Microbial Control Flashcards
What is sterilization
The killing or removal of ALL viable organisms ( including endospores)
Is clean and sterilized is the same
Hands can be clean, but not sterile
The cloth coming from autoclave can be dirty, but sterile
What is inhibition
Effectively limit microbial growth. We are not necessarily killing them. We just stop them from multiplying
What is decontamination
The treatment of an object to make it safe to handle ( removing food from the table)
What is disinfection
Directly targets the removal of all pathogens, not necessarily all microorganisms
Physical methods for antimicrobial control
Heat
Radiation
Filtration
Chemical methods for killing microbes are also called
Antimicrobes
What antimicrobes are used on external surfaces and internally
External: sterilants,disinfectants, antiseptics
Internally: antibiotics,antiviruls,antifungals
What is the most widely used physical control for controlling microorganisms
Heat
High temperatures ___ macromolecules
Denature
What is decimal reduction time?
Amount of time required to reduce viability tenfold ( from 100% to 10%)
The decimal reduction time is ___ correlated with the temperature
Inversely
The time necessary to kill a defined fraction is dependent of ____
The initial cell concentration
What will be the difference in decimal reduction time between mesophile and thermophile
Mesophile will have lower decimal time at lower temperatures, comparing to thermophile
What is the thermal death time
the time needed to kill all cells at a given temperature.
Thermal death time depends on
The population size of the microorganism tested, so you need to standardize the starting number of cells to be able to compare the sensitivity of different microorhanisms
What is the issue with endospores
They can resist the temperatures that will kill microorganisms. 5 min in boiling water for a decimal reduction
What is the autoclave
A sealed device that uses steam under pressure. it allows temperature of water to get above 100 C without boiling
What is the time and temperature for sterilization in autoclave
121 C in 10-15 minutes
What kills the microorganism in the autoclave
Not the pressure, but the temperature
What should you remember with autoclave and big objects
The object is a little colder than the environment and thus more time is required
What is Pasteurization
The process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids. It does not kill all microorganisms
What is the purpose of pasteurization?
Reduces the microbial load, increases the shelf life of the product
Pasteurization reduces what kinds of pathogens
Listeria monocytogenes Salmonella enterica Campylobacter E.coli Mycobacterium
The time and temperature for flash and bulk pasteurization
Flash: 72 C for 15 sec
Bulk: 65 C , 30 min
The principle of pasteurization
At first it is heated for a short period of time and then quickly cooled. Can be heated more for the milk that will undergo further processing
What radiation can reduce microbial grwoth
Microwaves UV X-rays gamma rays electrons
What does UV do to microorganisms
UV has enough energy to cause modifications and breaks in DNA, which inhibit replication, transcription and cause death
What is the barrier for UV light
Cannot penetrate solid,opaque or light-absorbing surfaces. Can sterilize only the top layer
UV light is useful for sterilization of
Water and Air
What is ionizing radiation
-Electromagnetic radiation that produces ions and other reactive molecules
How ionizing radiation stop the growth of microorganisms
Generates electrons and hydroxyl radicals that cause damage to DNA and proteins
What emits electrons and gamma rays
Electrons by cathode ray tubes
Gamma rays by radioisotopes
What rays have the highest energy
Gamma rays
What is specific about Deinococcus radiodurans
It does not have spores
But it has multiple copies of its genome, so as soon as one copy get damaged or destroyed, it has back up
Filtration is used on
Sensitive liquids and gases
Pores of filter are too small for organisms, but big enough for liquids and gases
What is depth filters
Where it is used and examples
Fibrous sheet or mat made from an array of fiber ( paper or glass)
Used to sterilize liquid,air
HEPA filters
Mmebrane filters: what is it and how it can be speeded up
It functions like a sieve. it has nucleopores as a filter. Can be speeded up by syringe, pump, or vacuum
Antimicrobial agents can be classified as
- Bacteristatic: inhibit growth of microorganisms
- Bacteriocidal: kill microorganisms
- Bacteriolytic: kill microorganism by inducing lysis
What is MIC
Minimum inhibitory concentration - the smallest amount of an agent needed to inhibit growth of a organism
What is MLC
Minimum lethal concentration- the lowest concentration of an agent that kills a test organism
What is MBC
Minimum bacteriocodal concentration - the lowest concentration of an agent that kills a test bacterium
To see MBC we need to
to plate on agar to see the growth
What is disc diffusion assay
Antimicrobial agent added to filter paper disc. MIC is reached t some distance from the disc
What is the zone of inhibition
Area of no growth around the disc
What kind of method is disc diffusion assay
Semiquantitative way
The bigger the zone of inhibition-> the more susceptible to the agent
What does it mean superficial bacterial infections
outside of the body, on the skin
Two categories of the antimicrobial agents
Products used to control microorganisms in commercial and industrial applications ( air-conditioning,textile,etc.)
