Microbiology Chapter 20 Flashcards

Questions and Answers

An antimicrobial medication is a chemical used to treat an infectious disease.

True

Antimicrobial medications are best defined as ______.

chemicals that inhibit the growth of or kill microorganisms

What was the first antibiotic discovered in 1928 by Alexander Fleming?

penicillin

Most antibiotics come from species of bacteria and fungi that normally live _______.

in soils Signup and view all the answers

Medically useful antimicrobial drugs exhibit _________, meaning they cause greater harm to microbes than to the human host.

selective toxicity Signup and view all the answers

What are chemicals used in the therapy of infectious diseases called?

antimicrobial medications Signup and view all the answers

Why is a urinary tract infection a good example for treatment with bacteriostatic antimicrobials?

Once bacterial growth is stopped, urination can usually be counted on to flush the pathogens. Signup and view all the answers

Chemotherapeutic agents that are used to treat microbial infections can be more specifically called?

antimicrobial medications Signup and view all the answers

In 1928, Alexander Fleming identified the mold producing the first discovered antibiotic as a species of?

Penicillium Signup and view all the answers

Which of the following species are the four major producers of antibiotics? (Select all that apply)

Streptomyces (bacterium) Signup and view all the answers

A broad-spectrum antimicrobial is most likely effective against?

A wide range of both Gram-positive and Gram-negative bacteria Signup and view all the answers

Effective antimicrobial drugs need to demonstrate selective toxicity. What does this mean?

They cause greater harm to microbes than to the human host. Signup and view all the answers

When antimicrobials are used in combination and their interaction is neither antagonistic nor synergistic, the combination is said to be?

additive Signup and view all the answers

When treating a case where the patient's defenses are unlikely to clear an infection, which would be the more appropriate choice of an antimicrobial drug?

One that is bactericidal Signup and view all the answers

What is a special consideration when giving antimicrobials to patients who have kidney or liver dysfunction?

They may excrete or metabolize drugs more slowly, so their dosages should be adjusted accordingly to avoid toxic levels. Signup and view all the answers

Antimicrobials that are effective against a wide range of bacteria are known as?

broad-spectrum antimicrobials Signup and view all the answers

When certain bacteria are said to have intrinsic (innate) resistance, this means they have ______.

some inherent property that makes them generally more resistant to the effect of some antimicrobials Signup and view all the answers

When treating an infection with a combination of antimicrobials, why might a bacteriostatic drug be antagonistic when used with a bactericidal drug?

The bactericidal drug relies on actively dividing cells to work; the bacteriostatic drug prevents cells from actively dividing. Signup and view all the answers

What does each class of antibacterial medication target?

Rifamycins - Nucleic acid synthesis Signup and view all the answers

Certain bacteria are inherently resistant to the effects of some antimicrobials. Inherent resistance is called ______.

intrinsic (or innate) resistance Signup and view all the answers

Among the most useful antibacterial medications that interfere with metabolic pathways are the ______ biosynthesis inhibitors: sulfonamides and trimethoprim.

folate Signup and view all the answers

Match each antibacterial medication with its appropriate mechanism of action.

Vancomycin = Cell wall (peptidoglycan) synthesis Fluoroquinolones = Nucleic acid synthesis Daptomycin = Cell membrane integrity Trimethoprim = Metabolic pathways (folate biosynthesis) Aminoglycosides = Protein synthesis Signup and view all the answers

How do certain antibacterial medications that interfere with cell membrane integrity lead to bacterial cell death?

They cause the cells to leak. Signup and view all the answers

What best explains why the first-line drugs are generally given in combination to patients who have active tuberculosis?

To reduce the chance that resistant mutants will develop. Signup and view all the answers

After testing to determine the susceptibility of an organism to various drugs, what are important considerations when choosing a drug to use?

The drug should act against the pathogen. Signup and view all the answers

Which of the following antimicrobials inhibit nucleic acid synthesis?

