Lecture 4) example bacteria pathogens Flashcards
what is an endogenous infection?
an infection caused by an agent already in the body that was previously inapparent or dormant
eg stapylococcus aureus
what is an exogenous infection?
an infection caused by an exogenous agent that has entered the body
eg C. diff
what is the difference between a HAI and HCAI?
HAI = hospital acquired infection, only found in hospitals HCAI = healthcare acquired infections, can be found in hospitals, clinics, dentists etc
what are some of the common HAIs?
GI infection infections post surgery IV cannulae skin infection urinary catheter
name some of the factors that impacts the spread and control of infections
social and environmental factors
health education
food safety
vector control - chemoprophylaxis - administration of antibiotics
outbreak investigation - infection control
what does chemoprophylaxis mean?
the use of drugs to control disease/infection
what are emerging infections?
infections that are rapidly in incidence/geographical range
what are some of the characteristics of emerging infections?
money is being invested to protect against outbreaks
viral outbreaks more common than bacterial outbreaks - viral generally more serious and harder to treat
global warming means new pathogens in different places leading to infections and diseases that have never been seen before in that location
how many phospholipid bilayers do gram negative bacteria have?
2
do gram negative bacteria have a thin or thick peptidoglycan layer?
thin
where do most gram negative bacteria fall into on the tree of life?
proteobacteria
describe the outside phospholipid bilayer of gram negative bacteria
asymmetric
why are gram negative bacteria called lipopolysaccharides?
they have carbohydrates on the outside of the polysaccharide layer
what infection does Neisseria meningitidis cause?
meningitis
how is Neisseria meningitidis classified?
by their serogroup
how are Neisseria meningitidis classified using serogroups?
due to how a panel of antibodies recognise certain carbohydrate groups on the bacteria
what is a serogroup?
a distinct variation within a species of bacteria use to classify them
what subsequent infection can meningitis cause?
septicaemia
is Neisseria meningitidis encapsulated? if so, describe it
encapsulated in a slime layer
what is the function of the capsule on N. meningitidis?
if it was uncapsulated it would be taken up by phagocytes and destroyed
it is a mechanism that has evolved to avoid the host’s immune system
what class is N. meningitidis?
beta proteobacteria (gram negative)
10-15% of the population have N. meningitidis in their nasopharynx but dont show symptoms of meningitis, why is this?
the bug is asymptomatic
N. meningitidis is said to have antigenic variation. what does this mean?
it can cross barriers and turn capsule on therefore avoiding phagocytes of the host’s immune system
can enter the meninges and cause infection
why is there currently no MenB vaccine?
the MenB subgroup express the exact structure of the host’s carbohydrate
hard to create a vaccine that will target the foreign cell when they have the same structure as the hosts cell
what concept has been introduce to solve the problem of having no MenB vaccine?
reverse vaccinology
what is reverse vaccinology?
used to predict the epitope of the virus
what is an epitope?
the part of the antigen that is recognised by the immune system
how would reverse vaccinology be used to create a vaccine for MenB?
from examining genes on the surface of MenB, found 4 protective surface lipoproteins that are unlike the host’s surface proteins
vaccine could be created to target one/all of these proteins
give an example of a gram positive bacteria?
diphtheria
what is the route of infection for diphtheria?
airborne
give a description of the morphology of diphtheria
asymmetric
club-like
all grouped at one end
where in the body does diphtheria pathogenise?
nasopharynx
is diphtheria an endogenous or exogenous infection?
exogenous
external pathogen that enters the host
what makes diphtheria toxic?
diphtheria releases a toxin that kills host cells and spreads systematically to the heart and lungs
what type of toxin does diphtheria release and what does it do?
AB toxin (main virulence factor of diphtheria) A = activity B = binding acts on EF2
the AB toxin in diphtheria acts on EF2. what is EF2 and what are the consequences of the toxin acting on this?
EF2 = elongation factor
involved in translation
when targeted by AB toxin = no proteins made = cell death = kills you
name the vaccine against diphtheria
DTap vaccine
what are the 4 levels of emerging infections?
1) exposure
2) infection
3) transmission
4) epidemic spread
describe the introduction factor of emerging infections
have to determine where these infections are coming from
predict what/when the next bad outbreak will be and make a vaccine for it before it can cause an epidemic
describe the establishment and dissemination factor of emerging vaccines
agents have to spread to be able to cause an epidemic
harder for pathogens to achieve this as hopefully introduction factor will have been achieved and therefore an epidemic will have been avoided
what technique is used to predict the next big epidemic?
genome sequencing
what is a zoonotic disease?
a disease that normally exists in animals but can infect humans
cases have now been reported of human infections spreading to animals
give an example of a zoonotic pathogen and describe it
steptococcus suis
gram positive
present in swine industry
what zoonotic infections can be caused from streptococcus suis?
meningitis
septicaemia
arthritis
describe the process of genome sequencing in streptococcus suis
sequence different strains
determine core genome and pan genome
the more genes that are sequenced, the less genes that are similar
therefore, core genome decreases in size and pan genome increases in size
what can the genome sequencing of step. suis tell us?
the strain infecting humans had a type 4 secretion system
proven by pulsed field gel electerophoresis
T4SS thought to stimulate host immune reaction observed with streptococcal toxic shock like syndrome (STSLS)