-Products designed to prevent growth of human pathogens in inanimate environments and on external body surfaces
What is a sterilants
They destroy all forms of microorganisms, including endospores. Called COLS STERILIZATION in contrast to autoclave
What is disinfectants/sanitizers
Applied to nonliving objects or surface( can be toxic for animals/humans). Do not kill endospores
What is antiseptic
Applied tot the surface of living tissues or skin. Do not kill endospores
What is antimicrobial drugs
Antibiotics, antifungals: applied outside or inside the body of animals/humans. DO not kill endospores
Phenol/phenolics are (D/A/S) and how they work
D, A
Disrupt cytoplasmic membrane, protein denaturant( in high concentration)
Alcohols are (D/A/S) and how they work
D,A
Lipid solvent and protein denaturants
Halogens are (D/A/S) and how they work
Chloride (S,D): oxidizing agent
Iodine(A): iodinate tyrosine residues in protein, oxidizing agent
Heavy metals are (D/A/S) and how they work
D
Modify proteins, interact with RNA,DNA.
Quaternanry ammonium is (D/A/S) and how they work
D,A
Interact with phospholipids of cytoplasmic membrane
Alkylating agents are (D/A/S) and how they work
D,S
Formaldehyde
Very toxic
Antimicrobial drugs are classified on the basis of
- Molecular structure
- Mechanism of action
- Spectrum of antimicrobial activity
Antimicrobial drugs should have what action in microorganisms
Batceriostatic or batceriocidal
Usually have a specific target
A good antimicrobial drug has
- No severe side effects, must be far more toxic for the microorganism than mammalian cells
- Low risk/benefit ration
- Broad stectrum of activity to facilitate rapid medical intervention
- Appropriate bioavaialbility and pharmacokinetics ( must reach the site of infection)
- Low cost to develop and manufacture
What are the targets for antimicrobial drugs
- Cell wall synthesis
- DNA gyrase (topoisomerase)
- RNA elongation
- DNA-directed RNA polymerase
- Protein synthesis (50 S inhibition or 30 S)
- Protein synthesis (tRNA)
- Lipid biosynthesis
- Cytoplasmic membrane structure and function
- Folic acid metabolism
Fungi, bacteria and viruses have different ___
Antimicrobial drugs
The drug with the broadest spectrum of action on bacteria
Tetracycline (obligatory parasytic and normal bacteria)
What is synthetic antimicrobial drugs
Invented in the lab
Selective toxicity is
The ability to inhibit or kill a pathogen without affecting the host
Who studied selective toxicity and the first antimicrobial drug made
Paul Ehrlich in early 1900s
Salvarsan- used to treat syphilus
What are growth factor analogs
Structurally similar to growth factors but not function in the cell
What is used a growth factor analog for folic acid
Sulfanilamide. It is analogous for p-aminobenzoic acid, Inhibits folic acid synthesis. Bacteriostatic
Sulfa drugs were discovered by and when
Gerhard Domagk
1930s
What are isoniaxid
A grwoth factor analog effective only against Mycobacterium. Interferes with synthesis of mycolic acid
What are nucleic acid base analogs
Formed by the addition of bromide or fluorine. Stop DNA replication
What are quinolones
They interfere with DNA gyrase (control DNA supercoiling). EX. ciprofloxacin
What are antibiotics
Antimicrobial agents naturally produced by a variety of bacteria and fungi to inhibit or kill other microorganisms
How can you modify antibiotics
To make them semisynthetic to increase efficiency
Why gram positive and gram negative bacteria vary in their sensitivity to antibiotics
Because of the cell wall
What are beta-lactams
One of the most important groups of antibiotics of all time. Include penicillins, cephalosporins, and cephamycins
Who discovered penicillin and when
Alexander Fleming in 1928
Isolated from mold
Penicillin is primarily effective against
Gram-positive bacteria. Some synthetic forms are effective against gram-negative bacteria
How does penicillins work
It inhibits cell wall synthesis
What is the important structure in penicillin
beta-lactam ring
Methicillins are
Cnanged R griup from penicilin G to Methicillin.
