Antibiotics Mode of Action and Mechanisms of resistance

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Antibiotics: Mode of Antibiotics: Mode of Action and resistance Action and resistance Antibiotic Antibiotic Chemical substance Chemical substance Natural, semi synthetic and wholly Natural, semi synthetic and wholly synthetic synthetic Effective at low concentration Effective at low concentration ( ( μ μ /ml) /ml) Bacteria static or bactericidal Bacteria static or bactericidal Dr Ellabib MS

description

Antibiotics: Mode of Action and Mechanisms of resistanceAntibiotic    Chemical substance Natural, semi synthetic and wholly synthetic Effective at low concentration (μ/ml) Bacteria static or bactericidalDr Ellabib MS Criteria for antibiotic for bacteria  Selectively toxicBactericidal (killing) Bacteriostatic (growth inhibition)  No harm to patient  Destroy structuresPresent in bacteria Not present in host Antibiotics work together with immune system M

Transcript of Antibiotics Mode of Action and Mechanisms of resistance

Page 1: Antibiotics  Mode of Action and Mechanisms of resistance

Antibiotics: Mode of Antibiotics: Mode of Action and resistanceAction and resistance

AntibioticAntibiotic Chemical substanceChemical substance Natural, semi synthetic and wholly syntheticNatural, semi synthetic and wholly synthetic Effective at low concentration (Effective at low concentration (μμ/ml)/ml) Bacteria static or bactericidalBacteria static or bactericidal

Dr Ellabib MS

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Criteria for antibioticCriteria for antibiotic Selectively toxic for bacteriaSelectively toxic for bacteriaBactericidal (killing)Bactericidal (killing)Bacteriostatic (growth inhibition)Bacteriostatic (growth inhibition)

No harm to patientNo harm to patientDestroy structuresDestroy structuresPresent in bacteriaPresent in bacteriaNot present in hostNot present in hostAntibiotics work together with immune Antibiotics work together with immune

systemsystem

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Minimal inhibitory concentrationMinimal inhibitory concentration

Lowest level stopping growthLowest level stopping growthe.g. zone of inhibition around a disk e.g. zone of inhibition around a disk

impregnated with antibioticimpregnated with antibioticAntibiotics inhibit cell wall are bactericidalAntibiotics inhibit cell wall are bactericidalWithout cell wall osmotic pressure cause Without cell wall osmotic pressure cause

bacteria to burstbacteria to burst

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Mode of ActionMode of Action Inhibitors of cell wall synthesis (Peptidoglycan)Inhibitors of cell wall synthesis (Peptidoglycan) Inhibit Peptidoglycan biosynthesis at various stagesInhibit Peptidoglycan biosynthesis at various stages Stage one:Stage one: inhibit UDP –N-Acetylmuramic acid through inhibit UDP –N-Acetylmuramic acid through

inhibition of tranferase enzymeinhibition of tranferase enzyme FosfomycinFosfomycin Stage two:Stage two: inhibit building pentapeptides side chain inhibit building pentapeptides side chain

through inhibition of synthetase enzymethrough inhibition of synthetase enzyme CycloserineCycloserine Stage three:Stage three: inhibit reaction leading to formation of a inhibit reaction leading to formation of a

linear Peptidoglycan polymer (pyrophosphtase enzyme)linear Peptidoglycan polymer (pyrophosphtase enzyme) Vancomycin & BacitracinVancomycin & Bacitracin Stage four:Stage four: preventing cross-linking and formation of preventing cross-linking and formation of

Peptidoglycan (transpeptidase enzyme)Peptidoglycan (transpeptidase enzyme) Bound covalently to various proteins called penicillin Bound covalently to various proteins called penicillin

binding proteins (PBPS)binding proteins (PBPS) B-lactam antibioticsB-lactam antibiotics

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Chemical modification changes of B-lactam Chemical modification changes of B-lactam and their biological activityand their biological activityEarly B-lactam antibioticsEarly B-lactam antibioticsPenicillin G &VPenicillin G &V Inactive against gram negativeInactive against gram negative No penetration of outer membraneNo penetration of outer membrane Unstable to B-lactamases enzymeUnstable to B-lactamases enzyme Active against Active against streptococcus pyogensstreptococcus pyogensPencilliinase-resistant penicillinPencilliinase-resistant penicillin More stable More stable Staphylococcus speciesStaphylococcus species E.g. Methicillin and OxacillinE.g. Methicillin and OxacillinAminopencillinAminopencillin activity against gram positiveactivity against gram positive increased activity toward gram negative (increased activity toward gram negative (E. coliE. coli)) Ampicillin, AmoxilAmpicillin, Amoxil

