19 - obat anti & steril 02 english

7/28/2019 19 - OBAT ANTI & Steril 02 English

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ANTIMICROBIAL DRUG

Dr. Muh. Nasrum Massi, Ph.DBagian Mikrobiologi Fak. Kedokteran Unhas


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Antimicrobial Agents

Microbiocidal kills, e.g. bacteriocidal Microbiostatic inhibits growth but does not kill, e.g.

bacteriostatic Narrow spectrum drug specific for one genus, e.g.

Mycobacterium, or one group of organisms, e.g. Gram negatives Broad spectrum good for all bacteria Selection of Drugs depends on: - microbial sensitivity - side effects - biotransformation will it remain active in the body? - distribution must reach correct site of infection


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Antibiotic ResistanceMechanisms:

1. Antibiotic is inactivated by microbial enzymes, e.g.penicillinase will destroy

penicillin

2. Antibiotic is prevented from reaching its target, e.g. effluxpumps in the bacterial

membrane pump actively pump out drugs; e.g. antibioticcannot penetrate across

the cell wall or membranes3. Target for the antibiotic has been altered by mutation Genes for several different drug resistance mechanisms

are often found on R plasmids which can be readily transferred from bacterium to

bacterium


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Antibacterial Agents1. Cell Wall Inhibiters

- excellent selective toxicity (means will only harmbacteria not us!)

- targets peptidoglycana) Penicillins and Cephalosporins

Penicillins Pen G, Ampicillin, Amoxicillin, Methicillin Cephalosporins Cefoxitin, Cephalothin, Cephadrine o all have similar structures and inhibit the cross-linking of

PG o only work on actively growing and dividing cells when PG

is being made


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o most differ due to particular side groups which are added toenhance

activity, e.g. Pen G only works with Gram positives but once youadd

the amino group (NH2) to make Ampicillin the drug can get past

the bulky LPS on Gram negative cell surfaces and work for them too o many penicillin resistant bacteria exist, make -lactamase (penicillinase) which cleaves the lactam ring structure of these antibiotics, cephalosporins are still left intactb) Vancomycin blocks linkage of NAG and NAM of the PG o used for MRSA (methicillin resistant Staphylococcus aureus)c) Bacitracin same function as vancomycin, very toxic so used

externally as an ointment, e.g. Polysporin


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2. Protein Synthesis

Inhibitersa. Aminoglycosides Streptomycin, Gentamycin, Neomycin o bind to ribosomes and block translation o good for aerobes, Gram negativesb. Tetracyclines Chlorotetracycline, Doxycycline, Methacycline o binds ribosome and prevents the addition of new amino acids to the growing peptide chain, blocks t-RNA o broad spectrumc. Erythromycin binds ribosome and prevents its movement along the mRNA o broad sprectrumd. Rifampcin (Rifampin) o blocks RNA Polymerase so inhibits transcription no mRNA made

o no mRNA means no protein o can penetrate tissues so good for treating abcesses, spinal cords infections, brain infections o orange colour so when excreted can get orange urine, tears, sweat o broad spectrum


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3. Membrane Inhibiters Polymyxin B o incorporates into the cell membrane and pokes holes causes cell lysis o very toxic targets our membranes too o used for antibiotic resistant bacteria , e.g. Pseudomonas aeruginosa

4. DNA Replication Inhibiters Quinilones Ciprofloxacin, Norfloxacin, Nalidixic Acid o binds DNA Gyrase and blocks unwinding of DNA o broad sprectrum5. Sulfa Drugs (Sulfonamides) Para-amino benzoic acid (PABA) analogs Trimethoprim,

Sulfamethoxazole PABA is the bacterial metabolic building block to make Folic Acid o Folic Acid is an essential metabolite o Drugs block folic acid production o We get folic acid from our diet and do not produce it like bacteria o Broad spectrum


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6. Isoniazid (INH)

o very narrow spectrum, only

Mycobacterium species, e.g. Mycobacterium tuberculosis

o blocks the synthesis of the

unusual compounds found only in mycobacterial cell walls (mycolic

acids)


