Bacte Lec - AST Flashcards
challenging a bacteria on what antibiotic they are susceptible or resistant
antimicrobial susceptibility testing
determines best antibiotic to be prescribed by doctors
antimicrobial susceptibility testing
3 stages of antimicrobial susceptibility testing
1) culture and sensitivity
2) isolation and identification of causative agent
3) susceptibility & resistance to antimicrobial agents
suspected organisms in urine sample
Providencia
Escherichia coli
Klebsiella
agar for Escherichia coli
Gram negative
EMB/MacConkey
Culture media commonly used for urine sample
MacConkey Agar
Eosin Methylene Blue Agar
CAP - not commonly used
BAP
CM for Staphylococcus saprophyticus
Blood Agar
CM for Gram negative cocci
Chocolate Agar
usual causative agent of UTI
Gram negative enteric
streaking pattern for culture of urine
clock method
heavy infection meaning
UTI
light infection meaning
only caused by normal flora
yellowing slant and butt meaning
organism is a lactose fermenter
with gas formation meaning
organism: Escherichia coli or enterobacter
broth for indole testing
tryptone broth
cm for indole testing, motility, h2s production
SIM
cm for assessing capability of utilizing citrate
simmon citrate agar
cm for assessing capability of producing acid/alkali (aceto___) based on carbohydrate fermentation
Methyl Red Voges Proskauer Medium
duration of C/S
3-5 DAYS
produced by microorganisms, inhibit growth of other microorganisms
antibiotics
destroy microorganisms through inihibiting their development or action
antimicrobial agents
mold with antibiotic activity
Penicillin notatum or Penicillin chrysogenum
means bacteria is capable of producing secondary metabolites which can inhibit growth of other bacteria
zone of inhibition/clear zone
which phase of bacterial growth curve shows symptoms
log phase
which phase of bacterial growth curve represents the bacteria still adjusting, just inoculated, synthesizing enzymes
lag phase
During this phase, the microorganisms are in a rapidly growing and dividing state.
log phase
During this phase, cells undergoing division is equal to the number of cell death, and finally bacterium stops its division completely
stationary phase
During this phase, the individual is feeling better
stationary phase
during this phase, the number of dead cells exceeds the number of live cells.
decline phase
RIP
Rifampicin, Isoniazid, Pyrizanamide
classif of antibiotic
specific attack
limited spectrum of action
narrow spectrum
examples of narrow spectrum antibiotic
vancomycin
penicillin
narrow spectrum antibiotic - effective against Gram +
PENICILLIN
narrow spectrum antibiotic- effective against Gram + ESP S. aureus
Vancomycin
classif of antibiotic
against Gram positive and gram negative
broad spectrum
disadvantage of broad spectrum antibiotic
may inhibit normal flora
examples of broad spectrum antibiotic
tetracycline, chloramphenicol, azithromax, augmentin
type of antibiotic not prescribed when C/S is already performed
broad spectrum antibiotic
result of primary infection
superinfection
superinfection of these 3 sites is difficult to treat
mouth, Respiratory tract, GUT,
Common agents of superinfection
Staphylococcus aureus
Candida albicans
Trichomonas vaginalis
Pseudomonas aeruginosa
classif of resistance to antimicrobial agents
before abuse
intrinsic resistance
Staphylococcus saprophyticus is resistant to
novobiocin
genus resistant to polymyxin
Proteus, Providencia, Morganella, Edwardsiella
classif of resistance to antimicrobial agents
may result from chromosomal mutations or from plasmid
acquired resistance
classif of resistance to antimicrobial agents
necessitates prior exposure to antimicrobial agent
acquired resistance
mechanisms of resistance [4]
modification of the target site
inactivation of antimicrobial agent
decreased permeability of cell wall
alteration of binding or ribosomes
mechanisms of resistance
antibiotic’s ability to bind to cell wall or ribosome is altered
modification of the target site
mechanisms of resistance
bacterial enzymes convert the active drug into inactive form
inactivation of antimicrobial agent
mechanisms of resistance
poor entry of antibiotic into bacterial cell wall
decreased permeability of cell wall
mechanisms of resistance
resistance of pseudomonas to certain aminoglycosides
