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ch 28
in antimicrobial therapy, the term selective toxicity refers to..

the ability of a drug to injure invading micorbes without injuring cells of the host

naroow-spectrum antibiotics..

are active against onl a few micororganisms

broad spectrum antibiotics

active againsta wide array fo microbes

bacteriacidal drugs

kill bacteria

bacteriostatic drugs

only supress growth

what is a major concern in antimicrobial therapy?

emergence of resisitance to antibiotics


is an method by which bacteria aquires resistance

- prcoess in which DNA coding for drug resistance is transferred from one bacterium to another

do antibiotics cause the genetic changes that underlie resistance?

- then what do they do


antibiotics promote emergence of drug-resistant organisms creating selection pressures to favor them

which promote resistance narrow or broad spectrum drugs?

broad spectrum drugs, such large killing spectrum could kill both normal and bad microbes

four basic ways to delay resistance:

1) preventing infection
2) diagnosing and treating infection effectively
3)using antimicrobial drugs wisely
4) preventing pt to pt transmission

what do livestock and antibiotics do?

use of antibiotics to promote growth in livestock
-promotes emergence of resistance

effective antimicrobial therapy requires..

that we determine both the identity and drug sensitivity of the infecting organism

Minimum inhibitory concentration (MIC)

the lowest concentration needed to completely supress bacterial growth

minimum bacteriacidal concentration (MBC)

the concentration that decreases the number of bacterial colonies by 99.9%

Host defenses

the immune system
phagocytic cells

-essential to success of antimicrobial therapy

should pts stop tkaing antibiotics when symptoms disappear..?

no, need to continue treatment until fully done to make effective

although combinations of antibiotics should be avoided, some apporpriate situations are...

1. intitial treatment of severe infection
2. infection w/ more than one organism
3. treatment of TB
4. treatment of an infection, which combination therapy can enhance antimicrobial effects

appropriate indications for prophylactic antimicrobial treatment..

a. certain surgeries
b. neutropenia
c. recurrent UTI's
d. pts w/ increase risk of bacterial endocarditis (prothetic heart valves, congenital HD)

misuses of antibiotics..

-treatment of untreatable infection (common cold, most other viral infections)
- treatment of fever of unkown origin
-treatment in the absence of adequate bacteriologic information
-treatment in the absence of appropriate surgical drainage

ch 83

-weaken the bacterial cell wall

-causing lysis and death

how can some bacteria resist penicillins?

-by producing penicillinases (beta-lactamases)
-are enzymes that inactivate penicillin

gram negatice bacteria

-are resistant to penicillins
b/c can't penetrate cell envelope

are they safe?

penicillins are the safest antibiotics out now

main A/E

allergic reaction
rnage from rash to anaphylaxis

if allergic to one penicillins , should take others?

no, b/c of cross-allergic reactions has a 1% chance with other cephalosporins

alternative drug to penicillin if allergic?


normally eliminated?

renal function...

rapidly by the kidney

-can accumulate to harmful levels if renal function is severly impaired

principal difference of penicillins is..

-relate to antibacterial spectrum
-stability in stomach acid
-duration of action

Penicillin G

narrow antibacterial spectrum
-unstable in stomach acid

Benzathine penicillin G

released slowly following IM injection
- b/c of this produces prolonged antibacterial effects

penicillinase- resistant penicillins

- used against penicillinase-producing strands of Staph Aureus.

in contrast to Penicillin G, the broad spectrum penicillins


-useful against gram negative bacilli

extended-spectrum penicillins

-used against P. aeruginosa

Beta lactamase inhibitors

Clavulanic acid, tazobactam, sulbactam
-are combined w/ certain penicillins to increase their activity against beta-lactamase-producing bacteria

what should penicillins not be combined with?

aminoglycosides (gentamicin)
-in same IV solution

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