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Bacteriology F > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

The 5 main target sites for antibacterial agents:

A
  • cell wall synthesis
  • cytoplasmic membrane function
  • protein synthesis
  • nucleic acid synthesis
  • metabolic pathway
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2
Q

Which antibacterial agent has the best selective toxicity?

A

Antibacterial agent targeting cell wall synthesis because human cells do not have cell wall

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3
Q

Famileis of drugs that inhibit Send wall synthesis

A
  • Beta lactams including monobactams, carbapenem, penicillin and cephalosporins.
  • Glycopeptides including vancomycin
  • bacitracin
  • subactams
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4
Q

Antibiotics inhibiting cell wall synthesis are bactericidal or bacteriostatic?

A

Bactericidal

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5
Q

What is the target beta lactams?

A

Penicillin binding proteins

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6
Q

What is beta-lactamase?

A

An enzyme produced by bacteria that provides multi resistance to beta-lactam antibiotics

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7
Q

Bacteria that beta-lactam can’t act on:

A

Bacteria that do not have a cell wall like mycoplasma and intracellular bacteria

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8
Q

Inhibitors of beta lactamase:

A

Clavulanic acid and sulbactam

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9
Q

Mechanism of action of beta-lactams

A

They will bind to transpeptidase active site of penicillin binding proteins thus inhibiting the formation of cross linking and cell wall synthesis

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10
Q

All penicillin antibiotics are sensitive to the acidity of the stomach except those two:

A

Amoxicillin and penicillin V

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11
Q

Penicillins that are resistant to beta lactamase:

A

Nafcillin, oxacillin and methicilin

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12
Q

Penicillin V:

A

Active against gram-positive bacteria

Sensitive to Beta lactamase

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13
Q

Oxacillin methicillin and nafcillin:

A

Less active against gram-positive and inactive against gram negative
Resistant to beta lactamase

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14
Q

Ampicillin and piperacillin:

A

Active against gram positive and gram negative bacteria

Sensitive against beta lactamase

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15
Q

Amoxicillin

A

Less sensitive to beta lactamase
Taken orally
Better absorbed than ampicillin

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16
Q

Penicillin V

A

Acts like penicillin G but taken orally

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17
Q

MRSE

A

Methicillin resistant staphylococcus epidermidis

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18
Q

MRSA

A

Methicillin resistant staphylococcus aureus

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19
Q

How resistance is acquired by staphylococcus bacteria?

A

They have a MECA gene which will Produce new penicillin binding proteins that have a lesser affinity to penicillin and at the same time inactivating normal penicillin binding proteins.

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20
Q

ESBL

A

Extended spectrum beta lactamase

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21
Q

How beta lactamase inactivate penicillin?

A

By converting the 6-aminopenicilanic acid which is the compound that has the anti-bacterial activity, into 6-aminopenicilloic acid inactive against bacteria but have a property of an hapten

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22
Q

Hapten:

A

It is a molecule that has lost its capacity to produce disease but has preserved its antigenicity and can stimulate the immune system causing an allergic reaction

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23
Q

manifestations of an allergic reaction due to penicillin;

A

Skin rash and edema

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24
Q

Clavulanic acid

A

It’s a suicide inhibitor that has the capacity to inhibit the activity of beta lactamase.
It can’t be administered alone since it has o anti-microbial or antibacterial properties so it should be combined with another antibiotic and the junction with beta lactamase will make this antibiotic more effective.

