INFECTION AND MICROBIAL PATHOGENECITY (HOST MICROBE RELATION AND DISEASE PROCESS )

1. INFECTION AND MICROBIAL PATHOGENECITY (HOST MICROBE RELATION AND DISEASE PROCESS) Infection and Immunity involve the interaction between the host and infecting organisms

2. Saprophytes - Free living organism found in soil, water, air - Depend on dead and organic matters - Incapable of multiplying in the tissue - B.subtilis infect devitalized host Parasites - Can establish and multiply in host Commensals Pathogenic capable of producing disease Based on their relationship Micro Organisms

3. Symbiosis is an association between 2 species (Living together) Spectrum of Associations: Mutualism (Benefit each other E. Coli synthesize Vit B12 of Vit K Commensalism (Neither benefit nor harm) parasitize on the skin surface Parasitism (One benefits but other is harmed) E.coli causing UTI.

4. CONTAMINATION, INFECTION, INFESTATION • Contamination: Micro-organism are present in inanimate object, surface of the skin and mucus membrane (lodgement) • Infection: Invasion and multiplication in or on host tissue • Infestation: Presence of large parasites or arthropodes (lice) in or on the surface of the body

5. CHARACTERISTIC OF INFECTION • Acute disease: Symptoms develop rapidly and runs quickly • Chronic disease: Symptoms develop slowly and disappears slowly • Sub acute: Intermediate between Acute and chronic • Latent infection: Symptoms appear/reappear long after infection • Primary infection: Initial infection with a parasite in host

6. Sec. infection: Infection by a new parasite in a host whose resistance is lowered by pre-existing infection • Re – infection: Subsequent infection by the same organism in the same host • Local infection: Confined to small part of the body (Boils, abscess) • Focal infection: Confined infection from where pathogen travel other region of the body (abscessed tooth, infected sinuses)

7. Cross infection: Pt have one disease. A new infection is set up from another host or ext. source • Nosocomial infection: Cross infection in a hospital • Iatrogenic infection: Physician induced infection • (By investigative of therapatic procedure) • Endogenous infection: Infection from Internal sources • Exogenous infection: Infection from hosts own body • Inapparent infection: Infection fail to produce full set of symptoms

8. Atypical infection: Typical or characteristic clinical manifestation of the disease not present • Mixed infection: Infection by 2 or more pathogens • Super infection: Sec infection that is usually caused by agent resistant to the treatment of Pr infection • Septicemia: Presence and multiplication of pathogens in blood

9. Bacteremia: Presence but not multiplication of bacteria • Viremia: Presence of viruses in blood • Toxemia: Presence of toxins in blood • Sapremia: Presence of metabolic products of saprophytes.

10. SOURCE OF INFECTIONS • Human Being Commonest source from Human being From patient or from carrier • Carrier: Harbors the organism but do not suffer - Healthy carrier: Never suffered - Convalescent Carrier: Recovered but harbor - Temporary Carrier: Harbors < 6 months - Chronic Carrier: Harbors for several months or rest of life - Contact Carrier: Got the organism from Pt - Paradoxical Carrier: Got the organism from carrier

11. ANIMALS: May be source of infection without suffering • Zoonosis: Transmission of infections from animals to man • Bacterial: Plague from rats, Brucellosis and Tuberculosis from cows, anthrax from sheep, leptospirosis from rats etc. • Viral: Rabies from Dog, J-E from Pig etc. • Parasitic: Hydatid disease ( Dog), tape worm infection (cattle and swine) • Fungal: Ring worms (cats, dogs) histoplasmosis (bird)

12. INSECTS Mosquito's, ticks, flies Vectors: Transmit Pathogens • Biological: Pathogens multiply and undergo developmental life cycle (Malaria, Filaria, Kala- azar) • Mechanical: Transmits pathogen mechanically (house fly carry amoebic cyst, giardia cyst etc.)

13. SOIL AND WATER • Soil Spores of tetanus and Gas gangrene bacilli, Histoplasmacapsulatum etc. • Water  V. Cholerae, Hepatitis ‘A’, ‘E’ etc. • Contaminated materials: Food poisoning (S. aureus, E. Coli etc.) pre-existed infection of meat, milk etc. (S.typhimurium, myc bovis)

14. METHODS OF TRANSMISSION • Contact Transmission • Transmission by Vehicle • Transmission by Vectors

15. Contact Transmission • Direct contact: - Horizontal transmission by shaking hands, kissing, touching (genitals- herpes, etc.) - Sexual contact (syphilis, gonorrhoea etc.) - Faeco – oral (unwashed heads) • Vertical transmission: - Mother to offspring across placenta, milk. • Indirect contact: fomites, nonliving objects • Droplet infection: (Through coughs, sneezes) particles inhaled or airborne.