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Antipseudomonase penicillinAntipseudomonase penicillin

Carboxypenicillin Carboxypenicillin Increased activity against -ve and decreased Increased activity against -ve and decreased

activity against +veactivity against +veCarbenicillin and ticarcillinCarbenicillin and ticarcillinUredopenicillinUredopenicillinIncreased activity against –ve and preserved Increased activity against –ve and preserved

activity against +veactivity against +vePiperacillin and mezalocillinPiperacillin and mezalocillinB-lactamases inhibitoryB-lactamases inhibitoryBinds strongly to beta-lactamaseBinds strongly to beta-lactamaseInhibit activityInhibit activityCalled suicidal agentsCalled suicidal agentsClavulanic acid & TazobactamClavulanic acid & Tazobactam

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Cephalosporin'sCephalosporin's

First generationFirst generation Old and narrow spectrum cephalosporin'sOld and narrow spectrum cephalosporin's Cephaloridine, CephalexinCephaloridine, Cephalexin 22ndnd generation generation -ve and some anaerobic bacteria-ve and some anaerobic bacteria Cefuroxime and cefoxitinCefuroxime and cefoxitin 33rdrd generation generation -ve such as pseudomonas-ve such as pseudomonas Ceftriaxone and CeftazidimeCeftriaxone and Ceftazidime 44thth generation generation Broad spectrum Broad spectrum cefpimecefpime

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Other B-lactam antibioticsOther B-lactam antibiotics MonobactamsMonobactams -ve -ve AztreonamAztreonam CarbapenemsCarbapenems -ve-ve ImipenemImipenem

Antifungal agentsAntifungal agents Chitin synthetaseChitin synthetase Polyxin and nikkomycinPolyxin and nikkomycin Glucan synthesisGlucan synthesis

cilofungincilofungin

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Compounds inhibit cell membraneCompounds inhibit cell membrane Concentration dependentConcentration dependent Effect integrity of CMEffect integrity of CM Leakage of K, proteins and nucleic acidLeakage of K, proteins and nucleic acid Disinfectants, antiseptics and polypeptidesDisinfectants, antiseptics and polypeptides

PhenolsPhenols Release compounds absorbed at 200nmRelease compounds absorbed at 200nm Inhibits electron transport chains (metabolic Inhibits electron transport chains (metabolic

activity)activity)AlcoholsAlcohols Interact with ester fatty acid and thiol group of Interact with ester fatty acid and thiol group of

proteinsproteins Used as 70% concentrationUsed as 70% concentration

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ChlorohexidineChlorohexidine Inhibit adenosine triphosphotase (ATPase)Inhibit adenosine triphosphotase (ATPase) Uptake of KUptake of K++

Polymyxin BPolymyxin B Inhibit phospholipids of –ve but not +veInhibit phospholipids of –ve but not +ve

Antifungal agents (inhibit Ergosterol)Antifungal agents (inhibit Ergosterol) Interact with phospholipids of CM directlyInteract with phospholipids of CM directly Pores and leakagePores and leakage Amphotericin B and NystatinAmphotericin B and Nystatin Indirectly inhibit ergosterol biosynthesisIndirectly inhibit ergosterol biosynthesis Cytochrome P-450Cytochrome P-450 Azoles antifungal (Miconazole, itraconazole, Azoles antifungal (Miconazole, itraconazole,

Clotrimazole )Clotrimazole ) Other non azoles such as terbifine morpholin and Other non azoles such as terbifine morpholin and

tolnaftatetolnaftate

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Inhibitor of protein synthesisInhibitor of protein synthesis

Mostly BacteriostaticMostly Bacteriostatic Selectivity due to difference in ribosome'sSelectivity due to difference in ribosome's Some toxicity –eukaryotic 70S ribosome'sSome toxicity –eukaryotic 70S ribosome's

