LAB 7 Flashcards
Non-ionizing, short-wavelength high-energy radiation
Ultraviolet (UV)
What are the 3 types of UV radiation
UV-A longest wavelength
UV-B 280-315
UV-C 100-280
molecular lesions
DNA strand is physically kinked and polymerases cannot replicate DNA resulting in cell death
Pyrimidine dimers
SOS system
activates when major DNA damage occurs
Will remove pyrimidine dimers and insert new pyrimidine molecules to restore the original state of DNA strand
chemical metabolites produced by some fungi and bacteria to kill or stop the growth of nearby competitors
*first one penicillium mold discovered by alexander fleming
natural antibiotics
are those produced chemically in the lab keeping active moiety intact but modifying the R (Sidechain) group
Semi-synthetic antibiotics
Antibiotics that target single groups
Narrow spectrum
are those that are entirely produced inside laboratories
Sulfonamides
Synthetic antibiotics
antibiotics kill bacteria
Bactericidal
antibiotics only inhibit growth but does not actually kill bacterial cells
Work in combo with your immune system to eliminate an infectious disease
bacteriostatic
What are 2 narrow-spectrum antibiotics?
- Vancomycin - active against gram + only
- Polymyxin B - active against gram - only
Antibiotics that target both gram types of bacteria
*disadvantage - remove normal microbiota, which could result in a superinfection
Broad-spectrum antibiotics
*tetracycline - targets gram + and - plus rickettesias and chlamydias
Superinfection
2nd infection that occurs immediately after 1st infection, usually by different pathogens
High selective toxicity
means that the drug targets bacteria and not human
Low selective toxicity
can cause more serious side effects in humans
*polymyxin B - use external only
Kirby-Bauer method
The test used to determine in vitro sensitivity of a particular bacteria to various antibiotics
Variables for the Kirby-Bauer method include
- Mueller-hinton II agar
- pH 7.2-7.4
- Agar thickness of 4mm
- Bacteria growth in liquid broth to the density of standard 10-7 bacterial cell/milliliter
*bacterial lawn - Disks impregnated with a known concentrations of antibiotics are applied
- Incubate plate at 37 c for 16-18 hours
Zone of inhibition
the area around the disk in which no bacteria grow
quantitative technique for determining antimicrobial susceptibility
The predefined gradient of antibiotic concentrations on a plastic strip
Where it crosses on the strip is telling me the min concentration needed for antibiotics concentration
E- Test
Vertical transmission
when genetic info is passed from parent cell to daughter cells as a result of binary fission
Horizontal gene transfer
when genetic info is passed between unrelated cells.
This includes conjugation, transformation, transduction, and transposons
Plasmids
Small, circular, double-stranded DNA molecules that use exist outside of bacterial chromosome
Conjugation
process of transferring genetic info from donor cell to recipient cell through sexual pilis
Antibiotic resistance genes
genes plasmids carry to help cell in selective environments
Recombinant cell
a recipient cell that has received a plasmid from a donor cell and is now an F+ cell
What is an example of a broad-spectrum antibiotic?
Tetracycline
Works on both gram-positive and negative
What are some pathways antibiotics work
- Inhibiting cell wall synthesis - penicillin
- target protein synthesis
- disruption of cell membrane - Polymyxin B
- Inhibit DNA and RNA synthesis - ciprofloxacin & rifampicins
What is the advantage of
Broad-spectrum and Narrow spectrum antibiotics
Broad - Advantage: inhibiting many types of bacteria when the infection is unknown
Disadvantage: removing normal microbiota, particularly in the colon = superinfection
Narrow- Advantage: Target single groups
Disadvantage: only target single groups
A test that determines the lowest concentration that inhibits the growth of the organism
MIC
Minimum Inhibitory Concentration
What wavelength is most damaging and lethal
Chemical metabolites produced naturally by some fungi and bacteria
Antibiotics
What was the first antibiotic used commercially
Penicillin dervied from penicillium
What test is used to determine the invitro sensitive pattern of a particular bacterium to various antibiotics and shows the zone of inhibition?
Kirby Bauer method
What are some factors that could influence the size of the zone of inhibition for an antibiotic?
Agar thickness
drug concentration
pH
What antibiotic test is essential for patients who have liver or kidney disorders which prevent metabolizing the antibiotic, requiring the smallest amount to be used?
E-test
What measurement is read here?
MIC
What value is read here and what kind of antibiotic would it be?
Bacteriocidal
What value is read here and what kind of antibiotic would it be?
bacteriostatic
What does Minimum inhibitory concentration mean?
Lowest concentration that inhibits the growth of the organism
Which UV has the most damaging wave lengths?
What is the number wave length that is most damaging?
UV C
260 nm
UV wave lengths at 254-260nm result in DNA damage by
What are some factors that are important in the lethal effects of UV light?
time of exposure
distance from UV light
barriers
Which is more resistant to UV light?
S. epidermidis or B. cereus?
B. cereus
If a cell is starved for nutrients would you think they are more or less susceptible to UV effects?
More, it overwhelms their repair system
Explain why UV light exposure results in skin cancer and not liver or lung
Because it cannot get into liver or lung
Why is conjugation important in a healthcare setting?
provides, for instance, a platform for the spread and persistence of antibiotic resistance genes