Fluoroquinolones, rifamycins, and metronidazole Signup and view all the answers

The Kirby-Bauer disc diffusion test is routinely used to determine ______.

the susceptibility of a given bacterial strain to an assortment of antimicrobial drugs Signup and view all the answers

Most antibacterial medications interfere with metabolic pathways.

False Signup and view all the answers

The lowest concentration of a specific antimicrobial drug needed to prevent the growth of a given bacterial strain in vitro is known as the ______.

minimum inhibitory concentration Signup and view all the answers

Antibacterials like daptomycin and polymyxin B essentially make holes in the bacterial membrane. Why is this deadly to bacteria?

It makes the membranes no longer selectively permeable. Signup and view all the answers

Compared to conventional methods, commercial modifications of antimicrobial susceptibility testing offer what advantages?

The results can be obtained more quickly. Signup and view all the answers

A group of medications called the _________ drugs are preferred for use against species of Mycobacterium.

first line Signup and view all the answers

Susceptibility of a pathogen to a specific antimicrobial drug is almost always predictable.

False Signup and view all the answers

Explain how drug resistance develops in bacteria and ultimately limits the usefulness of all known antimicrobials.

Antimicrobials kill or inhibit sensitive organisms, providing a selective advantage to resistant strains; these strains spread in the population. Signup and view all the answers

The minimum inhibitory concentration (MIC) is the ______.

lowest concentration of a specific antimicrobial drug needed to prevent the growth of a given bacterial strain in vitro Signup and view all the answers

Compared to conventional methods of antimicrobial susceptibility testing, commercial modifications are less labor-intensive.

True Signup and view all the answers

Match the antifungal medications listed with the correct cellular target.

Griseofulvin = Cell division Echinocandins = Cell wall synthesis Polyenes, Azoles, Allylamines = Plasma membrane synthesis and function Flucytosine = Nucleic acid synthesis Signup and view all the answers

What is targeted by antiviral medications such as acyclovir, ribavirin, and AZT?

Viral replication processes Signup and view all the answers

Which of the following mechanisms do antiviral medications work? (Select all that apply)

Preventing entry of the virus into the host cell Signup and view all the answers

Why do β-lactam antibiotics vary in their spectrum of activity? (Select two reasons)

Different groups of bacteria have different penicillin-binding proteins. Signup and view all the answers

What type of penicillin is produced by Penicillium chrysogenum?

Natural penicillins Signup and view all the answers

What type of penicillin was developed in response to resistant Staphylococcus aureus?

Penicillinase-resistant penicillins Signup and view all the answers

What type of penicillin is active against penicillin-sensitive Gram-positive and many Gram-negative bacteria?

Broad-spectrum penicillins Signup and view all the answers

What type of penicillin has greater activity against Pseudomonas aeruginosa?

Extended-spectrum penicillins Signup and view all the answers

What type of penicillin is a combination of agents resistant to enzymatic destruction?

Penicillins + β-lactamase inhibitor Signup and view all the answers

Why did the police officer die when tested with penicillin?

There wasn't enough purified penicillin available to cure him completely. Signup and view all the answers

For diseases caused by which pathogen would a medication inhibiting microtubule formation NOT be used?

Staphylococcus aureus Signup and view all the answers

What term describes compounds that cause greater harm to microbes than to the human host?

Selective toxicity Signup and view all the answers

What term describes the molecular method by which a compound might kill or inhibit a microbe?

Antimicrobial action Signup and view all the answers

What term is used to describe the range of different microbes that a compound can kill or inhibit?

Spectrum of activity Signup and view all the answers

Which class of antimicrobials would have the most selective toxicity?

Antimicrobials that inhibit cell wall synthesis. Signup and view all the answers

Antibiotics targeting which of the following would be effective against viruses?

None of the choices is correct. Signup and view all the answers

What enzymes are inhibited by β-lactam antibiotics?

Penicillin-binding proteins Signup and view all the answers

Why are few medications effective against Mycobacterium tuberculosis? (Select all that apply)

M. tuberculosis has developed resistance to many medications. Signup and view all the answers

Which type of antibiotic would be the most appropriate to prescribe for meningococcal meningitis?