Classes of ribosome's subunitClasses of ribosome's subunit 80s ribosome's (eukaryotic)80s ribosome's (eukaryotic) Dissociated to 60s and 40s as MgDissociated to 60s and 40s as Mg++ concentration concentration Protein to RNA (50:50)Protein to RNA (50:50) 70s (prokaryotic and eukaryotic) 70s (prokaryotic and eukaryotic) dissociate to 30s and 50sdissociate to 30s and 50s Protein to RNA (35:65)Protein to RNA (35:65) 50-55s ribosome's (mammalian mitochondria)50-55s ribosome's (mammalian mitochondria)

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Antimicrobial that bind to the 30sAntimicrobial that bind to the 30s Amino glycosidesAmino glycosides Such as Streptomycin, gentamicin, AmikacinSuch as Streptomycin, gentamicin, Amikacin Gram positive and –VeGram positive and –Ve Slight initial entry of the drug inside cellSlight initial entry of the drug inside cell Interact with chain elongation (PC) at 12sInteract with chain elongation (PC) at 12s Misreading of mRNAMisreading of mRNA abnormal protein abnormal protein formation of abnormal channelsformation of abnormal channels Increase and irreversible entry through channelsIncrease and irreversible entry through channels Blockage initiation of ribosome'sBlockage initiation of ribosome's Inhibit binding of aminoacyl-tRNA and peptide Inhibit binding of aminoacyl-tRNA and peptide

synthesis synthesis inhibit protein synthesisinhibit protein synthesis

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Tetracycline's ( Rickettsias and Tetracycline's ( Rickettsias and mycoplasma)mycoplasma)

Short acting Short acting ChlortetracyclineChlortetracyclineIntermediateIntermediate DemeclocyclineDemeclocyclineLong actingLong acting DoxycyclineDoxycyclineBlocking binding of aminoacyl-tRNA Blocking binding of aminoacyl-tRNA

acceptor site on the mRNA ribosome's acceptor site on the mRNA ribosome's complex complex

Prevent the addition of new amino acids to Prevent the addition of new amino acids to the growing peptide chainthe growing peptide chain

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Antimicrobials bound to 50s subunitAntimicrobials bound to 50s subunit

ChloramphenicolChloramphenicol Natural antibioticNatural antibiotic Meningitis, typhoid feverMeningitis, typhoid fever Associated with bone marrow toxicityAssociated with bone marrow toxicity Reversible effectReversible effect Bind to a region on 50s close to site bound Bind to a region on 50s close to site bound

aminoacyl-tRNA in peptidyltransferase centeraminoacyl-tRNA in peptidyltransferase center Blocking addition of new amino acidsBlocking addition of new amino acids Prevent growing of protein chainPrevent growing of protein chain Inhibit peptide bound formationInhibit peptide bound formation

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Macrolides (erythromycin, Macrolides (erythromycin, claritromycin and claritromycin and spiramycin)spiramycin) +ve bacteria, +ve bacteria, mycoplasma, legionellamycoplasma, legionella Resistant commonResistant common Stimulate dissociation of peptidy-tRNA from Stimulate dissociation of peptidy-tRNA from

ribosome's during translocation stepribosome's during translocation step Interrupting completion of peptide chain formationInterrupting completion of peptide chain formation

Lincosamides (Lincomycin & Clindomycin)Lincosamides (Lincomycin & Clindomycin) Similar to chloramphenicol and erythromycinSimilar to chloramphenicol and erythromycin +ve cocci+ve cocci Resistant commonResistant common Anaerobic bacteriaAnaerobic bacteria

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Inhibitors of protein synthesis

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Fusidic acidFusidic acid

Bind to 70s ribosome'sBind to 70s ribosome'sActive against gram positive cocciActive against gram positive cocciInhibits polypeptide chain elongationInhibits polypeptide chain elongation

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Inhibitor of nucleic acid synthesisInhibitor of nucleic acid synthesis

To toxicTo toxic Some are used to treat tumor, viral and serious Some are used to treat tumor, viral and serious

bacterial such as TBbacterial such as TB DNA inhibitionDNA inhibition result in cell division inhibitionresult in cell division inhibition Effect Extra chromosomal elements of DNA Effect Extra chromosomal elements of DNA

and plasmidsand plasmids Effect bacterial response to environmental Effect bacterial response to environmental

changeschanges RNA inhibitionRNA inhibition Inhibit protein synthesisInhibit protein synthesis

