Microbiology Chapter 10

Substances that are naturally produced by certain microorganisms that can inhibit or destroy other microorganisms are called __.

A. antibiotics.

Antimicrobials that are effective against a wide variety of microbial types are termed __.

D. broad-spectrum drugs.

Antibiotics are derived from all of the following except __.

C. Staphylococcus.

Important characteristics of antimicrobial drugs include:

D. All of the choices are correct.

The use of a drug to prevent a person at risk of an imminent infection is called __.

D. prophylaxis.

The use of any chemical in the treatment, relief, or prophylaxis of a disease is called __.

B. chemotherapy.

Penicillins and cephalosporins __.

D. block peptidases that cross-link glycan molecules.

Selective toxicity refers to

C. damage to the target organisms but not host cells.

Each of the following affect cell walls EXCEPT __.

D. erythromycin.

Aminoglycosides __.

C. attach to the 30S ribosomal subunit and disrupt protein synthesis.

Each of the following target bacterial ribosomes except __.

C. polymyxins.

Sulfonamides __.

B. block folic acid synthesis.

Sulfa drugs work on

D. folic acid biosynthesis.

Ampicillin, amoxicillin, mezlocillin, and penicillin G all __.

A. target the cell wall.

What type of chemical will allow some bacteria to be resistant to many penicillins?

B. penicillinase

Which antimicrobial does not inhibit cell wall synthesis?

A. gentamicin

Which drug is used to treat cases of tuberculosis?

D. isoniazid

What cell wall inhibiting drug is used in cases of penicillin and methicillin resistance?

B. vancomycin

Gram-negative rods are often treated with __.

C. aminoglycosides.

Which antimicrobial does not interfere with protein synthesis?

D. trimethroprim

Which of these drugs has the most narrow spectrum?

B. isoniazid

Which of the following antibacterial drug groups does not target protein synthesis?

D. sulfonamides

Which of the following is not true of polymyxins?

D. target cell walls

Ketoconazole, fluconazole, clotrimazole, miconazole are broad-spectrum azoles used to treat _____ infections.

B. fungal

Which of the following is not a drug group used to treat fungal infections?

A. quinolones

The drug used for several protozoan infections is __.

D. metronidazole.

There are fewer antifungal, antiprotozoan, and antihelminth drugs compared to antibacterial drugs because fungi, protozoa, and helminths __.

C. are so similar to human cells that drug selective toxicity is difficult.

Primaquine and chloroquine are drugs used in the treatment of __.

D. protozoan infections.

Which of the following is not a mode of action of antiviral drugs?

D. bond to ergosterol in the cell membrane

Antiviral drugs that target reverse transcriptase would be used to treat __.

B. HIV.

Acyclovir is used to treat __.

C. herpes simplex virus.

Which of the following block HIV binding to host cell receptors?

D. fuzeon

The cellular basis for bacterial resistance to antimicrobials include:

D. All of the choices are correct.

The multidrug-resistant pumps in many bacterial cell membranes function by __.

C. removing the drug from the cell when it enters.

Microbial resistance resulting from mutation occurs because:

D. All of the choices are correct.

Each of the following result in drug resistance except __.

B. drug used as a nutrient by the cell.

Each of the following is a mechanism for drug resistance transfer between microorganisms except __.

D. mutation.

Each of the following contributes to emerging drug resistance except __.

C. multiple drug therapy.

Nutrients that encourage the growth of beneficial microbes in the intestines are known as __.

A. prebiotics.

The use of vaginal inserts of Lactobacillus to restore healthy vaginal biota is an example of __.

B. probiotics.

Broad-spectrum drugs that disrupt the body's normal flora often cause __.

B. superinfections.

Side effects that occur in patient's tissues while on antimicrobial drugs include all the following except __.

A. development of resistance to the drug.

A superinfection results from __.

D. decrease in most normal flora with overgrowth of an unaffected species.

The _____ are drugs that deposit in developing teeth and cause a permanent brown discoloration.

D. tetracyclines

Drug susceptibility testing determines __.

B. the pathogen's response to various antimicrobials.

If pathogen A is more resistant to an erythromycin disc on a Kirby-Bauer plate compared to pathogen B, then pathogen A will have a(n) _____ zone of inhibition compared to pathogen B.

A. smaller

Which two antibiotics affect the DNA and RNA of bacteria?

C. rifampin and quinolones

__ - the use of chemotherapeutic drugs to control infection.

Antimicrobial chemotherapy

__ - all-inclusive term for any antimicrobial drug, regardless of its origin.

Antimicrobials

__ - drugs that are chemically modified in the laboratory after being isolated from natural sources.

Semisynthetic drugs

__ - drugs produced entirely by chemical reactions.

Synthetic drugs

__ - antimicrobials effective against a limited array of microbial types.

Narrow spectrum

__ - antimicrobials effective against a wide variety of microbial types for example gram positive and gram negative.

broad spectrum

Antibiotics are …

… common metabolic products of aerobic bacteria and fungi-produced to inhibit the growth of competing microbes in the same habitat.

