Antimicrobial Principles

Question 1

What factors (6) influence the antimicrobial agent chosen?

Answer 1

identity of organism, susceptibility, site of infection, patient factors, safety, cost

Question 2

How do you identify the organism?

Answer 2

culture, gram stain, detection of antigens or nucleic acids, or host inflammatory response– culture must be preformed prior to treatment

Question 3

As optometrists, drug choice is determined by:

Answer 3

site of infection and patient’s medical history… broad spectrum antibiotic is usually chosen

Question 4

What is bacteriostatic?

Answer 4

arrest the growth and replication of bacteria and let body’s immune system eliminate the infection

Question 5

What is bactericidal?

Answer 5

drugs kill bacteria, more aggressive and often used for seriously ill patients

Question 6

What is MIC?

Answer 6

minimum inhibitory concentration- lowest concentration of an antibiotic that inhibits bacterial growth, must reach this level clinically to have an effect

Question 7

What is MBC?

Answer 7

minimum bactericidal concentration- lowest concentration of antibiotic that kills the bacteria

Question 8

What three things are entry to the CNS influenced by?

Answer 8

lipid solubility, molecular weight, and protein binding

Question 9

What are some patient factors that can affect the immune system?

Answer 9

alcoholism, diabetes, HIV, malnutrition, autoimmune disease, pregnancy, age, immunosuppressive drugs

Question 10

What are the 5 major patient factors for drug selection?

Answer 10

renal function, hepatic function, poor perfusion, age, and pregnancy

Question 11

What happens if kidney function is poor?

Answer 11

accumulation of antibiotics

Question 12

What is an example of an antibiotic among the least toxic of all drugs?

Answer 12

penicillin

Question 13

What is an example of an antibiotic with serious potential for toxicity?

Answer 13

chloramphenicol

Question 14

What administration is preferred for mild infections and outpatient treatment?

Answer 14

oral

Question 15

Sometimes antibiotics are so poorly absorbed from GI….

Answer 15

they must have parenteral administration

Question 16

What is rational dosing based on?

Answer 16

pharmacodynamics (relationship of concentration to effect) and pharmacokinetics (ADME)

Question 17

What three properties have significant influence on rational dosing?

Answer 17

concentration-dependent killing, time-dependent killing, post antibiotic effect

Question 18

What is concentration-dependent killing?

Answer 18

certain agents show significant increase in the rate of bacterial killing as the concentration of antibiotic increases (favor once a day bolus infusion) ex: aminoglycosides

Question 19

What is time-dependent killing?

Answer 19

effect is best predicted by the percentage of time that blood concentrations remain above MIC– favor extended or continuous infusions exL b-lactam, macrolides

Question 20

What is PAE?

Answer 20

post antibiotic effect– persistent suppression of microbial growth that occurs after antibiotic levels have fallen bellow the MIC

Question 21

How does a long PAE affect dosing?

Answer 21

only requires one dose a day ex: aminoglycosides and fluoroquinolones

Question 22

What are the six major families of antibiotics?

Answer 22

penicillins, cephalosporins, tetracyclines, aminoglycosides, macrolides, and fluoroquinolones

Question 23

What is a narrow-spectrum antibiotic?

Answer 23

act on only a single or limited group of microorganisms

Question 24

What is an extended spectrum antibiotic?

Answer 24

effective against gram (+) and a significant amount of gram (-)

Question 25

What is a broad spectrum antibiotic?

Answer 25

affect a wide variety of microbial species and can alter normal flora

Question 26

Describe gram (+) organisms

Answer 26

surrounded by peptidoglycan cell wall (85% of eye infections) ex: Staph epidermis and aureus on the skin and strep pneumonia or streptococcus

Question 27

Describe gram (-) organisms

Answer 27

cell wall is surrounded by outer membrane. pores prohibit entry of many antibiotics because they need to be hydrophilic to pass through the pores

Question 28

What are the four groups of gram (-) organisms?

Answer 28

enterics, haemophilus influenza, neisseria and pseudomonas

Question 29

What organism is a cause of eye infections in adults?

Answer 29

staph aureus

Question 30

What organisms is a cause of eye infections in children and old peope?

Answer 30

haemophilus influenza

Question 31

Describe anaerobic infections

Answer 31

usually composed of mixed gram + and - bacteria, infections occur when bacteria invade poorly oxygenated tissues or tissues that are normally sterile-- encased in abscess wall and are foul smelling

Question 32

In general should you select one drug or a combination?

Answer 32

one best agent

Question 33

Why is it best to choose a single agent to treat in infection in most cases?

Answer 33

reduces possibility of superinfection, decreases resistance, minimizes toxicity

Question 34

What is resistance?

Answer 34

bacteria are resistant if the maximal level of the antibiotic that can be tolerated by the host does not halt the bacteria growth

Question 35

Resistance can be either ___ or _____

Answer 35

natural or developed

Question 36

What are the two ways resistance are developed?

Answer 36

genetic alterations and altered expression of proteins

Question 37

What are spontaneous mutations?

Answer 37

insertion, deletion, or substitution alterations in the chromosomal DNA-- may be lethal to the cell but if not the mutation will be passed to the progeny

Question 38

What is DNA transfer of resistance?

Answer 38

one bacterium may transfer resistance to another by plasmid

Question 39

What are three results of altered expression of proteins?

Answer 39

modification of target sites, decreased accumulation, enzymatic inactivation

Question 40

What does modification of a target site do?

Answer 40

a change in structure to an antibiotic binding site may produce resistance, often from a mutation

Question 41

What does decreased accumulation do?

Answer 41

decreased uptake or increased efflux do not allow the drug to gain access to the site of action of an organism

Question 42

What does enzymatic inactivation do?

Answer 42

some bacteria can destroy or inactivate the antimicrobial agent

Question 43

What are prophylactic antibiotics?

Answer 43

use of antibiotics for prevention rather than treatment-- should be restricted to situations where the benefits outweigh the potential risks because it can result in resistance

Question 44

What is an example of prophylactic treatment that optometrists might use?

Answer 44

treatment prior to surgical procedures like cataract surgery

Question 45

T/F since antibiotics are selectively toxic to an invading organism, the host will not have any adverse effects

Answer 45

false, still susceptible to adverse effects

Question 46

What are two major complications or antibiotics?

Answer 46

direct toxicity and superinfections

Question 47

What is direct toxicity?

Answer 47

high concentrations of antibiotics can directly affect host cellular processes ex: aminoglycosides and ototoxicity

Question 48

What are superinfections?

Answer 48

alterations in the normal microbial flora that permits overgrowth and the subsequent infections are difficult to treat ex: yeast infection after antibiotics