It is acid stable and beta-lactamase resistant- the enzymes that destroy penicillin
What other form of penicillin is resistant to beta-lactamase
Oxacillin
What is special about Ampicillin
Broadened spectrum of activity ( especially against gram-positive bacteria), acid-stable, sensitive to beta-lactamase
What is special about carbenicillin
Broadened spectrum of activity ( especially against Pseudomonas aeruginosa), acid-stable but ineffective orally, sensitive to beta-lactamase
What are cephalosporins
Produced by the fungus
same mode of action as penicillins
Common to treat gonorrhea
Explain in detail how penicillin works
transpeptidase is bound to b-lactam ring, which is broken, but it dissactivates transpeptidase
Beta lactams are ( bacteristatic/lytic, etc.)
Bacteriocidal or bacteriolytic ( depends on species,etc.)
Can be bacteristatic ( in isotonic solution)
The majority of antimicrobial drugs that are used clinically are coming from
Streptomyces
Example of streptomyces: aminoglycosides
- Target 30s subunit of the ribosome, cause misreading of mRNA
- Batcericidal
Example of streptomyces:Chloramphenical
- Bind to 23S rRNA and block peptide elongation
- Bacteriostatic
Example of streptomyces: Macrolides
- Broad spectrum antibiotics that target 50s subunit of the ribosome, block protein synthesis
- Bacteriostatic
Example of streptomyces: tetracyclines
- Broad-spectrum, bacteriostatic.
- Inhibit 30S ribosomal subunit, block protein synthesis
What is antimicrobial resistance
-The acquired ability of microorganism to resist the effects of a chemotherapeutic agent to which it is normally sensitive
Antibiotic producers are tolerant to ( how they are tolerant)
- Lack target sites (no peptidoglycan)
- Modify target sites
- Lack of uptake mechanism
Antibiotic resistant mechanism
- Destruction or modification of the antibiotic ( beta-lactamase)
- Modification of the target site
- Modification of uptake mechanism
- Efflux pumps: reduce intracelluar concentration
how do we know that the bacteria acquired antibiotic resistant
By the acquisition of a new gene that provides the cell with a new function
Where do most bacteria have antimicrobial gene
R plasmid
R plasmids can be transferred between
The same species or related species
Resistance can be minimized by
Using antibiotics correctly and only when needed ( reduce selection)
What is the issue with antiviral drugs
They target host structures as well. Risk to the host may not justify the use of antiviral
Most successful and commonly used antivirals are
The nucleoside analogs: block reverse transcriptase and production of viral DNA (RNA viruses)
What do protease inhibitors do
Inhibit the processing of large viral proteins into individual components
What are fusion inhibitors
Prevent viruses from successfully fusing with the host cell
Why fungi pose a special problem for chemotherapy
Because they have cellular machinery as that of human and animals
What drugs target fungi?
- Ergosterol synthesis( Fluconazole)
- Cell wall synthesis( inhibitor if chitin synthesis)