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Nucleic acid inhibitors (Two groups)Nucleic acid inhibitors (Two groups)

Compound interfere with precursor of Compound interfere with precursor of nucleic acid (purine, pyrimidine)nucleic acid (purine, pyrimidine)

Sulfonamides and trimethoprimSulfonamides and trimethoprim

Compounds interfere with nucleic acid Compounds interfere with nucleic acid synthesis at the polymerization stagesynthesis at the polymerization stage

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rifampinrifampinMycobacterium tuberculosisMycobacterium tuberculosisInhibit DNA-dependent RNA polymeraseInhibit DNA-dependent RNA polymerase

Minimal or core enzyme Sigma factor (RNA)

, , 1 and ω subunits

RNA polymerase inhibitorsRNA polymerase inhibitors

RNA polymeraseRNA polymerase

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Rifampin continuousRifampin continuous Form a tight one to one complex with Form a tight one to one complex with subunit subunit Prevent protein synthesis (chain initiation)Prevent protein synthesis (chain initiation)

DNA gryases or topoisomerase inhibitorsDNA gryases or topoisomerase inhibitors quinolonesquinolones Nalidixic acid, ciprofloxacinNalidixic acid, ciprofloxacin Called nick closing enzymeCalled nick closing enzyme Enzyme play important role in supercoil strand DNA Enzyme play important role in supercoil strand DNA Supercoiling is completed the single strand DNA is Supercoiling is completed the single strand DNA is

abolished by an enzyme that seals the nicked DNAabolished by an enzyme that seals the nicked DNA The enzyme is known as DNA gryase or The enzyme is known as DNA gryase or

Topoisomerase 2Topoisomerase 2

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DNA gryase or Topoisomerase 2DNA gryase or Topoisomerase 2

Four subunits and two were identified as Four subunits and two were identified as AA and and

AA subunit introduce the nick and seal subunit introduce the nick and seal the nick they produced initiallythe nick they produced initially

Nalidixic acidNalidixic acid subunit subunit Responsible for supercoil Responsible for supercoil Norofloxacin & ciprofloxacinNorofloxacin & ciprofloxacinMay interfere withMay interfere with AA andand subunitsubunit

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Inhibitors of Folic Acid SynthesisInhibitors of Folic Acid Synthesis SulfonamidesSulfonamides TrimethoprimTrimethoprim

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Anti- Mycobacterial AntibioticsAnti- Mycobacterial Antibiotics

Para-aminosalicylic acid (PSA)Para-aminosalicylic acid (PSA) BacteriostaticBacteriostatic

DapsoneDapsone BacteriostaticBacteriostatic

treatment of leprosy (treatment of leprosy (Mycobacterium lepraeMycobacterium leprae))

Isoniazid (INH)Isoniazid (INH) bacteriostatic bacteriostatic inhibits synthesis of mycolic acids.inhibits synthesis of mycolic acids.

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FurantoinFurantoin Gram positive and negativeGram positive and negative Urinary tract infectionUrinary tract infection Damaging DNADamaging DNA

Nitro-imidazole (metronidazole)Nitro-imidazole (metronidazole) Anaerobic bacteria and protozoaAnaerobic bacteria and protozoa Reduced to Nitro radical compoundsReduced to Nitro radical compounds Acts as nuclease and damaging DNAActs as nuclease and damaging DNA

GriseofulvinGriseofulvin Antifungal agentAntifungal agent Dermatophytes infection onlyDermatophytes infection only Effect nuclear functionEffect nuclear function Interfere with microtubules during separation of Interfere with microtubules during separation of

chromosomes in cell division at the metaphasechromosomes in cell division at the metaphase

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Antibiotic Mechanisms of Antibiotic Mechanisms of ActionAction

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Microbial resistance to antimicrobial Microbial resistance to antimicrobial agentsagents

Clinical resistanceClinical resistance By mutation or acquisition of a plasmidBy mutation or acquisition of a plasmid Provides a selective advantageProvides a selective advantage Single or multiple stepsSingle or multiple stepsCross resistance Vs multiple resistanceCross resistance Vs multiple resistance Cross resistanceCross resistance single mutationsingle mutation closely related antibioticsclosely related antibiotics Multiple resistanceMultiple resistance multiples mechanismsmultiples mechanisms Unrelated antibioticsUnrelated antibiotics

