are disorders in which tissue damage or dysfunction is produced by microorganisms. very prevalent worldwide and major cause of morbidity and mortality. US: two of top 10 COD are infectious diseases Pneumonia Septicemia . Developing countries: Respiratory and diarrheal disease amongst the common COD.

1. Infectious Diseases
med_students0

2. Infectious Diseases
are disorders in which tissue damage or
dysfunction is produced by microorganisms.
very prevalent worldwide and
major cause of morbidity and mortality.
US: two of top 10 COD are infectious diseases
Pneumonia
Septicemia .
Developing countries:
Respiratory and diarrheal disease amongst the
common COD.

3. Categories of infectious agents
1. Prions
2. Viruses
3. Bacteria
4. Chlamydiae,
5. Rickettsiae
6. Mycoplasma
7. Fungi
8. Protozoa
9. Helminths

4. Infection-Induced Inflammatory
Response

5. Morphological Patterns
1. Suppurative inflammation
2. Necrotizing inflammation
3. Ulceration
4. Fibrinous inflammation
5. Hemorrhagic inflammation
6. Pseudomembranous inflammation
7. Cytopathic/cytoproliferative inflammation
8. Mononuclear and granulomatous inflammation
9. Chronic inflammation and scarring

6. Suppurative Inflammation
Suppurative = Purulent = Pus containing
Acute and Chronic inflammatory response with
pus formation.
Abscess
Etiology
Cocci: pneumo-; gono-, meningo-, strepto-,
and staphylo-
Other: Mycobacterium tuberculosis,
Salmonella typhi, and many fungi

7. Suppurative Inflammation
Acute Bacterial Pneumonia

8. Suppurative Inflammation
Acute Meningitis

9. Suppurative Inflammation
Acute Appendicitis

10. Suppurative Inflammation
Chronic Brain Abscess &Chronic Osteomyelitis

11. Suppurative Inflammation
Chronic Abscess Contents
• Neutrophils
• Lymphocytes
• Macrophages
• Plasma Cells

12. Necrotizing Inflammation
Virulent organisms producing severe tissue
damage and extensive cell death.
Examples:
Gas gangrene (Clostridium perfringens and
septicum)
Necrotizing fasciitis (skin and subcutaneous
tissues, Streptococcus pyogenes)

13. Necrotizing Inflammation
Gas Gangrene
Clostridia perfringens
(Gram stain)

14. Necrotizing Fasciitis

15. Ulceration
Ulcer:
a defect of an organ surface produced by
shedding of inflamed necrotic tissue
Etiology:
H.pylori (peptic ulcer, stomach, duodenum)
HSV type I and II
Treponema pallidum (chancre, primary
syphilis)
Outcomes:
Shallow ulcer may heal without scarring
Deep ulcers usually heal with scarring

16. Acute and Chronic Ulcers
Acute Aphthous Ulcer Chronic Peptic Ulcer

17. Ulceration
Syphilitic Chancre Herpes Simplex Virus II

18. Ulceration
Syphilitic Chancre
Herpes Simplex Virus I

19. Fibrinous Inflammation
Increased permeability of blood vessel wall and fibrin
predominance among exudate components
Etiology:
Streptococcus pneumoniae pneumonia

20. Fibrinous & Fibrino-purulent Inflammation in
Pneumonia
Pseudomonas Fibrinous Pleurisy in Lobar Pnemonia
S. pneumoniae Legionella

21. Hemorrhagic Inflammation
Severe blood vessel wall damage and RBC
predominance among exudate components
Etiology
Influenza virus
Bacillus anthracis
Others:
Yersinia pestis
Rickettsia rickettsii
Neisseria meningitidis, etc
Outcome:
usually unfavorable

22. Hemorrhagic Inflammation
Influenza
MeningococcemiaAnthrax

23. Pseudomembranous Inflammation
Formation of pseudo- (false) membrane consisting
of necrotic tissue and fibrin and located on
mucosal surfaces
Etiology
Corynbacteria diphtheriae
Clostridium difficile

