L3: ANTIBIOTICS AND AST Flashcards
Chemicals produced by microorganisms that inhibit the growth of other
microorganisms
ANTIBIOTICS
ANTIBIOTICS Can be ___or ____
BACTERICIDAL or BACTERIOSTATIC
Antibiotics is classified as ___ or ___
NARROW spectrum or BROAD Spectrum
ANTIBIOTICS, with limited coverage against some specific bacteria
Narrow Spectrum
ANTIBIOTICS, that has a wide coverage to groups of bacteria
Broad spectrum
Antibiotics, (3) Routes of Administration:
Oral, IV, IM
occurs when microbes evolve mechanisms that protect them from the
effects of antimicrobials/antibiotics
Bacterial Resistance
Bacterial Resistance 4 types
1.Intrinsic Resistance
2. Acquired Resistance
3. Genetic Change
4. DNA Transfer
type of bacterial resistance: through evolution by changing their structure or
components.
Intrinsic Resistance
type of bacterial resistance: through a new genetic mutation that helps the
bacterium survive or by getting DNA from a bacterium that already is
resistant.
Acquired Resistance
Acquired Resistance ; Resistant strains outgrow Susceptible strains 🡪
new strains are R
Chromosomal Mutations:
Acquired Resistance ; extrachromosomal elements of DNA that are assoc with
virulence and antibiotic R
Plasmids
“jumping genes”; can transfer from plasmid to
plasmid or from DNA chromosome to plasmid
Transposons
Bacterium DNA change and alter the
production of protein 🡪 different bacterial components and
receptors 🡪bacteria unrecognized by the antibiotic
Genetic Change
Bacteria can share genetic components with other bacteria
and transfer the resistant DNA through a horizontal gene transfer.
DNA Transfer
Factors for Antibiotic Resistance
Natural Occurrence/Selection
Self-medication
Clinical Misuse/Overuse
Environmental Pollution/Improper discarding of unsused/used antibiotics
Overuse of disinfectants
Laboratory test/procedure in microbiology to determine which
drug will inhibit/kill the microorganism and which drug is
resistant to the microorganism
Antimicrobial Susceptibility Test
The result will help the physician to decide which drug
(antibiotic) is effective in killing the bacteria causing the
infection as well as what bacteria is present or causing the
infection
Antimicrobial Susceptibility Test
CLSI and EUCAST meaning
Clinical and Laboratory Standards Institute (CLSI)
European Committee for Antimicrobial Susceptibility Testing (EUCAST).
MC (best) use is ____ AGAR
MUELLER-HINTON AGAR
- low in Ca and Mg ions that interfere activity of antibiotic
- gives favorable growth on fastidious bacteria)
MUELLER-HINTON AGAR
Conc of bacteria that will be added to the agar or broth
Inoculum
used as a reference to adjust the turbidity of bacterial suspensions so that the number of bacteria will be within a given range to standardize
microbial testing
Usually at 0.5
McFarland standard
Methods of antibiotic sensitivity test
Disc Diffusion method
MIC method
E test
Automated Systems
Disc Diffusion method
KIRBY BAUER DISK DIFFUSION TEST
placing a strip impregnated with antimicrobials onto an agar
plate
E test
VITEK 2, BD Phoenix, and Microscan systems, are the most common methodology for AST
Automated Systems
culture-based microbiology assay used in diagnostic and drug
discovery laboratories, performed by inoculating the surface of an agar plate with bacteria isolated from a patient’s infection
Kirby Bauer test Method
circular area around the spot of the antibiotic
in which the bacteria colonies do not grow
Zone Of Inhibition:
Qualitative method: S___, I___, R___
Sensitive, Intermediate, Resistant
MIC means
Minimum Inhibitory Concentration
Quantitative method to determine the lowest concentration of an
antibiotic to prevent visible in vitro growth of bacteria
Minimum Inhibitory Concentration
the lowest concentration of an antibacterial agent required to kill a
bacterium over a fixed, somewhat extended period
*MBC: Minimum Bactericidal Concentration
