Antibiotics Flashcards
Organisms treated by metronidazole
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Giardia Entamoeba Trichomonas Gardnerella vaginalis Anaerobes (Bacteroides, C. Difficile) h. Pylori (used with bismuth and amoxicillin/tetracycline)
Anaerobic infection BELOW the diaphragm (as opposed to clindamycin
Antimicrobials to avoid in pregnancy
“Countless SAFe Moms Take Really Good Care”
Clarithromycin (embryotoxic)
Sulfonamides (kernicterus)
Aminoglycosides (ototoxicity)
Fluoroquinolones (cartilage damage)
Metronidazole (mutagenesis)
Tetracyclines (discolored teeth, inhibition of bone growth)
Ribavirin (teratogenic)
Griseofulvin (teratogenic)
Chloramphenicol ("gray baby")
Adverse Effects of Chloramphenicol.
Herschelle GIBS
H= Hypersensitivity G= Grey Baby syndrome (Stops feeding, hypotonia, abdomen distended, death) I= Irritative effects B= Bone marrow suppression (Aplastic anemia/Pancytopenia) S= Superinfections
Macrolides: MOA, Spectrum, Drugs, S/E.
MOA: Inhibits Translocation by binding to 50S ribosomal subunit. Prevents ribosome from moving along mRNA.
Spectrum:
Gram +ve and Gram -ve
Drugs:
- Erythromycin (Short acting and acid labile)
- Clarythromycin (More acid stable than Erythro, max oral BA)
- Azithromycin (T1/2 = 68 hours, OD)
S/E: MACRO M - Motilin receptor stimulation: Diarrhea and GI intolerance A - Allergy (hypersensitivity) C - Cholestasis R - Rashes O - Ototoxic (at high doses) Others: Hypertrophic pyloric stenosis QT prolongation (E>C>A)
Clindamycin : MOA, Spectrum, Uses, S/E
MOA: Inhibits Translocation by binding to 50S subunit of ribosome, this inhibits protein synthesis.
Spectrum:
1) Gram positive: Aerobes (Staph, strepto, Enterococcus) and Anerobes
2) Gram negative: Only anaerobes (Eg Bacteroides)
Uses: SPOTTED
SSI prophylaxis Pneumocystis jiroveci Odontogenic infections (anaerobes, above diaphragm) Toxic Shock syndrome (D.O.C) Toxoplasma Diverticulitis (Anerobes)
S/E:
- Pseudomembranous enterocolitis
- Neuromuscular toxicity
Treatment of Pertussis and effect on different stages of the disease.
DOC: Erythromycin (1-2 weeks)
- Incubation period: (10days) Prevents the disease
- Catarrhal stage: (1 week) May abort the next stageor reduce severity/duration of pertussis
- Paroxysmal stage: (2-4 week) No effect on severity or duration
- Convalescent stage: No effect
Name the Anti-retroviral drugs.
- Reverse Transcriptase Inhibitors (RTIs)
- NRTIs: AZT, ABC, Lamivudine, Tenofovir
- NNRTIs: Efavirenz, Nevirapine
2. Protease Inhibitors: Lopinavir, Ritonavir, Arazanavir
3. Entry Inhibitors: Enfuvurtide
4. CCR5 inhibitors: Maraviroc
6. Integrase inhibitors: Raltegravir, Dolutegravir
Aim of antiretrovital therapy (ART)
Currently followed regimen: HAART (Highly active anti retroviral therapy)
Aim:
1) Maximally inhibit viral replication
2) Maintain the patient’s immunity against potential mibrobial pathogens
3) Reduce the risk of transmission of HIV to uninfected sexual partner
Quinolones: Spectrum, MOA, Drugs, prototype drug, Uses, S/E.
Quinolones are synthetic AMAs.
Mainly active against GRAM NEGATIVE, though newer fluorinated compunds are also active against some gram+ve.
Spectrum:
1. Nalidixic acid and 1st gen FQs only for Gram-ve (maily intestinal and UTI)
2. 2nd gen FQ afor both Gram+ve and -ve
MOA: Inihibit Topoisomerase 2 (gram -ve) and 4 (gram+ve)
Drugs:
1st gen- Cipro (prototype) and Norfloxacin, Ofloxacin
2nd gen- Levo, Moxi, Gemi
Cipro uses: (Broad spectrum)
Mainly active against Grame-ve
Should not be used in minor infections or in Gram +ve infections.
Not active on anaerobes.
1) Diarrhea
2) UTI
3) Anthrax
4) Meningitis
5) Typhoid
6) Respiratory infections (should NOT be used as primary drug as it streptococci are not susceptible)
7) Chancroid
8) Gonorrhea
7) Gram -ve septicemia
8) Prophylaxis of neutropenic patients
9) Conjunctivitis by Gram -ve bacteria (topical)
10) Bone and soft tissye infections
S/E: The Good Clinical Practices (Tendonitis, GI side effects, CNS, Phototoxicity)
What is post antibiotic effect?
After a brief period of exposure to an antibiotic, when an organism is placed in a antibiotic-free medium, it starts to multiply again but only after a lag period. This lag period is the time required for reattainment of logarithmic growth, and is due to the Post-anti biotic effect (PAE).
In vivo PAE> in vitro PAE
Drugs with long PAE:
1) Aminoglycosides
2) Fluoroquinolones
3) Rifampicin
Antimicrobial drugs according to therapeutic index.
1) High therapeutic index (safer drugs): Penicillins, Cephalosporins
2) Low T.I. : Aminoglycosides, Tetracyclines, Chloramphenicol
3) Very low T.I. : Amphotericin B, Polymyxin B
Antibiotic resistance.
It refers to the unresponsiveness of a microorganism to an Antimicrobial agent. It is similar to the phenomenon of tolerance seen in higher organisms.
Type of resistance:
1) Natural
Eg. Gram -ve organisms to Penicillin G, Aerobic organisms to Metronidazole, anaerobes to Aminoglycosides
2) Acquired resistance:
- Development of resistance by an organism which was sensitive before to an AMA due to the use of the AMA for a period of time.
This is a major clinical problem and can happen with any microbe.
Mechanism of acquiring resistance:
a) Mutation - A sensitive population of microorganisms contain few mutant strains which require higher conc of AMA for inhibition. When sensitive cells are killed, these mutants selectively proliferate and become dominant population over time - aka VERTICAL transfer of resistance. Slow and mild.
b) Gene transfer - resistance causing gene is passed from one org to another - aka HORIZONTAL transfer of resistance. Rapid and high grade resistance.
Occurs by — Conjugation, Transformation, Transduction.w
What is cross resistance. Give examples.
Resistance to one AMA conferring resistance to another AMA to which the organism has not been exposed, is called cross resistance.
Usually occurs between chemically and mechanistically similar drugs eg. Resistance to one sulfonamide means resistance to all other sulfonamides.
However, it can also occur between some unrelated AMAs eg. Tetracyclines and Chloramphenicol.
It may not always occur in similar drugs. Eg. Microbes resistant to Gentamicin may remain sensitive to Amikacin.
Which AMAs show concentration dependent killing and time dependent killing?
Concentration dependent: Cool FAM
Fluoroquinolones
Aminoglycosides
Metronidazole
Time dependent: GMB
Glycopeptides (vanco, teico)
Macrolides
Beta lactams
3 reasons for using antimicrobial combination therapy.
- To achieve synergism
- To prevent emergence of resistance
- To broaden the spectrum of antimicrobial action
