142 terms

Chapter 26

chemical substance produced by a microorganism that kills or inhibits the growth of another microorganism
the acquired ability of a microorganism to grow in the presence of an antimicrobial drug to which the microorganism is usually susceptible
antimicrobial drug resistance
a chemical agent that kills or inhibits growth of microorganisms
antimicrobial agent
chemical agent that kills or inhibits growth of microorganisms and is sufficiently nontoxic to be applied to living tissues, i.e. mouthwash
antiseptic (germicide)
a sterilizer that destroys microorganisms with temperature and steam under pressure
an antibiotic, including penicillin, that contains the four-membered heterocyclic B-lactam ring
B-lactam antibiotic
an agent that kills bacteria
bacteriocidal agent
an agent that inhibits bacterial growth
bacteriostatic agent
treatment that renders an object or inanimate surface safe to handle
an antimicrobial agent used only on inanimate objects, i.e. lysol or bleach
directly targets the removal of all pathogens, not necessarily all microorganisms
an agent that kills fungi
fungicidal agent
an agent that inhibits fungal growth
fungistatic agent
a peptide that blocks the fusion of viral and target cytoplasmic membranes
fusion inhibitor
a chemical agent that is related to and blocks the uptake of a growth factor
growth factor analog
a high efficiency particulate air filter that removes particles, including microbes, from intake or exhaust air flow
HEPA filter
the reduction of microbial growth because of a decrease in the number of organisms present or alterations in the microbial environment
a cytokine protein produced by virus-infected cells that induces signal transduction in nearby cells, resulting in transcription of antiviral genes and expression of antiviral proteins, stimulates antiviral proteins in uninfected cells
the minimum concentration of a substance necessary to prevent microbial growth
minimum inhibitory concentration (MIC)
nonnucleoside analog used to inhibit viral reverse transcriptase
nonnucleoside reverse transcriptase inhibitor (NNRTI)
nucleoside analog used to inhibit viral reverse transcriptase
nucleoside reverse transcriptase inhibitor (NRTI)
reduction of the microbial load in heat-sensitive liquids to kill disease producing microorganisms and reduce the number of spoilage microorganisms; does not kill all organisms. Used on materials that are heat sensitive, like milk
a class of antibiotics that inhibit bacterial cell wall synthesis, characterized by a B-lactam ring
an inhibitor of a viral protease
protease inhibitor
a synthetic antibacterial compound that interacts with DNA gyrase and prevents supercoiling of bacterial DNA
an agent that reduces microorganisms to a safe level, but may not eliminate them
the ability of a compound to inhibit or kill pathogenic microorganisms without adversely affecting the host
selective toxicity
a chemical agent that destroys all forms of microbial life
sterilant (sterilizer) (sporicide)
the killing or removal of all living organisms and their viruses from a growth medium, i.e. autoclaving
an agent that stops viral replication and activity
viricidal agent
an agent that inhibits viral replication
viristatic agent
How are bactericidal, bacteriostatic, and bacterial lytic different?
Bacteriostatic: inhibit bacterial growth
Bacteriocidal: kills bacteria
Bacteriolytic: lyses bacteria
How does heat kill cells?
heat kills orgs because it denatures proteins
amount of time required to reduce viability tenfold
decimal reduction time
What are the standard operating conditions for the autoclave? What sort of items do you sterilize using the autoclave?
121 degrees C
15 minutes
15 psi
used to sterilize media that we use to grow bacteria
What are the standard operating conditions for the hot air oven? What types of things do you sterilize using the hot air oven?
170 degrees C
3 hours
empty test tubes
What causes the water in the autoclave to get above 100 degrees C?
What organism is used to quality control the autoclave and why?
Bacillus stearothermophilus
it grows at 56 degrees C and forms spores, thermophile. If it is not killed by the autoclave, it did not reach the necessary conditions for sterilization
What are the two most important aspects of sterilization?
time and temperature
How does UV radiation kill cells? What is it used for? What are its downfalls?
causes TT dimer mutations, more exposure causes more mutations and cells are unable to repair themselves.
