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Cology 2 Exam 2 > Intro to Antibiotics > Flashcards

Intro to Antibiotics Flashcards

1
Q

Define antibiotic

A

Natural compound produced by bacteria or fungi to suppress growth of other microorganisms

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2
Q

Define antimicrobial

A

Synthetic agents to suppress growth of microorganisms

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3
Q

Define bactericidal

A

Kills organism directly

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4
Q

Define bacteriostatic

A

Prevents reproduction

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5
Q

How long does it take for a bacteria to reproduce?

A

20 minutes

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6
Q

Penicillins are _________; Sulfonamides are _________

A

Penicillins are antibiotics/bactericidal

Sulfonamides are antibicrobials/bacteriostatic

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7
Q

Which drugs inhibit cell wall synthesis?

A

Bacitracin
B-lactams
Vancomycin
Cycloserin

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8
Q

Which drugs inhibit DNA replication?

A

Quinolones

Nitroimidazoles

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9
Q

Which drugs inhibit DNA-Dependent RNA polymerase?

A

Rifampin

Rifabutin

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10
Q

Which drugs inhibit protein synthesis?

A 
Aminoglycosides
Macrolides
Ketolides
Lincosamides
Streptogramins
Tetracyclines
Glycyclines
Chloramphenicol
Oxazolidinones
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11
Q

Which drugs inhibit Cell membranes?

A

Polymyxins

Daptomycin

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12
Q

Which drugs affect folic acid metabolism?

A

Trimethoprim
Sulfonamides
Sulfones

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13
Q

What are the factors influencing selection of an antimicrobial agent?

A 
Identify the organism
Resistance 
Microbial susceptibility
Bactericidal vs bacteriostatic 
Knowledge of the patient 
Pharmacokinetics/Metabolism
Other factors (allergies, prior adverse drug reactions, contraindications)
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14
Q

Describe “indiscriminant use” in terms of resistance

A

Increased exposure to antibiotics due to things like using antibiotics for viral infections and increasing use of antibiotics in animals for eating

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15
Q

Which examples of bugs are resistant to all known drugs?

A

Enterococci
Enterobactor
Pseudomonas

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16
Q

Where in the US is MRSA most prevalent?

A

Southeast

59% prevalence average in the US

17
Q

How does the US compare globally for MRSA?

A

US has 55% prevalence

Canada has 2.3% and Netherlands has

18
Q

What examples are there of sensitivity testing?

A

Disk diffusion
Microdilution
E-test

19
Q

Describe the disk diffusion test

A

Used to detect antimicrobial/antibiotic sensitivity

An agar plate is spread with bacteria, when filter papers soaked with different antimicrobials/antibiotics are placed on the plate with different doses

The bacteria are allowed to grow at 37 degrees for 18-24 hours, an the agents to which the bacteria are most susceptible have a large ring around them where the bacteria did not grow

20
Q

Describe the test for MIC

A

Minimum inhibitory concentration

A lot of test tubes are filled with growth medium
Then you have one control (no antibiotic) and slowly add more to increasing concentrations

The first test tube that has no growth in it is the MIC, which is the least amount of antibiotic needed to prevent replication (usually pick 2-3x the MIC for the dose)

21
Q

Describe the test for MBC

A

Minimum bactericidal concentration

Take the test tube from MIC and the ones beyond it (with higher concentrations) and plate them

The plate that has no growth is the lowest concentration at which you’ll kill ALL of the bacteria

22
Q

Why would you consider host immune defenses when selecting an antibiotic?

A

Bacteriostatic would not be ideal for someone that is immunocompromised because the drug can only stop replication, to get rid of the infection we depend on the host’s immune system to kill off what is left

23
Q

Why do we care about the status of the immune system for selecting an antimicrobial agent?

A

We care about white cell function (T cells and B cells)

He didn’t go into too much detail about this

24
Q

Why do we care about age when selecting an antimicrobial agent?

A

Avoid tetracyclines in children. Tetracyclines bind calcium and stain your teeth, do not use in children under 14 because their teeth are still growing

Also do not use chloramphenicol in babies - grey baby children
Chloramphenicol has to be glucuronidated, and the enzymes that do this aren’t developed until 6 months to 1 year, and that can lead to toxicity.

25
Q

Which drug causes teeth staining?

A

Tetracyclines

26
Q

Which drug causes gray baby syndrome? Why?

A

Chloramphenicol

Babies don’t have enzymes for glucuronidation, chloramphenicol use can cause toxicity

27
Q

Why do we care about diabetes when selecting an agent?

A

High blood sugar enhances bacterial growth, uncontrolled diabetic patients have poor wound healing

28
Q

Why do we care about pregnancy when selecting an agent?

A

Some antibiotics can cross the placenta. We do not want the baby to get the same dose of antibiotic as the mother.

Also be aware of breast feeding bc some agents pass through the breast milk. Passing antibiotics onto the baby may also increase resistance development.

29
Q

When do we use combination therapy? (multiple agents at once)

A

Treatment of life-threatening infections in which causative organism is unknown

Treatment of polymicrobial infections (esp abdominal contamination)

Enhanced antimicrobial activity (can use two agents to have synergistic effect, ie Penicillins and Aminoglycosides have synergistic effect in treating pseudomonas aeruginosa infection)

Treatment of resistant strains

Permits lower doses of each (lower toxicity)

Possibly reduces emergence of resistant strains (NEVER BEEN PROVEN CLINICALLY)

30
Q

Why do penicillins and aminoglycosides have a synergistic effect?

A

Penicillin affects the cell wall and makes it easier for aminoglycosides to get into the bacteria and have its effects

31
Q

What is the main mechanism by which ALL bacteria develop resistance?

A

Selection

As bacteria replicate, various small mistakes are made in DNA replication, these can lead to resistance

Can make bacteria more OR less sensitive!

32
Q

What role do enzymes play in resistance?

A

Penicillinase
Carbepenemases
Cephalosporinases

These can be developed in bacteria that will destroy the beta lactam structure of the antibiotics, which are essential for antibiotic activity

33
Q

How can bacteria change their permeability to drugs?

A

Through porins
(Beta lactamase activity)
Can decrease permeability of agents into the cell

34
Q

Which drugs have resistance developed against them bc of changes in efflux pathways?

A

Tetracyclines
Chloramphenicol
Macrolides

Transporters bind them and immediately send them back outside of the cell

35
Q

Which drugs are especially sensitive to resistance to changes in affinity of site of active drug?

A

Protein synthesis inhibitors bc there is a loss or alteration of binding proteins

36
Q

Which drugs are sensitive to resistance developed due to altered metabolic pathways?

A

Sulfonamides
Increased production of PABA in the cell makes sulfonamides useless bc there is less competition (more PABA = less binding of sulfonamides)

37
Q

What role do spores play in resistance?

A

Microorganisms can go into a dormant state (spores - anthrax). When conditions aren’t favorable for growth, they stop metabolic activity and form protective proteins around the DNA. After many years the spores can regenerate active bacteria

38
Q

What genetic changes contribute to resistance?

A

Mutational resistant (chromosomal)
Conjugation (Plasmid transfers - common among gram negative, vancomycin)
Transduction (bacterial DNA transferred through phages, important in S Aureus)
Transformation (free DNA is absorbed from the environment - can alter penicillin binding proteins)

39
Q

When is it appropriate to treat prophylactically with antibiotics?

A

Heart valves

Surgery

Cology 2 Exam 2 (18 decks)

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