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 2. Invasiveness 3. Toxicity 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 Endemic disease Epidemic Pandemic Epidemiology Zoonoses Nosocomial infections Types of Disease Acute disease Chronic

Disease Process Patterns of disease Stages of a 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 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 Pharyngitis or sore throat Pneumonia Diphtheria – Corynebacterium diphtheria Tuberculosis – Mycobacterium tuberculosis

Diseases of the gastrointestinal tract 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 Dermatomycosis - Trichophyton Asporotrichosis - Sporothrix

Diseases caused by Protozoa and Parasites Amoebiosis - Entamoeba histolytica Vulvovaginitis - Trichomonas vaginalis Trypanosomiaris - Trypanosoma gambiense Malaria - Plasmodium (transmitted by mosquitoes) Parasitic Diseases Tapeworms, Elephantiasis, Schistosomiasis