Chapter 20: Antimicrobial Drugs

Review for Exam 3

Fleming discovered penicillin in ____

1928

Penicillin is produced by

Penicillium

What is Prontosil red dye?

a type of sulfanilamide

What is selective toxicity?

selectively finding and destroying pathogens without damaging the host

Define Chemotherapy

the use of chemicals to treat a disease

What is an Antibiotic

a substance produced by a microbe that, in small amounts, inhibits another microbe

What are Antimicrobial drugs?

synthetic substances that interfere with the growth of microbes

where are the antibiotics sourced: Bacitracin and Polymyxin

Gram-Positive Rods

Bacillus subtilis

Paenibacillus polymyxa

Where are the following antibiotics sourced: Amphotericin B, Chloramphenicol, Chlortetracycline and tetracycline, Erythromycin, Neomycin, Streptomycin, and Gentamicin

Actinomycetes

Streptomyces nodosus

Streptomyces venezuelae

Streptomyces aureofaciens

Saccharopolyspora erythraea

Streptomyces fradiae

Streptomyces griseus

Micromonospora purpurea

Where are the following antibiotics sourced: Cephalothin, Griseofulvin, and Penicillin

Fungi

Cephalosporium spp.

Penicillium griseofuvum

Penicillium chrysogenum

drugs that affect a narrow range of microbial types:

Narrow spectrum of microbial activity

Broad-spectrum antibiotics:

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

the overgrowth of normal microbiota that is resistant to antibiotics is called

Superinfection

examples of superinfection:

Candida albicans

Clostridioides difficile

Bactericidal

Kill microbes directly

Bacteriostatic

Prevent microbes from growing

What is the action mode of penicillins, cephalosporins, bacitracin, vancomycin

inhibition of cell wall synthesis

What is the action mode of chloramphenicol, erythromycin, tetracyclines, and streptomycin

inhibition of protein synthesis {translation}

What is the action mode of quinolones and rifampin

inhibition of nucleic acid replication and transcription

What is the action mode of polymyxin B

injury to plasma membrane

What is the action mode of sulfanilamide and trimethoprim

inhibition of essential metabolite synthesis

penicillins prevent the synthesis of what?

peptidoglycan

What do antibacterial drugs target when inhibiting protein synthesis

bacterial 70s Ribosome subunit

What antibacterial is: A

Chloramphenicol

What antibacterial is: B

Streptomycin

What antibacterial is: C

Tetracyclines

What is occurring in this image {yeast cell}

Injury to the Plasma Membrane

antibiotics that change membrane permeability

Polypeptide

Antifungal drugs injure plasma membrane by

combining with membrane sterols

antibiotics that allow uncontrolled movement of cations {not for human use}

Ionophores

When inhibiting nucleic acid synthesis what is disrupted by blocking topoisomerase?

DNA replication

When inhibiting nucleic acid synthesis what is disrupted by blocking RNA polymerase

Transcription

Antimetabolites compete with normal substrates for an enzyme; what enzyme does Sulfanilamide compete with?

para-aminobenzoic acid

Sulfanilamide stops the synthesis of which metabolite

folic acid

Prokayrotic pathogens have many differences compared to humans, so antibiotics target those differences in order to be selectively toxic.

True

Eukaryotic pathogens (fungi, protozoans, helminths) are very similar to humans at the cellular level. Drugs that target these organisms are fewer in number and tend to have more severe side effects.

True

Eukaryotic pathogens have many differences compared to humans, so antibiotics target those differences in order to be selectively toxic.

False

Prokaryotic pathogens are very similar to humans at the cellular level. Drugs that target these organisms are fewer in number and tend to have more severe side effects.

False

Side-chain amino acids and cross-bridge amino acids link layers of

NAG and NAM

What does the following structure of peptidoglycan in gram-positive bacteria do?

Protects the cell from lysis

Penicillin prevent the cross-linking of _______, interfering with cell wall construction

peptidoglycan

There are many derivatives of penicillin, all of which work on Gram + organisms. A few have been synthetically modified to work on ______ as well

Gram (-)

Natural Penicillins are extracted from

Penicillium fungi cultures

What are the types of natural penicillin?

