Antimicrobial Treatments Overview

Overview

This lecture introduces antimicrobial treatments, focusing on how drugs control microbial growth, the challenges of resistance, and current strategies for combating infectious diseases.

Introduction to Antimicrobial Treatments

Antimicrobials revolutionized medicine by reducing deaths from infectious diseases.
We're approaching a "post-antibiotic era" due to increasing drug resistance.

Basics and Origins of Antimicrobials

Antibiotic: a substance that inhibits or kills other microorganisms; often made by bacteria or fungi.
Main drug sources: bacterial genera Streptomyces, Bacillus; fungi genera Penicillium, Cephalosporium.
The goal is selective toxicity: kill microbes without harming the host.

Challenges in Antimicrobial Use

The "perfect" drug would target microbes, be easy to administer, and cause minimal side effects.
Biofilms (microbial communities) are especially hard to treat due to drug penetration issues.
Identification of the pathogen, susceptibility testing, and patient condition are crucial for drug choice.

Testing and Effectiveness

Kirby-Bauer test: measures zones of inhibition to assess drug effectiveness.
Minimum Inhibitory Concentration (MIC) test: determines the lowest effective drug dose.
Treatment failure can result from poor drug selection, resistance, multiple pathogens, or patient noncompliance.

Drug Action and Spectrum

Five major drug mechanisms: inhibition of cell wall synthesis, nucleic acid synthesis, protein synthesis, cell membrane disruption, and metabolite synthesis.
Broad-spectrum drugs affect many microbes; narrow-spectrum drugs target specific groups.
Penicillin has evolved from narrow- to broader-spectrum through chemical modification.

Drugs Against Eukaryotic and Viral Pathogens

Fungal, protozoan, and helminth infections are hard to treat due to similarity to human cells.
Antiviral drugs target viral entry, replication, or maturation; vaccines remain the most effective prevention for many viruses.

Antimicrobial Resistance (AMR)

Resistance develops via mutations or gene transfer (conjugation, transformation, transduction).
Mechanisms: drug-inactivating enzymes, reduced uptake, increased efflux, altered targets, alternative metabolic pathways.
Persisters and epigenetic mechanisms can also confer temporary resistance.

Population-Level and Global Issues

Overuse and misuse of antibiotics accelerate resistance spread.
CDC and WHO consider AMR a global health crisis, predicting high mortality if trends continue.
Drug companies focus less on developing new antibiotics due to economic factors.

New and Renewed Strategies

RNA interference, antimicrobial peptides, CRISPR, and drugs from previously uncultivable bacteria are new approaches under study.
Bacteriophages and probiotics/prebiotics are being revisited as alternative or adjunct therapies.

Adverse Effects and Drug-Host Interactions

Major side effects: toxicity to organs, allergic reactions, and disruption of normal microbiota (leading to superinfections).
Overprescribing antibiotics, especially for viral infections, and self-medication contribute significantly to resistance.

Key Terms & Definitions

Antibiotic — compound that kills or inhibits microorganisms.
Selective toxicity — drug's ability to target microbes without harming host cells.
Broad-spectrum — drugs acting on a wide variety of microbes.
Narrow-spectrum — drugs targeting specific microbial types.
Biofilm — community of microbes adhering to a surface with unique resistance properties.
Kirby-Bauer test — lab test using drug-infused discs to assess microbial susceptibility.
Minimum Inhibitory Concentration (MIC) — lowest drug concentration preventing microbe growth.
Horizontal gene transfer — movement of genetic material between organisms (conjugation, transformation, transduction).
Therapeutic index — ratio of toxic dose to minimum effective dose.
Superinfection — overgrowth of non-target microbes due to disrupted microbiota.

Action Items / Next Steps

Review assigned textbook readings on antimicrobial treatments.
Complete lab exercises on susceptibility testing (Kirby-Bauer, MIC).
Prepare for quiz on mechanisms of drug action and resistance pathways.

Sure! Here's a 100-question multiple-choice test based on your notes about antimicrobial treatments. The questions cover definitions, mechanisms, drug types, resistance, testing, and more.

