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150 Cards in this Set
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The basus for selective action of seeral antibiotics that inhibit bacterial but not human protein sythensis is
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the difference between bacterial and human ribosomal compositions
bacterial=70s with 50s and 30s subunits human=80s with 40s and 60s subunits |
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Gram - bacteria is resistance to pencillins and cephalosporins bbecause of its
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periplasmic space between the outer membrane and the cel lwall, which contains beta lactamase enzymes
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Most common causes of ocular infectiosn
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Staph aureus
Strep pneumoniae |
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Antibiotics that inhibit bacterial cell wall synthesis
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Penicillins, Cephalosporins, Bacitracin, and Vancomycin
PC BV |
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Antibiotics that increase permeability of the acterial cell membrane
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Polymyxin B, Colistin and Gramicdine
PCG |
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Antibiotics that inhibit protein synthesisi
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Aminoglycosides, Tetracylines, Erythromicin, Chloraphenicol, Clindamycin
ATE CC |
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Antibiotics that inhibit bacterial intermediate metabolism (folic acid synthesis)
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Sulfonamides, pyrimethamine, and triethoprim
STP |
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Bacteria can share or exchange genetic material by these 4 ways
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Transformation
Transduction Conjugation Transposon insertions |
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Intrinsic resistance is
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a stable GENETIC property encoded in the bacterial chromosome and shared by ALL strains of the species
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Acquired Resistance is
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when certain strains of the species have DEVELOPED the ability to resist antbiotics. It is AQUIRED via a change in the DNA of the bacteria so that new phenotye is expressed
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Bacteria Acquire by either
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a mutation in the chromsome of the bacteria OR via transformation, transduction, conjugation or transposon insertions
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Bacteria in a resting state are not susceptible to antibiotics that inhibit cell wall synthesis, such as
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pencillins or cephalosporins
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T/F The higher the dose of the drug and the longer the drug is given to the patient, the higher the chance of developing resistance
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T
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Most EXTERNAL ocular infections can be managed with
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topically applied antibacterial agents.
However!, some forms of conjunctivitis require ORAL administration |
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Bactieral infections of the eyeldis or soft periopribal tissue like hordeoilums, dacryocystitis and blepharitis are treated with
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orally administered drugs.
MOST of these infections are caused by Gram + organisms so use highly pbactericidal penicillinase resistant antibacterial drugs |
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Most severe forms of acute dacrocystitis and perioobtal cellulitis may require this administration
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Parenteral!
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Endophthalmitis and panophthalmits require an aggresive antibacterial therapy of
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intramuscular, intravenous, subconctival and intravitreal routes of administration
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T/F Bacteristatid crugs are usually preferable to bactericidal drugs
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FALSE
Bactericidal drugs are preferred over bacteriostatic!! |
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T/F Combinations of acteriostati and bactericidal drugs may be antagonistic
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True
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Vancomycin specifically inhibits
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the transport processes of the NAM-NAG complex to the cell wall. (Stage 2 of cell wall synthesis)
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Bacitracin specifically inhibits
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The carrrier that recycles back into the cytoplasm to carry other cell wall precursors (Stage 3 of cell wall synthesis)
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Prnillins, cephalosporins, imipenem and aztreonam specifically inhibit
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transpeptidases that cause the cross linking between precursor and existing bacterial cell wall structures (Stage 4 of cell wall sythnesis)
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Pencillins which are highly effective against Gram + Bacteria
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Pencillin G and V
(Victory over Gram +) |
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Pencillins that are resistant to bacterial penicillinase
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Methacillin, Oxacillin, Cloxacillin, Dicloxacillin, and Naficillin
CD MON |
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Pencillins with extended spectra of activity
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Ampicillin and Amoxillin
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Pencillins that work on Pseudonoas
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Carbencillin, Ticarcillin, Piperacillin, Azlocillin, and Mezlocillin.
