Download Pathogenicity and virulence

Pathogenicity and virulence
Virulence factors of bacteria
Virulence
• Microorganisms cause resulting in human
diseases
• Disease causing microorganisms possess
virulence factors.
• Virulence factors are properties of pathogens
to overcome the host defenses and to
establish an infection and cause disease.
Virulence factors
• 1. Adhesion factors
– Capsules, slime layers, surface carbohydrates, proteins, flagella
and pili aid in attachment.
• 2. Invasiveness
• enzymes that enhance invasiveness by enabling the
microorganisms to destroy body tissue and cells. Eg.
Hyluronidase, collagenase etc.
• 3. Toxicity
– Pathogens produce toxins, that disrupt the normal functioning
of the body. Classified into Endotoxins and exotoxins.
– Intoxications are diseases that result from the entrance of a
specific toxin into the host body.
Toxins
• Exotoxins : Exotoxins are soluble heat-labile proteins
that are released as the bacteria grow
– Examples: i. Neurotoxin – Botulinum toxin
– ii. Cytotoxin – Haemolysin
– iii. Enterotoxin – Cholera toxin
• Endotoxins:
– Most Gram negative bacteria
have lipopolysaccharides (LPS) in
their outer membrane of their cell
envelope.
LPS is toxic to specific hosts.
Diseases Classification and Glossary
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Endemic disease
Epidemic
Pandemic
Epidemiology
Zoonoses
Nosocomial infections
Types of Disease
– Acute disease
– Chronic
Disease Process
• Patterns of disease
– Signs and symptoms
• Stages of a disease
– Incubation
– Prodromal stage
– Period of illness
– Period of decline
– Full recovery
Transmission of infectious agents
• Portals of Entry
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Respiratory tract
Gastro intestinal tract
Genitourinary tract
Skin and wounds and paraenterel routes
• Transmission is effected by
– Direct contact transmission
– Direct faecal – oral route
– Indirect contact transmission
• Portals of exit
– Pathogens of gastrointestinal and genitourinary systems exit through body
fluids or faeces
– Pathogens of respiratory systems exit through nose, mouth fluids – during
coughing, sneezing and speaking
Diseases of the respiratory systems
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Pharyngitis or sore throat
Pneumonia
Diphtheria – Corynebacterium diphtheria
Tuberculosis – Mycobacterium tuberculosis
Diseases of the gastrointestinal tract
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Staphylococcal food poisoning -Staph aureus
Salmonellosis-Salmonella
Shigellosis
Travelers' diarrhea
Other gastroenteritis
Diseases of Central Nervous System
• A. Meningitis - Neisseria meningitis,
Haemosphilus influenza
• B. Tetanus - Clostridium tetani
• C. Botulism - Clostridium botulinum
Diseases of the cardiovascular and lymphatic
system
• Septicemia or blood poisoning E.coli,
Pseudomonas qeruginosa, Proteus sp etc.,
• Typhoid fever – Salmonella typhi
• Plague – Yersinia pestis
Diseases of the Urino-genital tract
• Urethritis and cystitis – E.coli, Klebsiella
Enterobacter, Proteus, Pseudomonas etc.,
• Leptospirosis – Leptospira interrogans
• Gonorrhea – Neisseria gonorrhoeae
• Syphillis – Treponema palladium
Fungal human Diseases
• Diseases of the respiratory tract
– Histoplarma Capsulatum, Coccidioides immitis Aspergillus
• Diseases of the gastrointestinal tract
– Aspergillus sp.
• Diseases of Vaginal tract – by Candida
• Diseases of central nervous system
– Ergotism - by Claviceps purpurea
– Meningitis - Cryptococcus neoformans
• Diseases of the skin
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Dermatomycosis - Trichophyton
• Asporotrichosis - Sporothrix
Diseases caused by Protozoa and Parasites
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Amoebiosis - Entamoeba histolytica
Vulvovaginitis - Trichomonas vaginalis
Trypanosomiaris - Trypanosoma gambiense
Malaria - Plasmodium (transmitted by mosquitoes)
• Parasitic Diseases
– Tapeworms, Elephantiasis, Schistosomiasis