Antibakteri 2011
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Pengertian Antibiotik Substansi dihasilkan oleh mikroorganisme (:
bacteria, fungi, actinomycetes) utk menekan pertumbuhan mikroorganisme lain dan membunuhnya.
Sekarang istilah antibiotik sering disamakan dg antimikroba karena banyak yg merupakan senyawa semisintetik maupun senyawa hasil sintesis metabolit mikroba.
4
Antibiotik bersifat : Antibiotik bersifat :
• Toksik secara selektif pada bakteri, tetapi tidak toksik pada host • Merusak struktur yang ada pada bakteri, tetapi tidak ada pada host.
Kategori Antibiotik Bakteriostatik
Secara reversibel menghambat pertumbuhan bakteri
Bakterisidal Membunuh bakteri
SejarahSejarah In 1928, Sir Alexander Fleming, a In 1928, Sir Alexander Fleming, a
Scottish biologist, menemukan bahwa Scottish biologist, menemukan bahwa Penicillium notatum,Penicillium notatum, merusak merusak pertumbuhan bakteri staphylococcuspertumbuhan bakteri staphylococcus
Mekanisme Kerja
1.Menghambat sintesis dinding sel
2.Merubah permeabilitas membran
3.Menghambat sintesis protein
4.Menghambat sintesis asam nukleat
5.Menghambat biosintesis asam folat (anti metabolit)
Antibiotik Penghambat Sintesis Dinding Sel
Umumnya bersifat bakterisidal Menghambat sintesis peptidoglikan
Komposisi peptidoglikan : Peptido-glycan Polymer
(amino acids + sugars) Gula; NAG & NAM
N-acetylglucosamine (NAG)
N-acetylmuramic acid (NAM)
Asam Amino berikatan silang dg NAG & NAM
Mekanisme penghambatan sintesis peptidoglikan :
Pd sikloserin (analog D-ala) Menghambat konversi enzimatik L-ala mjd D-
ala Menghambat sintesis D-ala-D-ala
Pd basitrasin : Menghambat reaksi defosforilasi dalam
transport sub unit peptidoglikan menembus membran
TRANSPORT OF TRANSPORT OF PEPTIGOGLYCAN SUBUNIT PEPTIGOGLYCAN SUBUNIT ACROSS MEMBRANEACROSS MEMBRANE
Cell membraneCell membrane
undecaprenolundecaprenol
PPPP
Cell wallCell wall
TRANSPORT OF TRANSPORT OF PEPTIGOGLYCAN SUBUNIT PEPTIGOGLYCAN SUBUNIT ACROSS MEMBRANEACROSS MEMBRANE
Cell membraneCell membrane
undecaprenolundecaprenol
PP
PP
Cell wallCell wall
TRANSPORT OF TRANSPORT OF PEPTIGOGLYCAN SUBUNIT PEPTIGOGLYCAN SUBUNIT ACROSS MEMBRANEACROSS MEMBRANE
Cell membraneCell membrane
undecaprenolundecaprenol
PPPP
Cell wallCell wall
TRANSPORT OF TRANSPORT OF PEPTIGOGLYCAN SUBUNIT PEPTIGOGLYCAN SUBUNIT ACROSS MEMBRANEACROSS MEMBRANE
Cell membraneCell membrane
undecaprenolundecaprenol
PPPP
Cell wallCell wall
TRANSPORT OF TRANSPORT OF PEPTIGOGLYCAN SUBUNIT PEPTIGOGLYCAN SUBUNIT ACROSS MEMBRANEACROSS MEMBRANE
Cell membraneCell membrane
undecaprenolundecaprenol
PPPP
Cell wallCell wall
MINUSMINUS BACITRACINBACITRACIN
CellCell membranemembrane
undecaprenolundecaprenol
PP
Cell wallCell wall
TRANSPORT OF TRANSPORT OF PEPTIGOGLYCAN SUBUNIT PEPTIGOGLYCAN SUBUNIT ACROSS MEMBRANEACROSS MEMBRANE
21PLUSPLUS BacitracinBacitracin
Cell membraneCell membrane
undecaprenolundecaprenol
PPPP
Cell wallCell wall
TRANSPORT OF TRANSPORT OF PEPTIGOGLYCAN SUBUNIT PEPTIGOGLYCAN SUBUNIT ACROSS MEMBRANEACROSS MEMBRANE
Mekanisme penghambatan sintesis peptidoglikan (lanjutan) :
Pd vancomycin : Berikatan dg D-ala-D-ala Menghambat ikatan silang (transpeptidasi)
Pd antibiotik betalaktam (penisilin, sefalosporin, monobactam) :
Berikatan dan menghambat enzim (penicillin binding protein) yg mengkatalisis transpeptidasi
Antibiotik Perubah Permeabilitas Membran
Mekanisme pd polimixin B : Berikatan dengan lipid A (komponen dari
lipopolisakarida) Berikatan dg fosfolipid Sehingga merusak membran luar (pada gram
negatif)
Antibiotik Penghambat Sintesis Protein
Inhibitor Tahap Inisiasi 30S Ribosomal Subunit (Aminoglycosides,
Tetracyclines, Spectinomycin) 50S Ribosomal Subunit (Chloramphenicol,
Macrolides)
Inhibitor tahap Elongasi Elongation Factor G (Fusidic acid)
Review of Initiation of Protein Synthesis
30S1 32 GTP
1 2 3 GTP
Initiation Factors
mRNA
3
1
2 GTP
30S Initiation Complex
f-met-tRNA
Spectinomycin
Aminoglycosides
12
GDP + Pi 50S
70S Initiation Complex
AP
X mRNA
Review of Elongation of Protein Synthesis
GTP
AP
Tu GTP Tu GDP
Ts
TsTu
+
GDPTs
Pi
P ATetracycline
AP
Erythromycin
Fusidic Acid
Chloramphenicol
G GTPG GDP + Pi
