Chapter 20-Antimicrobial Drugs

__________ discovered penicillin and the first clinical trials in 1940 demonstrated its effectiveness as a chemotherapeutic agent. Alexander Fleming Louis Pasteur Robert Koch

*Alexander Fleming

__________are substances that inhibit other microorganisms and are produced by bacteria and fungi. Antibiotics polyenes protease inhibitors sulfa drugs

*Antibiotics

Bacterial infections are easier to treat using chemotherapy than are other types of infections caused by other types of microorganisms. Why? Bacteria are prokaryotic. Bacteria are smaller than the other types of pathogens. Bacteria grow more slowly. Bacteria are more sensitive to chemicals.

*Bacteria are prokaryotic.

Which of the following is NOT a mechanism by which antibiotic resistance spreads horizontally among bacteria? Bacterial transcription Plasmid transfer Bacterial conjugation Transduction

*Bacterial transcription (this occurs in the parent to the offspring. The other three mentioned occur only from donor to recipient). See set on chapter 8 for more info)

Which of the following types of antibiotics is most likely to be associated with the development of a superinfection? Narrow-spectrum antibiotics β-lactam antibiotics Broad-spectrum antibiotics Bactericidal antibiotics Bacteriostatic antibiotics

*Broad-spectrum antibiotics

Which drug would be used to treat athlete's foot? Amantadine Neomycin Polymyxin B Chloroquine Clotrimazole

*Clotrimazole

Which of the following antibiotics is a common choice to treat streptococcal infections in children? Tetracycline Neomycin rifampin Trimethoprim Erythromycin

*Erythromycin (check my pinterest board to see illustrations with different bacteria shapes)

Which of the following mechanisms is antifungal? Interfere with anaerobic metabolism Inhibit 70S ribosomes Cause muscle spasms Inhibit ergosterol synthesis Inhibit peptidoglycan synthesis

*Inhibit ergosterol synthesis

Which antimicrobial works by inhibiting the synthesis of mycolic acid?

*Isoniazid

What is the benefit of combining penicillins with potassium clavulanate (clavulanic acid)? It makes penicillin more stable in stomach acid. It decreases potency of penicillin. It inhibits penicillinase. It increases the spectrum of activity.

*It inhibits penicillinase.

Which of the following is an antihelminthic drug that causes paralysis of the worm? Ivermectin Praziquantel Niclosamide Mebendazole

*Ivermectin

The __________ test is a commonly used disk-diffusion method for evaluating antibiotic effectiveness. Ames test broth dilution test Kirby-Bauer

*Kirby-Bauer

Which of the following statements about antibiotics is true? Antibiotics are not typically produced by microorganisms growing in their natural environments. Penicillin was first discovered by two researchers named Florey and Chain. The finding of antibiotic-producing microorganisms is a rare event. Most of our antibiotics are produced by Streptomyces, a genus of filamentous soil bacteria

*Most of our antibiotics are produced by Streptomyces, a genus of filamentous soil bacteria

Which of the following is a broad-spectrum, topical antibacterial compound? Neomycin Bacitracin Polymyxin B Caspofungin

*Neomycin

Which drug is NOT a nucleoside analog? Zidovudine Lamivudine Acyclovir Ribavirin Nevirapine

*Nevirapine Nevirapine is NOT a nucleoside analog; rather it blocks RNA synthesis by other mechanisms.

Which antifungal drug was recently introduced to treat systemic fungal infections? Posaconazole Amphotericin B Clotrimazole Tolnaftate Miconazole

*Posaconazole

Which antifungal drug was recently introduced to treat systemic fungal infections? Tolnaftate Clotrimazole Miconazole Posaconazole Amphotericin B

*Posaconazole

Which of the following antibiotics inhibits folic acid synthesis? Neomycin Tetracycline Ampicillin Chloramphenicol Sulfanilamide

*Sulfanilamide

You are reviewing the following results of a disk- diffusion antibiotic susceptibility test on an isolate of Staphylococcus aureus: Antibiotic A: ZI (zone of inhibition) = 0 millimeters Antibiotic B: ZI = 23 millimeters > Antibiotic C: ZI = 16 millimeters Antibiotic D: ZI = 19 millimeters Which antibiotic is bactericidal? Antibiotic D Antibiotic A Antibiotic C Antibiotic B The correct answer cannot be determined from the information provided.

