar plate
  
  • measure at edge of elliptical shape of no growth

Question 18

Broth Dilution Method

Answer 18

• method for measuring susceptibility of bacteria to abx
• the MIC is the lowest concentration of abx that prevents visible growth

Question 19

What must the drug concentration be in order to be considered sensitive at the site of infection

Answer 19

• 8 times the MIC

Question 20

6 Ps of resistance

Answer 20

• penetration = PCN poorly penetrate into intracellula rspace
  
  • bacteria can hid in this compartment (Rickettsia and Legionella)
• Porins
  
  • located in some Gram negative bugs: E. coli, Proteus, Salmonella, Shigella
• Pumps
  
  • Efflux pump- prevent accumulations
    
    • pseudomonas aeruginosa
• Penicillinases (Beta-lactimases)
• PBPs - mutated
• Peptidoglycan - bugs that dont make peptidoglycan are not affected by PCN (Mycoplasma, chlamydia)

Question 21

Slow Fermenters

Answer 21

Citrobacter, Serratia

Question 22

What is the essential cofactor in DNA synthesis of bacteria ?

Answer 22

Tetrahydrofolate

Question 23

Faster fermenters

Answer 23

Klebsiella, E.coli, Enterobacter

Question 24

Gram positive bacilli

Answer 24

• Listeria
• Bacillus
• Corynebacterium
• Clostridium