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Genetic basis of resistanceGenetic basis of resistance

MutationMutation For the origin of some resistant variantsFor the origin of some resistant variantsAcquisitionAcquisition Transfer of genetics material from R to S microorganismTransfer of genetics material from R to S microorganism Confined by genes on Chromosomal or plasmidConfined by genes on Chromosomal or plasmid Chromosomal mediated resistantChromosomal mediated resistant Remain with the particular bacterial cellRemain with the particular bacterial cell And OffspringAnd Offspring Plasmid mediated resistantPlasmid mediated resistant Self replicating extra chromosomal DNASelf replicating extra chromosomal DNA Widely distributed in natureWidely distributed in nature Often transmissible Often transmissible Often Carry resistant determinants to many drugsOften Carry resistant determinants to many drugs

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Other function of plasmidOther function of plasmid

Carry genes allow bacteria to attach to mucosal Carry genes allow bacteria to attach to mucosal surfacesurface

Produce toxinsProduce toxins Invade and colonize host cellsInvade and colonize host cells

Transformation of plasmid resistantTransformation of plasmid resistant Conjugation (direct cell to cell contact)Conjugation (direct cell to cell contact) Transduction (bacteriophage vector)Transduction (bacteriophage vector) Transformation (uptake DNA from environment)Transformation (uptake DNA from environment) Transposition (transformation via transposonsTransposition (transformation via transposons

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Transduction (Transduction (bacteriophagesbacteriophages vector)vector)

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TransposonsTransposons

So called jumping genesSo called jumping genes Movable DNA elementsMovable DNA elements Carrying resistant genesCarrying resistant genes Jump or hop from plasmid to plasmid Jump or hop from plasmid to plasmid From plasmid to chromosomalFrom plasmid to chromosomal Found in many bacteriaFound in many bacteria Carrying resistant to many antibioticCarrying resistant to many antibiotic Main cause of hospital and community outbreaks Main cause of hospital and community outbreaks

resistant resistant

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Plasmid from Epidemiological Plasmid from Epidemiological viewpointviewpoint Most important type of resistantMost important type of resistant TransmissibleTransmissible Usually highly stableUsually highly stable Convert resistant to different class of antibioticsConvert resistant to different class of antibiotics

Often associated with other characteristicsOften associated with other characteristics Requirements for antibiotic activity and mechanisms resistantRequirements for antibiotic activity and mechanisms resistant

Properties of antibiotic required for efficacyProperties of antibiotic required for efficacy Penetration to target site in sufficient amountPenetration to target site in sufficient amount Evade inactivation enzymes by microorganismEvade inactivation enzymes by microorganism Interaction with target molecules to initiate an effectInteraction with target molecules to initiate an effect

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Steps of resistant mechanismsSteps of resistant mechanisms Cellular barrier to drug penetrationCellular barrier to drug penetration Reduce antibiotic activityReduce antibiotic activity Altered target moleculesAltered target molecules Interact less effectively with drug with retain Interact less effectively with drug with retain

functionfunction May use additional pathway insensitive to the May use additional pathway insensitive to the

drugdrug Modifying or inactivating enzymesModifying or inactivating enzymes Rendering antibiotic ineffectiveRendering antibiotic ineffective

Two or more of these mechanisms give rise to Two or more of these mechanisms give rise to high level of resistant than any one high level of resistant than any one mechanisms alonemechanisms alone

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Resistant due to permeabilityResistant due to permeabilityBeta lactamBeta lactam Poor permeabilityPoor permeability change in porin channelschange in porin channels MutationMutation Such asSuch as Neisseria gonorrhoeae Neisseria gonorrhoeae Outer membrane compositionOuter membrane composition Lipoplysaccharides, lipids and proteinsLipoplysaccharides, lipids and proteins Pseudomonas aeruginosaPseudomonas aeruginosa Usually display resistant to other antibioticsUsually display resistant to other antibiotics