Useful for decontamination of surfaces, often used in A/C ducts and surgery rooms to disinfect air
Cannot penetrate solid, opaque, or light-absorbing surfaces, or glass
How do Gamma/X-rays kill cells? What is it used for?
ionizing radiation, break DNA in cells
used with foods and fruits/spices as a way to decontaminate
How do microwaves kill cells?
do not penetrate cells but kill indirectly through heat
What is used to disinfect the air in A/C ducts and surgery rooms?
UV radiation
Why does it take more radiation to kill Clostridium than Saccharomyces?
Clos. has spores.
What is ethylene oxide?
gas used to sterilize plastic petri dishes and other plastic supplies
How are tissue grafts sterilized?
radiation; heat would destroy the tissue
How does filtration work for sterilization?
Used on liquids and gases that are heat sensitive. Fluid passes through the pores in the filter and anything larger than the pores is trapped in the filter.
What size filter should you use? What size filter should you use if your are trying to filter out Mycoplasma?
Usually 0.45 microns

Mycoplasma: 0.22 microns
HEPA filters are used to sterilize what?
used in A/C systems
Membrane filters are used to sterilize what?
media and supplements like antibiotic solutions
Explain how the MIC (minimum inhibitory concentration) test works
1. Series of test tubes with increasing concentrations of antibiotic is prepared in the culture medium
2. Each tube is inoculated with the same concentration of a test organism
3. incubate
4. Look for growth measured in turbidity, only occurs in test tubes with antibiotic concentrations below the MIC
5. Streak test tubes without turbidity onto a media to determine if cells are killed or inhibited to determine the MBC (minimum bactericidal concentration)
Explain how the Kirby Bauer (disk diffusion) test works
1. Have plate and swab test org onto plate
2. put disc with antibiotic or disinfectant on top of plate
3. incubate overnight
4. During incubation bacteria grow and disc with antibiotic/disinfectant diffuses onto plate
5. Determine effectiveness of the agent by looking at zones of inhibition. The bigger the zone, the better the killing
What type of test do you do if you want to determine a sensitivity test (which antibiotic would work best for a specific infection)?
Kirby Bauer (disk diffusion) test.
Which of the following is a good target for a chemotherapeutic used to treat a bacterial infection?
A. bacterial ribosomes
B. the peptidoglycan cell wall
C. DNA gyrase
D. A, B, and C
E. none of the above
Which chemotherapeutic agent interferes with the integrity of the bacterial cytoplasmic membrane?
A. polymyxin
B. streptomycin
C. chloramphenicol
D. tetracycline
Which chemotherapeutic agent blocks the formation of peptide cross links in bacterial cell walls?
A. rifampin
B. sulfonamide
C. tetracycline
D. penicillin
What effects would tetracycline likely have on an infecting bacterium?
A. a reduction in protein synthesis by interfering with tRNA
B. a weakened PG layer
C. disruption of the cell membrane
D. inability to replicate DNA by blocking DNA gyrase
Which of the following chemotherapeutic agents would prevent the formation of THF in a bacterial cell?
A. chlorampehnicol
B. fluoroquinolone
C. sulfonamide
D. penicillin
How does penicillin work?
Blocks the formation of peptide cross links in the PG cell wall
How does polymyxin work? Why is this method usually only used on the skin?
Attaches to phospholipids in the cytoplasmic membrane.
This method of action also interferes with human cell membranes, where outer layers of cells are already dead
How does tetracycline, erythromycin, chloramphenicol and streptomycin work?
prevent protein synthesis by inhibiting polypeptide formation, effect the ribosome of the bacteria
How does sulfonamide work?
block a step in the folic acid synthesis pathway by acting as a competitive inhibitor to PABA, prevents synth of folic acid and therefore nucleic acids, unable to reproduce
How does cipro (quinolones) work?
blocks the function of DNA gyrase
used to treat anthrax
How does rifampin work?
blocks function of RNA polymerase
How do quinolones/fluorquinolones work?
blocks function of DNA gyrase
How does isoniazid work?
Effective only against Mycobacterium
Disrupts synthesis of mycolic acid
The most effective single drug used for control and treatment of tuberculosis
What are the basic modes of action of antibiotics?
selective toxicity, targets what is different between bacteria and other cells (PG cell walls, DNA gyrase, folic acid pathways, etc.)
