Antibiotics One Shot Notes and MCQs

31 October 2024 by pharmanotes.org

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Antibiotics: Overview and Historical Development

Antibiotics are compounds that inhibit the growth of or kill bacteria and other microbes. Their discovery revolutionized medicine by providing treatments for bacterial infections, reducing mortality and complications. Here’s an overview of the historical development and classification of antibiotics:

Early Discovery (1900s):
- Paul Ehrlich (1909) discovered Salvarsan, the first chemotherapeutic agent against syphilis.
- Alexander Fleming discovered penicillin in 1928 from Penicillium notatum, which led to its use as the first natural antibiotic.
Further Developments:
- 1930s-1940s: Streptomycin and tetracycline were discovered from soil bacteria (Streptomyces spp.).
- 1950s-1980s: Synthetic modifications of antibiotics (e.g., cephalosporins, macrolides) were developed to enhance effectiveness and combat resistance.
Modern Antibiotics: With advancements in biotechnology, synthetic and semi-synthetic antibiotics are developed to target specific pathogens more effectively, reducing side effects and resistance risks.

Antimicrobial Spectrum

The antimicrobial spectrum refers to the range of microorganisms an antibiotic can target. Antibiotics can be classified into:

Broad-spectrum antibiotics: Effective against a wide range of bacteria (e.g., tetracyclines, ampicillin).
Narrow-spectrum antibiotics: Effective against specific types of bacteria (e.g., penicillin, vancomycin).

Standardization of Antibiotics

Standardization is crucial to ensure the potency and safety of antibiotics. Common methods include:

Microbial Assays: Determining minimum inhibitory concentration (MIC) or minimum bactericidal concentration (MBC) against a target microorganism.
Chemical Assays: Measuring active compounds through titration, chromatography, or spectrometry.
Biological Assays: Using bioassays to measure antibiotic activity on test organisms.

Screening of Soil for Antibiotic-Producing Organisms

Soil is a primary source for discovering antibiotic-producing microorganisms. The screening process involves:

Fermentation Process and Design

Fermentation is used to produce antibiotics on a large scale. Key elements include:

Fermenter Design:
- A fermenter is a bioreactor designed for microbial growth under controlled conditions.
- Essential features include agitators, pH and temperature control, oxygenation systems, and sterilization ports.
Control of Parameters:
- Temperature, pH, and oxygen levels are optimized to maximize microbial growth and antibiotic production.
- Nutrient supply is maintained to avoid depletion, and waste products are removed periodically.
Types of Fermentation:
- Submerged Fermentation (SmF): Microbes are grown in a liquid medium, commonly used for large-scale antibiotic production.
- Solid-State Fermentation (SSF): Microbes grow on a solid substrate; often used for secondary metabolites.

Isolation of Mutants and Factors Influencing Mutation Rate

Mutants with enhanced antibiotic production can be isolated through mutation and selection techniques. Common methods include:

Mutagenesis: Using UV light, chemicals, or radiation to induce mutations in microorganisms.
Selection: Screening mutated strains for increased antibiotic production or broader antimicrobial spectrum.
Factors Affecting Mutation Rates:
- Type of mutagen
- Exposure duration and concentration
- Growth phase of the organism

Design of the Fermentation Process

Inoculum Preparation:
- A pure culture is cultivated in small batches to increase biomass before transferring it to the main fermenter.
Production Phase:
- Fermentation conditions are optimized for maximum antibiotic yield. Key parameters include maintaining sterility and preventing contamination.
Harvesting and Downstream Processing:
- After fermentation, the broth is processed to isolate the antibiotic compound.

Isolation and Purification of Fermentation Products

Penicillin:

Fermentation: Produced by Penicillium chrysogenum through submerged fermentation.
Isolation: The culture broth is acidified, filtered, and penicillin is extracted with organic solvents.
Purification: Penicillin is further purified through crystallization and chromatography.

Streptomycin:

Fermentation: Produced by Streptomyces griseus.
Isolation: Filtration of the fermentation broth followed by adsorption techniques.
Purification: Streptomycin is precipitated and crystallized for further purity.

Tetracyclines:

Fermentation: Produced by Streptomyces aureofaciens and Streptomyces rimosus.
Isolation: Acid precipitation from fermentation broth and extraction into organic solvents.
Purification: Further refined using ion-exchange chromatography.

