Infectious Disease Part 1 Flashcards by joseph dizon

Explaining the infectious nature o PrP?

Abnormal PrP promotes transformation of normal PrP to abnormal forms

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Pathophysiology for prion

PrP found in neurons
Mutation
Abnormal PrP resistant to proteases
Neuronal damage

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Cellular prion protein

Non infectious
Monomer
Soluble
Alpha helical
Proteinase K sensitive

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Scrapple associated prion

Infectious
Aggregate
Insoluble
Rich in beta sheets 
Partial PK resistant

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Prion disease

Infectious fatal neuro degenerative disorders

Transmissible spongiform encephalopathies

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TSE in humans

Creutzfeldt-Jacob disease

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TSE in animals

Scrapie or bovine spongiform encephalopathy

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Prion disease

Upon oral ingestion

GIT
Epithelial cells 
Peyers patches via blood
Lymphoid via macrophages
Peripheral nervous tissue 
Synaptic damage

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Prion disease
TSE
Clinical presentation

Kuru (human cannibalism)

Symptomatic coordination malfunctions

Uncontrollable and inappropriate episodes of laughter (laughing death)

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Prion disease
TSE
Clinical presentation

Bovine spongiform encephalitis

Mad cow disease

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Prion disease
TSE
Clinical presentation

Creutzfeldt-Jacob disease

Spontaneous- sporadic
Inherited- familial
Latrogenic- surgery, organ transplantation, blood transfusion

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Viruses

Obligate intracellular parasites

Nucleic acid genome surrounded by a protein core (capsid)

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Viruses classification

Nucleic acid genome
Shape of capsid
Presence or absence of lipid envelope
Mode of replication
Tissue tropism
Type of pathology

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Bacteria cell wall is peptidoglycans except

Mycoplasma and ureaplasma no cell wall

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Bacteria classification

Gram staining
Shape
Need for oxygen
Production of spores

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Fungi eukaryotes

Cell wall

Chitin

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Fungi

Cell membrane

Ergosterol

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Fungi

Dimorphic

Yeast or hyphae

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Fungi

May produce sexual or asexual spores

Conidia

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Fungi other classification

Superficial, subcutaneous, cutaneous infections

Systemic or opportunistic

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Single called eukaryotes

Intracellular or extracellular replication

Protozoa

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Protozoa

E. Histolytica and G. Lambia

Cyst

Trophozoites

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Protozoa sexual or asexual reproduction

Binary fusion

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Parasitic worms
Highly differentiated
Complex life cycle

Helminths

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Helminths sexual reproduction in

Definitive host

Helminths asexual reproduction in

Intermediate hosts

Helminths do not multiply

Produce eggs or larvae

Special diagnostic techniques Most bacteria

Gram stain

Special diagnostic techniques Mycobacteria Nocardia

Acid fast stain

Special diagnostic techniques Viral products Fungi Most protozoans All helminths

H and E stain

Special diagnostic techniques Campylobacter Leishmaniae Malarial parasites

Giemsa stain

Special diagnostic techniques Fungi, Legionella Pneumocystis

Silver stain

Special diagnostic techniques Fungi Amebae

Periodic acid schiff

Special diagnostic techniques + specific IgM antibody after onset of symptoms diagnostic

Serology

Special diagnostic techniques Nucleic acid- based tests eg, HIV RNA quantification

Molecular diagnosis

Special diagnostic techniques Nucleic acid amplification test; routine for diagnosis of gonorrhea, chlamydia, TB and herpes enceph

