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.
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
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
g). Iatrogenic infection: Infections by means of Investigative & therapeutic procedures. 6
SOURCES OF INFECTION Types of carrier: Depending on origin: A. Healthy carrier B. Convalescent carrier C. Contact carrier: Acquires pathogen from patient. D. Paradoxical carrier. Acquires pathogen from another Carrier . 8
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