MEKANISME PERUSAKAN TOKSIN BAKTERI
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Transcript MEKANISME PERUSAKAN TOKSIN BAKTERI
MEKANISME PERUSAKAN
TOKSIN BAKTERI
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Agustina Setiawati
PENDAHULUAN
Toksin : substansi terlarut yang dapat mengubah metabolisme
normal sel host sehingga kondisi fisiologisnya jg berubah
Sel penghasil = bakteri, juga berperan dalam proses yg
disebabkan oleh protozoa, cacing dan fungi
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Toksin mikroba menjadi dibedakan menjadi 2:
1. Eksotoksin
2. Endotoksin
3. Eksoenzim
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EKSOTOKSIN
Protein yg diproduksi oleh bakteri, baik yg diekskresikan atau
terikat pada permukaan bakteri dan dilepaskan ketika bakteri lisis.
Ditransport ke dalam sel host
Mengubah fisiologi dan metabolisme sel host
Umumnya terdiri dari sub unit A dan B
Contoh eksotoksin: toksin diphteri, kolera dan anthrax
EKSOTOKSIN ….
Ekstoksin masuk sel host dgn cara:
1) Receptor mediated endocytosis
2) Bergabung dengan lisosom
3) Suasana asam pd lisosom memecah
ikatan disulfida dan melepas sub unit A
dalam sel
4) Sub unit A berperan dalam berbagai
toksisitas intraseluler
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EKSOTOKSIN ….
Mekanisme toksisitas oleh EKSOTOKSIN ada 3:
1. Menghambat sintesis protein : toksin dipteri
2. Hiperaktivitas ekskresi: toksin kolera
3. Penghambatan aktivitas neurotransmitter: toksin tetanus
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ANTIGENIK EKSOTOKSIN
Eksotoksin bersifat antigenik
Aktivitas eksotoksin diturunkan oleh antibody dalam tubuh host
Eksotoksin tidak stabil, pada suatu saat sifat toksisitasnya
hilang tetapi tetap bersifat antigenik
Sifat inilah yg dimanfaatkan utk pembuatan TOXOID
TOXOID: toksin yg dilemahkan tetapi masih mempunyai sifat
antigenik (memacu produksi antibodi).
Toxoid digunakan dalam imunisasi
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CORYNEBACTERIUM DIPHTHERIAE
Corynebacterium diptheriae
Produces AB exotoxin
Gram positive rod w/ tapered ends
Significant cause of mortality until 1950s
Decline due to vaccination with toxoid (DPT)
Spread by close contact via droplets from human carriers or humans
with active infection
Common location upper respiratory tract
Sign
and Symptoms
Local infection
Severe inflammatory reaction
Severe swelling in back of neck
Sore throat, nausea, vomiting
Formation of pseudomembrane
Systemic
Toxemia as toxin is absorbed
from throat and carried by
blood to target organs
Heart and nervous system
MEKANISME AKSI TOKSIN DIPTERI
A subunit…
Mengaktivitas
elongation factor-2)
(EF-2) yg diperlukan
untuk sintesis protein
VIBRIO CHOLERAE
Vibrio cholerae
Produces A + 5B exotoxin
Gram negative vibrio
Unusual disease
Cholerae does not invade tissue
Cholerae does not damage tissue
Lives in estuaries on copepods
Humans are incidentally infected
when ingesting contaminated food
or water
SYMPTOMS OF VIBRIO CHOLERAE
Symptoms
Secretory or watery diarrhea
No blood in diarrhea
Large watery bowel movements
Loss of electrolytes
Muscle cramps
Low blood pressure
Rapid heart rate & feeble pulse
Vomiting
White blood cell count usually normal
Treatment
Usually self limiting symptoms as long as IV fluids are administered with
oral rehydration solutions
CLINICAL MANIFESTATIONS
www.who.int/entity/water_sanitation_health/dwq/en/admicrob6.pdf
TREATING CHOLERA
Sack, David, et al. 2004. Seminar: Cholera. The Lancet. 363: 223-233.