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Antifungal Agents

- some risk of toxicity as fungi are eucaryotes like us - most target fungal lipid production so tend to be quite specific for fungi1. Polyenes o Amphoteracin B, Nystatin o Alter the permeability of fungal membranes by inserting into membranes and poking holes o Used topically for yeast infection, e.g. thrush, vaginitis2. Imidazoles o Miconazole, Ketoconazole o Interfere with fungal sterol production o Side effects liver damage and liver is the site of our sterol production o Yeast infections3. Griseofulvin

o interferes with fungal cell division o taken orally but locates in the skin and nails o used for nail infections o must take for 6-8 months, or until infected nail grows out


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Antiprotozoan Agents

- high toxicity problem - very few drugs, all highly specific for one type of

protozoa1. Quinine

o Chloroquinine, Fluoroquinine o Antimalarial agent o Interferes with DNA replication of the malaria protozoa

during a specific stage of its life cycle2. Metronidazole (shelf name Flagyl) o inhibits metabolism of anaerobic organisms o used for certain protozoa (Giardia lamblia beaver

fever), certain bacteria (Clostridium difficle), and yeast infections


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Antiviral Agents

1. Nucleotide Analogs

o block viral replication

o many, e.g. Acyclovir Herpes infections; AZT

targets Reverse Transcriptase of HIV

2. Interferons

o just like our naturally produce compound

o triggers cells to produce an enzyme thatblocks viral replication

o best for RNA viruses


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INTRODUCTION Antibiotic: chemical substance produced by mo (mainly

fungi) low concentration: inhibit growth of other mo used to treat infectious disease

Antimicrobials(AM): a substance that can prevent mogrowth or can kill mo:

Natural AM, synthetic or semisynthetic AM

Chemotherapeuticals: chemicals used to prevent or treatdisease.

Antibiotic as chemotherapeutical can work as:

Bacteriostatic and bactericidal


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Desired antibioticcharacteristic:

Prevent growth or disrupt pathogenic mo butcause no damage to host.

Bactericidal > bacteriostatic.

Does not result in bacterial resistance

Effective to as much bacteria as possible

Does not cause allergy or other side effects.

Must be steadily active in plasma, exudate, andother body fluid.

Soluble in water and stable.


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Rational treatment: right target, right dose, right

regiment and right method of drug administration

For a rational antibiotic treatment, it is important to

know:

1. Microbiology : the etiological agent of infection &

still sensitive tests are needed

2. Clinical: infected tissue

3. Pharmacology: drug mechanism, toxic

characteristic, side effects


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ANTIBIOTIC CLASSIFICATION BASED

ON ACTIVITY MECHANISM

A. Antimicrobials that inhibit cell wallsynthesis

B. Antibiotics that inhibit cell membranefunction

C. Antimicrobials that inhibit DNAstructure and function

D. Antimicrobials that inhibit proteinsynthesis


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A. Antimicrobial that inhibit cell wall

synthesis

Bacterial cell wall containmucopeptides=peptidoglycan

Gram positive bacteria: >> peptidoglycan incomparison to Gram negative bacteria

Peptidoglycan: polysaccharide that is cross boundwith polypetide. the cross binding is the resultof transpeptidase reaction.

Inhibiting substance to this enzyme inhibitcross binding formation inhibit cell wallsynthesis.


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-lactam antibioticA. Penicillin

Synthetic penicillin :methicillin, nafcillin, andisozazolyl penicillin (cloxacillin, dicloxacillin,

oxacillin) Penicillin with broad spectrum:

aminopenicillin ( ampicillin, amoxycillin),carboxy-penicillin ( : cerbenicillin, ticarcillin),and piperacillin.

Penicillin with broad spectrum could not stand penicillinase used together with antibiotics which inhibit -laktamase, exp. asam clavulanic, sulbactam.


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B. Cephalosporin Produced by Cephalosporin. Structure

and mechanism is similar to penicillin, structural basis of syntheticcephalosporin

Spectrum: broad. Toxicity : more toxic than penicillin

subtly nephrotoxic.


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Circulating Cephalosporin:

First generation cephalosporin : oral andinjection cefazolin, cephalexin, dancephalothin.

Second generation cephalosporin:ke>an injection: cefamandole,cefaclor, cefoxitin, dan cefuroxime.

Third generation cephalosporin: ke>aninjection cefotaxime, dan ceftriaxone.

Fourth generation cephalosporin: Ke>aninjection.