Vitamin B12:

Fermentation: Produced by Pseudomonas denitrificans or Propionibacterium.
Isolation: Vitamin B12 is isolated by centrifugation and precipitation.
Purification: Purified using chromatography for pharmaceutical use.

Microbial Assays of Antibiotics, Vitamins, and Amino Acids

Microbial assays are bioassays used to determine the potency of antibiotics, vitamins, and amino acids in pharmaceutical preparations:

Antibiotics: Assays measure the inhibition zone diameter to quantify antibiotic potency.
Vitamins: Specific bacteria are cultured to measure vitamin requirements.
Amino Acids: Assays quantify amino acid concentration based on microbial growth rate or metabolic response.

MCQs on Antibiotics

Who is credited with discovering penicillin?
- A) Louis Pasteur
- B) Alexander Fleming
- C) Robert Koch
- D) Paul Ehrlich
- Answer: B) Alexander Fleming
The first chemotherapeutic agent discovered to treat syphilis was:
- A) Penicillin
- B) Salvarsan
- C) Streptomycin
- D) Tetracycline
- Answer: B) Salvarsan
Which of the following is a broad-spectrum antibiotic?
- A) Penicillin G
- B) Tetracycline
- C) Erythromycin
- D) Vancomycin
- Answer: B) Tetracycline
What does the term “minimum inhibitory concentration (MIC)” refer to?
- A) Minimum drug concentration for therapeutic effect
- B) Lowest concentration inhibiting microbial growth
- C) Minimum dose causing side effects
- D) Maximum dose tolerated by the body
- Answer: B) Lowest concentration inhibiting microbial growth
Antibiotics that are effective against only a few specific bacteria are termed:
- A) Narrow-spectrum antibiotics
- B) Broad-spectrum antibiotics
- C) Bacteriostatic antibiotics
- D) Bactericidal antibiotics
- Answer: A) Narrow-spectrum antibiotics
Which is the main source of antibiotics?
- A) Soil microorganisms
- B) Plants
- C) Fungi only
- D) Insects
- Answer: A) Soil microorganisms
The process of identifying soil organisms that produce antibiotics involves:
- A) Direct extraction of antibiotics
- B) Testing for antimicrobial activity
- C) Chemical synthesis
- D) Genetic manipulation
- Answer: B) Testing for antimicrobial activity
Which method is used to sterilize fermenters?
- A) Filtration
- B) Chemical agents
- C) Steam under pressure
- D) UV radiation
- Answer: C) Steam under pressure
The design of a fermenter should include:
- A) Temperature control
- B) pH control
- C) Oxygen supply
- D) All of the above
- Answer: D) All of the above
Streptomycin was discovered by:
- A) Alexander Fleming
- B) Selman Waksman
- C) Paul Ehrlich
- D) Louis Pasteur
- Answer: B) Selman Waksman
Which antibiotic is typically isolated from the bacterium Streptomyces griseus?
- A) Penicillin
- B) Streptomycin
- C) Tetracycline
- D) Erythromycin
- Answer: B) Streptomycin
Which factor most affects the mutation rate in microorganisms?
- A) Temperature
- B) Type of nutrient
- C) Type of mutagen
- D) Amount of water
- Answer: C) Type of mutagen
Which is a solid-state fermentation process?
- A) Producing yogurt
- B) Brewing beer
- C) Antibiotic production
- D) All of the above
- Answer: C) Antibiotic production
Which fermentation technique is commonly used for large-scale antibiotic production?
- A) Solid-state fermentation
- B) Submerged fermentation
- C) Open fermentation
- D) Batch fermentation
- Answer: B) Submerged fermentation
Which antibiotic is known for being effective against a wide range of Gram-positive bacteria?
- A) Vancomycin
- B) Penicillin G
- C) Tetracycline
- D) Cephalexin
- Answer: B) Penicillin G
During fermentation, the primary purpose of aeration is to:
- A) Control temperature
- B) Prevent contamination
- C) Provide oxygen to aerobic microbes
- D) Remove by-products
- Answer: C) Provide oxygen to aerobic microbes
What type of fermenter is often used to produce vitamin B12?
- A) Continuous fermenter
- B) Fed-batch fermenter
- C) Solid-state fermenter
- D) None of the above
- Answer: B) Fed-batch fermenter
Who first observed antibiotic activity in penicillin?
- A) Paul Ehrlich
- B) Robert Koch
- C) Alexander Fleming
- D) Joseph Lister
- Answer: C) Alexander Fleming
Which antibiotic is known to have bacteriostatic action?
- A) Penicillin
- B) Streptomycin
- C) Tetracycline
- D) Ciprofloxacin
- Answer: C) Tetracycline
The effectiveness of an antibiotic against a microorganism can be tested by:
- A) Antibiotic resistance testing
- B) MIC and MBC assays
- C) Staining techniques
- D) Genetic sequencing
- Answer: B) MIC and MBC assays
Antibiotics produced in a fermenter are commonly recovered by:
- A) Centrifugation and extraction
- B) Sedimentation
- C) Precipitation only
- D) Filtration only
- Answer: A) Centrifugation and extraction
The mutation rate of microbes in fermentation can be increased by:
- A) Increasing pH
- B) Adding mutagens
- C) Reducing temperature
- D) Decreasing nutrients
- Answer: B) Adding mutagens
In which phase of microbial growth is antibiotic production typically maximized?
- A) Lag phase
- B) Log phase
- C) Stationary phase
- D) Decline phase
- Answer: C) Stationary phase
Which type of mutation may enhance antibiotic yield in microorganisms?
- A) Silent mutation
- B) Beneficial mutation
- C) Lethal mutation
- D) Neutral mutation
- Answer: B) Beneficial mutation
Penicillin production requires which type of microorganism?