alteration of binding of ribosomes
protein synthesis inhibition
bacteriostatic or bactericidal
bacteriostatic
cell wall synthesis inhibition
bacteriostatic or bactericidal
bactericidal
inhibition of cell wall synthesis
penicillin ampicillin methicillin carbenicillin vancomycin cephalosporin
interference with protein synthesis at 30S ribosomal subunit [7]
gentamicin amikacin neomycin tobramycin tetracycline spectinomycin streptomycin
interference with protein synthesis at 50S ribosomal subunit
chloramphenicol
competitive inhibition of folic acid synthesis
sulfonmethoxazole
trimethoprim-sulfamethoxazole
zones of inhibition measured by [2]
ruler or caliper
when can clinicians increase dose of drug
when the organism is found to be moderately susceptible to drug
indicator of relative susceptibility
DIAMETER of zone of inhibition
principle of kirby bauer disk diffusion method
diffusion
relationship between diameter of zone of inhibition and logarithm of MIC antibiotic
INVERSE LINEAR
lowest concentration of antibiotic that inhibits in vitro bacterial growth
minimum inhibitory concentration
highest dilution of antibiotic that inhibits in vitro bacterial growth
minimum inhibitory concentration
dilution factor
total volume/ amount of solute
indicates presence of growth
turbidity
well-defined chemical composition
medium
composition of medium for AST must be [2]
reproducible
constant
parameters in AST
Medium - MHA Agar depth pH Density of inoculum Barium sulfate
composition of MHA [6]
Beef infusions Nucleic acids vitamins casein hydrolysate [peptone source] agar [solidifying agent] cornstarch [neutralize fatty acids]
for fastidious bacteria, MHA is supplemented with
blood
increased Ca and Mg, effect to Aminoglycosides
decreased activity of AG against Pseudomonas aeruginosa
increased Ca and Mg, effect to tetracycline
decreased activity against all bacteria
decreased Ca and Mg, effect to Aminoglycosides
inc activity of AG against Pseudomonas aeruginosa
decreased Ca and Mg, effect to tetracycline
inc activity against all bacteria
pH for AST
7.2 TO 7.4
High pH levels (basic), effect
inc activity of aminoglycosides, erythromycin, clindamycin
Low pH levels (acidic), effect
dec activity of aminoglycosides, erythromycin, clindamycin
High pH levels (basic), effect to zone of inhibition
false susceptibility/ wider zone of inhibition
Low pH levels (acidic), effect to ZoI
false RESISTANCE/ narrow zone of inhibition
High pH levels (basic), effect to tetracycline
dec activity
Low pH levels (acidic), effect to tetracycline
inc activity
agar depth
4 mm
thick agar depth meaning
false resistant
thin agar depth meaning
false susceptible
composition of mcfarland standard
1% BaCl2 and 1% H2SO4
Standard cell density
1x10^8 CFU/mL
The higher the mcfarland standard, ___ turbid
higher/greater
too light (turbdidity)
false susceptible
too heavy
false resistant
susbtitute to mcfarland
spectrophotometer
wavelength for turbidity
600 nm
streaking pattern
overlapping method
used to fish out bacteria from pure young culture
STERILE cotton swab
after inoculation to MHA, allow it to stand for ___ before placing disks
3-5 min not longer than 15 min
after inoculation to MHA, allow it to stand for 3-5 before placing disks so as
allow absorption of excess moisture
within __ min, disks are applied firmly on MHA
15
how many disks can a plate 150 mm diameter accommodate
12 disks 8 outer ring, 4 center
in storing antibiotic disks, what type of freezer/ref be used
frost-free
antibiotic disks and disk dispensers kept with ___ to prevent deterioration
dessicant
to minimize condensation, should be adjusted to
room temp [antibiotic disk]
temp for long storage of antibiotic disk
14C below in a non-frost freezer
temp for working supply of antibiotic disk
2-8C
Incubation
temp
hrs
type of air
35C 16-18 hrs ambient air
lower temp of incubation results to
larger zones of inhibition
plates should not be stacked more than
5 high
at what temp MRSA not detected
> 35C
type of incubation/ ph level wherein activity of some antibiotic is altered
CO2 incubation
swarming motility
Proteus vulgaris or Proteus mirabilis
appears greenish due to thiocyanine
Pseudomonas aeruginosa
effect of prolonged incubation to zone of inhibition
smaller diameter
reason for the smaller diameter of ZoI after prolonged incubation
presence of contaminants