E. coli deficient mutant in porin channelsE. coli deficient mutant in porin channels Was sensitive to imipenem becauseWas sensitive to imipenem because Due to its compact zwitterionic structureDue to its compact zwitterionic structure Permit rapid penetrationPermit rapid penetration PBP2 per cell 20PBP2 per cell 20 Require only few drug molecules for antimicrobial Require only few drug molecules for antimicrobial

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AminoglycosidesAminoglycosides loss or reduction in outer membrane proteinsloss or reduction in outer membrane proteins Enterobacteriacae Enterobacteriacae Appearance of new outer membrane proteinsAppearance of new outer membrane proteins Or alteration in surface LipoplysaccharidesOr alteration in surface Lipoplysaccharides Affect intracellular uptake of AminoglycosidesAffect intracellular uptake of Aminoglycosides Ps. aeruginosaPs. aeruginosa MLS AntimicrobialsMLS Antimicrobials Intrinsic low level resistant to erythromycinIntrinsic low level resistant to erythromycin Limited drug permeabilityLimited drug permeability EnterobacteriacaeEnterobacteriacae Reduced drug uptakeReduced drug uptake Staph. epidermidisStaph. epidermidis ChloramphenicolChloramphenicol Loss of outer membrane proteinsLoss of outer membrane proteins Diminish uptake of drug in Diminish uptake of drug in Ps. aeruginosa Ps. aeruginosa (acquired)(acquired)

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Tetracycline'sTetracycline's Poor penetrationPoor penetration Change in outer membrane (proteins, porin)Change in outer membrane (proteins, porin) Alteration in LipoplysaccharidesAlteration in Lipoplysaccharides Ps. AeruginosaPs. Aeruginosa (intrinsic) (intrinsic) Poor penetration Poor penetration plasmid-mediated changes in transportplasmid-mediated changes in transport systemsystem AcquiredAcquired Anaerobic bacteriaAnaerobic bacteria

QuinolonesQuinolones Decrease level of major outer membrane proteinsDecrease level of major outer membrane proteins EnterobacteriacaeEnterobacteriacae Cross resistant with unrelated antibioticsCross resistant with unrelated antibiotics

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Folate pathway inhibitorsFolate pathway inhibitors Permeability barriersPermeability barriers IntrinsicallyIntrinsically Ps. aeruginosaPs. aeruginosa TrimethoprimTrimethoprim AcquiredAcquired Diminished level of putative proteinsDiminished level of putative proteins Enterobacteriacae Enterobacteriacae TrimethoprimTrimethoprim Cross resistant to other unrelated drugs classesCross resistant to other unrelated drugs classes Decrease intracellular penetrationDecrease intracellular penetration Intrinsic or acquiredIntrinsic or acquired Gram negative bacteriaGram negative bacteria sulphonamidessulphonamides

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Resistant due to altered target moleculesResistant due to altered target moleculesBeta-lactam antibioticsBeta-lactam antibiotics Altered penicillin-binding proteins (PBPS)Altered penicillin-binding proteins (PBPS) PneumococciPneumococci Staph. aureusStaph. aureus Methicillin Resistant Methicillin Resistant Staph. aureusStaph. aureus (MRSA) (MRSA) PBP2 alterationPBP2 alteration Lower affinity to drugLower affinity to drug Resistant gene located on transposable genetic elementResistant gene located on transposable genetic element Should be consider resistant to all beta-lactam drugsShould be consider resistant to all beta-lactam drugsAminoglycosidesAminoglycosides Mutation affecting binding to ribosomal target Mutation affecting binding to ribosomal target Streptomycin and kanamycinStreptomycin and kanamycin Alteration of 12s proteinAlteration of 12s protein Control binding of drugs to 30s ribosomal subunit Control binding of drugs to 30s ribosomal subunit Staph. aureus, Ps. aeruginosaStaph. aureus, Ps. aeruginosa and mycobacterium and mycobacterium

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Macrolides-LincosamidesMacrolides-Lincosamides

Barrier to penetrationBarrier to penetration Intrinsic In EnterobacteriacaeIntrinsic In Enterobacteriacae Alteration in 50s ribosomal subunitAlteration in 50s ribosomal subunit Plasmid-mediatedPlasmid-mediated Found on transposonsFound on transposons Staph. aureus., streptococci, Pneumococci, BacteroidesStaph. aureus., streptococci, Pneumococci, Bacteroides Demethylation of adenine group of 23s rRNADemethylation of adenine group of 23s rRNA Decrease binding to 50s ribosomal subunitDecrease binding to 50s ribosomal subunit

