02 AST protocols Flashcards
Performed on bacteria isolated from clinical specimens that are clinically significant
AST
T/F: S. pyogenes, S. agalactiae, N. meningitidis, L. monocytogenes are most frequently subject to AST
F (they are not subject to AST)
T/F: it is important in AST that the condition is not too acidic
T
Optimal pH for AST
7.2-7.4
Bacterial inoculum size of 0.5 McFarland Standard
1.5 x 10^8 CFU/mL
Colonies that are more than 1 day old are prone to false ___
susceptibility
Optimal concentration of Mg and Ca in AST
Ca: 25 mg/L
Mg: 12.5 mg/L
An increased cation concentration could lead to false resistance of ___ to ___
P. aeruginosa
Aminoglycoside
Incubation temperature when performing AST
35-37C
MRSA is incubated at ___
35C
Incubation period when performing AST
16-18 hrs
In performing AST, non-inhibitory medium such as ___, ___, ___ should be the source of 4-5 colonies
BAP
CAP
broth
Growth phase of the bacteria subject to AST after being transferred to a broth medium
log phase (3-5 hours)
Components of 0.5 McFarland Standard
99.5 mL 1% Sulfuric acid
0.5 mL 1.175% Barium chloride
0.5 McFarland standard is measured at ___ nm and should be at ___
625 nm
0.08-0.1