MEKANISME AKSI TOKSIN KOLERA
BACILLUS ANTHRACIS
Bacillus anthracis
Produces 2A + B exotoxin
Gram positive spore forming bacteria
Found in soil
Anthrax disease – direct exposure to spores
Inhalation – pulmonary
Ingestion – gastrointestinal
Invasion into surface wound – cutaneous
No cases involve person to person spread
SYGN AND MPTOMS OF BACILLUS ANTHRACIS
Cutaneous
Spores enter abrasions or
cut in skin
Germination of spore causes
local ulceration of the skin
Painless black eschar with
edema
Antibiotics prevent invasion
into blood stream
Usually heals completely
without scarring
SYMPTOMS OF BACILLUS ANTHRACIS
Pulmonary
Life cycle
Macrophages engulf spores
Travel to nodes
Spores germinate en route
Cells are released spreading toxins and vegetative cells into the
blood stream
Symptoms – caused by toxins
Fever and chills
Shortness of breath, & cough
Massive pleural effusions
Sepsis, shock & death
MEKANISME AKSI TOKSIN ANTRAK
Two primary toxins & capsule gene
All three genes are located on plasmids
Edema Factor A – toxin
Adenylyl cyclase enzyme – increase in cAMP
Causes edema and pro-inflammatory response
Lethal Factor A – toxin
Metalloprotease
Cleaves MAP kinase required from cell division and signaling
Causes an overall suppression of immune system
TRANSDUKSI SINYAL SELULER ADENILAT
SIKLASE-CAMP
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MEKANISME AKSI TOKSIN
ANTRAK
EF
LF
EDEMA
Increased expression
of pro-inflammatory
mediators
B
cAMP
EF
Endosome
B
MAPK
IMMUNE SUPPRESSION
WBCs do not divide in
the presence of
pathogens; overall
decrease in phagocytosis
Acidic
Environment
CLOSTRIDIUM TETANUS
Clostridium tetanus
Produces AB exotoxin
Produces irreversible muscle contraction
Spastic paralysis
Symptoms result entirely from toxin
Anaerobic gram + spore forming rod
Lives in soil usually on rusty metal
Enters from puncture wound or cut
Organism does not spread form entry point
Begins with stiff back and neck muscles
Death results from respiratory failure
MEKANISME AKSI TOKSIN TETANUS
Menghambat pelepasan ‘inhibitory neurotransmitter ‘ yaitu
GABA – aminobutyric acid γ
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ENDOTOKSIN
Endotoksin
Nama sering menyebabkan salah arti
Toksin tidak berada dalam sel bakteri, tetapi bagian membran sel
bakteri
Toksin terletak pada bagian luar membran sel bakteri
Lipopolisakarida (LPS)bakteri gram Asam lipotekoat bakteri gram +
Toksik pada konsentrasi yg tinggi
Dapat dilepaskan oleh bakteri saat lisis, spt: E.coli,
Salmonella, Shigella, Pseudomonas, Haemophilus
Menurunkan sistem imun host
Mempunyai efek farmakologis yg berbeda pada konsentrasi
rendah atau tinggi
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MECHANISM OF ACTION OF ENDOTOXINS
Endotoxins bind to
Receptors on
Macrophages
Neutrophils
Lymphocytes
Proteins of complement
Complement is a group of proteins which circulate at constant levels in the
blood
When activated complement is a powerful tool against invading pathogens
Increased inflamation, opsonization, & MAC
Endotoksin
Host cell receptors (TLR) bind to
endotoxin
TLR (Toll-like Receptor)
Inflammation
Opsonization
MAC
PIROGEN
Merupakan salah satu endotoksin, ada yg menyebutkan
ENDOTOKSIN=PIROGEN
Bagian Lipid A membran bakteri gram –
Potensi lebih rendah dibandingkan eksotoksin
Aksi tidak spesifik
Stabil terhadap pemanasan selama 30’,
Tidak bersifat antigenik (tidak bisa diubah menjadi toksoid)
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MEMBRAN SEL BAKTERI
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LIPOPOLISAKARIDA
Bagian paling luar membran sel
Total 3- 10% berat kering sel
3-4 juta molekul tiap sel
Bagian yg disebut pirogen: Lipid A
Lipid A menstimulasi sistem imun
manusia
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MEKANISME AKSI PIROGEN
LPS terikat pada protein plasma LPS binding protein (LBP)
LBP berikatan dgn reseptorpd makrofag dan monosit sehingga
menyebabkan:
1. Produksi sitokin (IL, TNF) memicu produksi prostglandin
& leukotrien inflamasi
2. Aktivasi komplemen pelepasan histamin yg
menyebabkan vasodilatasi
3. Koagulasi
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TES PIROGEN
Rabbit Pyrogen Test
Limulus Amoebocyte Lisate Test
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BACTERIAL EXOENZYMES
Enzim yg dieksresikan bakteri pada matriks ekstraseluler sel,
mempunyai berbagai aktivitas:
Merusak membran
Merusak membran sell host
Lisis sel eritrosit
Merusak matriks ekstraseluler (fibronectin, kolagen & MMP)
Mengubah aktivitas obat co: Penisilanase (hidrolisis penisilin)
EKSOENZIM
α toxin
Pore forming toxin
Common in Staphylococcus
aureus
Destroy red blood cells
Streptolysins – group of
hemolysins excreted by
Streptococcus
Streptokinase
Attacks fibrin clots
From Streptococcus pyogenes
Hyaluronidase
Hemolysins
Breaks down hyaluronic acids
in connective tissue
Similar function for
Collagenase
Elastases
DNase
DNA is viscous
Thins pus (DNA & debris)
released from WBC
CLOSTRIDIUM PERFRINGENS
Clostridium perfringens
Ananerobic gram + spore forming rod
Widely distributed in nature
Myonecrosis
Entry of spores by traumatic injury
Not highly invasive so it requires exoenzymes for a supportive growth
environment
Exoenzymes
Lecithinase lipase c – major toxin
Lyses mammalian cells indiscriminately
Substrate is phophatidylcholine
Collagenase & hyaluronidase
DNAase
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