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25
First generation of cephalosporins
Activity similar to ampicillin | More active against gram-positive and less against gram-negative
26
Second generation of cephalosporins
Expended activity against Enterobacteriaceae which our gram-negative bacilli except Pseudomonas Less active against gram-positive cocci Active against haemophilus and anaerobes and can cross the blood brain barrier
27
Third generation of cephalosporins
More expanded activity against Enterobacteriaceae including Pseudomonas Less active against gram-positive cocci and can cross the blood brain barrier
28
Fourth generation of cephalosporins
Active against pseudomonas | Active against streptococcus and methicillin susceptible staphylococcus
29
Superinfection
When we give an antibiotic which is more active against gram-negative bacteria for example in an E. coli infection, the normal flora will be imbalanced, this will activate certain bacteria like staphylococcus aureus causing a superinfection. In this case the antibiotic given is only treating the E. coli and complications will appear due to staph infection.
30
Broad-spectrum antibiotic
Antibiotic covering many types of bacteria like gram-negative, gram-positive, aerobics, anaerobic...
31
Most broad-spectrum antibiotic:
Carbapenems | They are active against gram-negative, gram-positive and anaerobes (Including Pseudomonas)
32
Monobactam
Limited to Gram-negative bacteria | Resistant against beta-lactamase
33
Origin of bacitracin
Bacteria called Bacillus Subtilis
34
Bacitracin
Active against positive bacteria It is poorly absorbed by the G.I. tract and has many toxic side effects so it is not given systemically it’s only given externally as an ointment against gram-positive bacteria. It prevents the phosphorylation of phospholipid carriers like Bactoprenol It prevents regeneration of carriers necessary for synthesis to continue.
35
Vancomycin
It’s a glycopeptide that acts only against gram-positive bacteria since it cannot cross the outer membrane of negative bacteria due to its size It prevents the separation of the fifth amino acid so it acts at the level of the element D Alanine-D-Alanine inhibiting formation of cross linking
36
Resistance to vancomycin
Some bacteria have D-alanine-D-lactate where vancomycin can’t act. Other bacteria like enterococci have a chromosomal mediated resistance to vancomycin
37
Antibiotic Associated Diarrhea
When we are taking an antibiotic against a certain type of bacteria other bacteria that are part of our normal flora will increase the number and become pathogenic causing bacteria
38
Antibiotic used to treat antibiotic associated diarrhea
Vancomycin and metronidazole
39
Polymyxin B
Active only against gram negative bacteria Binds to lipid A and phospholipids then cause disruption of cytoplasmic membrane causing the destruction of the whole bacteria cell
40
Antibiotics that bind 30 S subunit of ribosomes
Aminoglycosides and tetracyclines
41
Antibiotics that bind 50 S subunits of ribosomes
Lincosamides Chloramphenicol Macrolides Clindamycin
42
Aminoglycosides
Acts on anaerobic Gram negative bacteria | To be effective they should be used in combination with another antibiotic
43
-icin Aminoglycosides:
Amikicin Gentamicin Netilmicin
44
-ycin Aminoglycosides
``` Tobramycin neomycin kanamycin streptomycin spectinomycin ```
45
Least toxic aminoglycosides antibiotic:
Netilmicin
46
Amikacin:
A semi synthetic the riveter of kanamycin Active against gentamicin resistant gram-negative rods Used preoperatively and post operatively to suppress microbial flora and avoid infections
47
Gentamicin
Broad-spectrum aminoglycoside used against aerobic gram-negative and gram-positive bacteria Taken parenterally orally or as an ointment for the eye infections
48
Tobramycin
Activity similar to gentamicin but slightly better against Pseudomonas aeruginosa Nowadays Pseudomonas has acquired resistance against tobramycin so it is no longer used to treat it except when it is a non-resistant strain
49
Kanamycin
No longer in clinical use | Only used as a prophylaxis to suppress microbial flora and avoid infections
50
Neomycin
Topical use when contaminated mucosal surfaces, too toxic to be used to systemically
51
About spectinomycin:
Used via a single dose IM injection to treat gonorrhea caused by Beta lactamase producing gonococci. Alternative drug to penicillin cause pain at the site of infection nausea and fever.
52
Streptomycin
The oldest aminoglycosides What day is restricted for treatment of tuberculosis. Has acquired chromosomal mediated resistance and then plasmid mediated resistance No longer used alone but has to be combined with other drugs
53
Side effects of streptomycin
Tinnitus Vertigo Ataxia
54
Indications for aminoglycoside therapy
``` Only used for severe and life-threatening infections: Gram-negative septicemia Bacterial endocarditis Septicemia of unknown etiology Post surgical abdominal sepsis Pyelonephritis Staphylococcus aureus septicemia ```
55
Antibiotics acting on elongation phase of protein synthesis
Tetracyclines clothes on for Nicole chloramphenicol Lyncosamids macrolides fusidic acid
56
Members of tetracycline
Chlortetracycline Deoxycycline Oxytetracycline Tetracycline Minocycline
57
Tetracyclines are bacteriostatic or bactericidal
Bacteriostatic
58
Tetracycline shouldn’t be prescribed for
Pregnant women and children under 6 years old because tetracyclines will deposit on bone and cartilage leading to formation of yellow teeth
59
Chloramphenicol is bacteriostatic or bactericidal
Bacteriostatict
60
About chloramphenicol:
They bind 50s subunit of ribosome by blocking amino acid attachment It was previously used in the treatment of salmonella typhi but it had severe toxic side effects so it’s no longer used.
61
How bacteria synthesize its own folic acid?
PABA in the presence of dehydropteroate synthase Relate formation of dehydropteroic acid then dehydrofolic acid which in the presence of dehydrofolate synthase will produce tetrahydrofolic acid.
62
Antimetabolites
Sulfonamides Daspone Trimethoprim
63
Bactrim composition
One part of trimethoprim and five parts of sulfonamides
64
About Bactrim
It is effective against mini gram-negative and gram-positive bacteria. It can be used for urinary tract infections but can cause an overgrowth of fungi causing genital tract itching for females due to overgrowth of Candida albicans

Bacteriology F (16 decks)

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