Control of Microorganisms Flashcards
sterilization
the killing or removal of all viable organisms including endospores
inhibitin
effectively limiting microbial growth
decontamination
the treatment of an object to make it safe to handle
disinfection
directly targets the removal of all **pathogens not necessarily all microorganisms
physical methods (examples)
heat
radiation
filtration
chemical methods (antimicrobials) (examples)
external surfaces: sterilants, disinfectants, antiseptics
internal: antibiotics, antivirals, antifungals
heat
- high temps *denature macromolecules
- decimal reduction time
- time necessary to kill a defined *fraction is independent of the initial cell concentration
decimal reduction time
D
amount of time required to reduce viability tenfold
inversely correlated with temp
-organism specific
thermal death time
time needed to kill all cells at a given temp
dependent on the population size of the microorganism
To compare a standardized number of starting cells is needed.
Endospores and heat
survive heat that would rapidly kill vegetative cells
-need higher temp
(resistant to boiling for a long time - 5 min for a decimal reduction ie 90% dead)
autoclave
sealed device that uses steam under pressure
- the high temp NOT pressure kills microbes
- the sterilization time is when the object being sterilized reaches 120C (NOT the autoclave itself)
Pasteurization
process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids.
- increases shelf life
- reduces pathogens
- flash pasteurization 72C for 15s
- bulk pasteurization 65C for 30 min
Radiation
causes modifications and breaks in DNA, inhibits replication, transcription and cuases death
- cannot penetrate solid, obaque surfaces
- used in disinfection of water or air
*Ionizing radiation
radiation that produces ions and other reactive molecules
- has a decimal reduction time
- sources of radiation: cathode ray tube, X-rays
- used for sterilization in the medical field and food industry
Filter sterilization
- avoids the use of heat on sensitive liquids or gas
- pores of filter are too small for organisms to pass through, so they are caught.
Depth filters
fibrous sheet or mate made from an array of fiber
*HEPA filters
Membrane filters
- like sieve
- nucleopore filter
- filtration speed can increase by syringe, pump, or vacuum
antimicrobial agents
bacteriostatic: inhibit growth of microorganism
bacteriocidal: kill microorganism
bacteriolytic: kill microorganism by inducing lysis
(Think about the associated graphs)
minimum inhibitory concentration
smallest amount of an agen needed to inhibit growth of a microorganism
minimum lethal concnetration
the lowest concentration of an agent that kills a test *organism
minimum bacteriocidal concentration
the lowest concentration of an agent that kills a test *bacterium
Viable counts
** MLC and MBC are viable counts
disc diffusion assay
antimicrobial agent added to a filter paper disk
zone of inhibition
area of no growth around the disk
sterilants
destroy all forms of microorganisms, including endospores
disinfectants/sanitizers
applied to nonliving objects or surface
do NOT kill endospores
antiseptics
applied to the surface of living tissues
-nontoxic for humans
do NOT kill endospores
antimicrobial drugs
applied outside or inside the body of animals/humans
-nontoxic for humans
do NOT kill endospores
antimicrobial drugs - basic facts
- either **bacteriostatic or **bactericidal
- usually have a *specific target
synthetic antimicrobial drugs
- Paul Ehrlich studied **selective toxicity: the ability to inhibit or kill a pathogen without affecting the host
- *salvarsan: one of the first antimicrobial drugs (syphilis)
growth factor analogs
structurally similar to growth factors, but do not function in the cell
sulfa drugs
- *sulfanilamide is an analogue of p-aminobenzoic acid. Inhibits folic acid synthesis.
- bacteriostatic
isoniazid
growth factor analog
interferes with synthesis of mycolic acid
nucleic acid base analogs
formed by the addition of Br or F, stop DNA replication
quinolones
interfere with DNA gyrase
antibacterial compounds
antibiotics
-antimicrobial agents naturally produced by a variety of bacteria and fungi to inhibit or kill other microbes
-semisythetic antibiotics (modified antibiotics to enhance efficacy)
-B-Lactams
cell wall is a major factor in the susceptibility of microbes to antibiotics
*******Cephalosporins
- used to treat gonorrhea
- produced by the fungus Cephalosporium
- **can be bacteriolytic or bactericidal
- bacteriostatic in isotonic soutions
Penicillins
inhibit cell wall synthesis
Aminoglycosides
Ex. streptomycin
bactericidal
Antibiotic producers
tolerant to the antibiotic: -lack target sites -no uptake mechanism resistant: destriction or **modification of the antibiotic -modification of the target site etc
acquisition of resistance
- the use of antibiotics selects for the spread of R plasmids
- most drug-resistant genes are located in the R plasmid
protease inhibitors
inhibit the processing of large viral proteins into individual components
fusion inhibitors
prevent viruses from successfully fusing with the hose cell
Antiviral drugs
- target host structures, resulting in toxicity
- **risk to the host may not justify the use of antiviral
- most successful: nucleoside analogs - block reverse transcriptase
**Fluconazole
anti fungal drug that targets ergosterol synthesis