CAT PM |
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For anaerobic Gram nergative rods, staph, and strep, _________ is often administed in the form of fortified eyedrops, subconjuntival ingections, and possibly IV injections
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Penicillin G
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When Staph aureus and Staph epidermis strains produce penicillinase, we use
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Methicillin or oxacillin injected subonconj.
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Internal hordelums and acute dacryocystitis are treated with
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Cloxacillin or dicloxacillin
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Preseptal cellulitis is treated with
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Nafcillin/oxacillin and Pencillin G PLUS an Aminglycoside to cover Gram - bact.
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methicillin
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•Subconjunctival methicillin or oxacillin for corneal ulcer
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oxacillin (Ocuflox)
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•Oral cloxacillin or dicloxacillin for internal hordeolum
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cloxacillin
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•Oral cloxacillin, dicloxacillin or oxacillin for acute dacryosystitis
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dicloxacillin
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Oral cloxacillin, dicloxacillin or oxacillin for acute dacryosystitis
•Oral cloxacillin or dicloxacillin for internal hordeolum |
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nafcillin
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•Parenteral nafcillin or oxacillin and Penicillin G with aminoglycoside for preseptal cellulitis
•Parenteral methicillin or dicloxacillin with aminoglycoside for endophthalmitis |
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ampicillin
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•Less effective against bacterial sensitive to G but active against gram negatives such as Haemophilus, E. coli and Proteus
•Destroyed by penicillinase (beta lactamase) •Either by oral route with topical ciloxan for hyperacute conjunctivitis |
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amoxicillin
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•Less effective against bacterial sensitive to G but active against gram negatives such as Haemophilus, E. coli and Proteus
•Destroyed by penicillinase (beta lactamase) •Either by oral route with topical ciloxan for hyperacute conjunctivitis •Oral amoxicillin for Haemophilus acute dacryocystitis |
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carbenicillin
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•Effective against Pseudomonas, Proteus, Enterobacter & Acinetobacter
•Only carbenicillin by oral route |
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ticarcillin
piperacillin azlocillin mezlocillin |
•Effective against Pseudomonas, Proteus, Enterobacter & Acinetobacter
•All given by parenteral route (IV, IM) |
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Treatment of Clamydia?
What causes type f extremely debililating conjunctivitis? |
a. Tetracline QID 250mg. or E-mysin ointment
b. Trachoma |
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Polymyoxin is specific to what bacteria?
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a. Pseudomonas
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Cephalosporin interferes with the terminal step in bacterial cell wall formation by
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preventing proper cross liniking of the peptidogylcan. They also alter bacterial permeability, inhibit synthesis and cause bacteria to release autolysins. Some have lytic effects and others cause bacteria to grow into long filaments
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First generation cephalosporins are reactive against
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ALL start withe CEPH or CEF.
Have good gram + and modest gram - Cephalothin Cefazolin Cephaprin Cephradine Cephalexin Cefadroxil Chephalordine |
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Bacterial cornea ulcers are treated with this specific cephalosporin
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CEFAZOLIN
- active against staph. and strep, even better than bacitracin. - it can be administered both topically or subconj. injectons CEPHALORIDINE has sometimes been ubstituted for cefazolin in treatment |
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Initial treatment of endophthalmitis consits of using
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CEPHALORIDINE OR CEFAZOLIN
AND AMINOGYLCOSIDES |
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Acute dacryocystisis or mild/moderate preseptal cellulits is treated orally by what cephalosporin
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CEPHALEXIN
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Staph soft tissue periocular infections are treated with this cephalosporin
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CEFADROXIL
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Second generation cephalosporins consist of
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drugs that start with CEF
Cefamandole Cefoxitin Cefaclor Cefaranide Cefuroxime. More active then first gen. but must less active than 3rd generation |
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Third Generation Cephalosporins
(The T stands for 3rd generation) |
are MUST more active against gram - than any other generation
ALL have CEFT CEFTRIAXONE CEFTIZOXIME CEFOTAXIME CEFOPERAZONE CEFTAZIDIME |
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2 3rd generation cephalosporins that are active against P. auerginosa
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CEFOPERAZONE
CEFTAZIDIME |
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T/F because Pencillins and cephalosporins are very similar, patients who are allergic to penicillins may manifest a cross reacting allergy to cephalosporins
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TRUE
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Certain 3rd generation drugs can cause this vitamin deficieny
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vitamin K
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Bacitracin works by
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inhibiting bacterial cell wall synthesis by inhibiting the carrier which tansports the cell wall precursors from inside the cell to the cell wall.