Penicillin G (injected) and Penicillin V (oral)

Natural Penicillin are susceptible to ______

penicillinases

Semisynthetic penicillins are _________ because they contain chemically added side chains

resistant to penicillinases

Types of Semisynthetic penicillins are

Methicillin and oxacillin

Extended-spectrum penicillins are

Effective against gram-negatives & gram-positives

Broad spectrum Carbapenems

Imipenem and doripenem

Monobactam

Low toxicity; works against only certain gram-negatives

Cephalosporins

Grouped according to their generation of development

Name Polypeptide antibiotics

Bacitracin, Vancomycin, and Teixobactin

Name Antimycobacterial antibiotics

Isoniazid and Ethambutol

penicillin is bacteriocidal

True

What feature do these antibiotics have: Chloramphenicol, Streptomycin, Tetracycline, Macrolides

bacteriostatic

What is Nitrofurantoin?

Antibiotics that are converted to intermediates that attack bacterial

ribosomal proteins

What is bonded to the 50s subunit of the 70s ribosomal?

Chloramphenicol

What is a downside of Chloramphenicol?

Can suppress bone marrow and affect blood cell formation

What do Aminoglycosides do?

Changes the shape of the 30S subunit of the 70S ribosome so that proteins that are produced use the wrong amino acids

What is a downside of Aminoglycosides?

Can cause auditory damage and kidney damage

What is A?

Aminoglycoside

Name the Aminoglycosides

Streptomycin, neomycin, gentamicin

How do Tetracyclines interfere with the tRNA attachment to the ribosome?

Binds to the 30S subunit and block tRNA attachment

What is A?

Tetracyclines

What is A?

Macrolides

How do Macrolides prevent translocation?

Binds to the 50S subunit causing Ribosome to stall and it cannot proceed down the strand of mRNA

What is A?

Chloramphenicol

What is B?

Erythromycin

What is C?

Tetracyclines

What is D?

Streptomycin

Bacterial DNA must unwind in order to be replicated. The ________ prevent the unwinding by binding to Topoisomerase and DNA Gyrase.

quinolines

How does Rifamycin work?

Inhibits mRNA synthesis

How do antifungal drugs affect fungal sterols?

Interrupting the synthesis of ergosterol, making the membrane excessively permeable

Antifungal Drugs:

Polyenes, Azoles, Allylamines, Griseofulvin, Tolnaftate, and Pentamidine

Antiprotozoan Drugs:

Quinine, chloroquine, Artemisinin, Metronidazole, Tinidazole, Nitazoxanide, and Miltefosine

Quinine and chloroquine

Treat malaria

Artemisinin

Kills Plasmodium that causes malaria

Metronidazole, Tinidazole, Nitazoxanide

Treats Trichomonas, giardiasis, and amebic dysentery; Also interferes with anaerobic bacteria

Miltefosine

Treats amebic encephalitis and leishmaniasis; Inhibits cytochrome oxidase in mitochondria

Antihelminthic Drugs:

Niclosamide, Praziquantel, Mebendazole, albendazole, and ivermectin

Niclosamide

Prevents ATP production; Treats tapeworms

Praziquantel

Alters membrane permeability; Treats tapeworms and flukes

Mebendazole and albendazole

Interfere with nutrient absorption; Treat intestinal helminths

Ivermectin

Paralysis of helminths; Treats roundworms and mites

There are two methods to gain antibiotic resistance

Random mutations and acquisition of a gene from another bacterium

Resistance Gene:

These genes are usually located on a plasmid and passed via conjugation OR a transposon and passed via a bacteriophage

__________ selects for resistance mutants because the antibiotic exists at a level that is too low for complete killing/stasis

Misuse of antibiotics

Which of the following is not a misuse of antibiotics:

Taking them on an empty stomach

Which of the following is not a misuse of antibiotics:

Taking them after you are better

Persister cells:

microbes with genetic characteristics allowing for their survival when exposed to an antibiotic

Superbugs:

bacteria that are resistant to large numbers of antibiotics

Resistance genes are often spread _________ among bacteria on

plasmids or transposons via conjugation or transduction

horizontally

Bacterial pathogens that are resistant to nearly all antibiotics and cause healthcare-associated infections:

Acinetobacter baumannii

Pseudomonas aeruginosa

Members of the Enterobacteriaceae

What is mode one of Antibiotic Resistance

Blocking Entry

What is mode two of Antibiotic Resistance

Inactivation by Enzymes

What is mode three of Antibiotic Resistance

Alteration of Target Molecule

What is mode four of Antibiotic Resistance

Efflux(ejection) of Antibiotic

Disk-diffusion method (Kirby-Bauer test)

Tests the effectiveness of chemotherapeutic agents

In Kirby-Bauer test ________ with a chemotherapeutic agent are placed on agar that has been inoculated with the test organism

Paper Disks

In Kirby-Bauer test ___________ around the disk determines the sensitivity of the organism to the antibiotic

Zone of inhibition