Microbiology Chapter 10

What was the medical revolution introduced in the 1930s?

The introduction of modern drugs to control infections.

What is the goal of antimicrobial chemotherapy?

To administer a drug that destroys the infective agent without harming the host's cells.

What are the characteristics of an ideal antimicrobial drug?

Toxic to the microbe but nontoxic to host cells, microbicidal, soluble, remains potent, does not lead to resistance, complements host defenses, remains active in tissues, easily delivered, reasonably priced, and does not cause allergies.

What is prophylaxis in the context of antimicrobial therapy?

The use of a drug to prevent infection in a person at risk.

What is the definition of antimicrobial chemotherapy?

The use of drugs to control infection.

What are antibiotics?

Substances produced by the natural metabolic processes of some microorganisms that can inhibit or destroy other microorganisms.

What are semisynthetic drugs?

Drugs that are chemically modified in the laboratory after being isolated from natural sources.

What are synthetic drugs?

Drugs produced entirely by chemical reactions.

What is the difference between narrow-spectrum and broad-spectrum antimicrobials?

Narrow-spectrum is effective against a limited array of microbes, while broad-spectrum is effective against a wide variety.

What are the primary sources of antibiotics?

Bacteria in the genera Streptomyces and Bacillus, and molds in the genera Penicillium and Cephalosporium.

What three factors must be known before starting antimicrobial therapy?

The identity of the microorganism, its susceptibility to drugs, and the overall medical condition of the patient.

What is the Kirby-Bauer technique?

A standardized disc diffusion test to measure the zone of inhibition around antibiotic discs on an agar plate.

What does MIC stand for in antimicrobial testing?

Minimum inhibitory concentration, the smallest concentration that visibly inhibits growth.

What is the therapeutic index?

The ratio of the dose of the drug that is toxic to humans compared to its minimum effective therapeutic dose.

What does a smaller therapeutic index indicate?

A greater potential for drug reactions.

What factors should a physician consider before prescribing an antibiotic?

Preexisting conditions, history of allergies, underlying diseases, and interactions with other drugs.

What is the primary goal of antimicrobial drugs?

To disrupt cell processes or structures of bacteria, fungi, or protozoa, and inhibit virus replication.

What is the importance of identifying the infectious agent?

It should begin as soon as possible to ensure appropriate antimicrobial therapy.

What is the significance of drug susceptibility testing?

It determines the effectiveness of drugs against specific organisms, especially those with high resistance.

What can cause failure of antimicrobial treatment?

Inability of the drug to diffuse into the infection site, resistant microbes, or mixed infections.

What is the role of modern technology in choosing antimicrobial drugs?

It aids in quick access to information and decision-making regarding drug selection.

What is the difference between microbicidal and microbistatic?

Microbicidal kills microbes, while microbistatic inhibits their growth.

What does it mean if a drug is resistant?

The drug is ineffective against the microorganism causing the infection.

What does it mean if a drug is sensitive?

The drug is effective against the microorganism causing the infection.

What is the significance of the zone of inhibition in susceptibility testing?

It indicates the effectiveness of the antibiotic against the bacteria tested.

What is the relationship between the therapeutic index and drug safety?

A higher therapeutic index indicates a safer drug with a wider margin of safety.

What is the therapeutic index (TI) of Drug A?

1.2

What is the zone of inhibition for Drug B?

20 mm

Which drug is considered safer based on therapeutic index?

Drug B with a TI of 12

What does selective toxicity mean in the context of antimicrobial drugs?

It refers to the ability to kill or inhibit microorganisms without harming vertebrate cells.

What is a common mechanism of action for penicillins?

Inhibition of cell wall synthesis.

What type of bacteria are penicillins primarily effective against?

Gram-positive bacteria.

What are the main classes of antimicrobial drug categories?

Inhibition of cell wall synthesis, nucleic acid structure/function, protein synthesis, cell membrane function, and folic acid synthesis.

Which drug class is known for targeting the bacterial cell wall?

Penicillins.

Name a drug that is a carbapenem.

Imipenem.

What is the mechanism of action for aminoglycosides?

They target protein synthesis.

What is a potential adverse reaction (ADR) of tetracyclines?

Photosensitivity and discoloration of teeth.

What is the primary use of sulfonamides?

To interfere with folate metabolism.

What is the mode of action of fluoroquinolones?

They target DNA replication.

What type of infections is metronidazole used to treat?

Bacterial and protozoal infections.

What is the significance of biofilms in antibiotic treatment?

