infectious disease Flashcards
give 7 pathogens that cause infectious diseases
bacteria, viruses, prions, protozoa, helminths, arthropods
how can an organism cause a disease?
- maintain a reservoir
- gain access to a host
- adhere to host
- evade host’s defence mechanisms
- multiply in or on the host
- cause harm
define infectious
the ability to cause an invasion and transmit pathogens
what is a virus made up of?
nucleocapsid, either envelope or capisd, capsomere, nucleic acid
What are the steps of viral replication?
- attachment
- penetration
- alteration of hosts cellular machinery
- nucleic acid replication
- synthesis of protein coat
- assembly
- release
how does a virus attach to a cell?
- adsorption to cell surface
- specific interaction with host cell receptors via envelope/ capsid proteins
how does a virus penetrate into a cell?
- translocation
- receptor mediated endocytosis
- membrane fusion
- injection
what do early genes do of the host cell once it contains viral DNA?
-encode enzymes and regulatory proteins required to start viral replication
-RNA polymerase becomes viral specific
what do late genes of the host cell do once it contains viral DNA?
-encode structural proteins required for virus assembly
-capsid protein synthesis
how can viruses be released from the host cell?
-exit/ cell fate
-host cell lysis
-membrane budding
what type of virus is coronavirus?
enveloped ss positive-sense RNA viruses
For SARS CoV-2, what is the virus attachment protein? what human host receptor does it bind to?
-viron VAP glycoprotein which is a spike protein with S1 subuinit
-ACE2 angiotensin converting enzyme 2 receptor
what are the symptoms of SARS CoV-2
-pneumonia
-fever
-cough
-occasional diarrhea
-fatigue
-headache
what infections do prions cause
-in animals
-in humans
in animals
-BSE, FSE, Scrapie
-transmissible mink encephalopathy
humans
-kuru
-classical CJD
-nvCJD
what two ways CJD can be transmitted
-injestion of affected material
-latrogenic transmission of CJD
whats the disease process of CJD?
-incubation of up to 30 years
-cell atrophy
-loss of cerebral, sensory and motor function
-death
what are the pathalogical signs of CJD?
-sponge like appearance
-microfibril associated amyloid plaques
what are the three structural features of the bacterial cell wall?
-peptidoglycan cell wall
-bacterial chromosome not bound by nucelar membrane
-numerous ribosomes
what are the two categories of bacteria?
gram -ve which have thin cell wall
gram +ve which have thick cell wall
how do bacteria cause disease?
- adhere to host via cell surface glcoproteins or pili
- penetration (sometimes) via spiral bacteria through epthelia or invasins through phagocytosis
- otherwise they do colonosiation through microcolonies resisting phagocytosis
- exotoxins released cause toxic molecules to degrade cell membranes and intefere with host metabolism
- endotoxins are where the membrane its self is toxic causing a severe inflammatory response
what eye diseases are caused by:
GRAM positive cocci
gram positive bacilli
gram positive filaments
gram negative bacteria
-endophthalmitis, conjunctivitis
-endophthalmitis, meibomitis
-canaliculitis, dacrocystitis, corneal abcess, endophthalmitis
-conjunctivitis, corneal abcessm endophthalmitis
how does fungi cause disease?
- promoting infammation
- mycotpxin production
- infection
what eye disease is caused by yeast
endophthalmitis
what is the process of corneal infection?
- foreign body sensation
- loss of epithelium
- stromal necrosis, keratitis
- stromal thinning - perforation
give an occular infection due to toxoplasma
retinochoroiditis
what occular diseases can be due to athropods?
-mites in eyes = blepharitis
-lice = conjunctivitis
what is a prion
a type of virus with no RNA and DNA and contains only protein
What are the differences between the normal and pathologic prion proteins?
Normal: protease sensitive, high alpha helix content, low beta pleated sheet content, soluble, does not form aggregates
Pathologic prion proteins: protease resistant, low alpha helix content, high beta pleated sheet content, insoluble, aggregates to form fibres
give the steps in the coronavirus lifecycle
- he spike protein of S1 subunit binds to the human host cell receptor ACE2
- viral entry into cytosol so for SARS CoV 2, transmembrane serine protease 2 and S2 subunit binds via membrane fusion or receptor mediator- endocytosis
- viral genome is released into cytosol
- positive sense RNA has coding regions for nucleocapsid proteins (N) spike (S), envelope (E) and membrane (M) proteins
- used as an mRNA template for translation
- Early genes = translated => non-structural proteins (nsps); includes viral polymerase; RNA-dependent RNA polymerase (RdRP)
- vRNA replication via replication and transcription complexes
- transcription
- transcription of viral protein structures
- S, M and E are translated in the ER Golgi intermediate compartment (ERGIC)
- nucleocapsid made of viral rna and viral N proteins are assembled in the cytoplasm
- S, E and M bud from ERGIC and join N
- mature virion is exocytosed out the cell and in SARS CoV 2 theres lysosomal pathway causing pH changes and exocytosis