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3. Other -laktam antibiotics Carbapenem: imipenem: very broad

spectrum

Monobactam: Aztreonam : negative gram aerobic, member of Pseudomonas

B Other cell all s nthesis


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B. Other cell wall synthesis

inhibiting antibiotics

Cycloserine: autotoxic, should not be used

Produced by: Streptomyces orchidceus

Active to coliform, proteus & bsl tbc

Vancomycin: inhibit peptidoglycan

polymerization, narrow spectrum,

bactericidal to Gram positive coccus

> toxic than penicillin, renal toxicity target


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Bacitracin:

Produced by: Bacil lus subti l is,

Prevent peptidoglycan polymerization

Bactericidal to Gram positive bacteria

Nephrotoxic & autotoxic by parenteral

administration

> Used topically


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C. Antibiotic that inhibit membrane

function Cell membrane functions as osmotic barrier to

regulate diffusion of intracellular and

extracellular fluid.

Substance working on cell membrane is

independent and starts soon after bacterial cell

encounters the antibacterial agent

This substance can hardly differentiate betweenmicrobial cell and host tissue cell toxic seldom used.


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Antimicrobials that inhibit

membrane function

Polymyxin: produced by Bacil lus polymyxa (A, B, C, D, and E.) only polymyxin B

and polymyxin-E (colisin) are usedMechanism: forms bond with outer part ofcell membrane cell structure & osmoticfeatures change.

Bactericidal mainly for: P. aeruginosa

Not active against fungi.


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. Polyenes:

Microlide antibiotics selectively inhibit growth of

microorganism with sterol containing membrane.Important in this group: antifungal amphotericin B & nystatin yeast, fungi,other eukaryotic cells

Does not inhibit procaryotic bacteria that lack

sterol in their membranes.


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D. Antimicrobials that interfere with

DNA structure & function

Only few are clinically used because of its

toxicity

DNA have two main functions: duplication& transcription

All substances interfere with DNA

structure effects all levels ofmetabolism and cell growth


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Antimikrob yang mengganggu DNA

Mitomycin: produced by Streptomycesspp.

Bacteriostatic because interference in DNAreplication

Not recommended for treatment becase its toxic Quinolone (Nalidixic acid) & Fluoroquinolone

(oflxacine, ciprofloxacin)

All are synthetic, and have similar structure and

unique mechanism


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Obat golongan quinolone:

Nalidixic acid: first introduced from this group it was used for treatment withoutcomplication now replaced with newquinolones

Norfloxacine & Ciprofloxacine

Spectrum:belongs to enterococcus, streptococci,and Pseudomonas

Ciprofloxacine is the most potential activefor most part of gram negative and grampositive bacteria, used orally forrespiratory tract infection and digestivetract infection


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Metronindazole: for treatment of anaerobicinfection and infection of several protozoans

Not useful for facultative anaerobes and

aerobes

Synthetic as derivative of 5-nitromidazole

Novobiocin: Produced by Streptomyces

niveus, inhibit DNA multiplicationBactericide maily for Gram positive

bacteria. Currently not used for treatment


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E. Antimicrobials that inhibit

protein synthesis

Protein synthesis is the end result of two

processes:

RNA synthesis on DNA template(Transcription)

RNA dependent protein synthesis

(Translation)


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1. Antimicrobials that inhibit

transcription

In transcription inhibition the following

things occur:

- change in DNA template

Inhibition in RNA polymerase.


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Antibiotics that belong to this group are : Actinomycin, produced by Streptomyces inhibit RNA

polymerase along DNA template.

Spectrum: positive Gram and negative Gram bacteria-

Gram not much used for its toxicity. Rifampicin: produced by Streptomyces mediterrane

binds to RNA-polymerase enzyme so there is no RNA

formation.

Broad spectrum: mainly against Gram positive bacteria m& mycobacteria. Main drug to treat tuberculosis and

leprae & for meningitis prophylaxis or meningococci.


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2. Antimicrobials that inhibittranslation

Inhibiton of translation occur if:

a. There is disturbance to sub-unit 30S ribosome

b. There is disturbace to sub-unit 50S ribosome.

Inhibition to sub-unit 30S ribosome

Mechanism of activity of this group is: Prevent binding of m-RNA to template DNA

Inhibit acceptance of aminocyl


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Antimicrobials that belong to

this group are:

1. Aminoglykosides: similar chemical,pharmacological, toxic, and antimicrobialfeatures.

Included: Streptomycin, Neomycin, Kanamycin,Gentamycin, Tobramycin, Amikacin, andNetilmicin.

