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Microbiology Final > Chapter 10: Antimicrobial Treatment > Flashcards

Chapter 10: Antimicrobial Treatment Flashcards

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1
Q

Postantibiotic Era

A

Point in time where the drugs we currently have are no longer effective

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2
Q

Goal of antimicrobial Chemotherapy

A

administer a drug to an infected person that destroys the infective agent without harming the host’s cells

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3
Q

A drug must be able to…(3)

A

(1) be easy to administer and able to reach the infectious agent anywhere in the body; (2) be absolutely toxic to the infectious agent and absolutely nontoxic to the host; (3) remain in the body as long as needed and be safely and easily broken down and excreted

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4
Q

Why do bacteria and fungi produce antibiotics in nature?

A

to inhibit the growth of competing microbes in the same habitat

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5
Q

Genera of bacteria antibiotics are derived from

A

Streptomyces and Bacillus

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6
Q

Genera of molds antibiotics are derived from

A

Penicillium and Cephalosporium

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7
Q

3 factors that must be known before beginning antimicrobial therapy

A

(1) the nature of the microorganism causing the infection; (2) the degree of the microorganism’s susceptibility (or sensitivity) to various drugs; (3) the overall medical condition of the patient

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8
Q

Sources from which specimens can be obtained from the patient (3)

A

body fluids, sputum, stool

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9
Q

How would you treat a sore throat caused by Streptococcus pyogenes?

A

Penicillin

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10
Q

The two bacterium responsible for meningitis in children.

A

Streptococcus pneumoniae (most common) and Neisseria meningitidis

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11
Q

Bacteria that commonly show resistance to drugs (5)

A

Staphylococcus species, Neisseria gonorrhoeae, Streptococcus pneumoniae, Enterococcus faecalis, and aerobic gram-negative enteric bacilli

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12
Q

When is testing for drug susceptibility unnecessary? (2)

A

(1) fungal and protozoan infections; (2) If that patient is allergic to certain antibiotics (duh)

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13
Q

Kirby-Bauer Technique

A

(1) surface of an agar plate is spread with bacteria; (2) small discs containing a prepared amount of antibiotic are placed on the plate; (3) zone of inhibition surrounding the discs is measured and compared with a standard for each drug; (4) antibiogram provides data for drug selection

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14
Q

Tube Dilution Tests

A

A more sensitive and quantitative test than the Kirby-Bauer Technique that involves diluting antimicrobial solutions serially in tubes of broth; each tube is inoculated with pure culture

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15
Q

Minimum Inhibitory Concentration (MIC)

A

the smallest concentration (highest dilution) of drug that visibly inhibits growth

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16
Q

Purpose of tube dilution tests

A

useful in determining the effective dosage and providing a comparative index against other antimicrobials

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17
Q

Factors that contribute to the failure of a drug (3)

A

(1) the inability of the drug to diffuse into that body compartment (brain, joints, skin); (2) resistant microbes in the infection that didn’t make it into the sample collected for testing; (3) an infection caused by more than one pathogen (mixed), some of which are resistant to the drug

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18
Q

Therapeutic Index

A

the ratio of the dose of the drug that is toxic to humans as compared to its minimum effective (therapeutic) dose (dose required Vs minimum impact); the smaller the ratio, the greater the potential for drug reactions; the drug with the highest therapeutic index has the widest margin of safety

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19
Q

TI = 1.1

A

Risky choice on the therapeutic index

20
Q

TI = 10

A

Safer choice on the therapeutic index

21
Q

Factors that a physician must check for in a patient history before prescribing antibiotics (7)

A
  1. (1) preexisting conditions that might influence the activity of the drug;
  2. (2) history of allergy to a certain class of drugs;
  3. (3) underlying liver or kidney disease;
  4. (4) infants, the elderly, and pregnant women require special precautions;
  5. (5) intake of other drugs can result in increased toxicity or failure of one or more drugs;
  6. (6) genetic or metabolic abnormalities;
  7. (7) site of infection, route of administration, cost
22
Q

Goal of antimicrobial drugs (5)

A
  1. DISRUPT
  2. INHIBIT
  3. INTERFERE
  4. DESTROY
  5. SELECTIVELY TOXIC
23
Q

DISRUPT…

A

cell processes or structures of bacteria, fungi, or protozoa

24
Q

INHIBIT…

A

virus replication

25
Q

INTERFERE…

A

with the function of enzymes required to synthesize or assemble macromolecules

26
Q

DESTROY…

A

structures already formed in the cell

27
Q

SELECTIVELY TOXIC…

A

kill or inhibit the actions or synthesis of molecules in microorganisms but not vertebrate cells

28
Q

Drugs with excellent selective toxicity…

A

block the synthesis of the bacterial cell wall (penicillins); human cells lack the chemical peptidoglycan and are therefore unaffected by the drug

29
Q

Goals of Chemotherapy

A

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

30
Q

Antimicrobial Drug Categories (5)

A
  1. (1) inhibition of cell wall synthesis;
  2. (2) inhibition of nucleic acid structure and function;
  3. (3) inhibition of protein synthesis;
  4. (4) interference with cell membrane structure and function;
  5. (5) inhibition of folic acid (vitamin B) synthesis for several metabolic functions in the body
31
Q

Primary Sites of Action of Antimicrobial Drugs on Bacterial Cells (5)

A
  1. (1) Protein synthesis inhibitors on ribosomes;
  2. (2) Folic acid synthesis in cytoplasm;
  3. (3) DNA/RNA;
  4. (4) Cell membrane;
  5. (5) Cell wall inhibitors
32
Q

Broad-Spectrum Drugs

A

effective against more than one group of bacteria; tetracycline antibiotics

33
Q

Narrow-Spectrum Drugs

A

target a specific group; polymyxin

34
Q

DNase

A

Helps penetrate biofilms

35
Q

Why are drugs that are toxic to fungi also toxic to human cells?

A

Similarities between the two cells means the drug cannot be selectively toxic

36
Q

Quinine

A

principal treatment of malaria for hundreds of years

37
Q

Replacements of Quinine

A

synthesized quinolones, chloroquine and primaquine

38
Q

Why are viral infections difficult to treat?

A

disrupting viral metabolism requires disruption of cellular metabolism

39
Q

Drug resistance

A

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

40
Q

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

A

(1) SPONTANEOUS MUTATIONS in critical chromosomal genes; (2) ACQUISITION OF ENTIRE NEW GENES or sets of genes via horizontal transfer from another species

41
Q

Resistance (R) Factors

A

Plasmids containing antibiotic resistance genes; present BEFORE exposed to antibiotics; can transfer through conjugation or transformation

42
Q

Probiotics

A

preparations of live microorganisms fed to animals and humans to improve intestinal biota

43
Q

Prebiotics

A

nutrients that encourage the growth of beneficial microbes

44
Q

Fructan

A

Encourages the growth of Bifidobacterium

45
Q

Superinfection

A

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

46
Q

Overgrowth of this bacteria causes yeast infection or oral thrush

A

Candida albicans

47
Q

Overgrowth of this bacteria invades the intestinal lining and releases toxins that cause diarrhea, fever, and abdominal pain

A

Clostridium difficile

Microbiology Final (12 decks)

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