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ANTIMICROBIAL AGENTS ANTIBIOTICS: NATURAL COMPOUNDS PRODUCED BY MICROORGANISM WHICH INHIBIT THE GROWTH OF OTHER. CHEMOTHERAPY: SYNTHETIC COMPOUNDS.
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SELECTIVE TOXICITY: THE ABILITY TO KILL OR INHIBIT THE GROWTH OF MICROORGANISM WITHOUT HARMING THE HOST CELLS.
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BACTERICIDAL: KILLS BACTERIA BACTERIOSTATIC: PREVENTS MULTIPLICATION. SPECTRIM OF ACTIVITY: BROAD SPECTRUM: G+VE& G-VE NARROW SPECTRUM: SELECTIVE ORGANISM.
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THERAPEUTIC INDEX: THE RATIO OF THE DOSE TOXIC TO THE HOST TO THE EFFECTIVE THERAPEUTIC DOSE. EXAMPLES: PENICILLIN: HIGH AMINOGLYCOSIDES: LOW POLYMYXIN B: THE LOWEST
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MECHANISMS OF ACTION OF ANTIMICROBIALS 1) INHIBITION OF CELL WALL SYNTHESIS. 2) ALTERATION OF CELL MEMBRANES 3) INHIBITION OF PROTEIN SYNTHSIS 4) INHIBITION OF NUCLEIC ACID 5) ANTIMETABOLIC OR COMPETITEVE ANTAGONISM.
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MECHANISMS OF ACTION
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ANTIMICROBIALS THAT INHIBIT CELL WALL SYNTHESIS BETA LACTAMS PENICILLINS CEPHALOSPORINS CARBAPENEMS MONOBACTAM VANCOMYCIN BACITRACIN
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FIG. 1
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- LACTAM ANTIBIOTICS: BETA LACTAM RING &ORGANIC ACID. NATURAL &SEMISYNTHETIC CIDAL ACTION BIND TO PBP, INTERFERES WITH TRANSPEPTIDATION REACTION TOXICITY: HYPERSENS. ANAPHYLAXIS, DIARRHOEA,..ETC.
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PENICILLINS: BENZYLE PENICILLIN: PENIC. V, PROCAINE PEN., BENZATHIN PEN. 6-AMINOPENICILLANIC ACID: CLOXACILLIN STAPH. AMOXYCILLIN ENTEROBACTERIA PIPERACILLIN PSEUDOMONAS
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CEPHALOSPORINS: FIRST GENERATIONS: CEPHRADINE SECOND GENERATIONS: CEFUROXIME,CEFOXITIN THIRD GENERATIONS: EXPANDED SPECTRUM THIRD GEN: GRAM –VE ONLY CEFTRIAXONE CEFTAZIDIME FOURTH GEN: CEFEPIM CEFEXIME
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VANCOMYCIN: GLYCOPEPTIDE CIDAL ON G +VE BACTERIA ONLY. INHIBIT CELL WALL SYNTHESIS INJ. ONLY. USED FOR MRSA S.EDIDER. PESUDOMEM.COLITIS. NEPHROTOXIC & OTOTOXIC.
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ANTIBIOTICS THAT ALTER CELL MEMBRANES POLYMYXIN B PEPTIDE ACTIVE AGAINST G –VE BACTERICIDAL ONLY USED LOCALLY DUE TO SERIOUS NEPHROTOXICITY
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ANTIBIOTICS THAT INHIBIT PROTIEN SYNTHESIS AMINOGLYCOSIDES TETRACYCLINES CHLORAMPHENICOL MACROLIDES
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AMINOGLYCOSIDES: BACTERICIDAL GRAM –VE BACTERIA SRTEPT.& ANAEROBES RESISTANT ACTION: INTERFER WITH BINDING OF t RNA TO 30 S SUBUNIT GENTAMICIN, AMIKACIN, NEOMYCIN INJECTABLE NEPHROTOXIC& OTOTOXIC -DOSE RELATED
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TETRACYCLINES BROAD SPECTRUM, STATIC ORAL ABSORPTION INTRACELLULAR EG. MYCOPLASMA, CHLAMYDIA BRUCELLA ALSO FOR CHOLERA NOCARDIA TWO CLASSES: SHORT ACTING: TETRACYCLINE LONG ACTING: MINOCYCLIN,DOXY. SIDE EFFECTS: TEETH DISCOLORATION, GIT DISTURBANCE
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CHLORAMPHENICOL BROAD SPECTRUM, CIDAL BIND TO 50 s RIBOSOMAL SUBUNIT AFFECT BONE MARROW CELLS AND CAUSE APLASTIC ANAEMIA SEVERE INFECTIONS: TYPHOID FEVER, HI MENINGITIS, RICKETSIA…ETC.