PCR

Special diagnostic techniques All classes

Antibody probes Culture DNA probes

Agents of bioterrorism Category A

Anthrax Botulism Smallpox

Agents of bioterrorism Category A

``` Highest risk Readily transmitted from person to person High mortality in major public health Public panic Require special action ```

Agents of bioterrorism Category B

Easy to disseminate Moderate morbidity but low mortality Require specific diagnostic and disease Surveilance

Agents of bioterrorism Category C eg

Nipah and Hanta viruses

Agents of bioterrorism Category C emerging for mass dissemination due to

Availability Ease of production and dissemination Potential for high morbidity and mortality Great impact on health

Skin barrier inhibits growth microbes except normal flora

Keratinized skin Low skin pH 5.5 Fatty acid

Routes of entry: SKIN Potential opportunist

S. Epidermidis | C. Albicans

Routes of entry: SKIN Skin penetration:

Schistosoma larvae

Routes of entry: SKIN Schistosoma larvae release what enzyme to dissolve ECM

Collagenase Elastase Other enzymes

Routes of entry: SKIN Skin breaks

Superficial pricks (fungi) Wounds(staphy) Burns (aeruginosa)

Routes of entry: SKIN Others

IV catheters leads to local or systemic infections Needle sticks Insect or animal bites

Routes of entry: GIT Most GIT pathogens transmitted by food or drink contaminated with

Fecal material

Barriers to infection: GIT

``` Acidic Viscous mucous Lytic pancreatic enzymes and bile detergents Mucosal antimicrobial peptides(defensin) Normal flora IgA ```

Routes of entry GIT Infectious occurs when local defenses are weakened by

Low gastric acidity Intake of ATBC Mechanical obstruction Stalled peristalsis

Routes of entry GIT Infections occur when organism develop strategies to overcome defenses by

Entero toxins Exotoxins Invasion and damage of mucosa

Routes of entry Respiratory tract Barrier against droplet

Mucociliary blanket lining URTI

Routes of entry Respiratory tract Barrier against aerosols

Alveolar macrophages

Routes of entry Respiratory tract Other barrier

Cytokine recruitment of neutrophils

Routes of entry Respiratory tract Pathogens Attachment to epithelial cells in LRT

Influenza virus | H and N antigens

Routes of entry Respiratory tract Pathogens Impairment of ciliary activity

H. Influenza | B. Pertussis

Routes of entry Respiratory tract Pathogens Evasion of phagocytosis

M. Tb

Routes of entry: urinary tract Barriers

Regular flushing with urine | Vagina low pH (catabolism of glycogen)

Routes of entry: urinary tract Pathogens

Women short urethra Obstruction to urine flow and reflux Retrograde spread from bladder to kidney

Spread and dissemination Local spread at site of infection Lumen of hallow viscera

Vibrio choler are

Spread and dissemination Local spread at site of infection Epithelial cells

Papillomaviruses | Dermatophytes

Spread and dissemination Penetration of epithelial barriers Rabies

Via nerves

Spread and dissemination Penetration of epithelial barriers Secretion of lytic enzymes

Strep and staphy

Spread dissemination Major manifestations of infectious diseases may appear at sites distant from the point of entry eg.

Measles | Chickenpox

Spread dissemination Placental-fetal route eg

Congenital rubella | Congenital syphillis

Spread and dissemination Sexually transmitted infections Organism tends to be

Short lived outside the host

Spread and dissemination Sexually transmitted infections Usually depends on direct

Person to person spread

Spread and dissemination Sexually transmitted infections Initial site of infection

``` Urethra Vagina Cervix Rectum Oropharynx ```

Spread and dissemination Sexually transmitted infections

Most are asymptomatic carriers

Spread and dissemination Sexually transmitted infections Microbes that cause STI can be spread from a pregnant woman to the fetus

Severe damage to the fetus

Spread and dissemination Sexually transmitted infections Infection with one STI associated organism increases the risk for additional STIs

Same risk factors : chlamydia and gonorrhea

Spread and dissemination Release of microbes from the body

``` Skin shedding Coughing and sneezing Voiding of urine or feces Sexual contact Insect vectors Fomites ```

Mechanism of disease production Contact or entry host cells and directly cause cell death

Mechanical

Mechanism of disease production Release of toxins and enzymes

Chemical

Mechanism of disease production Induce host immune responses

Immune mediated

Factors affecting viral virulence Must possess cells expressing surface molecules recognized by a viral attachment protein (VAP)

Host range

Factors affecting viral virulence Oral or respiratory routes the most common means of viral entry