16. TRANSMISSION BY VEHICLES • Water-Borne: - Water contaminated with stools - polio, HVA, HVE - V. Cholera, shigella, campylobacter etc. • Air Borne: - Mainly transmission from soil, water, plants and animals. - Dust particles harboring pathogens (Staphylococci, Streptococci, Bacterial and Fungal spores. - Hospitalized patients are at a great risk. • Food Borne: - Unsanitarily cooked, refrigerated food. Gastroenteritis (botulinum toxin, aflatoxinsalmonellosis, listeriosis, HVA & HVE etc.

17. TRANSMISSION BY VECTORS • Mechanical vectors: flies (Amoebiasis, giardiasis, shigellosis etc. • Biological vectors: (Malaria, Filaria, kala-azar, plague, chagas disease etc.

18. MICROBIAL PATHOGENICITY Pathogenecity refers to the ability of microbial to produce disease or tissue injury Virulence There is a minor difference • Pathogenecity  Capacity to produce disease • Myc tuberculosis  Always pathogenic • Staph epidermidis  Rarely pathogenic • Virulence: - Intensity of the disease produced vary among different microbial species - Virulence varies among members of the same species - Organisms freshly discharged are more virulent.

19. MICROBIAL VIRULERCE FACTORS • Adhesion • Invasiveness • Toxigenicity • Enzymes and other bacteria • Inhibition of phagocytosis • Escape from host Immune response • Acquisition of Nutrients from host.

20. ADHESION • Must adhere to cell surface other wise will be swept away by the mucus of other BF • Adhesins are protein or glycoprotein found on pili (fimbrae) or capsule (receptors) • First step in the pathogenesis of many infectious diseases • Adhesion allows the organism to colonize

21. INVASSIVENESS • It is as active process • It is central to the infectious process • Some bacteria (Strepto, pneumo) release digestive enzymes that allow them to invade • Bacteria use a subs called cadherin

22. TOXIGENECITY PropertiesExotoxinsEndotoxins Chem. nature Protein LPS (Lipid) A Loc. in cell Extracellularly secreted Bound to cell wall. into the medium Released upon death Heat stability Unstable, denatured Heat stable, withstand above 60oC above 60oC Extraction Can be separated Obtained only by cell lysis Pharmacological (filtration) specific Non specific prop

23. Tissue affinity Sp. tissue affinity No tissue affinity Toxicity, high, active in very low, active in large minute dose dose Immunogenicity Highly antigenic Weakly antigenic can be toxoided can not be toxided Bacterial source GM+vebact (mostly) GM-ve Bact. Some GM-ve bact (vibrio EPTC) Fever Production Little or no fever High fever (IL-1,TNF-) Control Extra chrom. genes Chromosomal, (Plasmids) genus

24. Enzymes and other Bacterial products EnzymesBacteriaMode of action Coagulase Staph aureus Deposition of fibrin on the surface which prevents phagocytosis Hyaluronidase Str. pyogenes Spreading factor Collaginase and Cl. Perfringens facilitate spread of gas Lecithinase gangrene Haemolysin and Staph aureus, Kills RBC and WBC CytocidinStr.pyogenes, Cl.perfringenes Streptokinase Str. Pyogenes Dissolve the clot and spread infection

25. Inhibition of chemotaxis Inhibition of attachment of phagocytes Anti phagocytic subs Inhibition of Lysosome fusion Resistance to killing in phagolysosomes Escape from phagolysosome into cytoplasm Inhibition of Phagocytosis

26. ESCAPE FROM HOST IMM.RESPONSE • Antigenic variation - Trypanosomes, Malaria, Influenza virus, HIV, Borrelia sp. (Modify surface Ag) - Sch. Mansoni (Incorporate host Ag) • Super antigens • Reduction in expression of Ags - Persistent viral infection (Paramyxo, Areno, Retro virus etc.) • Immunosuppression • Antibody cleavage (Proteases cleave human Ig A)