Antibiotics Overview: Macrolides & More

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Questions and Answers

What is intrinsic resistance in bacteria?

Resistance developed through exposure to antibiotics

Natural resistance due to the absence of a target (correct)

Resistance due to enzymatic modification of antibiotics

Resistance acquired through genetic mutations

Which mechanism contributes to the inactivation of antibiotics?

Efflux pumping of the antibiotic

Alteration of the antibiotic target

Modification of metabolic pathways

Enzymatic breakdown of antibiotic molecules (correct)

What characterizes MRSA and VRSA as pathogens?

They can transfer resistance genes to other bacteria (correct)

They lack resistance gene islands

They only contain chromosomal resistance genes

They are susceptible to all classes of antibiotics

Which bacteria is known to contribute 90% of all vancomycin-resistant infections?

Enterococcus faecalis Signup and view all the answers

What is a common characteristic of Clostridium difficile?

It establishes superinfections in the intestinal tract Signup and view all the answers

What type of resistance occurs when a bacterium changes its genome to resist antibiotics?

Acquired resistance Signup and view all the answers

Which type of bacteria lacks a cell wall and is resistant to β-lactam antibiotics?

Mycoplasma species Signup and view all the answers

How do bacteria often acquire antibiotic resistance?

Through horizontal gene transfer and mutations Signup and view all the answers

What is the primary mode of action of macrolides?

Bind to the 50S ribosomal subunit Signup and view all the answers

Which antibiotic is classified under tetracyclines?

Doxycycline Signup and view all the answers

Which of the following antibiotics is specifically known as a sulfonamide?

Lincomycin Signup and view all the answers

What type of infections are lincomycins primarily used for?

Extra CNS anaerobic infections Signup and view all the answers

Which antibiotic is recognized for renal toxicity but powerful effectiveness?

Bacitracin Signup and view all the answers

Which of the following antibiotics is a polypeptide antibiotic?

Gramicidin Signup and view all the answers

Chloramphenicol is particularly effective against which infections?

Meningitis and typhoid fever Signup and view all the answers

What is a key characteristic of tetracyclines?

They share a common octahydronaphthacene skeleton Signup and view all the answers

What type of mycorrhizae penetrates the root cell wall?

Arbuscular mycorrhizae Signup and view all the answers

Which fungal partners are primarily associated with ectomycorrhizae?

Basidiomycetes Signup and view all the answers

What is the name of the thick-walled resting cell formed during sexual reproduction in Zygomycetes?

Zygospore Signup and view all the answers

Which of the following antiviral drugs is considered a prodrug?

Valacyclovir Signup and view all the answers

What is a common mechanism by which antiviral drugs operate?

They block viral entry into or exit from the cell. Signup and view all the answers

What is a challenge of antiviral therapy?

Viruses can mutate quickly, leading to drug resistance. Signup and view all the answers

In Ascomycetes, what is the asexual spore called?

Conidia Signup and view all the answers

What is the main action of Ganciclovir?

Acting similarly to Acyclovir against herpes viruses. Signup and view all the answers

Which antiviral drug incorporates into viral DNA and inhibits synthesis?

Acyclovir Signup and view all the answers

Which type of virus does Acyclovir specifically target?

Herpes simplex virus Signup and view all the answers

Which of the following is NOT a method of asexual reproduction in fungi?

Fertilization Signup and view all the answers

What is a significant side effect of nonselective inhibitors of virus replication?

Potential toxicity to normal host cells. Signup and view all the answers

Which type of fungi grows as both molds and yeasts?

Deuteromycetes Signup and view all the answers

What is the common name for spores produced by Zygomycetes in a swollen sac-like structure?

Sporangiospores Signup and view all the answers

What structure do ascospores develop within in Ascomycetes?

Ascus Signup and view all the answers

Which of the following is NOT an indication for Acyclovir use?

Hepatitis C Signup and view all the answers

What is the primary mechanism of action of beta-lactam antibiotics?

Inhibit cell wall synthesis by binding to Penicillin Binding Protein Signup and view all the answers

Which of the following agents is a beta-lactam antibiotic?

Imipenem Signup and view all the answers

Which method is typically used to differentiate viable and dead cells?

Propidium iodide and ethidium bromide staining Signup and view all the answers

What is the role of beta-lactamase inhibitors?

Increase the effectiveness of beta-lactam antibiotics Signup and view all the answers

Which of these antibiotics is known for having a very broad spectrum of activity?