100-Question Multiple Choice Test: Antimicrobial Treatments

What does the term "antibiotic" literally mean?
a) Against bacteria
b) Against life
c) Against viruses
d) Against fungi
Which two bacterial genera are main sources of antibiotics?
a) Escherichia and Salmonella
b) Streptomyces and Bacillus
c) Staphylococcus and Clostridium
d) Mycobacterium and Pseudomonas
Which two fungal genera produce important antibiotics?
a) Aspergillus and Candida
b) Penicillium and Cephalosporium
c) Rhizopus and Mucor
d) Saccharomyces and Cryptococcus
What is the primary goal of antimicrobial drugs?
a) Kill all microbes in the body
b) Destroy the infective agent without harming the host
c) Stimulate the immune system
d) Increase microbial growth
What is selective toxicity?
a) Killing all cells equally
b) Targeting microbes without harming vertebrate host cells
c) Killing only viruses
d) Killing only fungi
Which of the following is NOT a characteristic of an ideal antimicrobial drug?
a) Easy to administer
b) Toxic to the host
c) Reaches the infection site
d) Remains active as long as needed
Why are biofilms difficult to treat with antibiotics?
a) They are made of viruses
b) Antibiotics cannot penetrate well and microbes express different phenotypes
c) They only contain fungi
d) They are resistant to all drugs by default
What is the Kirby-Bauer test used for?
a) Identifying microbes
b) Measuring zones of inhibition to assess antibiotic effectiveness
c) Counting bacterial colonies
d) Detecting viral infections
What does MIC stand for?
a) Maximum Inhibitory Concentration
b) Minimum Inhibitory Concentration
c) Microbial Infection Count
d) Microbial Inhibition Coefficient
What does the MIC test determine?
a) The highest dose of drug tolerated by the host
b) The lowest concentration of drug that inhibits microbial growth
c) The number of microbes in a sample
d) The time it takes for a drug to work
Which of the following is a mechanism of antibiotic action?
a) Inhibition of cell wall synthesis
b) Increasing host cell metabolism
c) Enhancing viral replication
d) Stimulating fungal growth
Which antibiotic mechanism targets bacterial ribosomes?
a) Inhibition of nucleic acid synthesis
b) Inhibition of protein synthesis
c) Disruption of cell membrane
d) Inhibition of metabolite synthesis
Broad-spectrum antibiotics:
a) Target a specific group of bacteria
b) Affect many different types of microbes
c) Are always safer than narrow-spectrum drugs
d) Are ineffective against biofilms
Narrow-spectrum antibiotics:
a) Affect many types of microbes
b) Target specific groups of bacteria
c) Are less effective than broad-spectrum drugs
d) Kill viruses
Penicillin originally was:
a) A broad-spectrum antibiotic
b) A narrow-spectrum antibiotic
c) An antiviral drug
d) A synthetic drug
Which of the following is NOT a way bacteria can develop antibiotic resistance?
a) Spontaneous mutation
b) Horizontal gene transfer
c) Increased host immunity
d) Acquisition of resistance genes
Horizontal gene transfer includes all EXCEPT:
a) Conjugation
b) Transformation
c) Transduction
d) Binary fission
What is a persister cell?
a) A cell that produces antibiotics
b) A cell that temporarily shuts down metabolism to survive antibiotics
c) A cell that is always resistant genetically
d) A cell that causes allergic reactions
Which of the following is a common side effect of broad-spectrum antibiotics?
a) Increased immunity
b) Superinfection due to disruption of normal microbiota
c) Permanent immunity to all infections
d) Increased vitamin K production
What is a superinfection?
a) Infection caused by a virus
b) Overgrowth of non-target microbes due to disrupted microbiota
c) Infection cured by antibiotics
d) Infection caused by fungi only
Which organ is commonly affected by antibiotic toxicity?
a) Liver
b) Heart
c) Brain
d) Skin
Allergic reactions to antibiotics are most commonly caused by:
a) Penicillin and sulfonamides
b) Tetracycline and erythromycin
c) Cephalosporins and aminoglycosides
d) Fluoroquinolones and macrolides
What is the therapeutic index?
a) Ratio of toxic dose to minimum effective dose
b) Number of microbes killed by a drug
c) Time it takes for a drug to work
d) Spectrum of microbes affected
Which of the following drugs inhibits cell wall synthesis?
a) Tetracycline
b) Penicillin
c) Rifampin
d) Polymyxin
Which drug mechanism affects nucleic acid synthesis?
a) Penicillin
b) Rifampin
c) Tetracycline
d) Polymyxin
Which drug mechanism disrupts the cell membrane?
a) Penicillin
b) Polymyxin
c) Rifampin
d) Sulfonamides
Which drug mechanism inhibits metabolite synthesis?
a) Sulfonamides
b) Penicillin
c) Tetracycline
d) Rifampin
Which of the following is NOT a main group of antimicrobial drugs?
a) Broad-spectrum
b) Narrow-spectrum
c) Antiviral
d) Antihistamine
Why are fungal infections difficult to treat?
a) Fungi are prokaryotic
b) Fungal cells are similar to human cells
c) Fungi grow too fast
d) Fungi are resistant to all drugs
What is the main challenge in treating viral infections?
a) Viruses have cell walls
b) Viruses use host cell machinery for reproduction
c) Viruses are prokaryotic
d) Viruses are easily killed by antibiotics
Which of the following is NOT a common antiviral drug target?
a) Viral entry
b) Viral replication
c) Viral maturation
d) Bacterial cell wall synthesis
What is the main reason for the post-antibiotic era?
a) Lack of new antibiotics
b) Increased drug resistance
c) Decreased infections
d) Increased vaccine use
Which of the following is a new approach to antimicrobial therapy?
a) RNA interference
b) Penicillin
c) Sulfonamides
d) Tetracycline
What are antimicrobial peptides?
a) Small proteins that fight microbes
b) Large proteins that stimulate immunity
c) Synthetic drugs
d) Viral particles
What is CRISPR used for in antimicrobial research?
a) Cutting specific genes in microbes
b) Producing antibiotics
c) Vaccinating patients
d) Growing bacteria in labs
Why is it difficult to develop new antibiotics?
a) They are easy to make
b) Economic factors favor chronic disease drugs
c) Antibiotics are not profitable
d) Antibiotics are not needed anymore
What is a bacteriophage?
a) A virus that infects bacteria
b) A type of antibiotic
c) A fungal infection
d) A bacterial toxin
How do probiotics help in antimicrobial therapy?
a) Kill all microbes
b) Restore normal microbiota
c) Cause superinfections
d) Increase antibiotic resistance
What are prebiotics?
a) Live microbes
b) Nutrients that promote growth of beneficial microbes
c) Antibiotics
d) Viral particles
Which of the following is NOT a common side effect of antimicrobial drugs?
a) Toxicity to organs
b) Allerg