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MEKANISME PERUSAKAN TOKSIN BAKTERI

Agustina Setiawati

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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. Eksotoksin2. Endotoksin3. Eksoenzim

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

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EKSOTOKSIN ….

Ekstoksin masuk sel host dgn cara:1) Receptor mediated endocytosis2) Bergabung dengan lisosom3) 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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Mekanisme toksisitas oleh EKSOTOKSIN ada 3:1. Menghambat sintesis protein : toksin dipteri2. Hiperaktivitas ekskresi: toksin kolera3. Penghambatan aktivitas neurotransmitter: toksin tetanus

EKSOTOKSIN ….

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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

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 SymptomsLocal 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 bacteriaFound 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

Two primary toxins & capsule geneAll 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

MEKANISME AKSI TOKSIN ANTRAK

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TRANSDUKSI SINYAL SELULER ADENILAT SIKLASE-CAMP

B. Anthracis

EF

B

LF

BB

LFEF

LF

EF Endosome

Acidic Environment

BcAMP

MAPK

EDEMA Increased expression of pro-inflammatory

mediators

IMMUNE SUPPRESSION WBCs do not divide in

the presence of pathogens; overall

decrease in phagocytosis

MEKANISME AKSI TOKSIN ANTRAK

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

Menghambat pelepasan ‘inhibitory neurotransmitter ‘ yaitu GABA – aminobutyric acid γ

MEKANISME AKSI TOKSIN TETANUS

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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 tinggiDapat dilepaskan oleh bakteri saat lisis, spt: E.coli,

Salmonella, Shigella, Pseudomonas, Haemophilus

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Menurunkan sistem imun hostMempunyai efek farmakologis yg berbeda pada konsentrasi

rendah atau tinggi

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

EndotoksinHost cell receptors (TLR) bind to

endotoxinTLR (Toll-like Receptor)

Inflammation Opsonization

MAC

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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 inflamasi2. Aktivasi komplemen pelepasan histamin yg menyebabkan vasodilatasi3. Koagulasi

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TES PIROGEN Rabbit Pyrogen Test Limulus Amoebocyte Lisate Test

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

Hemolysins Destroy red blood cells Streptolysins – group of hemolysins excreted by Streptococcus

Streptokinase Attacks fibrin clots From Streptococcus pyogenes

Hyaluronidase 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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TERIMA KASIH