- A) Escherichia coli
- B) Streptomyces griseus
- C) Penicillium chrysogenum
- D) Aspergillus niger
- Answer: C) Penicillium chrysogenum

Which of the following is an example of a beta-lactam antibiotic?

- A) Streptomycin
- B) Tetracycline
- C) Penicillin
- D) Chloramphenicol
- Answer: C) Penicillin

What is the primary target of penicillin in bacterial cells?

- A) Cell membrane
- B) Ribosomes
- C) Cell wall synthesis
- D) DNA replication
- Answer: C) Cell wall synthesis

Streptomycin primarily targets which bacterial structure?

- A) Cell wall
- B) Ribosomes
- C) DNA
- D) Cytoplasm
- Answer: B) Ribosomes

In antibiotic standardization, which assay method is commonly used?
- A) MIC determination
- B) Zone of inhibition
- C) Colorimetric assay
- D) Titration
- Answer: B) Zone of inhibition
What is the function of a stirrer in a fermenter?
- A) Maintain pH balance
- B) Improve nutrient dispersion
- C) Control temperature
- D) Provide sterilization
- Answer: B) Improve nutrient dispersion
Which antibiotic class does tetracycline belong to?
- A) Aminoglycosides
- B) Beta-lactams
- C) Tetracyclines
- D) Fluoroquinolones
- Answer: C) Tetracyclines
The term “broad-spectrum antibiotic” refers to drugs effective against:
- A) Only Gram-positive bacteria
- B) Only Gram-negative bacteria
- C) A wide range of bacteria
- D) Viruses and bacteria
- Answer: C) A wide range of bacteria
Which of the following is an aminoglycoside antibiotic?
- A) Vancomycin
- B) Penicillin
- C) Erythromycin
- D) Streptomycin
- Answer: D) Streptomycin
An antibiotic produced by Streptomyces venezuelae is:
- A) Penicillin
- B) Tetracycline
- C) Chloramphenicol
- D) Erythromycin
- Answer: C) Chloramphenicol
What is the main byproduct of penicillin fermentation?
- A) CO₂
- B) Alcohol
- C) Lactic acid
- D) Ammonia
- Answer: A) CO₂
Which step is crucial for isolating antibiotics after fermentation?
- A) Filtration
- B) Sedimentation
- C) Centrifugation
- D) Crystallization
- Answer: C) Centrifugation
The primary antibiotic used to treat tuberculosis is:
- A) Tetracycline
- B) Rifampin
- C) Penicillin
- D) Erythromycin
- Answer: B) Rifampin
For what purpose is the shake flask method used in antibiotic production?
- A) Small-scale antibiotic production
- B) Large-scale antibiotic production
- C) Antibiotic purity testing
- D) Genetic modification
- Answer: A) Small-scale antibiotic production
Which instrument is commonly used to measure cell density in fermentation?
- A) Spectrophotometer
- B) Microscope
- C) Autoclave
- D) Refractometer
- Answer: A) Spectrophotometer
The primary microorganism used in the production of vitamin B12 is:
- A) E. coli
- B) Streptomyces griseus
- C) Pseudomonas denitrificans
- D) Saccharomyces cerevisiae
- Answer: C) Pseudomonas denitrificans
In antibiotic production, which phase involves rapid cell division?
- A) Lag phase
- B) Log phase
- C) Stationary phase
- D) Decline phase
- Answer: B) Log phase
The purpose of a chemostat in fermentation is to:
- A) Maintain continuous culture conditions
- B) Sterilize the medium