What is the difference between a broad spectrum and narrow spectrum antibiotic?
Broad: kills both G+ and G- bacteria
Narrow: kills either G+ or G- bacteria
What is selective toxicity and who was Paul Ehrlich?
Selective toxicity: the ability to inhibit or kill pathogenic microorganism without adversely affecting the host.
Paul Ehrlich developed this concept, searched for the "magic bullet" that would kill only pathogens. Discovered Salvarsan, an arsenic containing compound that killed the syphilis microbe
What is a growth factor analog? Give an example of one
look similar in structure to what the pathogen needs but when it gets the analog, leads to cell death.
Example: sulfa drugs and isoniazid
Why is alcohol a good degermer?
dissolves lipids and lifts bacteria off of skin, disrupts cytoplasmic membrane by dehydration
Which is better for killing, 100% or 80% alcohol and why?
60-80% because it stays on the surface longer and has a better chance of working, the higher the alcohol content, the quicker it evaporates
How does chlorine work?
oxidizing agent
How does hydrogen peroxide work?
oxidizing agent
used to disinfect water
iodine, ozone
Many disinfecting agents, like Lysol, are phenol derivatives. Who discovered phenol and why don't we use it anymore?
Lister, used it in operating rooms to improve patients chance of survival. Don't use anymore because it is carcinogenic.
used to kill algae in pools
copper sulfate
Antimicrobial drugs are classified on the basis of
A. molecular structure
B. mechanism of action
C. spectrum of antimicrobial activity
D. all of the above
What are the disadvantages of broad spectrum antibiotics?
kills normal flora, end up with diarrhea, allows patient to become susceptible to opportunistic infections like thrush and yeast from Candida albicans
What antibiotic is used to kill Rickettsia and Chlamydia?
What type of drugs are used to treat viral infections?
nucleic acid base analogs (ex. AZT), protease inhibitors, fusion inhibitors, adamantanes, neuraminidase inhibitors, interferons
Which of the following is true about penicillins?
A. discovered by Alexander Fleming
B. primarily effective against G+ bacteria with some synthetic forms being effective against some G- bacteria
C. target cell wall synthesis
D. all of the above
How do nucleoside analogs work as antivirals?
block reverse transcriptase and production of viral DNA
What is MRSA
methicillin resistant Staph. aureus
AZT is an analog to what base
Which of the following is NOT a semisynthetic penicillin?
A. methicillin
B. oxacillin
C. ampicillin
D. carbenicillin
E. penicillin G
produced by fungus Cephalosporium, same mode of action as penicillins, commonly used to treat gonorrhea
antibiotics that contain amino sugars bonded by glycosidic linkage. Examples: kanamycin, neomycin, amikacin. Not commonly used today because of neurotoxicity/nephrotoxicity; considered reserve antibiotics for when others fail
Erythromycin, contain lactone rings bonded to sugars, borad spectrum antibiotic that targets the bacterial ribosome
contain four rings, widespread medical use in humans and animals, broad spectrum inhibition of protein synth, also inhibits function of bacterial ribosome
Streptomyces is a
A. mold
B. penicillin
C. actinomycete
new structural class of antibiotic, broad-spectum, effective against MRSA and vancomycin-resistant enterococci
How do you separate staph from strep?
catalase test
Staph is catalase positive
Strep is catalase neg
inhibit the processing of large viral proteins into individual components, disrupt capsid formation
protease inhibitors
prevent viruses from successfully fusing with the host cell
fusion inhibitors
successful in limiting influenza infection, block attachment of flu virus
adamantanes, neuraminidase inhibitors
What do anti fungal drugs usually target?
chitin cell walls, sterols in cytoplasmic membrane, folate biosynthesis, disrupt microtubule aggregation
Are more G+ or G- bacteria resistant to antibiotics?
In a population of bacteria, how does presence of an antibiotic help resistant cells within that population?
