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
are active against onl a few micororganisms
broad spectrum antibiotics
active againsta wide array fo microbes
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: 1-4
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%
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 Penicillins
-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
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?
Vancomycin Erythromycin Clindamycin
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
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
Nafecillin Methcillin Oxacillin Dicloxacillin - used against penicillinase-producing strands of Staph Aureus.
in contrast to Penicillin G, the broad spectrum penicillins
-useful against gram negative bacilli
piperacillin Ticarcillin -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