Transcript Antibiotics Intro PPT

Intro to Antibiotics
By: Alaina Darby
Outline
 Intro to Antimicrobials Overview
 Practice Questions
 Specific Things to Remember
 Helpful Tips for the Test
Intro to Antimicrobials
Overview
Antibiotic vs Antimicrobial
 Antibiotics
 Produced by a microorganism
 Most of the older antimicrobials can be classified as antibiotics and
are, therefore, classified as antibiotics and antimicrobials
 Example: penicillin
 Antimicrobials
 Antibiotics are a subset of antimicrobials
 Antimicrobials inhibits growth or kills microorganisms
 Many newer antimicrobials are not natural products, so they are
antimicrobials but not antibiotics
Terms
 Gram stain
 Selective toxicity
 Post-antibiotic effect (PAE)
 Bactericidal
 Bacteriostatic
 Spectrum
 Biofilm
 Synergy
Concentration vs Time-Dependent Killing
 Concentration-dependent
 Cmax/MIC
 Cmax is the peak concentration
 Kills at high concentration but doesn’t really matter as much how long they are at
the high concentration
 Can have longer dosing intervals
 These have a long PAE
 Example: aminoglycosides
 Time-dependent
 T>MIC
 Has to be above the MIC for an extended period of time but really high
concentrations don’t usually increase killing
 Can give smaller doses more frequently
 If you are giving the drug IV, then a continuous infusion is good
 Has little to no PAE
 Example: vancomycin
Choosing Antibiotics
 DIAGNOSIS!!
 Specificity/Spectrum
 Bactericidal/Bacteriostatic
 PAE
 Site of infection
 Other factors at the site of infection
 Host factors
SITE OF ACTION
Helpful memory aid:
 Think about the stock market.
When you play the stock market,
you want to buy low and sell high.
 There are 2 subunits of the
ribosome – 50S and 30S.
 So… A smart person buys AT 30
and CELS for 50.
 AT:
A (aminoglycosides)
T (tetracyclines)
 CELS:
C (clindamycin/chloramphenicol)
E (erythromycin/other macrolides)
L (linezolid)
S (streptogramins)
Resistance
 Intrinsic vs Acquired
 Intrinsic: already present
 Acquired: mutation or transmission of genes
 Mechanisms
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Receptor alteration
Decreased transport into microorganism
Increased export (e.g. tetracyclines)
Inactivation (e.g. beta-lactams, aminoglycosides)
Alternative metabolic pathways (e.g. TMP/SMX)
Defect in activation (e.g. metronidazole, 5-flucytosine)
Practice Questions
Which of the following is a term that would not
apply to the treatment of a virus-caused condition?
a. Chemotherapy
b.Antibiotic
c. Antimicrobial
d.Selective toxicity
Which of the following describes post-antibiotic effect?
a. Suppression of bacterial growth after ceasing antibiotic
administration
b.Suppression of bacterial growth after ceasing antibiotic
administration and concentration is below MIC
c. Bacterial regrowth after ceasing antibiotic administration
d.Bacterial regrowth after ceasing antibiotic administration and
concentration is below MIC
Which of the following is the most important factor
in determining antimicrobial therapy?
a. Antibiotic specificity and spectrum
b.Bactericidal vs bacteriostatic function
c. Diagnosis of infecting organism
d.Post antibiotic effect
Why might one choose erythromycin over an
antibiotic like metronidazole that has a broader
spectrum?
a. Less alteration of GI microflora
b.Aid in organism identification
c. Target a specific area of the body
d.Decrease the MIC
Which of the following describes the latency period?
a. Time from administration until the drug kills all bacteria in a
cidal drug
b.Time from administration until the drug begins to inhibit
bacterial multiplication in a cidal drug
c. Time from administration until the drug begins to reduce the
number of pathogens in a cidal drug
d.Time from administration until the drug begins to reduce the
number of pathogens in a static drug
Which of the following relies upon host defenses to
aid in eliminating the pathogen?
a. Bactericidal
b.Bacteriostatic
c. Neither bactericidal or bacteriostatic
d.Both bactericidal and bacteriostatic
What would not be a reason for choosing a
bactericidal agent over a bacteriostatic agent?
a. More rapid acting
b.Reduced number of organisms
c. More effective
d.Effects without maintaining MIC
Which of the following cases would not require a
bactericidal agent?
a. Bacterial endocarditis
b.Pertussis
c. Meningitis
d.Transplant patient
Which of the following exhibits no post-antibiotic
effect?
