Chapter 10 Controlling Microbial Growth in the Body: Antimicrobial Drugs

An antimicrobial that inhibits cell wall synthesis will result in which of the following? A) Cells become more susceptible to osmotic pressure. B) Cells cannot attach to their hosts. C) Ribosomes lose their function. D) The sterols in the cell wall become nonfunctional. E) The replication of cells, including cancer cells, slows down.

A) Cells become more susceptible to osmotic pressure

Who discovered the first antibiotic widely available to the general public? A) Domagk B) Ehrlich C) Fleming D) Waksman E) Ehrlich and Waksman

A) Domagk

Broad-spectrum synthetic antimicrobials were discovered by A) Gerhard Domagk. B) Alexander Fleming. C) Paul Ehrlich. D) Selman Waksman. E) Joseph Lister.

A) Gerhard Domagk

Which of the following types of antimicrobial agent has the narrowest spectrum of action? A) antivirals B) azoles C) sulphonamides D) erythromycins E) Both azoles and erythromycins have equally narrow spectrums of action.

A) antivirals

Drug-resistant populations of microbes arise when A) exposure to drugs selectively kills sensitive cells, allowing overgrowth of resistant cells. B) exposure to drugs causes mutations that produce resistance. C) resistant cells become numerous in a population due to their greater vigor. D) the patient becomes immune to the drug. E) synergy between medications occurs.

A) exposure to drugs selectively kills sensitive cells, allowing overgrowth of resistant cells

The mechanism of action of erythromycin is A) inhibition of protein synthesis. B) inhibition of cell wall synthesis. C) inhibition of nucleic acid synthesis. D) inhibition of a metabolic pathway. E) disruption of cytoplasmic membranes.

A) inhibition of protein synthesis

Several antiviral medications used to treat HIV interfere with A) nucleic acid synthesis. B) protein synthesis. C) assembly of membranes. D) folic acid synthesis. E) cell wall synthesis.

A) nucleic acid synthesis

Most drugs that inhibit the synthesis of the cell wall act by A) preventing the cross-linkage of NAM subunits. B) blocking the secretion of cell wall molecules from the cytoplasm. C) preventing the formation of alanine-alanine bridges. D) disrupting the formation of the mycolic acid layer of the cell wall. E) preventing the formation of β-lactamases

A) preventing the cross-linkage of NAM subunits

Inhibiters of DNA synthesis specifically effective on prokaryotes are A) quinolones. B) actinomycin. C) rifampin. D) tetracycline. E) 5-fluorocytosine

A) quinolones

The first synthetic antimicrobial widely available for treatment of infections A) was an antimetabolite. B) was a nucleotide analog. C) was an attachment antagonist. D) disrupted cytoplasmic membranes. E) interfered with bacterial cell wall synthesis

A) was an antimetabolite

A newly discovered prokaryote produces a compound with promising antimicrobial effects. Devise a set of tests to determine whether the antimicrobial is broad or narrow spectrum and bactericidal or bacteriostatic

Answers will vary somewhat, but the following includes elements which should be present. The spectrum of action can be determined by testing the antimicrobial against representatives of the various groups of pathogenic bacteria: Gram positives such as Staphylococcus, Streptococcus and Bacillus, members of the Gram-negative Enterobacteriaceae and other Gram-negative bacteria (Neisseria for example), mycobacteria and chlamydias. These tests might be done on broth cultures as MIC tests, or plate cultures as Etests. One or more broad spectrum antibiotics should be included as controls. Once susceptible microbes have been identified, MBC tests can be conducted to determine whether the antimicrobial is bacteriostatic or bactericidal. Appropriate controls should be included

A recent publication from the CDC contained the following statement: "Carbapenem-resistant Enterobacteriaceae (CRE) are pathogens that have emerged in the United States as a serious public health threat. They are resistant to almost all drugs, difficult to treat, and are associated with high death rates (up to 40% in some studies)." The bacteria referred to as CRE are Gram-negative bacteria that are frequently part of the normal microbiota. Discuss some of the reasons for the high level of concern about CREs

Answers will vary; good answers will address multiple factors that contribute to the serious threat of CREs. To begin with, Gram-negative bacteria have natural resistance to the many antibiotics that do not cross the outer LPS membrane. Treatment of infections with Gram-negative bacteria can result in the release of the endotoxin Lipid A, which can severely exacerbate the infection by causing additional problems. Bacteria that can exist as part of the microbiota may be under frequent selection for antibiotic resistance when people take antibiotics for infections. Survival as part of the microbiota may contribute to people carrying and spreading CREs without signs of disease for a period of time. These bacteria may spread their multidrug resistance to other true and potential pathogens by means of conjugation.