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ContinuousContinuous Inducible or constitutiveInducible or constitutive

Inducible bacteriaInducible bacteria Show resistant to erythromycin and sensitive to Show resistant to erythromycin and sensitive to

ClindomycinClindomycin Sub inhibitory concentration of erythromycinSub inhibitory concentration of erythromycin Increase methylase enzymeIncrease methylase enzyme Induced cells became resistant to all MLSInduced cells became resistant to all MLS

Constitutive cellConstitutive cell Resistant to MLS without prior antibiotic Resistant to MLS without prior antibiotic

exposureexposure

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QuinolonesQuinolones Mutation in DNA gryase A and B subunitMutation in DNA gryase A and B subunit E. coliE. coli RifampinRifampin Single step mutation in B-subunit RNA Single step mutation in B-subunit RNA

polymerasepolymerase E. coliE. coliFolate pathway inhibitorsFolate pathway inhibitors Low affinity to dihydropteroate synthetaseLow affinity to dihydropteroate synthetase Hyper production of enzymeHyper production of enzyme Gram negative bacteriaGram negative bacteria TransposonsTransposons sulphonamidesulphonamide

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Folate pathway inhibitorsFolate pathway inhibitors

Low affinity to dihydrofolate reductaseLow affinity to dihydrofolate reductase Hyper production of enzymeHyper production of enzyme TrimethoprimTrimethoprim

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Resistant Resistant duedue to inactivation of to inactivation of

antimicrobialantimicrobial

Beta-lactam antibioticsBeta-lactam antibiotics Most common and understand mechanismsMost common and understand mechanisms Dozens of enzymesDozens of enzymes Differing in their substrate profileDiffering in their substrate profile Potential for inhibition by B-lactam inhibitorsPotential for inhibition by B-lactam inhibitors Physical characteristicsPhysical characteristics Divided into Four groups based onDivided into Four groups based on

Preferred antibiotic substratePreferred antibiotic substrate Inhibition by Clavulanic acidInhibition by Clavulanic acid Based on Bush Scheme classificationBased on Bush Scheme classification

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Classification schemes of Classification schemes of BushBush

Enzyme class OR Groups characteristicEnzyme class OR Groups characteristicExampleExample

OneOne cephalosporinase not inhibitedcephalosporinase not inhibited chromosomal chromosomal enzyme of enzyme of Ps. Ps. by Clavulanic acidby Clavulanic acid aeruginosaaeruginosa and and Ent. Ent. CloacaeCloacae

2a-2c2a-2c Pencilliinases and cephalosporinasePencilliinases and cephalosporinase plasmid mediated Tem-plasmid mediated Tem-typetype

inhibited by Clavulanic acidinhibited by Clavulanic acid Staph, Kleb, chromosmStaph, Kleb, chromosmGroup 3Group 3 MetalloenzymesMetalloenzymes Imipenem hydrolyzing Imipenem hydrolyzing

enzyme of enzyme of Ps. MaltophiliaPs. MaltophiliaGroup 4Group 4 Pencilliinases not inhibited Pencilliinases not inhibited chromosom enzyme of chromosom enzyme of

Clavulanic acid Clavulanic acid PsPs. . Cepacia Cepacia

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Gram positive bacteriaGram positive bacteria Presented by exoenzyme of Staph, EnterococcusPresented by exoenzyme of Staph, Enterococcus Less active against cephalosporin and stable Less active against cephalosporin and stable

penicillin'spenicillin's Inhibited by Clavulanic acidInhibited by Clavulanic acid

NB:NB: Border line Oxacillin resistant (hyper producer of Border line Oxacillin resistant (hyper producer of enzyme)enzyme)

Gram-negative bacteriaGram-negative bacteria Many has been describedMany has been described Plasmid or chromosomal mediatedPlasmid or chromosomal mediated Common among nosocomial pathogensCommon among nosocomial pathogens EnterobacteriacaeEnterobacteriacae Ps. aeruginosaPs. aeruginosa and Acinetobacter spp and Acinetobacter spp

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Plasmid-mediated B-Plasmid-mediated B-lactamaselactamase