If administered together with antibiotic goodsynergy, because both are bactericidal.

Toxic to the nervous system and kidney.


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2. Tetracyclines

Natural antibiotic produced by Streptomyces,(tetracycline and derivatives: chlortetracycline,oxytetracyclin.

Synthetic: methacyclin doxycyclin, and minocyclin

Bakteriostatic with broad spectrum.

Effective for intracellular bacterial infection &alternative drug to penicillin.

Tetracycline is not useful for treatment because it is notsecreted by kidney.

Tetracycline toxicity: GI & candida superinfection &other fungi

Not allowed for children & pregnant woman


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2. Inhibition to sub-unit 50S

ribosome

Inhibition to sub-unit 50S ribosome occur if

there is disturbance in:

binding of peptidyl-t-RNA peptidyl bond formation

translocation

A ti i bi l th t b l t thi


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Antimicrobials that belong to this

group are:

Chloramphenicol: first antimicrobia tobe synthesized in laboratory. Broadspectrum, anaerobic bacteria included.

First choice for treatment of tiphoidfever, and meningitis by N. meningitidis.

Toxicity : can cause pansitopenia

because of obstruction tohaematopoetik system


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The macrolides a (erythromycin, azitromycin): A specialantibiotic containing lactone macrocyclic circle consistsof 12-22 carbon atom binding to one or more sugars.

Narrow spectrum & toxic to the heart.

Antibiotic of this group:

Erythromycin: the most important in macrolides.Mainly bacteriostatic, but bactericidal if applied in highconcentration.

First choice in treatment ofMycoplasma pneumoniae, L.pneumophila, diphteria, and pertussis.

Also used as an alternetive to infection of strept. Group Aand patients allergic to penicillin.


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The linkomycines (lincomycin dan clindamycin).

Second spectrum of this drug = erythromycin, althoughthere is no chemical relationship.

Both are active against strept. group A, & staph.Producing penicillinase.

Clindamycin: lincomycin derivative absorbed bettercompared to lincomycin.

Activity > to anaerobic bacterial infection mainly

Bacteroides fragil is.

Because of its spectrum, low toxicity, and clinical efficay is most suitable to replace penicillin.


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Griseofulvin: specifically for treating

fungi with chitinous cell wall

Not useful for bacteria and fungi with cellwalls composed of cellulose, exp. Yeasts.


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F. Antibacteria that inhibit

metabolite intermediates

Most of bacteria need folic acid self synthesized

using PABA (para-amino-benzoic acid) as basic

material.

Antibiotic group that inhibit folic acid synthesis

and interferes with purine and pyrimidine

metabolism are antibiotics with similar structures

to PABA, such that folic acid synthesis isdisrupted because PABA is replaced by the

antibiotic.


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Antibacteria that belong to this

group are:

Sulphonamides: sulfadiazine,

sulfafurazole, sulfamethoxazole,sulfoxazole, sulfamethoxazole

Bacteriostatic with broad spectrum.

Well reabsorbed in the intestine inadequate amount in the blood after pre-

oral treatment.


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Minor features of sulphonamides:

Second administration could result in

hypersensitivity reaction.

High dosis administration: cause

haemotological abnormality & crystal

formation in genitourinary tract.

Causes: an. Haemolitic because of its toxic

effect to the liver.

Toxic to kidney.


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Trimetoprim: structure is similar to

hydrofolic acid able to bind to

dihydrofolate reductase enzyme needed

for folat metabolism.

Sulphamethoxazole-trimetoprim (co-

trimoxazole): combination synergistic

Frequently used for ISK and bacterial

gastroenteritis.


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Other drug similar to PABA

Sulphones

Sulphon derivative known as Dapsone:Treatment of infection by genus Mycob.,

commonly used for treating leprae.Toxic reaction in dapson administration: an.haemolytic, peripheral neuropathy, dermatitis,and eritema nodosum.

P-Aminosalicylic acid (PAS). PAS activity isspecifically against M. tbc

Bacteriostatic: similar structure to PABA invivo could be inhibited by PABA.


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BACTERIAL RESISTANCE TO

ANTIBACTERIAL DRUG

A. Intrinsic Resistance

B. Mutational Resistance

C. Acquisition of Resistance genes


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Intrinsic resistance

Related to bacterial structure: bacterial cell wall

permeability. Bacterial natural immunity is

carried by genes inside the chromosome. Exp.Immunity of P. aeroginosato antibiotic.