*The correct answer cannot be determined from the information provided.

While observing the results of a disk-diffusion susceptibility test, you note an enlarged oval zone of inhibition around two adjacent antibiotic disks. Which of the following is the most likely explanation? The two antibiotics are bactericidal. The two antibiotics are synergistic. The two antibiotics are bacteriostatic. The two antibiotics are antagonistic.

*The two antibiotics are synergistic.

You have a 200-milligram-per-milliliter antibiotic solution. You prepare serial dilutions (1:2, 1:4, etc.) of the antibiotic. You then inoculate each tube with Salmonella. Bacteria grow in tubes 4, 5, and 6. What is the MBC (minimum bactericidal concentration)?

*There is not enough information to determine the MBC. 12.5 mg/ml 25 mg/ml 50 mg/ml

Which of the following statements is true about superinfections?

*They may be caused by antibiotic-resistant bacteria.

The drug Flagyl is commonly used to treat an STD caused by __________. Herpesvirus Neisseria gonorrhoeae Trichomonas vaginalis HIV Treponema pallidum

*Trichomonas vaginalis

The drug Flagyl is commonly used to treat an STD caused by __________. Treponema pallidum Neisseria gonorrhoeae Herpesvirus HIV Trichomonas vaginalis

*Trichomonas vaginalis

A disk-diffusion test identifies __________. agents to which a test culture is sensitive, in terms of growth or survival bacteriostatic agents only minimal bactericidal concentration (MBC) bactericidal agents only

*agents to which a test culture is sensitive, in terms of growth or survival

Simultaneous use of penicillin and tetracycline is often less effective than when either drug is used alone. This is called __________. bioremediation antagonism synergism

*antagonism

A drug that inhibits peptidoglycan synthesis is __________. antiprotozoan antifungal antibacterial antiviral

*antibacterial

A chemical that kills gram-positive bacteria and gram-negative bacteria would best be described as __________.

*broad spectrum

Drugs that inhibit cell wall synthesis:

*cephalosporins *bacitracin *vancomycin *penicillins (prevents the synthesis of cell walls by preventing peptidoglycan from cross linking to form the cell wall. Peptidoglycan is the substance forming the cell wall of many bacteria) Penicillin is effective only against Gram-positive bacteria because Gram negative bacteria have a lipopolysaccharide and protein layer on top that surrounds the peptidoglygan layer of the cell wall, preventing penicillin from attacking. See image below.

A drug that binds with sterols would injure __________. DNA eukaryotic plasma membranes fungal cell walls bacterial cell walls

*eukaryotic plasma membranes With the exception of the mycoplasmas, the only bacteria that lack a cell wall, prokaryotic membranes lack sterols. Sterols are found in the membrane of plants, fungi and animals (all eukaryotic).

Polyenes, azoles, and allylamines interfere with __________. cell membranes in gram-positive bacteria viruses cell walls in gram-negative bacteria fungal cell membranes

*fungal cell membranes

Tetracyclines are effective against all of the following EXCEPT __________. intracellular rickettsias gram-positive bacteria intracellular chlamydias fungi gram-negative bacteria

*fungi Tetracyclines are effective against all EXCEPT fungi. Tetracyclines are a group of closely related broad-spectrum antibiotics produced by Streptomyces spp. The tetracyclines interfere with the attachment of the tRNA carrying the amino acids to the ribosome at the 30S portion of the 70S ribosome, preventing the addition of amino acids to the growing polypeptide chain. Fungi are eukaryotes do not have the 70S ribosome.

An antimicrobial drug that inhibits peptidoglycan synthesis is most likely to be effective against __________. viruses gram-positive bacteria protozoan parasites gram-negative bacteria fungi

*gram-positive bacteria

All of the following are antiprotozoan drugs EXCEPT __________. metronidazole chloroquine mebendazole mefloquine quinacrine

*mebendazole

Chloroquine-resistant malaria may be treated with __________. Quinacrine Tinidazole mefloquine Metronidazole

*mefloquine

Semisynthetic penicillins are __________ antibiotics than is natural penicillin. similarly effective more effective None of the answers is correct. These antibiotics do not exist. less effective

*more effective

Many antifungal drugs target __________ in the fungal cell membrane. proteins sterols fatty acids peptidoglycan

*sterols

Which of the following antibiotics inhibits protein synthesis? Streptomycin Isoniazid Rifampin Cephalosporin Vancomycin

*streptomycin.