Bacillus licheniformis secretes a compound that inhibits the growth of other Gram-positive bacteria. This is an example of a(n) A) analog. B) antibiotic. C) chemotherapeutic. D) porin. E) toxin.

B) antibiotic

Synthetic antimicrobials that block protein synthesis by binding to the mRNA are A) aminoglycosides. B) antisense nucleic acids. C) macrolides. D) beta-lactams. E) nucleic acid analogs

B) antisense nucleic acids

Beta-lactam antibiotics have an effect on which of the following types of cells? A) animal cells B) bacterial cells C) fungal cells D) virus-infected cells E) both animal and fungal cells

B) bacterial cells

The CDC issued alerts about a bacterial strain known as NDM1 (New Delhi metalo-lactamase 1). What type of antibiotic resistance is indicated by the name? A) alteration of the target of the drug B) inactivation of the drug C) change in the permeability of the drug D) overproduction of an enzyme in a key metabolic pathway E) removal of the drug via a pump

B) inactivation of the drug

Most broad-spectrum antibiotics act by A) inhibiting the synthesis of the cell wall. B) inhibiting protein synthesis. C) inhibiting nucleic acid synthesis. D) inhibiting metabolic pathways. E) disrupting the cytoplasmic membrane.

B) inhibiting protein synthesis.

The mechanism of action of the antibiotic vancomycin is A) inhibition of protein synthesis. B) inhibition of cell wall synthesis. C) inhibition of nucleic acid synthesis. D) inhibition of a metabolic pathway. E) disruption of cytoplasmic membranes.

B) inhibition of cell wall synthesis

In the compound lamivudine an -SH group replaces an -OH group found in cytosine. When used as a medication it will A) disrupt membrane structure. B) interfere with nucleic acid synthesis. C) interfere with protein synthesis. D) disrupt lipid membrane structure. E) interfere with cell wall synthesis.

B) interfere with nucleic acid synthesis

Which of the following is measured in the broth dilution test? A) the zone of inhibition B) lack of turbidity C) cell lysis D) lack of turbidity and zone of inhibition E) presence of turbidity and cell lysis

B) lack of turbidity

Alterations in the structure of which of the following are an important aspect of Gram-negative bacterial resistance to antimicrobial drugs? A) plasmids B) porins C) mitochondria D) cytoplasmic membrane E) ribosomes

B) porins

4) Which of the following is a primary advantage of semisynthetic drugs? A) They are less stable and consequently have fewer side effects. B) They work faster. C) They have a broader spectrum of action. D) They must be administered intravenously. E) They are not readily absorbed, so they persist longer.

C) They have a broader spectrum of action

Pentamidine is an example of an antimicrobial that A) disrupts cytoplasmic membranes. B) inhibits cell wall synthesis. C) binds to DNA. D) inhibits metabolic pathways. E) binds to ribosomes.

C) binds to DNA

Antimicrobial sugar analogs are effective for A) preventing bacterial protein synthesis. B) preventing cell membrane synthesis. C) preventing virus attachment. D) preventing nucleic acid synthesis. E) blocking a metabolic pathway.

C) preventing virus attachment

The therapeutic range of an antimicrobial is the A) ratio of the dose a patient can tolerate to the effective dose. B) range of microorganisms the antimicrobial effects. C) range of concentrations at which the antimicrobial is both effective and non-toxic. D) ratio of the concentration of antimicrobial in the blood to the oral dose. E) length of time the medication persists in the body after a single dose.

C) range of concentrations at which the antimicrobial is both effective and non-toxic.

A compound is extracted from a microbial culture and is modified in the laboratory for use as an oral medication. This product would be a(n) A) antibiotic. B) analog. C) semisynthetic antimicrobial. D) synthetic antimicrobial. E) probiotic.

C) semisynthetic antimicrobial

The cooperative activity of drugs such as beta-lactam antibiotics and clavulanic acid, a β-lactamase inhibitor, is known as A) cross resistance. B) antimetabolism. C) synergism. D) selective toxicity. E) chemotherapy.

C) synergism

Which of the following pathways is specifically inhibited by trimethoprim? A) the conversion of tetrahydrofolic acid to PABA B) the conversion of PABA to dihydrofolic acid C) the conversion of dihydrofolic acid to tetrahydrofolic acid D) the conversion of PABA to tetrahydrofolic acid E) the conversion of dihydrofolic acid to PABA

C) the conversion of dihydrofolic acid to tetrahydrofolic acid

The β-lactams are narrow spectrum antibacterials because A) they block a synthetic step unique to the Gram-positive bacteria. B) they are analogs for a compound metabolized only by Gram-negative bacteria. C) the outer membrane prevents their entry into cells. D) they are analogs for a unique cell membrane lipid. E) the thick peptidoglycan walls prevent their entry into cells.

C) the outer membrane prevents their entry into cells.