- C) Add mutagens to the culture
- D) Reduce temperature
- Answer: A) Maintain continuous culture conditions
Which antibiotic is primarily obtained from Penicillium notatum?
- A) Vancomycin
- B) Streptomycin
- C) Penicillin
- D) Erythromycin
- Answer: C) Penicillin
What is the purpose of adding a surfactant in the fermentation medium?
- A) Increase cell density
- B) Decrease viscosity
- C) Enhance oxygen transfer
- D) Prevent contamination
- Answer: C) Enhance oxygen transfer
An antibiotic with bactericidal action will:
- A) Stop bacterial growth
- B) Stimulate bacterial growth
- C) Kill bacteria
- D) Promote bacterial spore formation
- Answer: C) Kill bacteria
Which process is used to identify mutations in antibiotic-producing strains?
- A) MIC testing
- B) Replica plating
- C) Titration
- D) Gram staining
- Answer: B) Replica plating
Antibiotic resistance can result from:
- A) Overuse of antibiotics
- B) Mutation in bacteria
- C) Natural selection
- D) All of the above
- Answer: D) All of the above
A common impurity in antibiotics is:
- A) Fungal spores
- B) Bacterial endotoxins
- C) Excess glucose
- D) Sodium chloride
- Answer: B) Bacterial endotoxins
What is the purpose of pH control in antibiotic fermentation?
- A) Enhance microbial growth
- B) Ensure product stability
- C) Prevent contamination
- D) Both A and B
- Answer: D) Both A and B
Antibiotic activity against Gram-negative bacteria is commonly tested using:
- A) E. coli
- B) Staphylococcus aureus
- C) Bacillus subtilis
- D) Mycobacterium tuberculosis
- Answer: A) E. coli
A fermenter is typically equipped with a sparger to provide:
- A) Oxygen
- B) Nitrogen
- C) Carbon dioxide
- D) None of the above
- Answer: A) Oxygen
Which enzyme class is often targeted by beta-lactam antibiotics?
- A) Polymerases
- B) Proteases
- C) Transpeptidases
- D) Kinases
- Answer: C) Transpeptidases
The term “antimicrobial spectrum” refers to:
- A) Range of effectiveness against microbes
- B) Chemical composition
- C) Microbial classification
- D) Side effects
- Answer: A) Range of effectiveness against microbes
Which test is used to measure antibiotic potency?
- A) Disc diffusion assay
- B) Gram staining
- C) PCR
- D) Fermentation
- Answer: A) Disc diffusion assay
An antibiotic that binds to the 50S subunit of bacterial ribosomes is:
- A) Tetracycline
- B) Streptomycin
- C) Erythromycin
- D) Vancomycin
- Answer: C) Erythromycin
Tetracyclines are commonly derived from:
- A) Penicillium chrysogenum
- B) Aspergillus fumigatus
- C) Streptomyces rimosus
- D) Saccharomyces cerevisiae
- Answer: C) Streptomyces rimosus
Vitamin B12 production involves which type of fermentation process?
- A) Anaerobic
- B) Aerobic
- C) Both A and B
- D) None
- Answer: B) Aerobic
Mutants with enhanced antibiotic productivity are often obtained by:
- A) UV irradiation
- B) Freezing
- C) Increasing temperature
- D) Fermentation scaling
- Answer: A) UV irradiation
Penicillin belongs to which group of antibiotics?
- A) Aminoglycosides
- B) Tetracyclines
- C) Macrolides
- D) Beta-lactams
- Answer: D) Beta-lactams