Route of viral entry

Factors affecting viral virulence Major determinants

Tissue specificity (tropism)

Example of this determinant Presence of viral receptors on host cells

HIV

Example of this determinant Presence of type specific transcription factors on some cells and not in others

JC virus- restricted to oligodendrogilia

Example of this determinant Physical barriers

Enteroviruses- resistant to gastric acid | Rhinovirus- URT due to lower temperature

Factors affecting viral virulence Mechanism Prevent synthesis of host macromolecules(DNA, RNA or protein) Production of enzymes and toxins Induction of apoptosis

Direct cytophatic effect

Example of direct cytophatic effect

Poliovirus HSV Viral replication

Factors affecting viral virulence Mechanism Viral protein on surface of host cells recognized by immune system

Anti viral immune

Example of antiviral immune response

Hepatitis B infection

Factors affecting viral virulence Mechanism Oncogenic viruses

Transformation of infected cells

Inhibition of cellular protein synthesis

HSV | Poliovirus

Disruption of cytoskeleton

HSv

Negri bodies

Rabies

Owl's eye nuclear bodies

CMV

Cowdry type A nuclear Bodies

HSV

Immunosuppresion

HIV CMV Measles

Bacterial damage to host tissues depends on ability of the bacteria to

Adhere to host cells Invade cells and tissues Deliver toxins

Bacterial virulence enhanced Virulence genes

``` Pathogenicity islands (Caga of H. Pylori) Plasmids and bacteriophages ```

Bacterial virulence enhanced Increase expression of conc. of bacteria in tissue increases

Regulation of gene expression within a large population of organisms by quorum sensing

Bacterial virulence enhanced Enhance adherence Make the bacteria inaccessible to immune effector mechanisms Increase bacterial resistance to anti microbial drugs

Biofilm formation by communities of bacteria

Bacterial adherence to host cells Bacterial surface molecules bind to bacterial host cells or ECM S. Pyogenes- protein F and teichoic acid

Adhesins

Bacterial adherence to host cells E. Coli - P pilus to uroepithelial cells

Pili

Infect either or both Epithelial cells

Shigella | EIEC

Infect either or both Macrophages

M. Tb | M. Lep

Infect both

Salmonella Tupi

Intracellular bacteria: mechanism for host cell entry ``` M. Tuberculosis Activation of alternative pathway Opsonization with C3B Bind to CR3 on macrophages Endocytosis ```

Utilization of host immune response to enter macrophages

Intracellular bacteria: mechanism for host cell entry ``` Gram negative bacteria Bind to host cells Protein release Cytoskeletal rearrangement Entry ```

Utilization of complex secretion system to enter epithelial cells

Intracellular bacteria: mechanism for host cell entry Listeria monocytogenes Allow evasion of immune effector mechanisms

Manipulation of cell cytoskeleton spread directly from cell to cell

Endotoxins

Lipopolysaccharides Cytokines enhance T cell activation High level of TNF, IL-1 and 2

Exotoxins

Proteases and hyaluronidase A-B toxins Neurotoxins Super antigens (staphy)

Bacterial virulence mechanism

EAT RICE ``` Enzyme Adherence Toxin Resistance Invasion Circulation Evasion ```

Growth and replication in sites inaccessible to host immune response Concealed from CMI

Lumen of intestines (C. Difficile) | Gallbladder ( s. Thy phi)

Growth and replication in sites inaccessible to host immune response Rapid invasion of host cell before humoral responses become effective

Malaria (liver cells) Trichinella (skeletal muscle) T. Cruzi (cardiac muscle)

Growth and replication in sites inaccessible to host immune response Formation of cysts with dense capsules

Larva of tapeworms

Growth and replication in sites inaccessible to host immune response Viral genes not expressed Viral Ag not exposed to immune system

Vital latency

Growth and replication in sites inaccessible to host immune response Intracellular growth without inactivation

Inhibition of phagocytosis fusion by M. To

Abnormal forms of host protein

Prion protein or PrP

Infectious Disease Part 1 Flashcards

(114 cards)