infectious agents Flashcards
(21 cards)
Why are we interested in infectious agents
> 50million deaths/year
flu pandemic
HIV have huge effect on people’s lives
bacterial meningitis - nasal pharynx and coagulation in blood
c difficile - spores - difficult to get rid of
MRSA - drug resistant
TB - 4 drugs for 6 months, people reluctant to adhere
bioterrorism
new emerging infections/global spread
Why do infections continue to be a problem
high mutation rate
eg in virus - fewer checks
generation time
human similar mutation rate to bacteria, but bacteria shorter generation time so more mutations
What can we learn from studying infectious agents
vaccines - small pox
polio - iron lung respiratory paralysis, oral vaccine - political problems
papilloma virus causing cervical cancer
vaccine - glycoprotein/ glycomolecule
list the main types of infectious agent causing disease in humans
Virus bacteria - prokaryotes fungi - single cell protozoa - eukaryotes helminth parasite - multicellular
Virus features
obligate parasites
RNA/DNA
host specificity - but infect almost all life forms
various routes of infection
example of virus
HIV - retrovirus
reverse transcriptase
Bacteria example - shigella
gastrointestinal
low infectious dose
poor water supplies
faecal oral transmission
destroy epithelium
entry with vacuole - vacuole lysis - intracellular replication
cell to cell spread by host cell filaments - actin
bacterial example - Neisseria meningitis
in blood - invasive whole immune system shut down block bv in liver and loss of limbs blood brain severe inflam response airborne septicaemic disease - rapid progression, septic shock, severe inflam response high levels of bacteraemia
Fungi example
candida
depending on the nutritional condition switch between bud and hyphae
protozoa example - malaria
malaria belt - mosquito below certain altitude
protozoa example - leishmania spp
in macrophages skin lesions in dogs, flies transmit to humans swelling and distortion of skin swollen belly from swollen liver
helminth example - roundworms
faecal oral
helmith example - flukes
live as male and female
eggs migrate to gut
snail eradication - destroy immediate host
Virus replication
budding out of host cell
when the mutate they only have 1 copy of the gene - immediately has an effect - infection always expressed
bacteria features
prokaryotes chromosome of DNA - no nucleus various routes of infection some are pathogenic some have flagella
bacteria replication
binary fission
replicate protein and chromosome
Fungi features
eukaryotic
yeasts or filaments
cutaneous mucosal and or systemic mycoses
Fungi replication
yeast - bud
filaments - cross walls/septa
protozoa features
unicellular eukaryotic intestinal, blood, tissue parasites life cycle involves 2 hosts infection is acquired by ingestion/vector
protozoa replication
in host
binary fission
or formation of trophozoites inside a cell
Helminth
roundworm, flatworm, tapeworm metazoan eukaryotic multi cellular visible to naked eye life cycle out of human host life cycle complexity varies from embryonation to alterations of generations in different hosts affect nutrition and how we deal with other pathogens