Bacteria in biofilms are often unaffected by antimicrobials and have different susceptibility profiles.

What is the principal treatment for malaria historically?

Quinine.

What drug has replaced quinine for malaria treatment due to lower toxicity?

Chloroquine.

What is the role of artemisinin in malaria treatment?

It is a staple for malaria treatment and is often used in combination therapies.

What are the challenges of antihelminthic drug therapy?

Flukes, tapeworms, and roundworms have physiology similar to humans, making treatment difficult.

What is a common adverse effect of vancomycin?

Hearing loss and nephrotoxicity.

What type of infections does bacitracin treat?

Superficial skin infections caused by Gram-positive bacteria.

What is the mechanism of action for drugs that inhibit protein synthesis?

They interfere with the ribosomes' ability to produce proteins.

What is the significance of the therapeutic index in drug selection?

A higher therapeutic index indicates a safer drug with a larger margin between effective and toxic doses.

What is the mechanism of action for drugs that target folic acid synthesis?

They block enzymes required for the synthesis of tetrahydrofolate.

What is the role of daptomycin in biofilm treatment?

It has shown success in interrupting quorum sensing pathways.

What is a common adverse reaction of rifampin?

Liver toxicity.

What are azoles used for?

Oral thrush, vaginal candidiasis, and other fungal infections.

What is Amphotericin B used for?

Serious life-threatening fungal infections.

What is the principal treatment for malaria?

Quinine.

What has replaced quinine as a treatment for malaria?

Less toxic synthesized quinolones, such as chloroquine and primaquine.

What is Artemisinin used for?

It has become the staple for malaria treatment in most parts of the world.

What does Artemisinin combination therapy (ACT) involve?

Artemisinin combined with quinine derivatives or other drugs.

What is Metronidazole (Flagyl) primarily used for?

Treating intestinal infections and hepatic disease caused by Entamoeba histolytica.

What are Mebendazole and Albendazole used for?

They inhibit microtubules of worms, eggs, and larvae in antihelminthic therapy.

What is the challenge of antiviral drug therapy?

Viruses rely on host cells for metabolic functions, making it difficult to disrupt viral metabolism without affecting the host.

What is the role of vaccines in viral infections?

They prevent infections like measles, mumps, and hepatitis.

What is the function of Enfuvirtide (Fuzeon®)?

It inhibits virus entry by acting as a receptor/fusion/uncoating inhibitor.

What is the mechanism of Acyclovir (Zovirax®)?

It inhibits nucleic acid synthesis in viruses.

What are the challenges of drug resistance?

Microorganisms adapt to tolerate drugs that would normally be inhibitory.

How does chromosomal drug resistance develop?

It usually results from spontaneous random mutations.

What are R factors?

Plasmids containing antibiotic resistance genes that can be shared among microbes.

What is a superinfection?

An overgrowth of microbes that occurs when normal resident biota are destroyed by broad-spectrum antimicrobials.

What is the consequence of using broad-spectrum antimicrobials?

They can lead to superinfections and the development of drug-resistant pathogens.

What is the significance of probiotics?

They are live microorganisms that improve intestinal biota and can replace microbes lost during antimicrobial therapy.

What are prebiotics?

Nutrients that encourage the growth of beneficial microbes.

What is the purpose of fecal transplants?

To treat recurrent Clostridium difficile infections and ulcerative colitis.

What is the most common drug allergy?

Allergy to penicillins.

What can happen during the second exposure to a drug after sensitization?

It can lead to hives, respiratory inflammation, or anaphylaxis.

What is the CDC's 2013 'Threat Report' about?

It outlines a potentially catastrophic antibiotic resistance situation.

What are urgent threats identified by the CDC regarding antibiotic resistance?

Clostridium difficile, Carbapenem-resistant Enterobacteriaceae, and drug-resistant Neisseria gonorrhoeae.

What is the role of bacteriophages in antimicrobial therapy?

They are used to target specific bacterial infections and have narrow specificity.

What is CRISPR used for in antimicrobial therapy?

It can cause specific cuts in genes to treat antibiotic-resistant infections.

What is the issue with self-medication of antibiotics?

It leads to ineffectual treatments and contributes to drug resistance.

What is the impact of broad-spectrum antibiotics on normal biota?

They destroy healthy biota along with pathogens, leading to superinfections.

What is an example of a superinfection?

A vaginal yeast infection caused by Candida albicans after antibiotic treatment for a urinary tract infection.

What is the problem with the overprescription of antimicrobials?

It contributes to the development of resistance and adverse reactions.