Cefepime Signup and view all the answers

What happens to bacteria when the cell wall synthesis is inhibited by beta-lactam antibiotics?

They become lysed Signup and view all the answers

Which generation of cephalosporins would you classify Ceftriaxone?

3rd generation Signup and view all the answers

What is NOT a type of beta-lactam antibiotic?

Vancomycin Signup and view all the answers

Study Notes

Macrolides

Principally active against Gram-positive bacteria
Show useful activity against penicillin-resistant strains
Also effective against Gram-negative cocci
Mode of action: Bacteriostatic, bind to the 50S ribosomal subunit to prevent the translocation step of bacterial protein synthesis
Examples: Erythromycin, Azithromycin

Tetracyclines

Broad spectrum antibiotic
Characterized by their common octahydronaphthacene skeleton
Examples: Tetracycline, Doxycycline, Minocycline

Lincomycins

Known as Sulphur-containing Antibiotics
Mode of action: Act via 50S ribosomal subunit binding and protein synthesis inhibition.
Used in extra CNS anaerobic infections and in penicillin-sensitive patients
Examples: Lincomycin, Clindamycin

Polypeptide Antibiotics

Most powerful antibiotic agents but limited use due to renal toxicity.
Used mainly locally in burns.
Mode of action: Inhibit mucopeptide cell wall synthesis and interfere with semipermeability of the cell membrane
Examples: Bacitracin, Gramicidin, Polymyxin

Unclassified Antibiotics

Chloramphenicol: Used in meningitis, typhoid, and paratyphoid fever

Antibiotic Resistance

Two types of resistance: intrinsic and acquired.
Intrinsic resistance: Mycoplasma resistance to β-lactam antibiotics and other cell wall inhibitors due to the absence of a cell wall
Acquired resistance occurs when a change in the bacterial genome converts a sensitive bacterium to a resistant one

Mechanisms for Acquiring Resistance

Inactivation of the antibiotic through enzymatic breakdown (e.g., β-lactamase)
Efflux pumping of the antibiotic out of the cell
Modification of the antibiotic target
Alteration of the bacterial pathway

Beta-Lactam Antibiotics

Cell wall active agents
Prevent the final step in the synthesis of the bacterial cell wall
Range from very narrow spectrum to very broad spectrum

Mechanisms of Action for Beta-Lactam Antibiotics

Beta-lactam antibiotics bind to Penicillin Binding Protein (PBP).
Inhibition of PBP prevents the crosslinking of peptidoglycan chains.
This prevents the bacteria from synthesizing a stable cell wall, leading to lysis (cidal effects).

Antiviral Drugs

Antiviral agents block:
Viral entry into or exit from the cell
Viral replication inside the host cell

Mechanisms of Action for Antiviral Drugs

Alter the cell’s genetic material (e.g. Acyclovir blocks viral enzymes and assembly of viral proteins)
Prevent the newly formed virus from leaving the cell (e.g. Amantadine)

Challenges of Antiviral Therapy

Rapid viral replication makes it difficult to develop effective antivirals.
Rapid viral mutation can lead to drug resistance.
Finding a drug that targets the virus without harming normal cells is difficult.

Antiviral Drug Properties

They are virustatic, meaning they are active only against replicating viruses, and not latent viruses.

Herpes Simplex Virus (HSV) & Varicella-zoster Virus (VZV) Infections

Herpes simplex viruses (HSV) cause repeated, blister-like lesions on the skin, genitals, and mucosal surfaces.
HSV-type 1 is non-genital.
HSV-type 2 causes genital infections.

Acyclovir

Acyclovir is a guanosine analog that is primarily taken up by virus-infected cells.
It selectively inhibits herpes virus DNA polymerase.

Clinical use of Acyclovir

Treatment of Herpes simplex, Herpes zoster, Chickenpox and Epstain-Barr virus infections.

### Ganciclovir

Ganciclovir is an analog of acyclovir effective against all Herpes viruses and CMV.
Limited oral bioavailability, given intravenously.

Valacyclovir

Valacyclovir is a prodrug of acyclovir.
It has better bioavailability than acyclovir.

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Description

Explore the essential features of various antibiotics, including macrolides, tetracyclines, lincomycins, and polypeptide antibiotics. Learn about their modes of action, spectrum of activity, and key examples. This quiz will challenge your understanding of these important antibacterial agents.