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Lab pract. 3
antiseptics are used on living tissue such as skin and disinfectants are used on inanimate surfaces/objects
What is the difference between an antiseptic and a disinfectant?
bacteriostatic means limiting the growth of bacteria, while bactericidal means "killing" bacteria
What is the difference between bacteriostatic and bactericidal?
it may be ineffective or only bacteriostatic (limiting) instead of bactericidal (killing).
What is a potential problem of over-diluting a disinfectant concentrate?
it may leave toxic residues that are harmful to humans who come into contact with them
What is a potential problem of under-diluting a disinfectant concentrate?
phenol , joseph lister
To determine the efficiency of an antimicrobial chemical agent, what chemical is it compared with? and who is credited with discovering/applying the antimicrobial activity of this chemical?
substances a & b are more effective than phenol and substance c is less effective than phenol
Which of the following substances is more effective than 5% phenol?/
*substance a: phenol coefficient = 2.5
*substance b: phenol coefficient = 1.5
*substance c: phenol coefficient = 0.5
that the diffusing chemical is effective against the bacteria growin there.
What does a zone of inhibition tell you when reading a filter paper disk-diffusion test?
colonies that grow within a zone of inhibition which means they represent resistant cells from the original population that are not affected by the chemical agent
What are satellite colonies?
antimicrobial chemotherapeutic agents
What are antibiotics?
antibiotics are like antiseptics and disinfectants because they interfere with the bacterial cell and inhibit it in some way.
How are antibiotic like disinfectants and antiseptics?
unlike antiseptics and disenfectants, antibiotics usually work inside our bodies and therefore should exhibit selective toxicity
How are antiobiotics unlike disinfectants and antiseptics?
most antibiotics are made by various fungi and bacteria
Where do most antibiotics come from?
Who discovered penicillin?
penicillin and ampicillin
One way antibiotics work is by inhibiting cell wall synthesis and 2 examples are____________ and ___________.
One way antibiotics work is by injuring the cell membrane and an example is ________.
One way antibiotics work is as competitive inhibitors of enzymes needed to produce essential compounds and an example is _______.
tetracycline, streptomycin, erythromycin and chlorampenicol
One way antibiotics work is by interference with protein synthesis at a 70s ribosome and ____________, ________, _________, and __________ are examples.
methicillin resistant staphylococcus aureus
What does MRSA?
vancomycin resistant enterococcus
What is VRE?
vancomycin intermediate staphyloccus aureus
What is VISA?
vanconmycin resistant staphylococcus
What is VRSA?
the antibiotic is effective
What does a zone of inhibition mean?
resistance to the antibiotic within the original bacterial population
What does a satellite colony represent?
Penicillin is a narrow - spectrum antibiotic that is primarily effective on gram _____ (-/+) bacteria?
Polymixin b is a narrow 0 spectrum antibiotic that is primarily effective on gram ____(-/+) bacteria?
Ampicillin, chloramphenicol, tetracycline, and erythromycin are all _____ (broad/narrow) spectrum antibiotics that work on both gram+ and gram- bacteria.
any conflicting results may be due to mutant strains
How can you explain any conflicting results of broad-spectrum testing?
Kirby-bauer testing of antibiotics
This proceduce of measuring the size of the zones of inhibiton (in mm) is meanigful only if test substances have been calibrated for concentration, such as what type of testing?
b,d,e or g
The colony of Penicillium fungus produced an antibiotic that did what to the growth of Staphylococcus aureus?
If a chemical concentration kills the bacteria with ___ minutes of exposure, it is probably too strong to be safe for human use.
If a chemical concentration doesnt kill the bacteria with ___ minutes of exposure, it is considered ineffective.
the lowest concentration of a chemical that kills the bacteria in ten minutes of exposure, but not in five minutes is divided by the effective dilution of 5% phenol
How do you establish a numerical value for each tested chemical, compared to 5% phenol called the phenol coefficient.
If the phenol coefficient is (1), it means that the effectiveness of the chemical agent is what to that of 5% phenol.
I the phenol coefficient is greater than one (1), ite means that the chemical agent is what to that of 5% phenol.
If the phenol coefficient is less than one (1), it means the chemical agent is what to that of 5% phenol.
you would have to use it at a greater concentration or for a longer period of time to achieve the desirable effect
What would you have to do to a test chemical with a phenol coefficient of less than one (1)?
filter paper disk-diffusion test
What is ofter used in teaching laboratories to determine the effectiveness of chemical agents such as household disinfectants and antiseptics?
a large variety of gram+ and gram - bacteria
Broad-spectrum antibiotics are effective against what?
only effective against gram+ (penicillin) or gram- (polymixin b) species
Narrow-spectrum antibiotics are effective agains what?
MRSA, VISA,VRE AND VRSA
What are the four pathogenic strains that are now resistant to most or all available antibiotics?
Is staphylococcus aureus gram- or gram+?
Is escherichia coli gram- or gram+?
gram- and is ofter resistant to antimicrobials
Is pseudomonas aeruginosa gram- or gram+ ?