Broad-spectrum, high therapeutic index Signup and view all the answers

All of the following statements about the Kirby-Bauer test are true EXCEPT

A large zone of inhibition indicates extreme sensitivity to a drug. Signup and view all the answers

Antiviral medications that interfere with genome integration will be useful against all animal viruses.

False Signup and view all the answers

Why should a patient with 'walking pneumonia' NOT be given penicillin?

Some bacteria, such as Mycoplasma species, are intrinsically resistant to penicillin. Signup and view all the answers

How does an antibiotic that inhibits protein synthesis achieve selectivity?

Antibiotics bind to the 70S bacterial ribosomes but not to the 80S eukaryotic ribosomes. Signup and view all the answers

What antibacterial medications inhibit cell wall synthesis?

β-Lactam antibiotics (Penicillins, Cephalosporins, Carbapenems, Monobactams); Glycopeptide antibiotics (Vancomycin); Bacitracin Signup and view all the answers

How do beta-lactam antibiotics interfere with peptidoglycan synthesis?

Inhibiting enzymes called penicillin-binding proteins (PBPs) that help form cross-links between adjacent glycan chains. Signup and view all the answers

What family of Beta-lactam antibacterial medications has different groups that vary in their spectrum of activity and their susceptibility to beta-lactamase?

Penicillins Signup and view all the answers

What family of Beta-lactam antibacterial medications has later generations that are generally more effective against Gram-negative bacteria but less susceptible to destruction by most beta-lactamases?

Cephalosporins Signup and view all the answers

What family of Beta-lactam antibacterial medications has a broad spectrum of activity and is not destroyed by most beta-lactamases, including extended-spectrum beta-lactamases?

Carbapenems Signup and view all the answers

What Beta-lactam antibiotic is primarily active against members of the family Enterobacteriaceae?

Monobactams Signup and view all the answers

How do Glycopeptide antibiotics interfere with peptidoglycan synthesis?

Binding to the amino acid side chain of NAM molecules, blocking formation of cross-links between adjacent glycan chains. Signup and view all the answers

How does bacitracin inhibit cell wall synthesis?

Interferes with the transport of peptidoglycan precursors across the cytoplasmic membrane. Signup and view all the answers

What antibacterial medications inhibit protein synthesis?

Aminoglycosides, tetracyclines, macrolides, chloramphenicol, lincosamides, oxazolidinones, pleuromutilins, and streptogramins. Signup and view all the answers

What protein synthesis medication is bactericidal against aerobic and facultative bacteria?

Aminoglycosides Signup and view all the answers

What protein synthesis medication is bacteriostatic against some Gram-positive and Gram-negative bacteria?

Tetracyclines and glycylcyclines Signup and view all the answers

What protein synthesis medication is bacteriostatic against many Gram-positive bacteria?

Macrolides Signup and view all the answers

What protein synthesis medication is bacteriostatic and broad-spectrum?

Chloramphenicol Signup and view all the answers

What protein synthesis medication is bacteriostatic against a variety of Gram-positive and Gram-negative bacteria?

Lincosamides Signup and view all the answers

What protein synthesis medication is bacteriostatic against various Gram-positive bacteria?

Oxazolidinones Signup and view all the answers

What protein synthesis medication is bacteriostatic against a variety of Gram-positive bacteria?

Pleuromutilins Signup and view all the answers

What protein synthesis medication is a synergistic combination of two medications?

Streptogramins Signup and view all the answers

What antibacterial medications inhibit nucleic acid synthesis?

Fluoroquinolones (ciprofloxacin, moxifloxacin), rifamycins, metronidazole. Signup and view all the answers

What nucleic acid synthesis medication is bactericidal against a wide variety of Gram-positive and Gram-negative bacteria?

Fluoroquinolones Signup and view all the answers

What nucleic acid synthesis medication is bactericidal against Gram-positive and some Gram-negative bacteria?

