1. Introduction Classification Sources of infection immunity Factors influencing level of innate immunity Exotoxins and endotoxins Virulence determinants Types of infectious diseases Method of transmission of infection

2. Pathogens Saprophytes Parasites commensals

3. Primary infection Re-infection Secondary infection Focal infection Cross infection Nosocromial infection Iatrogenic infection

4. Endogenous infection Exogenous infection CLINICAL BASIS Unapparent (subclinical) Atypical infection Latent infection

5. 1. MAN: Carrier :- Healthy carrier Convalescent carrier Temporary or chronic carrier Contact carrier Paradoxical carrier 2. ANIMAL : Asymptomatic, reservoir host Zoo noses 3. INSECTS: Vectors, mechanical, biological, extrinsic incubation period 4. SOIL AND WATER: Tetanus spores, H. capsulatuses, Water- vibrio cholerae, infective hepatitis 5. FOOD- staphylococcus

6. contact: direct- syphilis and gonorrhoea Contagious diseases Indirect contact- fomites Inhalation: respiratory infection like tuberculosis, influenza, small droplets (>0.1mm), droplet nuclei (1-10 microns diameter) Ingestion: Inoculation: tetanus spores, rabies- s/c Arbvirus- insect vectors Needles- iatrogenic- HIV AND HBV Insects: mechanical or biological congenital Iatrogenic or laboratory infection

7. Adhesion Invasiveness Toxigenecity- toxins communicability Other bacterial products- coagulase haemolysein Bacterial appendages- e.g. capsulated organisms Infecting dose-MISD (minimum infecting dose) MLSD( minimum lethal dose) Route of infection

8. Bacteraemia- transient bacteraemia Septicaemia- bacterial circulate and multiply in bloods (high, swinging fever) Pyaemia- pyogenic bacteria causing septicaemia leading to multiple abscesses in internal organs like spleen, liver, kidneys

9. endemic epidemic Pandemic Prosodemic- slowly creeping epidemics e.g. CSF Fever

10. EXOTOXINSENDOTOINS Proteins Protein polysaccharides, lipid complexes(PPL) Heat labile Heat stable Actively secreted by cells, diffuse in surrounding medium Forms part of cell wall. do not diffuse Action often enzymic No enzymic action Highly antigenic Weakly antigenic Action specifically neutralized by antibodies Neutralization by antibodies ineffective Specific pharmacological effect for each exotoxin effect non specific action common to all endotoxin Specific tissue affinity No specific tissue affinity can be toxoided cannot be toxoided Separation from culture by physical methods e.g. filtration Obtained only by cell lysis Produced mainly by gram positive bacteria and some gram negative ones like Shigella ands vibrio Produced by gram negative bacteria