MM Chapter 20
The following results were obtained from a disk-diffusion test for microbial susceptibility to antibiotics. Staphylococcus aureus was the test organism. Antibiotic Zone of Inhibition A 3 mm B 7 mm C 0 mm D 10 mm In the table, the most effective antibiotic tested was
10 mm
The following data were obtained from a broth dilution test. Concentration of Antibiotic X Growth Growth in Subculture 2 μg/ml + + 10 μg/ml - + 15 μg/ml - - 25 μg/ml - - In the table, the minimal inhibitory concentration of antibiotic X is
10 μg/ml
The following data were obtained from a broth dilution test. Concentration of Antibiotic X Growth Growth in Subculture 2 μg/ml + + 10 μg/ml - + 15 μg/ml - - 25 μg/ml - - 5) In the table, as illustrated by the data shown, the minimal bactericidal concentration of antibiotic X is
15 μg/ml
In what way are semisynthetic penicillins and natural penicillins alike?
Both are based on β-lactam.
What is meant by selective toxicity?
Chemotherapeutic agents should act against the pathogen and not the host.
Quinolones and fluoroquinolones act against what bacterial target?
DNA gyrase
Which of the following is mismatched?
Florey and Chain identification of Penicillium as the producer of penicillin
Why are chemotherapeutic agents that work on the peptidoglycan cell wall of bacteria a good choice of drug?
Humans and other animal hosts lack peptidoglycan cell walls.
Which of the following statements is FALSE?
Interferon inhibits glycolysis.
Why is polymyxin only used on the skin?
It can also damage living human cell membranes, but the drug is safely used on the skin, where the outer layers of cells are dead.
Which of the following statements about drug resistance is FALSE?
It is found only in gram-negative bacteria.
Which of the following organisms would MOST likely be sensitive to natural penicillin?
Streptococcus pyogenes
Which of the following statements about drugs that competitively inhibit DNA polymerase or RNA polymerase is FALSE?
They cause cellular plasmolysis.
Which of the following does NOT constitute an advantage of using two antibiotics together?
Two are always twice as effective as one.
Why is it difficult to find good chemotherapeutic agents against viruses?
Viruses depend on the host cell's machinery, so it is hard to find a viral target that would leave the host cell unaffected.
Which of the following antibiotics causes misreading of mRNA?
aminoglycoside changes shape of 30S units
Which of the following antimicrobial agents is recommended for use against fungal infections?
amphotericin B
The following results were obtained from a disk-diffusion test for microbial susceptibility to antibiotics. Staphylococcus aureus was the test organism. Antibiotic Zone of Inhibition A 3 mm B 7 mm C 0 mm D 10 mm In the table, which antibiotic would be most useful for treating a Salmonella infection?
answer cannot be determined based on information provided
The following results were obtained from a disk-diffusion test for microbial susceptibility to antibiotics. Staphylococcus aureus was the test organism. Antibiotic Zone of Inhibition A 3 mm B 7 mm C 0 mm D 10 mm In the table, the antibiotic that exhibited bactericidal action was
answer cannot be determined based on information provided
Lamisil is an allylamine used to treat dermatomycoses. Lamisil's method of action is similar to that of
azole antibiotics.
Mebendazole is used to treat cestode infections. It interferes with microtubule formation; therefore, it would NOT affect
bacteria
Most of the available antimicrobial agents are effective against
bacteria
See MM question 20
competitive inhibition
The following data were obtained from a broth dilution test: Concentration of Antibiotic X Growth 2.0 μg/ml - 1.0 μg/ml - 0.5 μg/ml - 0.25 μg/ml + 0.125 μg/ml + 0 + Bacteria from the 0.25 μg/ml tube were transferred to new growth media containing antibiotic X with the following results: Concentration of Antibiotic X Growth 2.0 μg/ml - 1.0 μg/ml + 0.5 μg/ml + 0.25μg/ml + The data in the table show that these bacteria:
developed resistance to antibiotics
Antimicrobial peptides (AMPs) frequently work by
disrupting the plasma membrane.
Which of the following would be selective against the tubercle bacillus?
ethambutol inhibits mycolic acid synthesis
True/False PABA serves as the competitive inhibitor in the action of sulfanilamides.
false
True/False Penicillin and streptomycin are commonly used in synergism because they display the same mode of action.
false
True/False Undergrowth of fungi after antibiotic use is commonly referred to as a superinfection.
false
true/false Phage therapy has been used in the past as an antiviral treatment.
false
Which compound would be the most useful to treat candidiasis? A. flucytosine B. guanine C. uracil D. thymine E. penicillin
flucytosine
A drug that inhibits mitosis, such as griseofulvin, would be more effective against
fungi
Which of the following antibiotics are used to treat fungal infections? 1. aminoglycosides 2. cephalosporins 3. griseofulvin 4. polyenes 5. bacitracin
griseofulvin and polyenes
Niclosamide prevents ATP generation in mitochondria. You would expect this drug to be effective against
helminths.
Which of the following methods of action would be bacteriostatic?
inhibition of protein synthesis
In the presence of penicillin, a cell dies because
it undergoes lysis
Which of the following is an antiprotozoan drug that interferes with anaerobic metabolism?
metronidazole
Which of the following antimicrobial agents has the fewest side effects?
penicillin
Which of the following antibiotics is NOT bactericidal?
polyenes
Which of the following antibiotics is recommended for use against gram-negative bacteria?
polymyxin
Which of the following does NOT affect eukaryotic cells?
semisynthetic penicillins
Which of the following drugs does NOT act by competitive inhibition?
streptomycin
Which one of the following does NOT belong with the others? A. cephalosporin B. bacitracin C. streptomycin D. monobactam E. penicillin
streptomycin
The antimicrobial drugs with the broadest spectrum of activity are
tetracyclines
Use of antibiotics in animal feed leads to antibiotic-resistant bacteria because
the antibiotics kill susceptible bacteria, but the few that are naturally resistant live and reproduce, and their progeny repopulate the host animal.
Protozoan and helminthic diseases are difficult to treat because
their cells are structurally and functionally similar to human cells.
The antibiotic actinomycin D binds between adjacent G-C pairs, thus interfering with
transcription
True/False An antibiotic that attacks the LPS layer would be expected to have a narrow spectrum of activity.
true
True/False Antiviral drugs target viral processes that occur during viral infection.
true
True/False Both trimethoprim and sulfamethoxazole inhibit reactions along the same metabolic pathway.
true
True/False Community-acquired MRSA is typically more virulent than health care-associated MRSA.
true
True/False Due to its target, rifamycins can be effective over a broad spectrum.
true
Drug resistance occurs
when antibiotics are used indiscriminately.