Rifamycins Signup and view all the answers

What nucleic acid synthesis medication is bactericidal against anaerobes?

Metronidazole Signup and view all the answers

What antibacterial medications inhibit folate biosynthesis?

Sulfonamides and trimethoprim. Signup and view all the answers

What folate biosynthesis medication is bacteriostatic against a variety of Gram-positive and Gram-negative bacteria?

Sulfonamides Signup and view all the answers

What folate biosynthesis medication is used with a sulfonamide for synergistic effect?

Trimethoprim Signup and view all the answers

What antibacterial medications inhibit cell membrane integrity?

Daptomycin and polymyxins. Signup and view all the answers

What cell membrane integrity medication is bactericidal against Gram-positive bacteria?

Daptomycin Signup and view all the answers

What cell membrane integrity medication is bactericidal against Gram-negative bacteria?

Polymyxins Signup and view all the answers

What medications are effective against Mycobacterium tuberculosis?

Ethambutol, isoniazid, and pyrazinamide. Signup and view all the answers

How is ethambutol effective against TB?

Inhibits the synthesis of a component of the mycobacterial cell wall. Signup and view all the answers

How is isoniazid effective against TB?

Inhibits the synthesis of mycolic acids. Signup and view all the answers

How is pyrazinamide effective against TB?

Interferes with a process that mycobacterial cells use to restart stalled ribosomes. Signup and view all the answers

Study Notes

Antimicrobial Medications Overview

Antimicrobial medications are chemicals intended to treat infectious diseases by either inhibiting the growth or killing microorganisms.
Selective toxicity allows these medications to harm microbes while minimizing damage to human cells.

Historical Context

Penicillin, the first antibiotic, was discovered by Alexander Fleming in 1928 from the mold Penicillium.
Most antibiotics originate from bacteria and fungi found in soil.

Mechanisms of Action

Broad-spectrum antimicrobials are effective against both Gram-positive and Gram-negative bacteria.
Specific classes target different bacterial mechanisms:
- β-lactam drugs inhibit cell wall synthesis.
- Rifamycins interfere with nucleic acid synthesis.
- Polymyxin B targets cell membrane integrity.
- Sulfonamides inhibit metabolic pathways like folate biosynthesis.
- Tetracyclines affect protein synthesis.

Treatment Considerations

Bactericidal drugs kill bacteria, while bacteriostatic drugs inhibit growth; the latter relies on the host's immune system to clear the infection.
When treating patients with kidney or liver dysfunction, dosages may need to be adjusted due to slower excretion or metabolism of drugs.
The minimum inhibitory concentration (MIC) indicates the lowest concentration of a drug needed to prevent bacterial growth.

Resistance and Combination Therapy

Drug resistance occurs when antimicrobials favor resistant strains, leading to challenges in treatment; intrinsic resistance is an inherent characteristic of some bacteria.
Combination therapy reduces the risk of developing resistant bacterial mutants and enhances treatment efficacy.

Laboratory Testing

The Kirby-Bauer disc diffusion test assesses the susceptibility of bacterial strains to various antimicrobial drugs.
Commercial modifications of antimicrobial susceptibility testing are quicker and less labor-intensive.

Special Drug Categories

First-line drugs, like isoniazid and ethambutol, target processes unique to Mycobacterium tuberculosis for effective and lower-toxicity treatment.
β-lactam antibiotics exhibit a high therapeutic index due to their targeted action against bacterial cell walls.

Consequences of Misuse

Stopping antibiotics prematurely can lead to the development of resistance.
Antivirals target viral nucleic acid synthesis and block various stages of the viral life cycle, including entry and maturation.

Antifungals and Mechanisms

Different antifungal medications target various cellular components, including:
- Griseofulvin for cell division.
- Echinocandins for cell wall synthesis.
- Polyenes, Azoles, and Allylamines for plasma membrane function.
- Flucytosine for nucleic acid synthesis.