A. the antibiotic kills or inhibits competitors, allowing the resistant cell to grow without competition
B. the antibiotic is metabolized by the resistant cell, providing more energy for growth
C. the sensitive cells must devote energy to destroying the antibiotic, slowing their growth
D. the antibiotic mutates sensitive cells, making them incapable of growing
All antibiotic-resistant pathogens
A. will be killed by the antibiotic
B. will have mutations in their DNA
C. will not be killed/inhibited by antibiotic
D. obtained their resistance from a bacteriophage
E. have R plasmids
Antibiotic resistance due to horizontal gene transfer could involve which of the following?
A. the uptake of DNA from its surroundings
B. transfer of R plasmid via bacterial conjugation
C. DNA mutation making an altered enzyme that can degrade the antibiotic
D. A and B
E. A and C
How might a mutation result in antibiotic resistance?
A. it facilitates R-plasmid transfer during bacterial conjugation
B. mutations could allow DNA fragments to be taken up by cells
C. mutations can result in a modification of an enzyme that could interfere with the action of the antibiotic
D. mutations allow for bacteriophages to spread DNA to other bacteria
If a bacterium acquired an antibiotic resistance gene via conjugation, the DNA would most likely originate from
A. a bacteriophage
B. an R-plasmid
C. a sensitive bacterial cell
D. a fragment of DNA in the environment
Which of the following are a reason that microorganisms are naturally resistant to certain antibiotics
A. org lacks structure the antibiotic inhibits
B. org is impermeable to antibiotic
C. org can inactivate antibiotic
D. org may modify the target of antibiotic
E. org may develop a resistant biochemical pathway
F. org may be able to pump our antibiotic (efflux)
G. all of the above
Antibiotics may be selectively inactivated by chemical modification or cleavage. T/F
Most drug resistant bacteria isolated from patients contain drug-resistance genes located on ______
R plasmids
Why do bacteria become resistant to antibiotics?
overuse of antibiotics, not taking complete prescriptions
Which of the following is true about antibiotic resistance?
A. almost all pathogenic microbes have acquired resistance to some chemotherapeutic agents
B. resistance can be minimized by using antibiotics correctly and only when needed
C. resistance to a certain antibiotic can be lost if antibiotic is not used for several years
D. all of the above
Which organism was the first to develop antibiotic resistance?
Staph aureus
What is phage therapy? What is a problem with this?
use a bacteriophage to lyse a pathogen.
Possible because phages are very specific
Problem: G- bacteria release endotoxin from their LPS when lysed, which would cause abrupt drop in blood pressure and possibly death
How do beta lactamases help to overcome antibiotics with beta-lactam rings?
A. they pump the antibiotics out of the cell
B. they modify the enzymes that these antibiotics act upon
C. they actively destroy the chemical structure of the antibiotic
D. they prevent the antibiotic from entering the cell
Which of the following statements about efflux pumps is true?
A. they work by bringing in molecules they normally synthesize from their environment to allow the affected mechanism to continue
B. the great number of efflux pumps a bacterial cell has, the more resistant to the antibiotic it will be
C. they change the chem structure of the antibiotic
D. they can never be modified to broaden the spectrum of antibiotics they work against
Which is a mechanism that enables a bacterial cell to overcome the effects of sulfonamides?
A. the enzyme targeted by sulfonamide can be modified to have and increased affinity for PABA
B. Beta-lactamases are secreted to destroy the sulfonamide
C. efflux pumps remove the sulfonamide from the cell
D. protein channels modify their specificity, preventing sulfonamide from entering cells
The modification of existing cell structures could result in the resistance to which antibiotics?
A. tetracycline
B. sulfonamide
C. penicillin
D. A and B
E. all of the above
Tetracycline resistance is likely due to which mechanism?
A. efflux pumps
B. beta lactamases
C. modification of an enzyme
D. modification of a porin
E. importing of a molecule outside of the cell to allow a metabolic pathway to continue
Agents that kill bacteria are said to be
A. inhibitory
B. bacteriocidal
C. bacteriostatic
D. all of the above
The complete elimination of all microorganisms, including viruses, is called
A. disinfection
B. sterilization
C. decontamination
D. any of the above, depending on the circumstances
The process by which macromolecules lose their structure and ability to function is called
A. denaturation
B. sterilization
C. thermal death
D. none of the above
Of all the known antibiotics that have been identified in nature, ____ are clinically useful.