G
GDP
AP
+GTP
X ikatan peptida
X translokasi
X EF-G
X aminoasil tRNA
Aminoglikosida (bactericidal)streptomycin, kanamycin, gentamicin, tobramycin, amikacin, netilmicin, neomycin (topical)
Macrolides (bacteriostatic)erythromycin, clarithromycin, azithromycin, spiramycin
Chloramphenicol, Lincomycin, Clindamycin (bacteriostatic)
Tetracyclines (bacteriostatic)tetracycline, minocycline, doxycycline
Spectinomycin (bacteriostatic)
Inhibitor sintesis RNA :
Menghambat enzim RNA polimerase
Rifampin, Rifamycin, Rifampicin, Rifabutin (bactericidal)
Inhibitor sintesis DNA :
Menghambat enzim DNA girase (menghambat supercoiling)
Quinolones (bactericidal)nalidixic acid, ciprofloxacin, ofloxacin, norfloxacin, levofloxacin, lomefloxacin, sparfloxacin
Antimetabolit (Penghambat Biosintesis Asam Folat)
Sulfonamides, Sulfones (bacteriostatic)
merupakan analog para-aminobenzoic acid (PABA) dan menghambat pembentukan asam dihidropteroat.
Trimethoprim, Methotrexate, (bacteriostatic)
These antimicrobials binds to dihydrofolate reductase and inhibit formation of tetrahydrofolic acid
p-aminobenzoic acid + Pteridine
Dihydropteroic acid
Dihydrofolic acid
Tetrahydrofolic acid
Pteridine synthetase
Dihydrofolate synthetase
Dihydrofolate reductase
Thymidine
Purines
Methionine
Trimethoprim
Sulfonamides
Kombinasi sufonamid dan trimetoprim
ResistensiResistensi (klinis) terjadi bila Kadar Hambat
Minimum (MIC) antibiotik thd strain bakteri melebihi konsentrasi aman scr in vivo.
mekanisme resistensi
Perubahan permeabilitas membran sel :
- Influx : menyebabkan obat tdk bs masuk
sel (krn mutasi transporter)
- Efflux : Menyebabkan obat dikeluarkan dr sel
(mis pd tetrasiklin) Obat diinaktivasi oleh enzim mikroba (-
lactamase, Chloramphenicol Acetyl Transferase)
mekanisme resistensi (lanjutan)
Target berubah (krn mutasi) : Penicillin binding proteins (penicillins) RNA polymerase (rifampin) 30S ribosome (streptomycin)
Terbentuknya enzim sensitif dg enzim resisten : Plasmid mediated acquisition of a resistant enzyme (sulfonamides, trimethoprim)
Antimicrobial Resistance
Relative or complete lack of effect of antimicrobial against a previously susceptible microbe
Increase in MIC
What Factors Promote Antimicrobial Resistance?
Exposure to sub-optimal levels of antimicrobial
Exposure to microbes carrying resistance genes
Inappropriate Antimicrobial Use
Prescription not taken correctlyAntibiotics for viral infectionsAntibiotics sold without medical
supervisionSpread of resistant microbes in
hospitals due to lack of hygiene
Inappropriate Antimicrobial Use
Lack of quality control in manufacture or outdated antimicrobial
Inadequate surveillance or defective susceptibility assays
Poverty or war Use of antibiotics in foods
Antibiotics in Foods
Antibiotics are used in animal feeds and sprayed on plants to prevent infection and promote growth
Multi drug-resistant Salmonella typhi has been found in 4 states in 18 people who ate beef fed antibiotics
MRSA “mer-sah”
Methicillin-Resistant Staphylococcus aureus
Most frequent nosocomial (hospital-acquired) pathogen
Usually resistant to several other antibiotics
Antimicrobial peptides Broad spectrum antibiotics from plants and
animals Squalamine (sharks) Protegrin (pigs) Magainin (frogs)
The Future of Chemotherapeutic Agents
Antisense agents Complementary DNA or peptide nucleic acids that
binds to a pathogen's virulence gene(s) and prevents transcription
The Future of Chemotherapeutic Agents
Antibiotic susceptibility testing (in vitro)
Bacteriostatic Antibiotics Minimum inhibitory concentration (MIC) Lowest concentration that results in
inhibition of visible growth (colonies on a plate or turbidity of liquid culture)
Bactericidal Antibiotics Minimum bactericidal concentration (MBC) Lowest concentration that kills 99.9% of
the original inoculum
Metode Uji Aktivitas AntimikrobaMetode Dilusi cair atau dilusi padat Pada prinsipnya, antibiotik diencerkan hingga
diperoleh beberapa konsentrasi. Pada dilusi cair, masing-masing konsentrasi obat ditambah suspensi kuman dalam media. Pada dilusi padat, tiap konsentrasi obat dicampur dengan media agar, lalu ditanami kuman.