Antibiotics are derived from …

… bacteria in the genera Streptomyces and Bacillus molds in the genera Penicillium and Cephalosporium.

Which technique for testing drug susceptibility:

• Surface of an agar plate is spread with bacteria

• Small discs containing a prepared amount of antibiotic are placed on the plate

• Zone of inhibition surrounding the discs is measured and compared with a standard for each drug

Kirby-Bauer technique

__ - provides data for drug selection.

Antibiogram

What are the goals of chemotherapy?

Identifying structural and metabolic needs of a living cell and removing, disrupting, or interfering with these requirements.

What are these categories of:

cell wall

nucleic acid

protein

cell membrane

folic acid

Antimicrobial drug categories

__ - effective against more than one group of bacteria, tetracycline antibiotics.

Broad-spectrum drugs

__ - target a specific group, polymyxin.

Narrow-spectrum drugs

What are these characteristics of:

• Original penicillin was narrow-spectrum and susceptible to microbial counterattacks

• Molecule has been altered and improved upon over the years-later penicillins overcome the limitations of the original molecule

Penicillins

Drugs designed to act on bacteria are ineffective against __.

fungi.

Why are treatments against fungi difficult?

Similarities between fungal and human cells means that drugs toxic to fungi will harm human tissues. Only a few agents with special antifungal properties have been developed.

What are these characteristics of:

• Quinine-principal treatment of malaria for hundreds of years

• Has been replaced by synthesized quinolones, chloroquine and primaquine

• Several species of Plasmodium and many stages in its life cycle means that no drug is universally effective

Antimalarial Drugs (Antiprotozoal)

__ - widely used amoebicide treats intestinal infections and hepatic disease caused by Entamoeba, also treats Giardia lamblia and Trichomonas vaginalis.

Metronidazole

What are these characteristics of:

• Their physiology is much more similar to humans

• Blocking reproduction does not affect adult worms

• Most effective drugs immobilize, disintegrate, or inhibit the metabolism of all stages of the life cycle

• Challenges of antihelminthic drug therapy

Antihelminth

__ - infectious agent relies on a host cell for the vast majority of its metabolic functions. Disrupting viral metabolism requires disruption of cellular metabolism.

Antiviral

Major modes of action of antiviral agents are:

Inhibition of virus entry

Inhibition of nucleic acid synthesis

Inhibition of viral maturation

__ - an adaptive response in which microorganisms begin to tolerate an amount of drug that would normally be inhibitory.

Due to the genetic versatility and adaptability of microbial populations, can be intrinsic as well as acquired.

Drug resistance

Resistance to penicillin developed in some bacteria as early as in the years __, __, and __ scientists began to observe treatment failures on a large scale.

1940, 1980s, and 1990s

Microbes become newly resistant to a drug after one of the following occurs …

… spontaneous mutations in critical chromosomal genes.

What are these characteristics of:

• Any large population of microbes will contain a few cells harboring drug resistance

• If the population is exposed to drugs, the drug resistant population will have a selective advantage

• Offspring inherit the drug resistance

• Replacement population evolves to have the drug-resistant form as the dominant species

Natural Selection for Drug Resistance

__ - preparations of live microorganisms fed to animals and humans to improve intestinal biota, can replace microbes lost during antimicrobial therapy.

Safe and effective-useful in the management of food allergies.

Probiotics

__ - nutrients that encourage the growth of beneficial microbes

Prebiotics

What interaction does this represent?

• Drug is administered to the host even though its target is a microbe, the effect of the drug on the host must be considered

• Selective toxicity is the ideal, but chemotherapy involves contact with foreign chemicals that can harm the host

• 5% of all persons taking an antimicrobial drug will experience an adverse side effect

Interactions between drug and host

What are the side effects of drugs?

direct damage to tissues

allergic reactions

disruption of normal biota

__ - heightened sensitivity to a drug and stimulates the allergic response.

Allergy

__ - normal microbial colonists of healthy body surfaces, normally consist of harmless or beneficial bacteria, a few may be pathogens.

Broad-spectrum antimicrobials destroy healthy biota along with pathogens.

Biota

What are superinfections?

Microbes that were once small in number overgrow when normal resident biota are destroyed by broad-spectrum antimicrobials.

What is urinary tract infection?

Caused by E. coli treated with antibiotics

lactobacilli in the female vagina are killed by the broad-spectrum cephalosporin used to treat the UTI

overgrowth of Candida albicans occurs, causing a vaginal yeast infection or oral thrush

What are characteristics of Antibiotic-associated colitis?

Oral therapy with tetracyclines, clindamycin, and broad-spectrum penicillins kills off normal biota of the colon

overgrowth of Clostridium difficile invades the intestinal lining and releases toxins that cause diarrhea, fever, and abdominal pain

___% of antibiotic prescriptions written are for pharyngeal, sinus, lung, and upper respiratory infections that are viral in origin.

This has lead to superinfections and other adverse reactions caused the development of resistance in "bystander" microbes (normal biota) that were exposed to the drug as well, leading to the spread of resistant pathogens growing awareness has lead to the reduction of this practice.

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