FOUND-viruses and bacteria Flashcards
what are the different modes of transmission and examples of diseases transmitted this way?
- Respiratory-TB/ COVID
- oral/faecal- polio
- Contact-(skin-skin/mucous/mucous)
- blood-borne-HIV
- Vector-mosquitos-malaria
- vehicle-non-living thing
- nosocomial-contracted in hospital
- zoonotic-viruses
what is the approx size of bacteria?
-1000 x2-3000nm
what is the function of flagella?
movement and adhesion
what is the function of pili?
adhesion, conjugation (transfers genetic material to another through direct contact) and movement found in many gram negatives
what is the capsule of bacterias function?
adhesion
protection
contribute to disease
what is the role of chromosomes in bacteria?
contain genetic code
what is the role of plasmids?
contain some genes-can confer advantage-antibiotics
what is the difference between gram-positive and gram-negative?
gram-positive
- thick peptidoglycan layer
- no LPS
gram-negtaive
- lipopolysaccharide and proteins
- thin peptidoglycan layer
what does LPS act as when released?
an endotoxin
what are examples of endospore-forming bacteria?
Bacillus
- B. anthracris -anthrax
- B. cereus -food poisoning
Clostridium (strict anaerobes)
- C. botulinum- botulism
- C. difficile-diarrhoea
- C. perfringens- gas gangrene
- C. tetani- tetanus
what is virulence?
the relative ability of a pathogen to cause disease in the host
what is an opportunistic pathogen?
normally harmless but can cause disease due to lowered host immunity
what is the incubation period?
between time of infection and appearance of symptoms
what are the two types of toxins produced by bacteria?
exotoxins endotoxins (LPS)
Explain the steps in bacteria pathogenicity
-exposure to pathogens
-adherence to skin or mucosa
-invasion through epithelium
-colonisation and growth
(production of virulence )
-toxin effects local or systemic
-or invasiveness-further growth at original site and distant site
-tissue damage/ inflammation/ disease
what are the 2 types of infection response?
extracellular
intracellular
describe extracellular infection response
- main response is antibody response
- also innate immunity-phagocytosis by neutrophils, monocytes and tissue macrophages
describe intracellular infection response
specific cell-mediated responses
-eg macrophage activation
are streptococcal species of bacteria gram positive or gram negative?
spherical gram + bacteria
what can streptococcus species can be classified into?
either alpha-haemolytic or beta-haemolytic depending on ability to haemolyse RBCs
what can beta-haemolytic streptococci be further divided into?
groups A-T based on polysaccharide capsular structure- Lancefield serotyping
what are the 3 main clinically important species of streptococci?
-S. pyogenes- group A
(strep throat, scarlett fever, toxic shock, necrotising fasciitis)
-S. agalactiae- group B
(neonatal sepsis and meningitis)
-S.pneumoniae
(lobar pneumonia)
describe the features of streptococcus pneumoniae
- gram positive alpha-haemolytic non-motile coccus
- over 90 capsular serotypes
how is DNA organised in bacteria?
singular circular chromosomes and plasmids
not contained within nucelus
what are the features of gram positive bacteria?
- phospholipid bilayer
- thick peptidoglycan layer
- no extra phospholipid bilayer with lipopolyscaccharide
what are some examples of gram-positive bacteria?
- staphlococcus aureus (cocci)
- stretococcus pyogenes (cocci)
- clostridium sporogenes (rod)
what colour does gram positive bacteria stain?
blue/ purple
what are the features of gram negative bacteria?
- phospholipid bilayer
- thin peptidoglycan layer
- extra phospholipid bilayer-integration of lipopolysaccharide
what are some examples of gram negative bacteria?
- neisseria gonorrhoeae (cocci)
- pseudomonas aeruginosa (rod)
- haemophilus influenzae (rod)
what colour does gram negative bacteria stain?
red/pink
what is a virus?
a small, infectious, obligate intracellular parasite
what is a parasite?
an organism that benefits at the expense of the host
what do viruses need to do to function?
can only function after they are replicated in a cell as they are obligate molecular parasites
how do viruses cause disease?
viruses make mRNA that can be translated by host ribosomes-they then hijack host protein synthesis machinery
what is a virion and what is their function?
virus paticle that protects the genome as it is transmitted from one host to another
why is it important to be able to classify viruses?
classification makes possible predictions about the properties of a virus
-particularly important when a new virus is identified
what properties are used for classification of viruses?
- size of virion and capsid
- presence or absence of an envelope (membrane)
- symmetry of protein shell (capsid)
- nature and sequence of nucleic acid (virus genome)
- symptoms
- routes of transmission
what are the steps in virus infection and replication?
- infecting virus attaches to host cell
- capsid penetrates host cell
- capsid uncoats- is shed
- repication-synthesis of mRNA (direct or via host machinery) synthesis of viral protein for new capsid, synthesis of viral nucleic acid
- assembly-capsids from around nucleic acid
- viral nuclic acid is released by cytolysis
how is bacteria replicated?
binary fission
are virus genomes DNA or RNA?
can be either
are virus genomes single or double stranded?
can be either
if the viral genome is single-stranded is it +ive or -ive sense?
can be either
is viral genome linear or circular?
can be either
is viral genome single or segment?
can be either or more than 1
why do viral genomes have to be abLe to make mRNA?
- to be translated by ribosomes to make viral proteins
- to make new virus particles-virions
what is Baltimore classification?
- based on mRNA as the common theme
- viruses (genomes) classified depending on how they make mRNA (+sense)
what are the different methods of viral transmission?
- respiratory
- oral/faecal
- blood borne viruses
- other bodily fluids
- arboviruses (vector)
define the infectious period
the period when you are releasing virus which can infect others
define the incubation period
period in between when you are first infected with the virus, the virus is replicating
what’s the difference between droplet and airborne transmission?
droplet infection-coughs and sneezes can spread droplets of saliva and mucus
(more than 5 microns)
airborne transmission-tiny particles, possibly produced by talking, are suspended in the air for longer and travel further (less than 5 microns)
what is the basic reproductive number?
R0
A means of expressing how many uninfected people can be infected by one infectious person
what does R0<1 mean?
the infection will generally dies out in the the population
what does R0>1 mean about an infection?
the infection will be maintained and spread in the population
what does a high R0 mean?
the virus will spread quickly
what is viral pathogenesis?
mode of production or development of disease
do all viruses cause noticeable disease?
no some may be asymptomatic
what are systemic infections?
- spread of virus throughout the body multiple organs are infected
- virus gains access into blood stream (lymph system)
- extreme rapid virus dissemination throughout the body
what is the definition of viraemia?
the existence of viruses/ virus particles in the blood stream
what is lytic infection?
infection as a result of active replication of the viral genome, characterised by making of new viral particles
what is latent infection?
when virus is in a state of non replication-quiescent state
