GENERAL PATHOLOGY OF INFECTIOUS DISEASES

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GENERAL PATHOLOGY OF INFECTIOUS DISEASES

• LUMINITA MARINESCU, MD

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INFECTIOUS AGENTS

• VIRUSES
• BACTERIA
• RICKETTSIAE
• FUNGI
• PARASITES
• BACTERIOPHAGES AND PLASMIDS
• CHLAMYDIA
• MYCOPLASMA

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BACTERIA

• Unicellular, prokaryotic cells (no nc/endoplasmic
  reticulum)
• Gram positive or negative
• Identified in micro lab by cultures and chemical
  properties
• Bacteriophages and plasmids are genetic elements
  that infect bacteria, encoding for virulence and
  enzymes that confer drug resistance

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BACTERIA INDUCED INJURY

• -adhere to cells and deliver toxins
• -bacterial endotoxins cause septic shock, DIC,
  ARDS. Secreted by Gram-negative
• -bacterial exotoxins are potentially harmful. Act
  in different ways exdiphteria toxin

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Spread of infection

• Local
• Lymphatic
• Hematogenous
• Tissue fluids
• Neural spread

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Types of inflammation

• Acute can lead to the formation of pus
• Chronic granulomatous, like TB,lepra,
  cat-scratch disease, Yersinia enterocolitica,
  syphilis

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Mycobacterium tuberculosis

• Acid fast bacillus
• Seen on Ziehl- Nielsen stain
• TB, treated with tuberculostatic antibiotics
• Produces granulomatous inflammation

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ACTINOMYCES ISRAELII

• Causes granulomatous inflammation, like chronic
  abscess of the neck, appendix
• Yellow granules in the discharge

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TREPONEMA PALLIDUM

• Causes syphilis
• Transmitted through sexual contact
• Pattern-primary
• -secondary
• -tertiary
• Congenital syphilis

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CHLAMYDIA

• Intracellular agents
• GU tract, causing sterility in women
• Conjunctivitis- blindness

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MYCOPLASMA

• Spread from person to person
• Bind to airway epithelial cells and causes
  atypical pneumonia
• Can cause autoimmune hemolytic anemia

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RICKETTSIA

• Intracellular cocco-bacilli, transmitted by tick
  bites in general
• Rocky Mountains spotted fever - R. rickettsii.
  Transmitted by ticks. Symptoms hemorrhagic rash,
  encephalitis.
  
• Typhus - R. prowazekii. From louse
• Q fever - R. burnetti. By inhalation or ingestion

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VIRUSES

• Intracellular agents
• Contain either DNA/RNA but not both
• Inclusion bodies may help in identification HSV,
  CMV, rabies v
• Most common agents of human illness

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VIRUS INDUCED-INJURY

• -bind to surface proteins on cells
• -penetrate the cell
• -uncoats and replicates
• -kill host cell by inhibiting DNA/RNA or protein
  synthesis, by damaging the membranes integrity,
  by lysing the cell, by damaging the cells
  involved in defense

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FUNGI

• Thick cell wall organisms
• Can be dermatophytes or can invade deep organs
• Ex Histoplasma (Ohio River Valley)
• Coccidiodes (west)
• Blastomyces (tropical areas)

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Coccidioides and Blastomyces
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Aspergillus fumigatus
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PROTOZOAN

• Motile, single-celled eukaryotes
• Ex Trichomonas vaginalis, causes vulvovaginitis,
  sexually transmitted disease

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Protozoan infection

• CNS-Acanthamoeba, Toxoplasma, malaria
• Lymphoid tissue- Toxoplasma, Leishmania
• Heart- Trypanosoma cruzi (Chagas disease)
• Liver- Entamoeba, Plasmodium, Leishmania
• Blood- Trypanosoma, Plasmodium
• Gut- Entamoeba, Giardia, Cryptosporidium,
  Isospora
• Genital- Trichomonas
• Skin- Leishmania (cutaneous leishmaniasis)
• Lung- Pneumocystis carinii

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HELMINTHS

• Multicellular worms that have strict
  specificities for the definitive host, in which
  sexual reproduction takes place or for the
  intermediate host or vector, in which
  reproduction is asexual

• Categories-trematodes (flukes)
• Nematodes (roundworms)
• Cestodes (tapeworms)

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TREMATODES

• SCHISTOSOMA
• -North Africa
• -fresh water
• -chronic inflammation of the bladder/squamous
  carcinoma

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CESTODES

• TAENIA SOLIUM
• -undercook infected pork
• -many sites but the most importantbrain and
  spinal cord where it produces cysts.
• -severe symptoms when the cyst dies

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NEMATODES

• ASCARIS LUMBRICOIDES
• -in children
• -small intestine
• -abdominal pain and failure to thrive if the
  infestation is heavy

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PRIONS

• Normal host protein called prion
• In many tissues unknown function
• Structural change makes it infective
• Diseases CREUTZFELD-JAKOB disease
• KURU disease
• SCRAPIE
• BOVINE SPONGIFORM
• ENCEPHALOPATHY