A. <1%
B. 8-10%
C. 18-20%
D. 25-30%
Which of the following are classified as electromagnetic radiation?
A. microwaves
B. UV rays
C. x-rays/gamma rays
D. all of the above
The type of filter used when a syringe, pump, or vacuum is used to force the liquid through the filtration apparatus into a sterile collection vessel is called
A. depth filter
B. membrane filter
C. nucleation track filter
D. microblast filter
UV radiation is antimicrobial because
A. the radiation generates significant amounts of heat within the given cell
B. the energy present causes modifications or breaks in the DNA molecules
C. the radiation generates magnetic poles that denature the cellular components
D. all of the above
The antimicrobial effectiveness of which of the following is limited to exposed surfaces?
A. microwaves
B. UV rays
C. x-rays/gamma rays
D. eletrons
In the agar diffusion method of studying antimicrobial action, the ____ is measured.
A. diameter of the zone of inhibition
B. diameter of the individual microbial colonies
C. turbidity of the medium
D. distance between the microbial colonies
Interferon is
A. host specific
B. virus specific
C. both host and virus specific
D. neither host nor virus specific
The type of filter most often used for liquid sterilization in the microbiology lab is
A. depth filter
B. nucleation track filter
C. membrane filter
D. microbistat filter
Which statement is true about heat sterilization?
A. microbial death is more rapid at acidic pH
B. high concentrations of sugars and salts influence sterilization time
C. the amount of water in a substance is a major factor in heat resistance
D. all of the above
The action of some bacteriolytic chemical agents can be observed by noting a(n)
A. increase in the turbidity of the medium
B. decrease in the turbidity of the medium
C. change in the color of the medium
D. change in the surface tension of the medium
Antimicrobial drugs are often grouped according to
A. molecular structure
B. spectrum of antimicrobial activity
C. mechanism of action
D. all of the above
The beta-lactam antibiotics (like penicillin)
A. inhibit plasma membrane synth
B. inhibit protein synth
C. prevent chromosomal replication
D. inhibit cell wall synth
___ are applied to living tissues; ___ are used on inanimate objects
A. disinfectants/sterilants
B. antiseptics/sterilants
C. antiseptics/disinfectants
D. disinfectants/antiseptics
Which is a unique macromolecule present in certain viruses that is a target for antiviral agents?
A. ribosomes
C. reverse transcriptase
Which of the following is a chemical agent that is used to inhibit microbial growth inside the human body?
A. disinfectant
B. sanitizer
C. antiseptic
D. chemotherapeutic agent
Which is not a reason why microorganisms may have an inherent resistance to an antibiotic?
A. the org may be impermeable to the antibiotic
B. the org may be able to pump out an antibiotic entering the cell
C. the org may be able to alter the antibiotic to an inactive form
D. the org may be protected from the drug by its nuclear membrane
Semisynthetic antibiotics
A. are natural antibiotics that have been chemically modified in the lab
B. have an artificially constructed core that stimulates the production of "natural products"
C. are found in nature but their rate of production is enhanced in the lab
D. are natural antibiotics that have been purified by artificial means
The vegetative cells of Mycobacterium tuberculosis are resistant to many germicides because of
A. an extra membranous layer between the cell wall and the plasma membrane
B. the complex nature of the plasma membrane itself
C. the waxy nature of the cell wall
D. the lattice work found in the glycocalyx
The use of a HEPA filter in a biological safety cabinet is an application of filter sterilization using what type of filter?
A. depth filter
B. membrane filter
C. nucleation track filter
D. nucleospore filter
Important targets of antibiotics in Bacteria are
A. the cell wall
B. the cytoplasmic membrane
C. DNA replication and transcription elements
D. all of the above
Sulfamilamide is an analog of
A. p-aminobenzoic acid
B. folic acid
C. sulfuric acid
D. citric acid
The most successful agents used for antiviral chemotherapy are
A. protein synth inhibitors
B. ATP reductase inhibitors
C. nucleoside analogs
D. nucleotide analogs
The polyoxins interfere with
A. cell membrane structure
B. chitin biosynth
C. fungal mitosis
D. all of the above