A disadvantage of using broad-spectrum antibiotics for treating bacterial infections is the potential for __________. superinfection infections synergism diseases

*superinfection

Some drug combinations are __________; therefore, when taken together, they are more effective. inhibitory bioremediation synergistic antagonistic

*synergistic

Clindamycin binds to the 50S ribosomal subunit to inhibit translocation. This antibiotic stops __________. translation in prokaryotes DNA synthesis in eukaryotes transcription in prokaryotes transcription in eukaryotes

*translation in prokaryotes

You have a 200 mg/ml antibiotic solution. You prepare serial dilutions (1:2, 1:4, etc.) of the antibiotic; the first tube contains 100 mg/ml. You then inoculate each tube with Salmonella. Bacteria grow in tubes 4, 5, and 6. You subculture bacteria from tubes 1 through 3 to nutrient broth. Growth occurs in the tube 3 subculture. You can conclude that the MIC is __________. 25 mg/ml 50 mg/ml 12.5 mg/ml 200 mg/ml

25 mg/ml

You have a 200-milligram-per-milliliter antibiotic solution. You prepare serial dilutions (1:2, 1:4, etc.) of the antibiotic. You then inoculate each tube with Salmonella. Bacteria grow in tubes 4, 5, and 6. You subculture bacteria from tubes 1 through 3 to nutrient broth. Growth occurs in tubes 2 through 3. What is the MBC (minimum bactericidal concentration)?

5 mg/ml *100 mg/ml YOU WERE UNSURE AND INCORRECT 12.5 mg/ml 50 mg/ml

In 1928, who observed that the growth of bacteria was inhibited on a Petri plate contaminated by a mold? •Alexander Fleming •Paul Ehrlich •Robert Koch •Louis Pasteur

Alexander Fleming. He noticed that the juice that the mold was producing was inhibiting the growth of the bacteria.

Which one of the following groups of pathogens are the easiest to treat with antimicrobial agents? •Viruses•Fungi•Bacteria •Protozoa

Bacteria. You do not treat viruses with antimicrobial agents.

Which of the following are common targets for bacterial resistance to antibiotics?

Blocking the drug's entry into the cell *All are common targets for bacterial resistance to antibiotics. Inactivation of the drug by enzymes Alteration of the drug's target site

What is the method of action of nucleoside analogs?

Disruption of plasma membrane *Inhibition of DNA synthesis Inhibition of protein synthesis Inhibition of cell wall synthesis Nucleic acid synthesis is an important target for antivirals, especially for the treatment of HIV and herpes infections. Many of these drugs are analogs of nucleic acids (nucleoside analog), which inhibit DNA synthesis once the analog is incorporated.

Antibiotics

Drugs that block the growth and reproduction of bacteria. They can kill both good and bad bacteria

Some antiprotozoan drugs: Quinine, chloroquine, mefloquine

Drugs used to treat Malaria. Affects are serious psychiatric side affects.

What is the difference between vertical and horizontal gene transfer?

In vertical gene transfer, the transfer of genetic material is from parents to offspring. It may be through sexual or asexual reproduction. In contrast, the horizontal gene transfer is the movement of genetic material from a donor organism to a recipient organism that is not its offspring.

Which of the following is used for treating influenza infections?

Interferon Indinavir *Oseltamivir Acyclovir Pentamidine isethionate

Antibiotic Misuse

Misuse of antibiotics selected for resistance mutants •Misuse includes: •Using outdated or weakened antibiotics •Using antibiotics for the common cold and other inappropriate conditions •Using antibiotics in animal feed •Failing to complete the prescribed regimen •Using someone else's leftover prescription

Antihelminthic drugs Helminths-Parasitic worms

Niclosamide -prevents ATP Production -treats tapeworms Praziquantel -alters membrane permeability -treats tapeworms and flukes Mebendazole and albendazole -interfere with nutrient absorption

The birth of modern chemotherapy is credited to the efforts of •Alexander Fleming.•Paul Ehrlich.•Robert Koch.•Louis Pasteur.

Paul Ehrlich

Which of the following is the drug of choice for the treatment of malaria?

