Lecture 9: Control of Microorganisms Flashcards
What is sterilization?
Killing all viable organisms (including spores)
What is inhibition?
Effectively limiting microbial growth.
What is decontamination?
Washing object so it’s safe to handle
What is disinfection?
Directly targets removal of all pathogens, not necessarily all microorganisms.
What are the physical methods of antimicrobial control?
Heat, Pasteurization, Radiation, Filters.
What is decimal reduction time?
Amount of time required to reduce viability tenfold. Inversely correlated with temperature. (100%->10%)
What is thermal death time?
Time needed to kill all cells at a given temperature. Dependent on cell #.
How long can endospores resist boiling?
5 min for 1 decimal reduction.
How does an autoclave sterilize things?
Uses steam under pressure that reaches 121C, sterile in 10-15 min.
What is pasteurization?
Using precisely controlled heat to reduce microbial load in heat sensitive liquids.
What is flash pasteurization?
72C for 15s
What is bulk pasteurization?
65C for 30 min (Harsher on milk)
What kind of radiation is used for antimicrobial control?
Microwaves, UV, X rays, gamma, electons
How does UV decontaminate surfaces?
Has enough energy to modify DNA
Why can C.botulinum and O. radiodurans withstand radiation?
Botulinum forms spores, Radiodurans is very effective at repairing DNA.
What is ionizing radiation?
electromagnetic radiation, produces ions/reactive molcs. Damage DNA and proteins.
What is filter sterilization?
Pores of filters too small for organisms to pass=left on filter.
Whats the difference between depth and membrane filters?
Depth=Fibrous sheet, lots of strands.
Membrane=nucleopores
What are the different kinds of chemical methods to combat microbial growth?
Antimicrobial agents, Antimicrobial drugs, Antivirals, antifungals
What does bacteriostatic mean?
Inhibit growth of microorganisms.
What does bacteriocidal mean?
Kill Microorganisms
What does bacteriolytic mean?
Kill microorganism by inducing lysis. (triangle graph)
What is the minimum inhibitory concentration? (MIC)
Smallest amount of an agent needed to inhibit growth of microorganism
What is the minimum lethal concentration? (MLC)
Lowest concentration of agent that kills a test organism
What is the minimum bacteriocidal concentration? (MBC)
Lowest concentration of agent that kills test bacteria
What is a disk diffusion assay?
Antimicrobial disk added to agar=MIC reached at some distance (further away=less antibiotic)
What is a sterilant?
Destroys all forms of microorganisms, including endospores. (Cold sterilization)
What are disinfectiants/sanitizers? (ie lysol)
Don’t kill endospores. Can be toxic to humans.
What are antiseptics?
Don’t kill endospores. Non toxic
What are antimicrobial drugs?
Ie antibiotics, antifungals, antivirals. Non toxic, don’t kill endospores.
What are Phenols?
a. Disinfectant
b. Sterilant
c. Antiseptic
A and C
What are Alcohols?
a. Disinfectant
b. Sterilant
c. Antiseptic
A and C
What are Halogens?
a. Disinfectant
b. Sterilant
c. Antiseptic
All of the above.
What are heavy metals?
a. Disinfectant
b. Sterilant
c. Antiseptic
A
What is ammonium?
a. Disinfectant
b. Sterilant
c. Antiseptic
A and C
What are alkylating agents?
a. Disinfectant
b. Sterilant
c. Antiseptic
A and B
Why do many antimicrobial drugs target 30s rRNA?
It is the ribosome subunit present in prokaryotes but not eukaryotes.
What are growth factor analogs? (ie sulfanilamide)
Structurally similar to GFs, but don’t function.
What does sulfanilamide (Sulfa drug) inhibit?
Is an analog of P-aminobenzoic acid, bacteriostatic. Inhibits folic acid synth.
What is isoniazid an analog of?
Growth factor, stops synth of cell wall component.
How do nucleic acid base analogs work?
Formed by addition of Br or F to base, it stops DNA replication.
How to quinolones work?
Antibacterial, interfere with DNA gyrase. Controls DNA supercoiling.
What are antibiotics?
Antimicrobial agents that are naturally produced.
What is penicillin primarily effective against?
Gram positive bacteria. Synthetic forms can be effective against gram -
True or false. The Beta lactam ring has a modifiable R group.
True
What are cephalosporins produced by?
Fungus
What two rings are in cephalosporins?
B lactam and dihydrothiazine rings. Commonly used for gonorrhea.
What does the B lactam ring inhibit?
The final transpeptidation step in peptidoglycan synthesis. It is facilitated by a transpeptidase which is a penicillin binding protein. Inactivated when bound.
How does the B lactam ring inhibit peptidoglycan synthesis?
No transpeptidase=hole in cell wall.
Are B lactams bacteriocidal or bacteriolytic?
Both. Can actually be bacteriostatic in isotonic solution.
True or false. Many antibiotics effective against bacteria are also produced by bacteria.
True
What are aminoglycosides made by? (Streptomycin)
Prokaryotes
What is Chloramphenicol made by?
Prokaryotes
What are macrolides (erythromycin) made by?
Prokaryotes
What are tetracyclines made by?
Prokaryotes
What do aminoglycosides target?
30s subunit=misreading of mRNA. Bacteriocidal
What does Chloramphenicol target?
Bind to 23s subunit, block peptide elongation. Bacteriostatic.
What do macrolides (erythromycin) target?
50s subunit, block protein synth. Bacteriostatic.
What do tetracyclines target?
30s subunit, block protein synth.
How do microbes gain antibiotic resistance?
Acquire new gene on R plasmid.
What do most successful antivirals do?
Block reverse transcriptase and production of viral DNA.
What do protease inhibitors do? (Antiviral)
Inhibit processing of large viral proteins into components.
What do fusion inhibitors do? (Antiviral)
Prevent viruses from successfully fusing with host cell
What particular problem do antifungals have?
Fungus are eukaryotes=use a lot of the same functions as humans.
What do antifungals target?
ergosterol synthesis (Fluconazole) , cell wall synthesis.
What are the mechanisms microbes use to become resistant to antibiotics?
- Destruction/modification of antibiotic structure
- modification of target site
- Modification of antibiotic uptake mechanism
What are the mechanisms microbes use to become tolerant to antibiotics?
- lack target sites (ie no peptidylglycan)
- modify target sites
- lack uptake mechanism
