1. Infections are caused by the invasion and multiplication of microbes in body tissues, which may result in local cellular injury or clinically apparent infectious disease. 2. Infections can be classified based on their occurrence, source, clinical effects, and how they spread. Common sources of infection include human beings, insects, animals, soil, water, and food. 3. The pathogenicity and virulence of microbes are determined by their ability to adhere, invade tissues, produce toxins, and spread from person to person.

1. INFECTION AND PATHOGENECITY 1

3. 2 Definition Invasion (entry,fixation) and multiplication of microbes in body tissues, which may be clinically unapparent or result in local cellular injury due to competitive metabolism, toxins, intracellular replication or antigen antibody response. All infections not results in Infectious disease.

4. Classification of infections 1.Based on Occurrence: a).Primary infection: Infection is first time with a microbe. b).Reinfection: Subsequent infections with same microbe. c).Secondary infection: Infection followed by lowered Host immunity by preexisting disease. 4

5. d). Focal infection: Localized infection with generalized symptoms. Ex: Appendicitis, Tonsillitis e).Cross infection: New infection in a patient from another host or source. f).Nosocomial infection: If cross infections occur in hospitalized individual (Hospital acquired infection). 5

6. g). Iatrogenic infection: Infections by means of Investigative & therapeutic procedures. 6

10. 3).ANIMALS: Infectious diseases transmitted from animals to man. ZOONOSES. a).Bacterial: Leptospira, plague from Rat. b).Viral : Rabies from dog. c).Protozoa: Leishmaniasis from dog. d).Helminths : Hydatid disease from dog Tape worms : Cattle , Pig. e).Fungal: Zoophilic dermatophytes - Dog. 10

12. 1.Contact: i) Direct ex: STDs. ii) Indirect : Through contaminated fomites like Toys, Pencils, Clothing. Ex: Diphtheria, Trachoma. METHODS OF TRANSMISSION 12

15. 5. Congenital transmission: (Transplacental , Vertical transmission) Placental defects results in Congenital transformation of microbes and results in malformations. ( Teratogenic infections ). Ex : To R C H complex . 15

25. TYPES OF INFECTIOUS DISEASES 1. Depending on location: Superficial a). Localized Deep seated. b). Generalized. Bacteremia : Septicemia : Bacteria + Toxins. Pyemia : Bacteria , Toxins and Multiple abscesses in internal organs. 26

26. 2. Depending on Spread : A. Endemic : Constantly present in a particular area. Ex: Typhoid, Malaria. B. Epidemic : Rapid spread with involving many persons. Ex: Influenza. 27

28. BE AWARE of INFECTIONS & INFECTIOUS DISEASES