Antimicrobials Flashcards

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1
Q

Chemotherapeutic agents

A

a chemical used to treat a disease; ex: salvarsan and prontosil (produces sulfa)
Also called antimicrobials

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2
Q

Penicillin

A

Fleming found that colonies around a mold were being killed. The mold had penicillin. It kills many different bacteria. He was not able to purify the penicillin substance so he stopped studying it.

First antibiotic found

Penicillin G is the best serotype

Antibiotics are naturally produced by microorganisms

The chemical structure can be altered to kill other bacteria as well; ampicillin, methicillin

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3
Q

Streptomyocin

A

second antimicrobial susbstance found; produced by a bacterium (S. griseus)

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4
Q

Where do most antibiotics come from?

A

Soil

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5
Q

Semisynthetic antibiotics

A

a substance that is chemically altered to kill other bacteria; ampicillin (derived from penicillin)

hard to make because it is expensive and the microorganisms can being to resist the new antibiotics and then it will be harder to cure

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6
Q

Selective toxicity

A

Medication is more toxic to the microbe than the human
Therapeutic index; high-less toxic (acts against an essential biochemical process of the microorganism, humans lack this process…EX: Penicillin G)…Low therapeutic index- more toxic to humans (if its too toxic for bloodstream use, they use a topical application which is applying it to the skin)

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7
Q

Antimicrobial action

A

Bactericidal (chemical kills the bacteria; depends on dosage and stage of bacteria) vs Bacteriostatic (relies on the humans immune defenses to eliminate the microorganims after it has been inhibited and stops growing)

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8
Q

Spectrum of activity

A

Narrow range (less disruptive to the normal microbiota vs Broad range (important for treating acute life threatening diseases because there isn’t time to identify the pathogen…but can also affect normal microbiota so it can be harmful)

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9
Q

Tissue distribution/metabolism/excretion

A

Meningitis; needs med. that crosses the blood into the cerebrospinal fluid

Meds that are unstable at low pH are destroyed by stomach acid when swallowed….so they are given by an IV

Dosage; depends on the half life of the med. If the med is excreted fast, you need to be given more doses per day…if the med is excreted slow (kidney or liver damaged patients), you need to be given less doses per day to avoid toxicity

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10
Q

Effects of combinations

A

Has to be chosen carefully to prevent antagonistic combinations (one antimicrobial prevents the action of the other antimicrobial)

Ideal combination; Synergistic (one antimicrobial enhances the action of the other)

Additive; one microbial doesn’t effect the other one at all

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11
Q

Adverse effects

A

Allergies; given an alternative antimicrobial

Toxic Effects; low therapeutic index causes damage.

Pregnant women should avoid some because it could give adverse effects to the fetus

Suppression of normal microbiota; causes dysbiosis (an imbalance in the microbial pop)…can cause other pathogens to multiply without competition and cause disease

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12
Q

Resistance to antimicrobials

A

Intrinsic resistance (inherently resistant to the med…mycoplasm lacks cell wall needed for the antimicrobial to work)

Acquired resistance; previously sensitive microorganism that becomes resistant (through spontaneous mutation or horizontal gene transfer)

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13
Q

Target of antibacterial medications (cell wall synthesis…peptidoglycan)

A

b lactam antibiotics; competitively inhibit enzymes that help from cross-links between adjacent glycan chains…human cells dont have peptidogylcan…ex; penicillin carbapenems, monobactams, and cephalosporin (they all have the b lactam ring and have a high therapeutic index)…the b lactam antibiotics are bactericidal only against growing bacteria
Gram negative is more resistant, because their cell wall and because the penicillin binding proteins are different.
B lactamase; enzyme that breaks down b lactam ring…bacteria that have this are resistant…carbapenemases inhibit most

Glycopeptide antibiotics; bind to the amino acid side chain of NAM molecules which blocks formation of cross links between the gylcan chains…only effect gram positive bactera…ex vancomycin

Bacitracin; interferes with the transport of peptidoglycan precursors across the cytoplasmic membrane

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14
Q

Target of antimicrobial mediations

A

Nucleic acid synthesis; fluoroquinolones; bactericidal against a wide range of bacteria.
Rifamycins; block transcription…bactericidal agains a wide range and mycobacterium
Metronidazole; only effects anaerobic microorganisms (metabolism of anaerobic mirco. converts the medication to its active form)

Cell membrane integrity; polymixins, daptomycin

Metabolic pathways (folate biosynthesis); sulfomaides, trimethoprim

Protein synthesis; target the 70s ribosome of bacteria…ex aminoglycosides, tetracyclines, glyclyclines, macrolides, chloramphericol, linocosamides, oxazolidinones, pleuromutilins, streptogramins

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15
Q

Different types of penicillins

A

Natural penicillins;

Penicillinase-resistant penicillins; methicillin and dicloxacillin…some S. aureus are MRSA (methicillin resistant s. aureus)…only cephalosporins are effective against MRSA

Broad-spectrum penicillins; inactivated by b lactamases, ex ampicillin and amoxicillin

Penicillin family + b lactamase inhibitor; combination of agents, ex; augmentin (amoxicillin and clavulanic acid)

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16
Q

Developing resistance to antimicrobials

A

make an enzyme that destroys the antimicrobial; b lactamase

mutate the protein/rRNA to which the drug binds; modification of the PBP’s

Decrease the uptake of the drug; change the porin proteins that allow antimicrobials to be let in (small holes in outer membrane)

Increase the elimination of the medication; make more efflux pumps

These strategies are implemented through spontaneous mutation, and acquisition of resistance genes via plasmids and other forms of horizontal gene transfer.

17
Q

Suceptibility to antimicrobial medication

A

Minimum inhibitory concentration; decreasing the concentration of the antimicrobial drug by finding the lowest concentration needed to prevent growth….the higher the MIC the more resistant the microorganism is

Disk diffusion (kirby-bauer) test; Diameter of zone of inhibition

18
Q

Examples of emerging resistance;

A

neisseria gonorrhoeae, S. aureus, S. pneumoniae, mycobacterium tuberculosis, Enterococcus

19
Q

Antimicrobial stewardship

A

slowing the emergence and spread of antimicrobial resistance; Responsibility of physicians and health care workers (prescribe medications only when appropriate)
Responsibilities of patients (take medications as prescribed)
Importance of an educated public (antibiotics are not effective against viruses