Summary of Antibiotic Classes

Natural penicillins: Narrow-spectrum, effective against specific Gram-positive bacteria.
Penicillinase-resistant penicillins: Developed for resistant Staphylococcus aureus strains.
Broad-spectrum penicillins: Effective against various Gram-positive and Gram-negative bacteria.
Extended-spectrum penicillins: Enhanced activity against Pseudomonas aeruginosa.

Key Points on Antibiotic Resistance Mechanisms

Increase in elimination through efflux pumps.
Decreased uptake of medications via altered porins.
Altered target sites to prevent binding.
Production of drug-inactivating enzymes which neutralize the antibiotics.### Penicillin and β-Lactam Antibiotics
Discovered by Alexander Fleming, penicillin was first tested on a police officer with Staphylococcus aureus but was ineffective due to insufficient purification and the bacterium's intrinsic resistance.
Since Staphylococcus aureus lacks peptidoglycan, it demonstrates intrinsic resistance to penicillin, revealing limitations of this antibiotic.
β-lactam antibiotics target penicillin-binding proteins (PBPs), inhibiting bacterial cell wall synthesis.

Selective Toxicity

Selective toxicity refers to compounds that selectively harm microbes while sparing human cells, a crucial concept in antibiotic development.
Antimicrobials that act on bacterial cell walls show high selective toxicity because human cells lack this structure.

Antimicrobial Action

Antimicrobial action describes the mechanisms by which compounds kill or inhibit the growth of microbes.
The spectrum of activity is the range of different microbes affected by a specific antimicrobial agent.

Antibacterial Spectrum and Treatment

Penicillins offer a specific action against cell wall synthesis and maintain high selective toxicity.
Broad-spectrum antibiotics, with high therapeutic indexes, are preferred for treating infections like meningococcal meningitis caused by Neisseria meningitidis.

Kirby-Bauer Test

The Kirby-Bauer test evaluates bacterial sensitivity to antibiotics, measuring the zone of inhibition around antibiotic discs; smaller zones do not necessarily indicate extreme sensitivity.

Mycobacterium tuberculosis Challenges

Mycobacterium tuberculosis poses treatment challenges due to slow generation time, cell wall properties, and resistance to multiple medications.
Drugs like ethambutol, isoniazid, and pyrazinamide are effective against TB through mechanisms that disrupt cell wall synthesis and ribosomal function.

Protein Synthesis Inhibitors

Various antibiotics inhibit protein synthesis at different ribosomal subunits:
- Aminoglycosides cause misreading of mRNA on the 30S subunit.
- Tetracyclines block tRNA attachment to the 30S subunit.
- Macrolides prevent protein synthesis elongation on the 50S subunit.

Nucleic Acid Synthesis Inhibitors

Fluoroquinolones inhibit DNA gyrase, while rifamycins block RNA polymerase. Metronidazole works by damaging anaerobically activated DNA.

Folate Biosynthesis Inhibitors

Sulfonamides and trimethoprim inhibit folate biosynthesis; sulfonamides mimic PABA, while trimethoprim targets downstream enzyme activity.

Membrane Integrity Disruption

Daptomycin and polymyxins compromise the integrity of bacterial membranes, with daptomycin effective against Gram-positive and polymyxins against Gram-negative bacteria.

Resistance Mechanisms

β-lactam antibiotics face challenges from β-lactamases, which degrade the antibiotic, while resistant strains may require treatment with specific drug classes to overcome resistance.

Summary of Antibacterial Classes

Antimicrobials are categorized by their mechanisms: cell wall synthesis inhibitors (β-lactams), protein synthesis inhibitors (aminoglycosides, tetracyclines, macrolides), nucleic acid synthesis inhibitors (fluoroquinolones, rifamycins), and folate synthesis inhibitors (sulfonamides, trimethoprim). Each class has specific targets within microbial cells that contribute to their bactericidal or bacteriostatic effects.

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This quiz features flashcards related to Chapter 20 on antimicrobial medications. It includes true or false questions and definitions to reinforce your understanding of how these medications work against infectious diseases. Perfect for microbiology students aiming to review key concepts.