1 / 33

INFECTIOUS DISEASES Dr Noha

INFECTIOUS DISEASES Dr Noha. INFECTIOUS DISEASES. Definition: Infection is the Invasion of a living tissue by pathogenic organisms and development of pathological changes. INFECTIOUS DISEASES. Mode of Infection: (1) Exogenous infection: - From the environment, a patient or a carrier.

mfridley
Télécharger la présentation

INFECTIOUS DISEASES Dr Noha

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. INFECTIOUS DISEASES Dr Noha

  2. INFECTIOUS DISEASES • Definition:Infection is the Invasion of a living tissue by pathogenic organisms and development of pathological changes.

  3. INFECTIOUS DISEASES • Mode of Infection: (1) Exogenous infection: - From the environment, a patient or a carrier. - The routes of exogenous infection are: (a) Direct contact (through skin & mucous membrane). (b) Inhalation. (c) Ingestion. (2) Endogenous infection: When commensals become pathogenic (e.g. E. coli in the intestine). - Infection occurs when defensive mechanisms of the body are overcomed (if immunity is lowered).

  4. INFECTIOUS DISEASES • Types of infectious diseases: Bacterial, Viral, Parasitic, & Fungal infections

  5. BACTERIAL INFECTIONS I - Acute bacterial infections II - Chronic bacterial infections.

  6. Effects of acute bacterial infections: 1- Cell injury 2- Inflammation 3- Immunity &/ hypersensitivity 4- Bacterial invasion of the blood &/ its products: A- Toxemia B- Bacteraemia C- Septiceamia D- Pyaemia

  7. TOXAEMIA • Definition: Circulation of bacterial toxins in the blood causing pathological and clinical manifestations.

  8. Bacterial toxins may be: - Exotoxins: Produced by gram positive bacteria as diphtheria bacilli, shigella organisms and some types of streptococci and staphylococci. - Endotoxins: Released from the bodies of dead gram negative bacteria as typhoid bacilli. - Sapremia: Toxemia occuring in cases of gangrene due to action of saprophytes on dead tissues.

  9. TOXAEMIA • Types: (1) Acute toxaemia: Occurs in acute infections as abscess, pneumonia, and diphtheria. (2) Chronic toxaemia: Occurs in chronic infections as tuberculosis

  10. TOXAEMIA • Clinical manifestations of Toxaemia:Fever, headache, general aching, and anaemia (due to bone marrow depression by the toxins).

  11. TOXAEMIA • Pathological manifestations of Toxaemia: The pathologic effects vary: - from mild effects such as degeneration & focal necrosis in parenchymatous organs (e.g. liver, kidney, heart, …), - to fatal changes that may cause death of the patient.

  12. TOXAEMIA • Severe toxaemia may kill the patient by:- toxic myocarditis → acute heart failure- acute tubular necrosis → acute renal failure. - necrosis and haemorrhage of the adrenal cortex → acute adrenal cortical insufficiency. - septic endotoxic shock.

  13. TOXAEMIA • Some bacterial toxins may show a selective involvement of living tissues:- Diphtheria toxins→ affection of peripheral nerves. - Clostridium tetani toxins→ affection of motor end plate → tetanic muscular spasm. - V. cholera enterotoxin→ massive, watery diarrhea

  14. BACTERAEMIA • Definition: Transient presence of small number of bacteria in the blood stream without toxic manifestations.

  15. BACTERAEMIA • Pathogenesis: Bacteraemia can occur in the following conditions: - After tooth extraction (Strept. viridans bacteria). - Blood spread of small number of bacteria derived from a septic focus (e.g. tonsillitis, sinusitis..). - During the course of some bacterial infections (e.g. in typhoid fever).

  16. BACTERAEMIA • Effects of Bacteraemia:(1) In most cases: the bacteria are rapidly eliminated by immune mechanisms, causing no pathological effects. (2) In some cases: the bacteria may localize in the tissues causing a pathological lesion. This is usually predisposed by an underlying cause (e.g. streptococcal viridans bacteraemia → endocarditis on top of diseased cardiac valves).