a. Aminoglycosides
b.Fluoroquinolones
c. Clindamycin
d.Vancomycin
Which of the following exhibits no post-antibiotic
effect?
a. Time-dependent
b.Concentration-dependent
c. Time-dependent and concentration-enhanced
d.Concentration-dependent and time-enhanced
Which of the following is a protected site into which
antibiotic will not be readily available?
a. Bladder
b.Kidney
c. Prostate
d.Lungs
Which of the following is not a major concern when
selecting an antibiotic for its concentration at the
site of infection?
a. Patient compliance
b.Metabolism and excretion
c. Route of administration
d.Anaerobic conditions
Which of the following would not be reason to use
combination chemotherapy?
a. Increase bactericidal activity at the same site
b.Prevent emergence of resistant organisms
c. Permit lower doses of the antibiotics
d.Treat infection of unknown etiology
Which of the following is not an infection that is
often treated with combination chemotherapy?
a. Tuberculosis
b.Malaria
c. HIV
d.Meningitis
What would not be a reason to choose a single
agent for therapy?
a. Same site toxicity
b.Mixed bacterial infection
c. Static plus cidal combination
d.Increased cost
Which of the following is not true of
superinfections?
a. They are due to alterations in the normal flora
b.Incidence increases with broad spectrum agents
c. They are a reappearance of the primary infection
d.They appear during treatment
Which of the following is not true of antibiotic resistance?
a. Natural resistance is present before antibiotic therapy
b.Acquired resistance is caused by the antibiotic
c. Acquired resistance occurs in a species that was once
sensitive
d.Acquired resistance is a consequence of antibiotic
therapy
Which of the following is not an indication for prophylaxis?
a. Prevent infection by a specific organism
b.Prevent all potential secondary infections in a patient ill
with other diseases
c. Prevent infection from rupture of a viscus or a surgical
procedure
d.Prevent bacterial endocarditis or recurrence of rheumatic
fever
Which of the following would not be true of the
ideal antimicrobial?
a. Alkaline stable
b.Orally absorbed
c. Bactericidal
d.Good distribution to bones
Which of the following would not be true of the
ideal antimicrobial?
a. Readily excreted
b.Widest spectrum possible
c. Low MLC
d.High tissue concentration
Specific Things to Remember
Important points for certain bugs and drugs.
Metabolism/Excretion
 Almost everything that works on the cell
wall is renally excreted.
 Almost everything that works anywhere
else is metabolized.
Spectrum
 Gram negatives only
 Aztreonam
 Pseudomonas
 Cefepime
 Ceftazidime
 Piperacillin/Tazobactam (Zosyn)
 MRSA
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Vancomycin
Ceftaroline
Linezolid
Streptogramins
Daptomycin
 Anaerobes
 Clindamycin
 Metronidazole
 VRE
 Linezolid
 Streptogramins (faecium only)
 Daptomycin
 Cephalosporines DO NOT treat
enterococcus!
Adverse Effects
 Almost everything can cause GI
disturbances
 Clindamycin
 Aminoglycosides
 Chloramphenicol
 Nephrotoxicity
 Ototoxicity
 Tetracyclines
 Dental discoloration
 Photosensitivity
 Fluroquinolones
 Photosensitivity
 Tendon ruptures
 Penicillins (and sometimes
Cephalosporins)
 Hypersensitivity
 C. difficile infection
 Gray baby syndrome
 Telithromycin
 QT prolongation
 Sulfonamides
 Hypersensitivity
 Hematologic (G6PD deficiency)
 Kidney stones
 Metronidazole
 Disulfram-like reaction
 Isoniazid
 Liver failure
Drug Interactions
 Tetracyclines
 Ca2+ chelation
 Macrolides
 Strong CYP inhibitors
 Especially erythromycin
 Exception: azithromycin
 Rifampin
 Induces everything
Helpful Tips for the Test
Some fun memory aids for you!
 Clindamycin has good activity in the bone. (That was a
question my P1 year!)
 Tigecycline is hepatically and renally excreted… Tigers poop
and pee a lot. (I didn’t come up with that.)
 TMP/SMX treats…
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T: Tree (respiratory)
M: Mouth (GI tract)
P: Pee (genitourinary)
S: Syndromes (AIDS… like PCP)
 CefTAZidime and cefEPIme are the only cephalosporins that
are EPIc enough to TAZe Pseudomonas.
 Quinolones are a “flock of sinners” (-floxacins) that gyrate
(DNA gyrase) their hips at night (photosensitivity). They dance
and party so much that their tendons rupture and they have
heart problems (QT prolongation).
The End!