Quinacrine Nifurtimox Flagyl *Chloroquine Iodoquinol

Which of the following antibiotics is frequently used as an alternative for those who are allergic to penicillin?

Streptomycin *Erythromycin Vancomycin Ethambutol Amoxicillin The mode of action of erythromycin is the inhibition of protein synthesis. However, erythromycin is not able to penetrate the cell walls of most gram-negative bacilli. Its spectrum of activity is therefore similar to that of penicillin G, and it is a frequent alternative drug for people that are allergic to penicillin.

Effects of Combinations of Drugs

Synergism-giving two drugs together is more effective than either one individually Antagonism: the effect of two drugs together is less than the effect of either alone

What is the difference between transcription and translation.

The Central Dogma of Molecular Biology states that DNA makes RNA makes proteins (Figure 1). The process by which DNA is copied to RNA is called transcription, and that by which RNA is used to produce proteins is called translation. Reverse transcription In reverse transcription, RNA is "reverse transcribed" into DNA. This process, catalyzed by reverse transcriptase enzymes, allows retroviruses, including the human immunodeficiency virus (HIV), to use RNA as their genetic material. Reverse transcriptase enzymes have also found applications in biotechnology, allowing scientists to convert RNA to DNA for techniques such as PCR. TRANSLATION The mRNA formed in transcription is transported out of the nucleus, into the cytoplasm, to the ribosome (the cell's protein synthesis factory). Here, it directs protein synthesis. Messenger RNA is not directly involved in protein synthesis − transfer RNA (tRNA) is required for this. The process by which mRNA directs protein synthesis with the assistance of tRNA is called translation. The ribosome is a very large complex of RNA and protein molecules. Each three-base stretch of mRNA (triplet) is known as a codon, and one codon contains the information for a specific amino acid. As the mRNA passes through the ribosome, each codon interacts with the anticodon of a specific transfer RNA (tRNA) molecule by Watson-Crick base pairing. This tRNA molecule carries an amino acid at its 3′-terminus, which is incorporated into the growing protein chain. The tRNA is then expelled from the ribosome. Figure 7shows the steps involved in protein synthesis. (see https://www.atdbio.com/content/14/Transcription-Translation-and-Replication)

Which of the following drugs inhibits the synthesis of mRNA in bacteria?

Trimethoprim Polymyxin B Ethambutol *Rifampin Ampicillin The best-known derivative of the rifamycin family of antibiotics is rifampin. These drugs are structurally related to the macrolides and inhibit the synthesis of mRNA. By far the most important use of rifampin is against mycobacteria in the treatment of tuberculosis and leprosy. A valuable characteristic of rifampin is its ability to penetrate tissues and reach therapeutic levels in cerebrospinal fluid and abscesses.

Broad-spectrum antibiotics:

affect a broad range of gram-positive or gram-negative bacteria

More than half of our antibiotics are produced by species of a) Mycobacterium.b) Streptomyces. c) Clostridium.d) Bacillus.

b) Streptomyces.

Rifampin blocks RNA polymerase and therefore inhibits __________.

cell wall synthesis *transcription translation DNA synthesis The best-known derivative of the rifamycin family of antibiotics is rifampin. These drugs are structurally related to the macrolides and inhibit the synthesis of mRNA, which inhibits transcription. By far the most important use of rifampin is against mycobacteria in the treatment of tuberculosis and leprosy.

Fungal cell wall is made of:

chitin

Drugs that inhibit protein synthesis:

chloramphenicol, erythromycin, tetracylines, streptomycin

Antibotic Safety:

damage to organs risk to fetus

chemotherapy

discovered by Paul Ehrlich. Came up with one of the first treatments for syphilis using chemicals. He stained bacteria to make it easier to see and noticed that some of these stains actually killed the bacteria. So then he thought maybe some of these stains can be used to treat diseases in people.

Narrow spectrum of microbial activity:

drugs that affect a narrow range of microbial types

Ethambutol inhibits incorporation of mycolic acid into cell walls; therefore, it is effective against __________.

fungi mycoplasmas gram-positive bacteria *mycobacteria (Mycolic acids are unique long chain fatty acids found in the lipid‐rich cell walls of mycobacteria)

Superinfection:

infection occurring after or on top of an earlier infection, especially following treatment with broad-spectrum antibiotics.

in the presence of penicillin, a cell dies because...

it undergoes lysis (the disintegration of a cell by rupture of the cell wall or membrane.)