it is BACTERICIDAL against staph strep and c. difficle |
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T/F Bacitracin is bacteriostatic against gram positive organisms
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F
bacteroCIDAL |
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T/F Since polymyxin B has a gram negative spectrum, the combination of polymyxin B and Bacitracin can be used for many surface ocular infections
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T
Bacitracin is great on gram +, so the combo covers all bases |
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Topical bacitracin preparations are effective against
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staph belpharitis. Apply to lids 1 or 2 times a day after a lid scrub. After improvement, reduce to once before bed for 1 month.
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oral use of bacitracin results in
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nephron necrosis
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Vancomycin works by
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binding to the free end of the pentapeptide and interferes with elongation of the peptidogylcan backbone.
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Vancomycin is highly effective against
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Gram +, clostridium, Corneobacteriam diphtheria and N. gonorrhoeae
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T/F Vancomycin is ototoxic and nephrotoxic
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T
Since it is topxi, it is reserved for serious infections |
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Polmyxin B and Polymyxin E work by
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acting like cationic detergents that bind to bacteria cell membrane and changes permeability of membrane by interacting with phospholipids. This allows fluid to enter the cell causing it to swell.
thus it is BACTERICIDAL |
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Polymyxin B and E are efective against
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gram - and serious Psuedonomas infections.
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Polysporin is the combo of
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Bacitracin and Polymyxin B
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T/F Topical applications or subconj infections of Polymyzin B is the drug of choice to treat corneal ulcers caused by psuedonomas
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F
Newer and less toxic penicillins and aminoglycosides are the drug of choice |
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The two most important side effects associated with systemic adminitration of Polymyxin B and E is
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neurotocitiy and nephrotoxity
HOWEVER< adverse reactions to TOPICAL polymyxin are mild. Due to the large molecular size, topically applied polymyxin does not result in significatn systemic absorption. |
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Gramacidin is
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similary to polyxin B and E, effective against gram + bacteria.
Works by altering membrane permeability causing it to swell and burst |
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T/F Aminoglycosides bind to the 30s subunity at the P12 site
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T
It inhibits fmet tRNA from binding, disrupting the code |
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Aminoglycosides are effective against
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gram - bacteria and many strains of gram + staph
STREPTOMYCIN NEOMYCIN GENTAMICIN TOBRAMYCIN AMIKACIN KANAMYCIN |
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t/f Pencillins and cephalosporeins enhance the actions of aminoglycosides
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T
they prevent cell wall repair |
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Neomycin is
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an aminoglycolyside
it is active against both gram + and -. MOST TOXIC of family. |
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Gentamycin is
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an aminglycolyside. Used topically for many gram + and gram - rods.
A good antibiotic for initial treatment of bacterial infectriosn of external eye. |
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Gentamycin treatment is
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1-2 drops QUID, and in severe cases 2 drops Q 1 hour.
Ointment is applied 2-3 times per day for 7-10 days. |
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Tobramycin is
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an aminoglycolyside that is active against P. auerginosa! and is LESS toxic then gentamycin.
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Amikacin is a semi snythetic
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aminoglycoside that is not inactivated by aminoglycoside inactivating enzymes.
It is active against many gram - bacilli and has been used for BACTERIAL ENDOPHTHALMITIS |
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T/F The aminoglycosides are the drug of choice for treating CORNEAL ULCERS DUE TO MYCOBACTERIA
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TRUE
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Side effects of aminoglycosides
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Both vestibular and auditory dysfunction can occur from systemic use. So can Nephrotoxicity, and rarely results in neuromiscular blockade.