24. Pseudomembranous Inflammation
Colitis (Cl. difficile)

25. Cytopathic/Cytoproliferative Inflammation
Etiology: viruses
Morphological features
Cell alteration:
Apoptosis (Councilmen bodies-Viral hepatitis)
Multinucleation (HSV)
Intranuclear/cytoplasmic inclusion bodies
Negri bodies- rabies; cytomegals- CMV)
Cell proliferation
T-lymphocytes (EBV, infectious
mononucleosis)
Syncytium formation
Respiratory Syncitial Virus (RSV)

26. Cytopathic/Cytoproliferative Inflammation
HSV HBV
RabiesCMV

27. Mononuclear Inflammation
Common feature of all chronic inflammatory processes
Sometimes Acute process
Etiology
Intracellular parasites: Chlamydiae,
Rickettsiae, Plasmodia
Viruses: e.g., Hepatitis viruses, poliovirus,
EBV
Morphology:
if accompanied with marked exudate
accumulation → serous inflammation
(Varicella virus; Treponema pallidum,
secondary syphilis)

28. Mononuclear Inflammation
Chronic Pyelonephritits Chronic Cholecystitis
Acute Viral Myocarditis Chronic Hepatitis B

29. Mononuclear (Serous) Inflammation
Herpes simplex virus infection
Vesicles, Varicella Secondary Syphilis

30. Causative Organism:
Mycobacterium tuberculosis
Lungs are primarily affected
Major histological manifestation:
TB granuloma
Central zone of caseous necrosis
Wall of epithelioid cells with Langhans giant cells
Rim of lymphocytes
+/- Collar of fibrous tissue
Diagnosis: mycobacterium identification
Microscopy: AFB, Ziel-Nielson stain
Culture
PCR
Granulomatous Inflammation: TB

31. Tuberculosis
Focus of Caseous Necrosis Granuloma
AFB

32. Chronic Inflammation with Scarring
Common sequel of many infections
Pyogenic Bacteria
Chronic abscess and osteomyelitis
Other Bacteria:
Chronic bronchitis, Pyelonephritis, and
Cholecystitis
Viruses:
Hepatitis B
Protozoans:
Schistostoma
Helminths:
Echinococcus, Trichinella, Cysticercus

33. Inflammation leading to Scarring
Chronic Hepatitis with Scarring Liver Cirrhosis
Chronic Pyelonephritis Nephrocirrhosis

34. Visualization and Identification of
Microorganisms
Stain Micro-organism
H&E, Giemsa,
Pap stain
Viral inclusions, few Bacteria,
Bacterial clumps, few Fungi, most
Protozoans, all Helminths
Gram stain Bacteria: (Gm+) blue; (Gm-) pink
AFB stain Mycobacteria, Nocardia
Sliver stain Fungi, Spirochetes, Pneumocystis
PAS Reaction Fungi, Protozoans, Helminths
India Ink,
Mucicarmine
Cryptococcus
KOH preparation Dermal and Nail Fungal Infection

35. Hematoxylin and Eosin stain
Actinomyces israelii
Granules
Candida albicans
Pseudohyphae

36. Giemsa Stain
Trichomonas vaginalis Helicobacter pylori
Neisseria gonorrheae Plasmodium falciparum

37. Papanicolaou or Pap Stain
Herpez Simplex Virus
Trichomonas vaginalis

38. Gram stain: Gram Positive organisms
Streptococcus pneumoniae Streptococcus pyogenes
Actinomyces israelii (Sulphur granule) Staphylococcus aureus

39. Gram Stain: Gram Negative Organisms
Neisseria meningitidis Rickettsia rickettsii
Escherichia coli Klebsiela pneumoniae

40. Acid Fast Stain or Ziehl Nielson stain
Mycobacterium tuberculosis Mycobacterium avium intracellulare
Mycobacterium leprae Nocardia asteroides

41. Silver Methanamine Stain
Candida albicans Aspergillus fumigatus
Histoplasma capsulatum Pneumocystis carinii

42. Silver Stain
Legionella pneumophila
Treponema pallidum

43. Periodic Acid-Schiff (PAS) Stain
Fungi within Blood Vessel Aspergillus fumigatus
Cryptococcus neoformans Echinococcus granulosum
(Hydatid Cyst)

44. Cryptococcus neoformans
Mucicarmine Stain
India Ink Stain

45. KOH Preparation for Fungal Infection of Skin and/or Nails
Pityrosporum