Bacterial Infection PDF

ion f e ct l In ria c t e Ba DR. ZAKARIA ELTAHIR  Bacterial Infection It is the invasion of the body by pathogenic bacteria and the development of pathological changes  Mode of Infection 1. Exogenous...

ion f e ct l In ria c t e Ba DR. ZAKARIA ELTAHIR  Bacterial Infection It is the invasion of the body by pathogenic bacteria and the development of pathological changes  Mode of Infection 1. Exogenous infection — From environment — Patients or carriers — Routes of infection: 1. Skin & mucus membrane contact 2. Inhalation 3. Ingestion  Mode of Infection 2. Endogenous infection q By pathogenic bacteria that are normally present in the body such as: — Streptococcus viridans in the mouth — Pneumococci in the nasopharynx — E. coli in the intestine q Infection occurs when the defense mechanisms of the body are overcome.  Effects of Infection 1. Inflammation 2. Toxemia 3. Blood invasion by bacteria (bacteremia, septicemia) 4. Sapraemia 5. Immunity & hypersensitivity  Toxaemia It is the circulation of bacterial toxins in the blood causing pathological & clinical manifestation  Types of Bacterial Toxins 1. Exotoxins: produced by gram positive bacteria as Diphtheria bacilli, Shigella, Streptococci, staphylococci 2. Endotoxins: released from the bodies of dead gram negative bacteria as Typhoid bacilli  Manifestations — Fever, headache, weakness, increased metabolic rate — Degeneration- heart, kidney & liver — Anaemia- bone marrow depression — Necrosis & hemorrhage of adrenal cortex [fatal] Adrenal Gland Necrosis  Bacteraemia q It is transient presence of small number of bacteria in the blood stream without toxic manifestation q Bacteria enter the blood from a septic focus as: tonsillitis, sinusitis, extraction of tooth.  Effect of Bacteraemia q Bacteria are phagocytosed by reticulo-endothelial system. q Sometimes localized in tissues forming lesions as: osteomyelitis, sub acute bacterial endocarditis.  Septicemia q It is the circulation and multiplication of large number of virulent bacteria and their toxins in the blood stream q The condition is highly fatal  Causative Organisms q Pyogenic bacteria- Streptococci, Staphylococci, Pneumococci q Bacilli- Bacillus proteus, bacillus anthrax, bacillus pestis  Effect of Septicemia Ø Red cell hemolysis- anemia Ø Petechial hemorrhage due to capillary destruction Ø Degeneration & necrosis- heart, liver & kidney Ø Acute swelling of the spleen Ø Acute bacterial endocarditis Petechial Hemorrhages  Pyaemia — It is the circulation of septic emboli in the blood stream and their arrest in different organs causing multiple small abscesses — It has a high mortality rate — Pyogenic bacteria- especially Pyaemic Abscess- Myocardium Staph aurous  Pathological Picture Ø Organs affected showed multiple small abscesses- lung, kidney, liver brain,… Ø Toxemia- degeneration of organs Ø Leukocytosis- infection Ø Leucopenia- more common due to toxemia  Sapraemia q The presence of toxic metabolites in the blood stream derived from the action of saprophytic bacteria on necrotic tissue q The condition occurs in gangrene