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Inhibition of cell wall synthesis
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All bactericidal
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Increasing permeability of cell membrane
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All bactericidal
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Inhibition of protein synthesis
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Some bactericidal and some bacteriostatic
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Inhibition of intermediary metabolism
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Some bactericidal and some bacteriostatic
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Inhibition of DNA synthesis
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All bactericidal
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The 4 MECHANISMS OF BACTERIAL RESISTANCE
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Enzyme induction: drug modification or inactivation by bacterial enzymes
Receptor site adaptation: Alteration of receptor so drug can no longer bind Conformation membrane change: Formation of permeability barrier so drug can’t reach target Alteration of metabolic pathway: development of alternate pathway which bypasses reaction inhibited by drug |
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Major adverse effect of Penicillins
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Major adverse effect: ALLERGY
Cross sensitivity between drugs in group Non allergic reactions due to high conc.: CNS disturbances Hypokalemia Inhibition of normal platelet aggregation |
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ADVERSE EFFECTS OF CEPHALOSPORINS
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ALLERGY MOST COMMON
Cross sensitivity with penicillins Cause vit. K deficiency leading to bleeding Renal impairment |
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Major adverse effect of Bacitracin
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CONTACT DERMATITIS
With topical use no significant systemic absorption = no side effects |
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This type of drug is given via parenteral administration for systemic use due to poor absorption from gut and has
synergism with penicillins and cephalosporins |
Aminoglycosides
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Tetracyclines and clortetracyclines are
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BACTERIOSTATIC antibiotics isolated from streptomyces.
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Can be short, intermediate, or long acting.
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Broad spectrum against both + and -, aerobic and anaerobic bacteria, spirochetes, mycoplasma, richettisa and chlamydia and protoza
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What is Tetracycline available in
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1% suspension and ointment for topical use.
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Oral administration is available but it should not be taken with meals and dairy products
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Tretracyclines inhbits the
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bacteria's protein synthesis by bindings to the 30s but ACTING on 50s by preventing tRNA from binding.
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Tetracycline is recommended for
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prophylaxis of gonococcal opthalmia neomatum.
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Chylamidial can also be treated topically with tetracyclien but is not fulyl effective because it also needs to be treated systemically.
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In adults ora tretracycline is the DRUG OF CHOICE FOR TREATING
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CHLAMYDIAL DISEASES INCLUDING CONJUNCTIVITS AND TRACHOMA.
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oral tetracyclines can be effective for
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notuberculous phlyctenular keratoconjunctivitis, non infected corneal ulcers, lepharitis, keratitis, meiobmianitis and chalazia
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Tetracyclines should not be given to women in the last half of pregnancy, lactating women and children under 8 years old BECAUSE
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it causes negative nigtrogen balance and increase blood urea nitrogen --> INHBITIS BONE growth and discolor teeth.
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Psudotumor cerebri can occur
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Drug of choice for treating chlamydial diseases including inclusion conj and trachoma
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ORAL TETRACYCLINE
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Doxycycline/Vaibramycin is diffrent from tetracycline because it can be taken
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orally without regard to meals and diary products
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Tetracycline analogs include
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Doxycycline/Vibramycin
Minocycline |
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Macrolide Antibiotics include and work by
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Erythromycin, Azithromycin, Clarithromycin
|
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Erthyromycin is this type of antibiotic and works via
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its a macrolide and works by inhibiting protein sythensis by binding to 50s subunit.
It is bacterioSTATIC ONLY available in 5 mg ointment for topical use |
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Drug of choice for legionnaire's disease and mycoplasma pneumoniae
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Erythromycin, a macrolide
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Drug of choice for legionnaire's disease and mycoplasma pneumoniae
it is also good against gonococcal neonatorum and neonatal conj. due to chlyamidia trachomatis. |
Erythromycin
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Which macrolide is the drug of choice for Chlamydial inclusion Con?