Such as TEM (Hydrolyzing ampicillin)Such as TEM (Hydrolyzing ampicillin)TEM3 (CTX) hydrolyzing cefotaximeTEM3 (CTX) hydrolyzing cefotaximeTEM5 (CAZ) hydrolyzing CeftazidimeTEM5 (CAZ) hydrolyzing CeftazidimeInhibited by B-lactamase inhibitorsInhibited by B-lactamase inhibitorsInducible chromosomally-mediatedInducible chromosomally-mediated Produced at low concentration before antibiotic Produced at low concentration before antibiotic

exposureexposure Hyper production after exposureHyper production after exposure Resistant to many B-lactam antibioticsResistant to many B-lactam antibiotics Ps. aeruginosaPs. aeruginosa, Enterobacter, Enterobacter

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AminoglycosidesAminoglycosides Acetylation of amino groupsAcetylation of amino groups Adenylation Adenylation Phosphorylation of hydroxyl group Phosphorylation of hydroxyl group Plasmid or chromosomal modifying enzymesPlasmid or chromosomal modifying enzymes Enzyme may be located on transposonsEnzyme may be located on transposons Staph. aureusStaph. aureus or or Ps. AeruginosaPs. Aeruginosa

MLSMLS Esterase enzymeEsterase enzyme Plasmid bornPlasmid born Klebseilla pneumoniaeKlebseilla pneumoniae E. coliE. coli ErythromycinErythromycin

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ChloramphenicolChloramphenicol Drug inactivation by enzymeDrug inactivation by enzyme Major mechanisms of resistant Major mechanisms of resistant Gram positive bacteriaGram positive bacteria By acetyltransferase enzymeBy acetyltransferase enzyme Plasmid and inducible in Plasmid and inducible in Staph. aureus Staph. aureus andand

EnterococciEnterococci Constitutive in gram negative and plasmid located on Constitutive in gram negative and plasmid located on

transposonstransposons Anaerobic bacteriaAnaerobic bacteria Enzyme identified as nitroreductaseEnzyme identified as nitroreductase Bacteroides fragilisBacteroides fragilis

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Tetracycline'sTetracycline's

Transposons element mediated resistantTransposons element mediated resistant Promoting active drug effluxPromoting active drug efflux Drug detoxificationDrug detoxification Bacteroides fragilisBacteroides fragilis

Notes:Notes: active efflux I a mechanism involving certain protein by active efflux I a mechanism involving certain protein by

which the cell pumping the drug outwhich the cell pumping the drug out

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Antimicrobial cross resistantAntimicrobial cross resistant

Between drugs from same classBetween drugs from same class Beta-lactam (MRSA)Beta-lactam (MRSA) AminoglycosidesAminoglycosides Inactivating enzymesInactivating enzymes Ps aeruginosaPs aeruginosa MLSMLS Staph. AureusStaph. Aureus Different classesDifferent classes Permeability mutantPermeability mutant Altered outer membrane proteinAltered outer membrane protein

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Different classesDifferent classes Gram negative bacteriaGram negative bacteria Quinolones, trimethoprim, chloramphenicolQuinolones, trimethoprim, chloramphenicol Single or many plasmidsSingle or many plasmids Resistant to multiple classes of antibioticsResistant to multiple classes of antibiotics

Reduction of antimicrobial resistant and synergismReduction of antimicrobial resistant and synergism SynergismSynergism Two drug combined togetherTwo drug combined together 0.25 of MIC of each drug0.25 of MIC of each drug Exert higher activity than that achieved by each drug Exert higher activity than that achieved by each drug

alonealone Used to prevent resistantUsed to prevent resistant Rifampin and streptomycin for TBRifampin and streptomycin for TB

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ContinuousContinuous

Rifampin plus Vancomycin for endocarditisRifampin plus Vancomycin for endocarditis B-lactam plus aminoglycosides for –ve B-lactam plus aminoglycosides for –ve Amphotericin B plus 5-flourocytosine for Amphotericin B plus 5-flourocytosine for

Cryptococcus neoformansCryptococcus neoformans Empirical for unknown organisms or mixed Empirical for unknown organisms or mixed

infectioninfection Metronidazole plus gentamicinMetronidazole plus gentamicin