2. Summary
• Definition.
• Categories of Infectious Agents
• transmission and Dissemination of Microbes.
• Spectrum of inflammatory Responses to
infection.
• Special tests
3. How microorganisms cause disease?
• They can contact or enter host cells and directly
cause cell death .
• They may release toxins that kill cells at a
distance , release enzymes that degrade tissue
components or damage blood vessels and cause
ischemic necrosis .
• They can induce host immune response that ,
though directed against the invader , cause
additional tissue damage (double–edged sword ).
5. Transmission and dissemination
• Skin
• Gastrointestinal tract
• Respiratory tract
• Urogenital tract
• Some microorganisms proliferate loccally , at the site
of infection, whereas others penetrate the epithelial
barrier and spread to other site via the lymphatic the
blood or nerves.
• The major manifestations of infectious disease may
arise at site distant from those of microbe entry.
6.
7. Viruses
• Many viruses cause transient illnesses.(e.g, colds,
Influenza).
• Other viruses persist within cells of the host for
years (e.g, chronic infection with hepatitis B virus)
• Some viruses can transform a host cell into a tumor
or cancer cell (e.g, human papilloma viruses cause
benign warts and have been implicated in cervical
carcinoma.
• Different species of viruses can produce the same
clinical picture (e.g ,upper respiratory infection).
13. FUNGI
• Fungi may cause superficial or deep infections .
Superficial infection involve the skin. Hair and
nail.
• Fungal species that are confined to superficial
layers of the human skin are known as
dermatophytes (tinea).
• Certain fungal species invade the subcutaneous
tissue, causing abscesses or granuoloma .( e.g
sporotichosis and tropical mycoses)
14. • Deep fungal infection can spread systematically
and invade tissues, destroying vital organs in
inmunocompromaised hosts.
• Common species.
(Candida,Aspergillus,Cryptococcus ,
Coccidioides).
16. Spectrum of inflammatory responses
to infection
There are five patterns of tissue reaction in
infections.
• Suppurative ( purulent ) inflammation.
• Mononuclear and granulomatous inflamma-
tion.
• Cytopathic –Cytoproliferative inflammation.
• Necrotizing Inflammation.
• Chronic inflammation and scarring
17. Suppurative inflammation
• Is characterized by the production of large
amounts of pus or purulent exudate consisting
of neutrophils , necrotic cells, and edema fluid.
• Pyogenic bacteria ( pus producing) are present
in the suppurative infection.
• A common example is Acute appendicitis
• Abscesses are localized collections of pus
caused by suppuration buried in a tissue an
organ or a confined space .They are produced by
deep seeding of pyogenic bacteria into a tissue.
29. Mononuclear and granulomatous
inflammation
• Diffuse , predominantly mononuclear , intersticial
infiltrates are common feature of all chronic
inflammatory processes.
• Spirochetes and helminths provoke chronic
inflammatory responses .
• Plasma cells are seen in the primary and secondary
lesions of syphilis .
• Lymphocytes predominate in hepatitis B virus.
• Granulomatous inflammation is a distinctive form of
mononuclear inflammation.(e.g M.tuberculosis ,
Histoplasma capsulatum , schistosome .
41. Cytopathic –Cytoproliferative
inflammation
• These reaction are usually produced by
viruses.
• Characterized by cell necrosis or cellular
proliferation with inclusion bodies within
cell and multinucleate cells
• e.gs Herpes viruses or adenovirus
• Theses viruses can cause dysplastic change
and contribute to the development of
malignant neoplasms.
44. Necrotizing Inflammation.
• Is characterized by organisms that secrete
powerful toxin , can cause rapid and severe
necrosis (Gangrenous necrosis).
• Eg clostridium perfringens,c. diptheriae, e.
histolytica
45. Chronic inflammation and scarring
• The final common pathway of many
infections is chronic inflammation . For
example, chronic HBV infection may cause
cirrhosis of the liver , in wish dense fibrous
septae surround nodules of regenerating
hepatocytes
51. 1. Muir’s Textbook of Pathology, edition above 13th
2. General Pathology by Walter and Israel
3. Robbins and Cotran, Pathologic Basis of disease,
editions above 7th
REFERENCE