How does resistance to drugs spread in bacterial populations? A) Exposure to drugs causes mutations in bacterial genes. B) Horizontal gene transfer between bacteria spreads R (resistance) plasmids. C) The formation of biofilms protects bacteria from the effects of drugs. D) Both horizontal gene transfer and the growth of biofilms spread drug resistance. E) Exposure to drugs alters gene expression in bacteri

D) Both horizontal gene transfer and the growth of biofilms spread drug resistance

The antimicrobial polymyxin is primarily effective for treating superficial infections with A) Staphylococcus bacteria. B) fungi. C) viruses. D) Gram-negative bacteria. E) any bacteria.

D) Gram-negative bacteria

The E-test determines which of the following? A) susceptibility B) MBC (minimum bactericidal concentration) C) MIC (minimum inhibitory concentration) D) both susceptibility and MIC (minimum inhibitory concentration) E) both MBC (minimum bactericidal concentration) and MIC (minimum inhibitory concentration)

D) both susceptibility and MIC (minimum inhibitory concentration)

Infection of the ________ would be the hardest to treat with antimicrobial drugs. A) heart B) kidneys C) liver D) brain E) colon

D) brain

A medication which specifically targets cell walls that contain arabinogalactan-mycolic acid is A) vancomycin. B) penicillin. C) methicillin. D) isoniazid. E) bacitracin.

D) isoniazid

Ribavirin is an antiviral that interferes with A) protein synthesis. B) cell wall synthesis. C) cell membrane component synthesis. D) nucleic acid synthesis. E) viral attachment.

D) nucleic acid synthesis.

A sulfonamide and trimethoprim may be administered in combination to A) provide broad-spectrum action. B) inhibit multiple metabolic pathways. C) reduce relative toxicity. D) reduce development of antibiotic resistance. E) treat infections with microbes that require folic acid

D) reduce development of antibiotic resistance.

Disruption of the normal microbiota can result in infections caused by which of the following microbes? A) Mycobacterium B) Candida albicans C) Clostridium difficile D) both Mycobacterium and Clostridium difficile E) Candida albicans, Mycobacterium, and Clostridium difficile

E) Candida albicans, Mycobacterium, and Clostridium difficile

Which of the following antibiotics disrupts cytoplasmic membrane function? A) streptomycin B) erythromycin C) tetracycline D) penicillin E) amphotericin B

E) amphotericin B

Which of the following interferes with cell wall synthesis by blocking alanine bridge formation? A) beta-lactams B) cycloserine C) bacitracin D) vancomycin E) both cycloserine and vancomycin

E) both cycloserine and vancomycin

Which of the following can result when antibiotic therapy disrupts the normal microbiota? A) anaphylactic shock B) black hairy tongue C) pseudomembranous colitis D) thrush E) both pseudomembranous colitis and thrush

E) both pseudomembranous colitis and thrush

A new antibacterial medication prevents the assembly of ribosomes on mRNA. The new medication would be A) an antisense RNA. B) a type of macrolide. C) a type of oxazolidinone. D) either an antisense RNA or a type of macrolide. E) either an antisense RNA or a type of oxazolidinone.

E) either an antisense RNA or a type of oxazolidinone

Antiviral medications can best be described as A) broad spectrum antimicrobials. B) extremely narrow spectrum antimicrobials. C) antibiotics produced by bacteria. D) synthetic antimicrobials. E) extremely narrow spectrum synthetic antimicrobials.

E) extremely narrow spectrum synthetic antimicrobials

A medication that inhibits synthesis of ergosterol would be effective in treating A) bacterial infections. B) Mycobacterial disease. C) protozoal infections. D) viral disease. E) fungal infections.

E) fungal infections

Bacterial DNA replication requires the enzyme gyrase, but eukaryotic replication does not. Ciprofloxacin ("Cipro") inhibits gyrase activity. This is an example of A) antimicrobial resistance. B) use of an analog. C) synergism. D) an antimetabolite. E) selective toxicity

E) selective toxicity

A compound is structurally similar to PABA and inhibits folic acid synthesis. It is most likely a(n) A) nucleic acid analog. B) penicillin. C) tetracycline. D) azole. E) sulfonamide.

E) sulfonamide

Medications which should NOT be prescribed for a pregnant woman include A) penicillins. B) aminoglycosides. C) sulfonamides. D) tetracyclines. E) sulfonamides and tetracyclines.

E) sulfonamides and tetracyclines

True of False? A side effect known as "black hairy tongue" may result from antifungal therapy

FALSE

True of False? If a subculture of an MIC test grows in an MBC test, the concentration of the drug was bactericidal

FALSE

True of False? Nucleic acid analog drugs act by inhibiting ribosome function.

FALSE

True of False? Paul Ehrlich coined the term antibiotics for the "magic bullet" antimicrobials he pursued.

