Chapter 10 Microbiology Smartbook

What is an antibiotic?

Natural agents used only against bacterial infections

A drug isolated then modified in the lab is called?

Semisynthetic

Semisynthetic drug

Natural antibiotic chemically modified in the lab

Prophylaxis

Use of a drug to prevent infection

Antimicrobial chemotherapy

Use of drugs to control infections caused by microbes

All-inclusive term for infection-fighting drugs

Antimicrobial

Natural metabolic product made by microbes to reduce competition

Antibiotic

Drug wholly made by chemical synthesis

Synthetic

Antimicrobial entirely produced chemically

Synthetic

Use of a drug to prevent infection

Prophylaxis

Kirby-Bauer test measures ___?

Antibiotic susceptibility

General term for using drugs to control infection

Antimicrobial chemotherapy

Major bacterial sources of antibiotics

Streptomyces and Bacillus

3 factors before selecting drug

1. Nature of microbe

2. Sensitivity

3. Patient condition

Susceptibility testing needed when…

Pathogen commonly shows resistance

Drug testing NOT used for

Prions

E-test function

Gives MIC value

MIC

Minimum inhibitory concentration (highest dilution that inhibits growth)

MBC

Minimum bactericidal concentration

Therapeutic index

Ratio: toxic dose / therapeutic dose

Therapeutic window

Blood drug range where effective without toxicity

Largest zone of inhibition (image)

Tetracycline

All inclusive infection control drug

Antimicrobial

Why do susceptibility tests?

Pathogen commonly shows resistance

Natural Antimicrobial: definition

Antibiotic

Drug testing used for all except

A. Bacteria

B. Protozoa

C. Fungi

D. Prions

D. Prions

A drug produced chemically =

= Synthetic

Kirby-Bauer determines ___susceptibility

Antibiotic

In this image of a Kirby-Bauer Test, the zone of inhibition is greatest for the antibiotic _____

Tetracycline

Which genus of fungus is not a major source of antibiotics?

A. Penicillium

B. Cephalosporin

C. Aspergillus

C. Aspergillus

Factors before selecting Antimicrobial?

Nature of microbe, sensitivity, medical condition

Based of the information in the table below, which of the antibiotics would be good choice to treat an infection caused by Staphylococcus aureus?

Chlorampenicol

Essential to test all infectious agents

False

The image shows a diffusion procedure known as the _____ -test, which can establish the minimum inhibitory concentration for a microbe

E

Drug testing is unwarranted for fungi/protozoa

False

Lowest concentration inhibiting growth =

= MIC (minimum inhibitory concentration)

The ____ technique is an agar diffusion test used to determine antibiotic susceptibility of a particular bacterial strain.

Kirby-Bauer

Purpose of MBC

Determine if microbes were killed

Examine the Kirby-Bauer antibiotic susceptibility plate shown below. Based on the zones of inhibition, which antibiotic is this bacterial strain resistant to?

VA—Vancomycin

Which drug would be a poor choice for treating this infection?

Penicillin G

E-test advantage?

Provides MIC

Drug failure may be due to resistant bacteria?

True

MIC definition?

Highest dilution that still inhibits growth

Smallest concentration to kill =

= MBC

Therapeutic index = ratio of

Toxic dose / therapeutic dose

MIC

Minimum inhibitory concentration

Which antibiotic has the broadest spectrum of activity?

A. carbapenems

B. tetracyclines

C. Streptomycin

D. Penicillins

tetracyclines

Therapeutic window =

Range where drug is effective without toxicity

Tetracycline mechanism?

Blocks tRNA on A-site → inhibits protein synthesis

Beta-lactam ring is part of?

Penicillin

Drug inhibiting translocation?

Erythromycin

Drugs can’t penetrate what?

Biofilms

Synercid targets?

Protein synthesis

Fungal drugs toxic because both are?

Eukaryotic

Which inhibit helicase?

Fluoroquinolones

Narrow-spectrum antibiotics

Isoniazid, Polymyxin

Antifungals (drug groups)?

Azoles, Macrolide polyenes

Active part of penicillin?

Beta-lactam ring

Azoles MOA?

Interfere with sterol synthesis

Biofilm bacteria express different?

Genes

Echinocandins interfere with?

Fungal cell wall synthesis

Drugs that are effective against fungi have a strong possibility of being toxic to humans because both organisms are eukaryotes.

True

Fluoroquinolones stop transcription of DNA by inhibiting unwinding enzymes called

Helicase

Narrow-spectrum antibiotics

Isoniazid, Polymyxin

Antifungals (drug groups)?

Azoles, Macrolide polyenes

Active part of penicillin?

Beta-lactam ring

Azoles MOA?

Interfere with sterol synthesis

Biofilm bacteria express different?

Genes

Echinocandins interfere with?

Fungal cell wall synthesis

Quinine is a drug used to treat the protozoan infection known as

malaria

Quinine has been replaced by the synthesized quinolones, mainly ____ and primaquine, for treatment of malaria, because they have less toxicity in humans.

chloroquine

Drugs blocking influenza fusion?

Oseltamivir, Zanamivir

Common antimalarials today?

Chloroquine, Primaquine

SARS-CoV-2 RNA replication inhibitor?

Remdesivir

Ivermectin + praziquantel treat?

Helminths

Adaptive tolerance = drug ____?

Resistance

Why viral infections hard to treat?

Rely on host cells for molecular processes

Antifungal that blocks cell wall?

Echinocandin

Major antiviral modes of action?

Block entry, block replication, block maturation

Influenza entry blockers?

Oseltamivir, Zanamivir

Which antibiotics inhibit protein synthesis?

Streptomycin

Drug for penicillin allergy?

Aztreonam

Bacteria persisters do what?

Slow/stop metabolism

Beta-lactamase role?

Drug inactivation

Horizontal transfer mechanisms?

Conjugation, Transduction, Transformation

Gene silencing RNA?

Interfering RNA (RNAi)

Correct statements about gene sharing?

Transposons move resistance; viruses can transfer resistance genes

Epigenetic resistance in fungi is?

Reversible

Resistance genes from chromosomal mutation?

True

R factor is a type of?

Plasmid

Erythromycin/clindamycin resistance from altered?

50S ribosomal subunit

Natural selection applies pressure from?

Environment

RNAi is explored for?

RSV, Hepatitis C virus

CRISPR used to cut?

Antibiotic resistance genes

Post-antibiotic era =

= Some infections untreatable

Probiotics are?

Preparations of live microbes

Major drug side effects categories?

Toxicity, Allergies, Flora disruption

Nephrotoxic drugs damage?

Kidneys

Drug reaction when immune system activated =

= Allergy

Damage from drugs can be?

Permanent or reversible