  17. SEPTICAEMIA • Definition: The circulation and multiplication of large number of virulent bacteria and their toxins in the blood stream. The condition is highly fatal.

  18. SEPTICAEMIA • Aetiology:Causative organisms: (1) Pyogenic bacteria as streptococci, staphylococci, pneumococci and gonococci. The commonest is streptococcus haemolyticus. (2) Bacilli as bacillus proteus, bacillus anthrax and bacillus pestis.

  19. SEPTICAEMIA • Aetiology: Predisposing factors:Low immunity (e.g. immunosuppressed pts, uncontrolled diabetic pts, ..). Source of infection: infected septic wounds, puerperal sepsis, acute osteomyelitis, meningococcal meningitis…

  20. Pathological featuresof Streptococcus Haemolyticus Septicaemia: 1- Effects of acute toxaemia: - Fever, headache, general aching, …. - Degenerations & focal necrosis in parenchymatous organs (liver, kidney, heart, ..). - Bone marrow depression causing anaemia (Leucopenia may occur in severe cases) - fatal complications may occur (toxic myocarditis, acute adrenal insufficiency, septic shock, ..)

  21. Pathological featuresof Streptococcus Haemolyticus Septicaemia: 2- Vascular & Haematological disorders:- Red cell haemolysis by haemolysin: causing anaemia and red staining of the intima of the vessels by the liberated haemoglobin. - Capillary haemorrhages (due to capillary destruction by streptococcal toxins) → Petechial hges in different tissues as the skin, mucous membranes.

  22. Pathological featuresof Streptococcus Haemolyticus Septicaemia: 3- Serous membranes: Serofibrinous or suppurative inflammation in the serous sacs. 4- Heart, Liver & Kidney: toxic injury

  23. Pathological featuresof Streptococcus Haemolyticus Septicaemia: • 5- Spleen:Acute Splenic Swelling Grossly:The spleen is enlarged, soft and friable. Cut surface shows a dark red semi-fluid red pulp. Microscopically:The sinuses are dilated, congested and contain excess neutrophils and macrophages. - Littoral cells lining the sinuses show active phagocytosis. - The lymph follicles are early hyperplastic. Later on they show necrosis and atrophy.

  24. PYAEMIA • Definition: Pyaemia is the circulation of septic emboli in the blood stream and their arrest indifferent organs causing multiple small pyogenic abscesses. Pyaemia has a high mortalityrate.

  25. PYAEMIA • Pathogenesis: - When a septic focus involves a vein, septic thrombophlebitis occurs. - Proteolytic enzymes in the inflamed area break down fragments from the septic thrombus. These fragments circulate in the blood stream as septic emboli. - Next the septic emboli get impacted in the small vessels of different organs producing multiple small pyaemic abscesses.

  26. PYAEMIA • Types:(1) Systemic pyaemia. - The septic emboli circulate in the systemic venous blood. - They are derived from acute osteomyelitis, puerperal sepsis, suppurativeotitis media, cellulitis and acute bacterial endocarditis. - They get arrested in the lung forming multiple pyaemic abscesses. - Smaller emboli from the lung reach the kidney, liver, brain ... etc.

  27. PYAEMIA • Types: (2)Portal pyaemia: - The septic emboli circulate in the portal venous blood. - They are derived from acute suppurative appendicitis, infected piles, acute cholecystitis, diverticulitis and septic lesions in the colon. - The emboli get arrested in the liver forming multiple pyaemic abscesses.

  28. Types: :(3) Pulmonary pyemia - The presence of septic emboli in the pulmonary circulation. - They are derived from thrombi in the systemic veins.

  29. PYAEMIA • Pathological Features: (1) The affected organ shows multiple small abscesses. The abscesses are nearly of the same size, peripheral in position, rounded in shape, yellow in colour and surrounded by a dark red zone of congestion.

  30. PYAEMIA • Pathological Features: (2) Effects of toxaemia: e.g. Cloudy swelling and fatty change in the parenchymatous organs. (3) Leucocytosis may occur in pyaemia as it is a pyogenic infection, however leucopenia is more common due to bone marrow depression by the associated toxaemia.

  31. Thank you

More Related