MODULE 19 and 20

What is a magic bullet?

A chemical that targets a pathogen without harming the host.

Who discovered penicillin and when?

Alexander Fleming discovered penicillin in 1928.

What are natural antibiotics?

Compounds produced by microorganisms that kill or inhibit the growth of other microorganisms.

Who was Selman Waksman?

The scientist who discovered streptomycin, the first antibiotic effective against tuberculosis.

Why is Streptomyces important?

About 50% of antibiotics used in medicine come from the genus Streptomyces.

What is a narrow-spectrum antimicrobial?

An antimicrobial that targets only a few types of bacteria.

What is a broad-spectrum antimicrobial?

An antimicrobial that targets many Gram-positive and Gram-negative bacteria.

What is a superinfection?

A secondary infection caused when broad-spectrum antimicrobials eliminate normal microbiota.

What is the difference between bacteriostatic and bactericidal drugs?

Bacteriostatic drugs inhibit bacterial growth, while bactericidal drugs kill bacteria.

What is synergism?

When two drugs work together to produce a greater effect than either drug alone.

What is antagonism?

When two drugs used together produce a weaker effect than either drug alone.

What is the Kirby-Bauer disk diffusion test?

A test that measures bacterial susceptibility to antibiotics using disks placed on Mueller-Hinton agar.

What is the zone of inhibition?

The clear area around an antibiotic disk where bacteria do not grow.

What does a large zone of inhibition indicate?

That the bacteria are susceptible to the antibiotic.

What medium is used for the Kirby-Bauer test?

Mueller-Hinton agar.

What is selective toxicity?

The ability of a drug to harm pathogens without harming the host.

What are the major antimicrobial targets?

Cell wall, cell membrane, ribosomes, metabolic pathways, DNA, and RNA synthesis.

How do beta-lactam antibiotics work?

They prevent cross-linking of peptidoglycan in the bacterial cell wall.

What are examples of beta-lactam antibiotics?

Penicillins and monobactams.

How do vancomycin and bacitracin work?

They inhibit steps in peptidoglycan synthesis.

Which drugs target the plasma membrane?

Polymyxin B and daptomycin.

How does polymyxin B kill bacteria?

It disrupts the bacterial membrane, causing cell death.

How does streptomycin work?

It binds the 30S ribosomal subunit, causing incorrect protein synthesis.

What type of drug is streptomycin?

An aminoglycoside.

How does tetracycline work?

It prevents tRNA from binding to the ribosome.

Which ribosomal subunit does tetracycline target?

The 30S subunit.

What ribosomal subunit do many other protein synthesis inhibitors target?

The 50S subunit.

How does sulfamethoxazole work?

It blocks the production of dihydrofolic acid in bacterial metabolism.

Is sulfamethoxazole broad-spectrum or narrow-spectrum?

Broad-spectrum.

How does isoniazid work?

It interferes with mycolic acid synthesis in Mycobacterium.

How does ciprofloxacin work?

It inhibits DNA gyrase, preventing bacterial DNA replication.

What type of antimicrobial is ciprofloxacin?

A fluoroquinolone.

How does rifampin work?

It inhibits bacterial RNA polymerase, preventing transcription.

Why are diseases caused by eukaryotic microorganisms harder to treat?

Eukaryotic cells are more similar to human cells, making selective toxicity more difficult.

What drug treats fungal infections such as yeast infections?

Miconazole.

What class of drug is miconazole?

An imidazole antifungal.

What drug is used to treat malaria?

Mefloquine.

What drug is commonly used to treat roundworm infections?

Ivermectin.

What are persister cells?

Bacterial cells that survive antibiotic treatment due to characteristics that allow temporary survival.

What are superbugs?

Bacteria that are resistant to many different antibiotics.

How can antibiotic resistance spread?

Through horizontal gene transfer, such as plasmid transfer by conjugation.

What are the major mechanisms of antibiotic resistance?

Enzymatic destruction, drug inactivation, preventing drug entry, altering the drug target, and pumping the drug out of the cell.

What are common ways antibiotics are misused?

Not finishing prescriptions, using old antibiotics, using antibiotics for viral infections, and adding antibiotics to animal feed.

Why is it difficult to develop new antibiotics?

Drug development is expensive and resistance reduces profitability.

What is the difference between infection and disease?

Infection is the invasion of a host by microorganisms, while disease is when the infection causes damage or changes in health.

What is a sporadic disease?

A disease that occurs irregularly and infrequently.

What is an endemic disease?

A disease consistently present at a low frequency in a population.

What is an epidemic?

A disease outbreak with more cases than expected in a short period.

What are the three major reservoirs of disease?

Humans, animals, and nonliving sources.

What is a zoonotic disease?

A disease transmitted from animals to humans.

What is a fomite?

An inanimate object that can transmit disease.

What is an acute disease?

A disease that develops quickly and resolves or results in death.

What is a latent disease?

A disease that becomes dormant after infection and may reactivate later.

What is a localized infection?

An infection confined to one area of the body.

What is a systemic (generalized) infection?

An infection that spreads throughout the body.

What is bacteremia?

The presence of bacteria in the bloodstream.

What is septicemia?

The growth and multiplication of bacteria in the bloodstream.

What is toxemia?

The presence of bacterial toxins in the bloodstream.

What is viremia?

The presence of viruses in the bloodstream.

What are the major routes of pathogen entry?

Respiratory, gastrointestinal, sexual, and parenteral.

What is the parenteral route of infection?

Entry through cuts, punctures, or breaks in the skin.

What is a primary infection?

The first infection in a healthy person.

What is a secondary (opportunistic) infection?

An infection that occurs in a person who is already infected or immunocompromised.

What is a nosocomial infection?

An infection acquired in a hospital or healthcare setting.

What are Koch's postulates?

A set of criteria used to determine whether a specific microorganism causes a particular disease.