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MACROLIDES: ERYTHROMYCIN & CLINDAMYCIN BACTERIOSTATIC LEGIONELLA, CAMPYLOBACTER, G +VE INFECTIONS IN PTS. ALLERGIC TO PEN. CLINDAMYCIN ACT ON ANAEROBES GIT DISTURBANCE, PMC (CLIND) NEW MACROLIDES: AZITHROMYCIN, CLARITHRIMYCIN
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ANTIMICROBIALS THAT ACT ON NUCLEIC ACID RIFAMOICIN QUINOLONES METRONIDAZOLE
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RIFAMPICIN: SEMISYNTHETIC, CIDAL G +VE COCCI RESERVED FOR TB INHIBIT DNA DEP.RNA POLYMERASE RESISTANCE DEVELOP QUICKLY USED IN COMBINATION DISCOLORATION OF BODY FLUIDS HEPATOTOXIC
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QUINOLONES : SYNTHETIC,CIDAL, INHIBIT DNA GYRASE NALIDIXIC ACID : OLD,G _VE ONLY FLOUROQUINOLONES: CIPROFLOXACIN, NORFLOXACIN SYSTEMIC INFECTIONS, UTI BROAD EPECTRUM BETTER PHARMACOLOGICALLY AFFECT CARTILAGE IN ANIMALS
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Fig. 3
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ANTIMETABOLITES: SULFONAMIDES TRIMETHOPRIM COMBINATION: BACTRIM/ SEPTRIN BLOCK SEQUENTIAL STEPS IN FOLIC ACID SYNTHESIS NOCARDIA,CHLAMYDIA,PROTOZOA,P.CRANII UTI LRTI, OM.. GIT.HEPATITIS, BM DEPRESSIN, HYPERSENSITIVITY
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ANTITUBERCULOUS AGENTS FIRST LINE: INH RIFAMPICIN ETHAMBUTOL PYRAZINAMIDE SECOND LINE: STREPTOMYCIN PASA CYCLOSERINE, CAPREOMYCIN
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ISONIAZIDE (INH) BATERICIDAL INTRA& EXTRA CELLULAR MYCOBACTERIA TREATMENT & PROPHYLAXIS PREPHERAL NEURITIS
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ETHAMBUTOL CIDAL CONC.IN PHAGOLYSOSOME OF ALVEOLI OPTIC NEURITIS PYRAZINAMIDE ACID ENVIRONMENT OF MACROPHAGES HEPATITIS & ARTHRALGIA
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ANTIBIOTIC RESISTANCE IN BACTERIA INDISCRIMINATE USE OF ANTIMICROBIALS SELECTIVE ADVANTAGE OF ANTIBIOTICS TYPES OF RESISTANCE: PRIMARY: INNATE eg. STREPT. &ANAEROBES RESISTANT TO GENTAMICIN
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ANTIBIOTIC RESISTANCE IN BACTERIA (Continue) AQUIRED: 1-MUTATION: MTB R TO SRTEPTOMYCIN 2- GENE TRANSFER: PLASMID MEDIATED OR TRANSPOSONES CROSS RESISTANCE: R TO ONE GROUP CONFER R TO OTHER OF THE SAME GROUP EG ERYTHROMYCIN & CLINDAMYCIN DISSOCIATE R: R TO GENTA. DOES NOT CONFER R.TO TOBRAMYCIN
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MECHANISMS OR RESISTANCE 1-PERMIABILITY CANGED 2-MODIFICATION OF SITE OF ACTION, EG. MUTATION 3-INACTIVATION BY ENZYMES.EG. BETA LACTAMASE, AMINOGLYCOSIDES INACTIVATING ENZYMES BYPASSING BLOCKED METABOLIC REACTION EG. PABAFOILC ACID BY PLASMID MEDIATED DFR.
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PRINCIPLES OF ANTIMICROBIAL THERAPY: INDICATION CHOICE OF DRUG ROUTE DOSAGE DURATION DISTRIBUTION EXCRETION TOXICITY COMBINATION PROPHYLAXIS: SHORT TERM: MENINGITIS LONG TERM: TB, UTI, RHEUMATIC FEVER
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CRITERIA FOR IDEAL ANTIMICROBIAL: SELECTIVE TOXICITY NO HYPERSENSITIVITY PENETERATE TISSUES QUICKLY RESISTANCE NOT DEVELOP QUICKLY NO EFFECT ON NORMAL FLORA BROAD SPECTRUM
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ANTIFUNGAL AGENTS: NYSTATINLOCAL AMPHOTERICIN BSYSTEMIC ANTIVIRAL AGENTS IODOXURIDINE VIDARABINE AMANTADINE INTERFERON
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