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Azithromycin, administered orally
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Chloramphenicol works by
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binding to the P site on the 50S subunit
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T/F
Cloramphenicol is bacteriocidal |
It is BACTERIOSTATIC
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active against Gram +,-, rickettsia, chlamydia, sprochetes and mycoplasm
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The use of chloramphenicol is limited due to _______- and is only given whne
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its ability to cause fatal aplastic anemia, even when used topically on the eye!!
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it is limited to treatment of endopthalmitis following trauma or surgery, as it can easily penetrate the blood aqueoues barrier
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side effects of Chloramphenicol include
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reversible bone marrow depression, reticulocytopenia, anemia, aplastic anemia.
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Side effects of cloramphenicol first occur
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These commmonly occur weeks to months AFTER therapy.
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Toxic reaction to chloramphenicol is known as
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Toxic reaction is known as "gray syndrome".
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Can also lead to OPTIC ATROPHY
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Which drug can lead to optic atrophy?
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Chloramphenicol
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Clindamycin works by
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binding to the 50s subunit.
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It is BACTERIOSTATIC, and can be used alone or in combo with sulfadizzine to treat ocular toxoplasmosis.
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treating with Sulfacetamide can lead to an opportunistic infection of
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Can lead to C. difficle
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Sodium sulfacetamide and sulfisoxazole work by
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inhiiting folic acid synthesis. They are BACTERIOSTATIC against +,-, actinomyces, chlamydia, plasmodia, and toxoplasma.
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Are only used topically!
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T/F A number of staph are completely resistant to sulfa drugs
|
T
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What % of Sodium sulfacetamide soln is most common for treating routine bac. conj?
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10%
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Side effects to Sodium sulfacetamide include
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photosensitization, hypersensitivity reactions, topical 30% is reported to produce a decrease in corneal sensitivity.
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Oral short acting sulfa drugs are used to treat
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trachoma, and ocular toxoplasmosis
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Pyrmethamine and Trimethprin work by
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inhibiting folic acid synthesis, not allowing the reduction step to occur.
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These drugs are bacterioSTATIC
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Are powerful synergists with sulfa drugs
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Pyrmethamine and Trimethprin side effectins include
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white blood cell and plately depression, or megaloblastic anemia, may also cause stinging, itching, and hyperemia
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Nalidix acid is a
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1st generation quinolone, against Gram +, no ocular applications
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2nd generation quinolones include
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ciprofloxacin, norfloxacin, and ofloxacin. Good gainst + and some -
|
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Third generation quinolone includes
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levofloxacin, very effective against gram + and atypical pathogens
|
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4th generation quinolones include
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Moxifloxacin and gatifloxacin, vast increase against gram + and against anaerobic organisms and atypical pathogens
|
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Ciprofloxacin is a 2nd gen quinolone that is avaiable
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sstemically and topically .3%
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it inhibits supercoling
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2 drops q 2 hours for 2 days and then 2 drops q 4 hours for next 5 days
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Ciropoflaxin is used in the treatment of
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bacterial ulcerse and conjunctivitis
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Norfloxacin is a 2nd gen quinolone that is available as a topical opthalmic sol called
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Chibroxin, used for surface ocular infections
|
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Ofoxacin is a 2nd gen quinolone that is topically available and is called
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ocuflox, indicated for surface ocular infections
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Levofloxacin is a 3rd gen quinolon called
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Quizin
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Moxifloxacine and gatifloxacin are 4th gen quinolones avaible in _______% solutiosn
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Mox is .5%
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Gat is .3%
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these block DNA gyrase AND topisomerase 4 --> works well against gram -
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Also has a large bicylclic amino side change at psotion C-7, making it a large ize and thus blocking the bacterias ability to pump out the drug.
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T/F research hasd determiend that 4th gen quinolones are more efficacious against gram + then second and third drugs and equally efficacious from gram -
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TRUE
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