intro antibiotics

Question 1

Describe cell wall

Answer 1

• all bacteria have a cell wall that consists of PEPTIDOGLYCAN

–> Peptidoglycan = a macromolecule comprosed of peptides and sugars that provide a rigid support structure that is found ONLY IN BACTERIA

• Gram + = thick wall of peptidoglycan
• Gram - = Thin wall of peptidoglycan

Question 2

Lipoplysaccharide (LPS)

Answer 2

• Lipopolysaccharide makes up the OUTHER MEMBRANE STRUCTURE of GRAM (-) bacteria cell wall and consists of phospholipid and polysaccharides

Question 3

Cytoplasmic membranes in bacteria

Answer 3

• Similar in structure to eukaryotic cell membrane EXCEPT FOR STEROLS

Question 4

Describe lipopolysaccharide effects on antibioitcs

Answer 4

• retards or prevents penetration of BULKY, HIGH MOLECULAR WEIGHT antibiotics such as ERYTHROMYCIN

Question 5

Lipid bilayer of cytoplasmic membrane effects on antibiotics

Answer 5

• Penetration of water-soluble drugs is SEVERELY HINDERED

Question 6

hydrophillic pores effects on antibiotics

Answer 6

• allow penetration of water-soluble molecules up to 650 daltons, such as SULFONAMIDES

Question 7

Nutrient receptor proteins on outer membrane effects on antibiotics

Answer 7

• agents strucurally related to nutrients (sideromycins) utilize these natural receptors

Question 8

Teichoic and teichuronic acid effects on antibiotics

Answer 8

found in gram positive bacteria

• Strong anionic character of these polymers may affect RATE OF PENETRATION

Question 9

What are common strategies for killing or inhibiting microorganism growth..

Answer 9

1) disrupt coding/genetic machienery (target folate syntheis need to make DNA, disruping mRNA synthesis)
2) blocking protein synthesis
3) disrupting cell wall or membrane synthesis

Question 10

Bactericidal vs bacteriostatic

Answer 10

Bactericidal = an agent that will kill the bacteria

• once the organism is exposed to the drug, it is no longer viable

Bacteriostatic = an agent that will inhibit growht of the bacteria but will not kill the bacteria

–> therapeutic success is depdent upon the host defense mechanisms to clear the infection

–> if drug is removed, the bacteria will once again begin to grow

Question 11

describe MIC

Answer 11

minimum inhibitory concentration (MIC)

• the lowest conc of an antimicrobial agent that will inhibit the visible growth of bacteria in liquid culture

Question 12

describe MBC

Answer 12

Minimum bactericidal conc (MBC)

• conc of antibiotic from the original MIC plate that shows NO GROWTH after subculture

Question 13

Define resistance

Answer 13

• chemotherapeutic agent is no longer or less effective towards an organisms
• develops due to:

–> reduce drug entry in the organism

–> increased drug export from the organisms

–> expression of enzymes by the organism that destroy the drug

–> changes in expression enzymes that activate the drug (pro-drug)

–> imapired drug binding to the original target

–> development of new or different pathways that are not inhibited by the drug

• DEVELOP RESISTANCE THROUGH ACQUISITION OF NEW GENETIC MATERIAL OR MUTATION IN THE EXISTING GENOME

Question 14

ESKAPE

Answer 14

• Enterococcus faecium
• staphyloccus aureus
• Klebsiella pneumoniae
• Acinetobacter baumanni
• Pseudomonas aeruginosa
• Enterobacter species

Question 15

Daptomycin

Answer 15

• used in the TX of complicated skin infections, bacteremia and endocarditis
• Specific gene mutation results in a change in membrane charge –> overall increase in net positive charge which will repel the antibiotics with cationic properties (REDUCED DRUG ENTRY IN THE ORGANISMS)

Question 16

Tetracycline

Answer 16

• Use as a Broad spectrum antibiotic in the tx of acne, bronchitis, gonorrhea and syphilis
• Resistance occurs through expression of an EFFLUX PUMP –> INCREASED DRUG EXPORT FROM THE ORGANISM

Question 17

Metronidazole

Answer 17

• Use in the TX of abdominal infections, vaginitis, CLOSTRIDIUM DIFFICILE Colitis, and brain abscess
• Resistance occurs due to a mutation in rdxA gene (oxygen-insensitve nitroreductase) which alters or decreases the activation of the drug

–> CHANGE IN EXPRESSION OF ENZYME THAT ACTIVATES THE PRO-DRUG

Question 18

Aminoglycosides (streptomycin)

Answer 18

• USED in combo with other agents to tx unusal and severe conditions such as endocarditis, tularemia, plaque and tuberculosis
• REsistance occurs via aminoglycoside-modifying enzymes chemically modify the antibiotic and alter binding of the drug to its target

–> EXPRESSION OF ENZYMES BY THE ORGANISMS THAT DESTROY THE DRUG

Question 19

Amoxicillin

Answer 19

• USED as borad spectrum antibiotic used for variety of infections
• RESISTANCE OCCURS BY expression of enzyme Beta-Lactamase which can hydrolyze the lactam ring of amoxicilin and render the compound ineffective

–> EXPRESSION OF ENZYMES BY ORGANISMS THAT DESTORY THE DRUG

Question 20

Trimethoprim and sulfonamides

Answer 20

• Used in combo to treat urinary tract infections
• resistance occurs via drug-insensitive enzymes dihydropteroate synthase and dihydrofolate reductase

–> IMPAIRED DRUG BINDING TO THE ORIGINAL TARGET

Question 21

VANCOMYCIN

Answer 21

• USED in the tx of bloodstream infections, endocarditis and meningitis
• REsistance occurs by subsitition of the peptidoglycan stem so that agent can no longer bind to the target

–> development of new or different pathways that are no inhibited by the drug