infectious diseases Flashcards
(46 cards)
virulence factors of staphylococcus and their function
- Cell wall anchored (CWA) proteins: Adhere to host matrix proteins (ECM) bound to host tissues/cells
- Capsule: Inhibits chemotaxis and phagocytosis; inhibits proliferation of mononuclear cells
- Slime layer: Facilitates adherence to foreign bodies
- Peptidoglycan: Provides osmotic stability; stimulates production of endotoxin- like activity; inhibits phagocytosis
- Teichoic acid: Binds to fibronectin
- Protein A: Inhibits antibody-mediated clearance by binding IgG Fc receptors; leukocyte chemoattractant; anticomplementary
biological effects of secreted factors in staphylococcus aureus
enzymes:
- coagulase: Converts fibrinogen to fibrin
- hyaluronidase: Hydrolyzes hyaluronic acids in connective tissue
- nuclease: Hydrolyze DNA
- lipase: Hydrolyze lipids
toxins:
- cytotoxins: Toxic to erythrocytes, fibroblasts, leukocytes, macrophages and platelets
- exfoliative toxins: Serine proteases, disrupt skin epidermis layer
classify streptococci
- alpha-haemolytic: partial haemolysis
- beta-haemolytic: complete haemolysis
- gamma-haemolytic: no hemolysis
virulence factors of streptococci pyogenes
Adhesins: Proteins expressed on surface
• Lipoteichoic acids
· Facilitate binding to host cells, colonisation
• F-protein
· binds to host fibronectin in epithelial cells -> internalisation of bacteria into host cells
• M-protein
· fibrils on cell surface
· bind plasma proteins and fibronectin
· anti-phagocytic and anti-complement
· invasion into epithelial cells
• M-like proteins
Toxins and Enzymes
• C5a peptidase (SapA)
· immune-modulating serine endopeptidase
· inactivates human C5a -> hinders complement & neutrophil response
· mediates resistance to phagocytosis
• Streptolysin S
· responsible for β-hemolysis
· lyses erythrocytes, lymphocytes, neutrophils, platelets
· affect phagocytes and help to introduce bacteria across skin barrier
Hyaluronidase:
• their producer attaches to ephitelia
• allow pathogen to invade deeper tissues
Streptokinase:
• disolves clot
• release pathogen to bloodstream and deeper tissues
which type of bacterial infections can streptococci pyogenes cause
skin infections:
- impetigo
- erypelas
- cellulitis
super respiratory track infections
what is diphtheria toxin and which bacteria causes it
definition: cell damage or death
caused by corynebacterium diphtheriae
what does corynebacterium diptheria affects
- tonsils
- throat
- nose
- skin
what bacteria causes bronchitis and pneumonia
haemophilus influenzae and streptococcus pneumoniae
clasification of pneumonia
- community-acquired pneumonia (CAP)
- hospital-acquired pneumonia (HAC)
- walking/atypical pneumonia
- ventilator-associated pneumonia (VAC): early and later infections
immunity of fungi and bacteria
intracellular phase:
· cytotoxic T cells: kill host infected cells and activate macrophages
· helper T cells: activate macrophages (IFN) to kill bacteria by MHC recognition
extracellular phase:
· Phagocytes
· Antibody
· Complement
immunity of viruses:
intracellular phase:
· interferon
· NK cells
· cytotoxic T cells
extracellular phase:
· antibodies
viruses characteristics
- NOT CLASSIFIED AS CELLS
- Nucleic acid wrapped in a protein coat
- Require a host cell for replication and ‘energy production’
- Extracellular form -> virion
- Receptors (e.g. CCR5 for HIV)
- Classification is based on:
· Envelope
· Nucleic Acid
bacteria characteristics
- Unicellular organisms
- Fully independent existence
- Genome and machinery necessary for survival
- Prokaryotes
- Extracellular or intracellular
how can the cell wall of bacterias be
gram-positive (e.g. staphylococcus): thicker peptidoglycan layer and no outer lipid membrane
acid-fast (e.g. micobacterium tuberculosis)
gram-negative (e.g. E.coli): thinner layer
which diseases can bacteria cause
gut diseases / skin diseases / respiratory diseases
differences between a vegetative form and a resting form
vegetative form (trophozoite):
resting form (cyst)
steps of lung injury caused by Strep. pneumoniae
LytA causes bacterial autolysis
2. Release of pneumolysin -> pore formation in neutrophil membrane
3. induction of neutrophil cell death
4. neutrophil elastase released by dead neutrophils
5. impairs phagocytic activity of macrophages impaired
6. neutrophil elastase may induce IL-8 production from alveolar epithelial cells
7. neutrophil elastase triggers epithelial cell death
Pathogenicity island types and definitions
PI-I encodes a salmonella-secreted invasion proteins
Type III secretion system: unique virulence mechanism enabling them to inject bacterial effector proteins directly into the host cell cytoplasm
PI-II: Intracellular replication / immune system evasion
phenotypes of Escherichia coli and diseases they cause
· Intestinal / Diarrhoeagenic E. coli (DEC)
Gastroenteritis
·Extra-intestinal E. coli (ExPEC)
UTIs
Meningitis
Sepsis
antimicrobial definition and types
A natural or synthetic chemical that kills/inhibits microbial growth.
- Antibiotics
* Produced by variety of bacteria and fungi
* Sole function of inhibiting or killing other microorganisms
- Antiseptics and Germicides
* Chemical compounds that kill/inhibit microbial growth * Nontoxic – can be applied to living tissues
* Often added to soaps, mouthwash, detergents
define susceptible and resistant in antimicrobials
· Susceptibility - level of vulnerability of a microorganism to an antimicrobial
· Resistance - ability of microorganism to avoid the harmful effects of an antimicrobial
Antimicrobial drug resistance is based on
· mutation of existing genes (SNPs) e.g. PBPs
· acquisition of foreign resistance determinants due to horizontal gene transfer (Plasmids, Transposons, Resistance islands)
definition drug resistance
Acquired ability of microorganism to resist effects of an antimicrobial compound to which is it normally susceptible
peptidoglycan cell wall
10-65 glycan chains connected by short peptides