Metode Difusi Cara Kirby Bauer Cara Sumuran (Cup Plate) Cara Pour Plate
•Skema penyiapan suspensi bakteri
Diambil 1 koloni bakteri dari stok bakteri
(Staphylococcus aureus atau Escherichia coli)
Dimasukkan dalam BHI 1 ml
Diinkubasi 18-24 jam pada suhu 37ºC
Diambil 100 µl, dimasukkan dalam 1 ml BHI
Diinkubasi 4-8 jam pada suhu 37ºC
Diencerkan dengan NaCl 0,9% sampai konsentrasi bakteri 108 CFU/ml
(Kekeruhan disamakan dengan Standar Mc Farland)
Diencerkan sampai 106 CFU/ml dengan BHI DS
(diperoleh suspensi bakteri dg konsentrasi 106 CFU/ml)
CONTOH
1 2 3 4 K1 K4K3K2
Tabung uji
+ suspensi bakteri 106 CFU/ml
Tabung kontrol
K1 : Kontrol media
K2 : Kontrol pelarut
K3 : Kontrol sampel
K4 : Kontrol suspensi bakteri
Diinkubasi selama 24 jam pada suhu 37C
Diamati kejernihan dalam tabung uji (Menentukan KHM)
Digores ke media padatAgar darah (Staphylococcus aureus) atau Agar Mc.Conkey ( Escherichia coli)
Diinkubasi selama 24 jam pada suhu 37C
Diamati tumbuh tidaknya koloni bakteri di atas media agar (Menentukan KBM)
Metode Dilusi Cair
NoTabung
Perlakuan% b/v
(kadar akhir)
HASIL PENGAMATAN
Kejernihan Koloni
1. 0,6125% K +2. 1,25% J -3. 2,5% J -4. 5 % J -5. K -6. K -7. K.I J -8. K.II J -9. K.III K -
10. K.IV K +
Contoh Hasil Uji Aktivitas
Keterangan :KK = Kekeruhan + = Ada koloni bakteriJ = Jernih - = Tidak ada koloni bakteriK = Keruh
Kadar akhir = kadar ekstrak awal dibagi 2Jadi, KHM = 1,25% b/v KBM = 1,25% b/v
Kontrol (data dan gambar belum ditampilkan)K.I (Kontrol media) = 1 ml BHI DSK.II (Kontrol pelarut) = 0,5 ml aquadest + 0,5 ml BHI DSK.III (Kontrol sampel) = 0,5 ml lart obat + 0,5 ml BHI DSK.IV (Kontrol bakteri) = 0,5 ml suspensi bakteri dlm BHI DS + 0,5 ml akuades
1 2 3 4
12
34
KHM
KBM
1 2 3 4 K1 K4K3K2
Petri uji
suspensi bakteri 106 CFU/mlDg cara spread plate
Petri kontrol
K1 : Kontrol media
K2 : Kontrol pelarut
K3 : Kontrol sampel
K4 : Kontrol suspensi bakteri
Diinkubasi selama 24 jam pada suhu 37C
Diamati tumbuh tidaknya koloni bakteri di atas media agar (Menentukan KHM/KBM)
Metode Dilusi Padat
+ media padat + media padat
No No growthgrowth
Kirby-BauerKirby-Bauer
SusceptibleSusceptible Not susceptibleNot susceptible
BacterialBacterial lawnlawn
GrowthGrowth
Antibiotic diskAntibiotic disk
Chl Amp
Ery
Str
Tet
Disk Diffusion Test
Size of zone of inhibition depends on sensitivity, solubility, rate of diffusion. Compare results to
MIC tables generated using standards.
Zone diameter (mm) Approx. MIC(ug/ml) for:Antimicrobial agent
(amt. per disk)and organism R I MS S R S
Ampicillin (10ug/disk)
Enerobacteriacae <11 12-13 >14 >32 <8
Haemophilus spp. <19 >20 >4 <2
Enterococci <16 >17 >16
Tetracycline (30 g) <14 15-18 >19 >16 <4
Zone Diameter Standards for Disk Diffusion Tests
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