FALSE

True of False? The outer membrane of Gram-negative bacteria enables many antimicrobial drugs to enter the cell more easily.

FALSE

The abbreviation (MIC/MID/MBC) stands for the smallest amount of a drug that will inhibit the growth and reproduction of a pathogen.

MIC

Why can microbial resistance to antibiotics and other drugs be considered a primarily genetic phenomenon?

Microbial resistance is considered a genetic phenomenon because there are two major ways that bacteria acquire resistance: through mutations of chromosomal genes or through acquisition of new genes carried on R-plasmids. In both cases, the cell gains the ability to resist the activity of a particular drug through the modified structure or activity of proteins that are coded for by the genes in question. For example, some of these altered proteins can be cytoplasmic membrane proteins or porin proteins that no longer allow a drug such as penicillin to enter the cell. Also, some of the proteins coded for by these genes may be enzymes of various sorts that serve to inactivate a particular drug, such as the inactivation of beta-lactam antibiotics by β-lactamases. Furthermore, these altered genes and proteins are then heritable by the offspring of the cell that acquired the resistance, leading quickly to entire populations of bacteria or other microbes that are resistant to a drug. When selective pressure is then brought to bear (through the administration of a particular drug) on a population that contains both susceptible and resistant cells, the result is that the susceptible cells die off, leaving the resistant cells to grow and flourish.

True of False? A compound that slows the activity of efflux pumps, when administered with an antibiotic which requires high concentration to be effective, the combination is highly effective for treating bacterial infections. This is an example of synergy.

TRUE

True of False? Antisense nucleic acids are designed to have no side effects against humans

TRUE

True of False? Medications administered intravenously can provide much higher effective concentrations than other delivery methods.

TRUE

True of False? R-plasmids are extrachromosomal DNAs that contain genes for antimicrobial resistance.

TRUE

True of False? Some bacterial cells are resistant to a variety of antimicrobials because they actively pump the drugs out of the cell.

TRUE

While not the first person to discover antibiotics (Domagk/Fleming/Waksman) discovered the sources of many useful antibiotics

Waksman

Discuss the cellular factors that might make a drug's spectrum of action narrow rather than broad.

When a drug is labeled "narrow-spectrum," meaning that it has activity against only a limited number of microbes, generally the reason is that many microbes possess some form of natural resistance against the drug. For example, many drugs work better against Gram-positive organisms than Gram-negative ones because Gram-negative cells possess an outer membrane that does not allow these drugs to enter the cell as readily as they enter Gram-positive cells. Other cellular factors that can have an effect on the spectrum of action of a particular drug include the presence of R-plasmids in the cell that carries resistance genes, the presence of altered cytoplasmic membrane or cell wall proteins that prevent the passage of some types of drugs, and alterations in a cell's metabolic pathways, which can make the cell more resistant to certain types of drugs. Other antimicrobials have a narrow spectrum of action because they target a metabolic or structural feature unique to a single pathogen or small group of pathogens. One example of this type of narrow-spectrum antimicrobial is antisense RNA, which complements a specific nucleotide sequence that may be present in only one pathogen. Another example is isonizid which blocks the synthesis of a cell wall component unique to the Mycoplasmas.

Nucleotide or nucleoside (analogs/antisense/acids) are antimicrobial agents that mimic the chemical structure of DNA building blocks.

analogs

Competition between beneficial microbes and potential pathogens is called microbial (synergy/antagonism).

antagonism

Drugs that slow bacterial growth would be (competitive/synergistic/antagonistic) to penicillin.

antagonistic

A (bacteriostatic/bacteriocidal/minimum) concentration of a drug is one at which microbes survive but are not able to grow and reproduce.

bacteriostatic

Some bacteria develop resistance to groups of drugs because the drugs are all structurally similar to each other; this is a phenomenon known as (cross/multiple) resistance.

cross

Antiviral medications frequently block unique (proteins/enzymes/molecules) to prevent production of new virus.

enzymes

Macrolides inhibit protein synthesis by blocking (catalysis/binding/movement) of the ribosome.

movement

The majority of broad spectrum antibacterial medications inhibit (DNA/protein/RNA) synthesis.

protein

Second-generation drugs are semisynthetic drugs developed to combat (immunity/resistance) against an existing drug

resistance

Secondary infections that result from the killing of some of the normal microbiota are called (antagonism/superinfections/resistance).

superinfections

External infections can be treated by (surface/topical) administration, in which a drug is applied directly to the site of infection.

topical

Selective (toxicity/action/treatment) means that a given antimicrobial agent is more toxic to a pathogen than to the host being treated.

toxicity

The action of some antivirals prevent (attachment/synthesis/uncoating), an event shortly after entry of the virus into the cell.

uncoating