Drugs that cause injury to plasma membrane in bacteria:

polymyxin B

What are interferons and what do they do?

proteins (cytokines) secreted by T cells and other cells to aid and regulate the immune response. It serves as a warning signal to the near by unaffected cells, causing them to heighten their anti-viral defenses.

A nucleoside analog used to treat HIV infection is __________.

ribavirin *zidovudine acyclovir amantadine praziquantel A well-known example of a nucleoside analog to treat HIV infections is is zidovudine. HIV is an RNA virus, and its reproduction depends on the enzyme reverse transcriptase, which controls the synthesis of RNA from DNA. In fact, the term antiretroviral currently implies that a drug is used to treat HIV infections.

Difference between gram positive and gram negative bacteria

see image to right. Gram positive bacteria, as you can see, has a thick peptidoglycan layer on the outside of the cell and underneath is the cytoplasmic membrane. Gram negative bacteria have a thin layer of peptidoglycan sandwiched between the outer membrane and cytoplasmic membrane. It also has a layer of lipopolysaccharides on the outside that gram positive do not. If you remember this then it will make sense why gram negative bacteria are more susceptible/sensitive to drugs like Polymyxin, which attack the cell membrane. It will also make sense why penicillin is more effective on gram positive bacteria (because it breaks apart the peptidoglycan that makes the cell wall)

Drugs that cause inhibition of essential metabolite synthesis:

sulfanilamide, trimethoprim

DNA-RNA-Proteins (DNA makes RNA, which makes proteins. )

the process of DNA making RNA is called transcription the process of RNA making protein is called translation mRNA carries the coded information for making specific proteins from DNA in the nucleus to the ribosomes. tRNA molecules recognize specific codons and transport amino acids (proteins)

Eukaryotes have 80S ribosomes, whereas prokaryotes have ________ ribosomes. •90S •80S •70S •60S

•70S

Russian scientists have experimented with which agents as a means of therapy for killing pathogenic bacteria? •Helminths •Bacteriophages •Fungi •Protozoa

•Bacteriophages

Mechanisms of antibiotic resistance in bacteria:

•Enzymatic destruction or inactivation of the drug •Prevention of penetration to the target site within the microbe •Alteration of the drug's target site •Rapid efflux (ejection) of the antibiotic •Variations of mechanisms of resistance

Antibiotic Safety

•Therapeutic index: risk versus benefit •Reactions of antibiotics with other drugs •Damage to organs •Risk to the fetus

If an antibiotic prevents bacteria from growing, then its action is termed •bactericidal. •selectively toxic. •bacteriostatic. •toxic.

•bacteriostatic.

Penicillin works by inhibiting ________ synthesis. •protein •cell wall •plasma membrane •nucleic acid

•cell wall

The relationship between the antimetabolite sulfanilamide and para-aminobenzoic acid (PABA) is an example of •antagonism. •competitive inhibition. •synergism. •bacteriostasis.

•competitive inhibition.

One disadvantage to using broad-spectrumantibiotics is that they •destroy normal microbiota. •are easily inactivated by the host. •are extremely toxic •target host cells.

•destroy normal microbiota.

The mode of action of chloramphenicol is to •inhibit cell wall synthesis. •inhibit nucleic acid synthesis. •injure the plasma membrane. •inhibit protein synthesis.

•inhibit protein synthesis.

The mode of action of antifungal drugs that target sterols is to •inhibit the synthesis of essential metabolites. •injure the plasma membrane. •inhibit nucleic acid synthesis. •inhibit cell wall synthesis.

•injure the plasma membrane. (sterols are found in the plasma membrane of fungus, plants and animals)

If one measures a large zone of inhibition in a disk-diffusion test, one can assume that the bacteria are: •sensitive to the antibiotic .•resistant to the antibiotic. •unaffected by the antibiotic. •producing the antibiotic.

•sensitive to the antibiotic

The chemotherapeutic effect of two drugs given simultaneously that is greater than the effect of either given alone is known as •symbiosis. •commensalism. •synergism. •antagonism.

•synergism.

At least 80% of antibiotics produced in the United States each year are •used for treating disease. •exported to other countries. •used in animal feed to promote growth. •available over the counter.

•used in animal feed to promote growth.