Resistance caused by mutation (Mutational

resistance)

Bacterial resistance is the result of chromosomal

mutation bacteria previously sensitive to

antimicrobial drug becomes resistant.


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Mutations


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Acquisition of resistance genes

Bacteria resistance occur as the result of:

- movement of plasmid carryingresistance gene ( R ) from other bacteria

already resistant to a particular antibiotic.

- formation of a new chromosomal gene.


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MECHANISM OF BACTERIAL

RESISTANCE TO ANTIBIOTIC

Antimicrobial inactivation by enzym activity(Enzymatics inactivation)

Resistance occur by change in bacterial cell wall

permeability. Change in target molecule.

Bacteria alters synthetic pathway utilized byantimicrobials.

Antimicrobials is actively excreted out ofbacterial cell.

Occurrence of tolerance


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A. Inactivation of antimicrobials by enzyme

activity (Enzymatics inactivation)

Penicillin inactivation: hydrolysis of -lactam ring by -lactamases.

Aminoglycoside inactivation: alteration

caused by acetyltransferase andphophorylase, nucleotidases activities unable to bind to ribosome.

Chloramphenicol inactivation:

chloramphinecol acetyltransferases havesimilar activity mechanism to aminoglycosidetransferases.


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B. Resistance by change in cell wall

permeability.

Porin: outer membrane protein specific to Gramnegative bacteria plays a role in entrance ofhydrophilic antimicrobials.

Porin mutation: antimicrobial transportation into thecell is hindered bacteria becomes resistent tomultiple antimicrobials (multi-resistant)

Lipopolysaccharide (LPS): inhibit the entrance ofhydrophilic antimicrobials through the cell wall.

Mutant containing small amount of polysaccharidecapsules & small amount of LPS will be morepermeable to many antimicrobials.


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Membr. transport proteins. Mutation of

membrane transport protein causes bacterial

resistance to tetracycline as the result of

reduction of transportation into the cell. Electron transport. The entrance of

aminoglycosides into the cell is dependent on

electron transport into oxygen. Thats why

aminoglycoside is not effective against

anaerobic bacteria & facultative bacteria in

anaerobic environment, like abscess.


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D. Change in target molecule.

Antimicrobial targets could be:

Cytoplasm: penicillin-binding protein (PBP),

Membr. Cytoplasm: ribosom 30S atau ribosom 50S.

Change in target molecule reduced bacterial affinitytowards antibacterial.

Example

Change of 30S ribosome bacterial resistance toaminoglyside.

Change of 50S ribosome bacterial resistance tomacrolide

Change of DNA gyrase: bacterial resistance toquinolone.


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E. Bacteria changes synthetic pathway

utilized by antimicrobials.

The formation of mutant enzyme change

in synthetic pathway. Exp. Bacteriaresistant to vancomycin produce an enzyme

with low affinity to vancomycin.


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F. Antimicrobials are actively excreted from the

bacteria.

Bacterial resistance to tetracycline is caused by

the formation of a new transport protein whichcould actively excreted antimicrobials out of

bacterial cell.

G. Occurrence of tolerance

With the lost of outer membrane permeability &

autolytic enzyme inactivation, changes of

bactericidal substance into bacteriostatic

substance would occur.

THE DANGER OF IRRATIONAL


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THE DANGER OF IRRATIONAL

ANTIMICROBIAL USE

Increase in strains resistant ( R) to

antibody.

Disease suffered by patients gets moresevere.

Increase in mortality.

Increase in infection.

Increase in treatment cost.


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ANTIBACTERIAL SENSITIVITY

TESTING

Sensitivity testing: to understand bacterial

sensitivity towards a particular antibiotic.

There are two methods frequently used toobserve sensitivity to antibiotic, which are:

Tube Dilution Method

Diffusion Method


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Diffusion Method: only to see resistance

Diffusion Method is recommended by the

National Committee of ClinicalLaboratory Standard (NCCLS) United

States.


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Tube Dilution Method : to determine MIC &

MBC

MIC : minimum concentration ofantibacterials which could still inhibit the

growth of bacteria.

MBC :minimum concentration ofantibacterials which could still kill

bacteria.

19 - obat anti & steril 02 english

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