Infection Flashcards
what are parasites?
organisms which are dependent on another for its survival, to the detriment of its hosts survival
what are considered parasites?
helminths
insects
protozoa
what are endoparasites and what do they include?
parasites that live inside the body
they include helminths and protozoa
what are ectoparasites and what do they include?
they live outside the body which include insects such as fleas, lice, bedbugs and ticks
give an example of a protozoan endoparasite
entamoeba histolyca
this invades the large bowl lining, causing dysentery - excreted with faeces and spread via contaminated food and water - has a higher risk with poor hygiene
plasmodium falciparium (malaria) has a lifecycle in both humans and mosquitoes. it infects red blood cells and liver. gives fever, headache and joint pain and can lead to kidney failure , coma and death
what are 3 types of helminths
crestodes
termatodes
nermatodes
give an example of a crestode?
tape worms - segemnted and flat
causes abdominal pain and malnutrition.
diagnose by microscopy of the stool for eggs
cattle is intermediate host
give an example of trematodes
schistosoma haematobium (bilharzia) - flukes, unsegmented and flat
infection of veins around the bladder, casuing inflammation and bleeding into urine (haematuria)
intermediate host = freshwater snail
diagnose by urine microscopy
what are nematodes
round worms that have cylindrical digestive tract with lips, teeth and anus
give an example of an ectoparasite
begbugs
cimex lecturlaris
wingless insect, worldwide infestation of human dwellings, they hide in cracks in furniture and walls. they emerge at nigh for blood meal
gives an itchy rash after bite and can transmit other infections
what is the mode of transmission of malaria
malaria is transported by mosquito vectors (anopheles spp)
what is the mode of transmission of tapeworms
tapeworms (cestodes) use cattle as intermediate hosts - oncospheres hatch and penetrate intestinal wall and circulate to muscles where they develop into cysticerci. when humans ingest raw or uncooked meat they contract the disease
what is the mode of trasnmission of schistosoma?
schistosoma haematobium (bilharzia) is a trematode it uses fresh water snails as intermediate hosts. first the intermediate host is infected, the cercariae leave the snail and penetrate the skin of the human who is in the water and enters the blood stream (immature worms). the worms reach sexual maturity in the veins of abdominal cavity and females lay eggs which enter intestinal tract/ bladdder and passed by urine into fresh water
what are some common fungal infections and their cause
tinea pedis (athletes foot) cuased by superficial fungal infection
tinea corporis (ringworm) caused by superficial fungal infection)
crytococcus neorformans (yeast) - infects patients with failing immune system (HIV) casuing meningitis (inflammation of membranes lining the brain), headache, neck stiffness, confusion, coma and death - sever invasive fungal infection
describe the basic classifation of bacteria
shape - round=coccus, rod=bacillus
grouping - clusters, chains or pairs
what is a virus?
dependent on infection of a host cell for metabolism and replication
they contain a protein core surrounding genetic material (DNA or RNA), protein coat and sometimes outer membrane.
can only be seen with powerful electron microscope
what virus causes the common cold?
rhinovirus
what virus causes winter vomiting disease?
norovirus
what virus causes chicken pox?
varicella zoster virus (primary infection)
what virus causes shingles?
varicella zoster virus (from dormant chickenpox virus in densory nerve root which reactivates years later)
what virus causes glandular fever
epstein barr virus
what does acute mean?
microbe living inside host for a limited period of time
what does chronic mean?
persitant infection that is eventually cleared
what does latent mean?
persistant virus which stays until cell dies
what are 2 viruses associated with cancer?
EBV (epstein barr virus) and HBV (hepatitis B virus)
why is EBV associated with cancer?
infects immune cells and contributes to certain cancers
why is HBV associated with cancer?
it can damage DNA in cells and inflammation of the liver which interferes with how cells behave
what are prions?
smallest infective agent k known
proteinaceous infectious particle that lack a nucleus and are not living organisms.
the proteins are abnormal and accumulate in mainly neural tissue
they are very difficult to destroy, standard sterilisation techniques do not work
what are 3 diseases that prions cause?
CJD (cretzfeldt-jakob disease)
variant CJD - though to be derived from bovine spongiform encephalopathy (BSE or mad cow disease)
Kuru - similar to vCJD, spread by cannibalism, especially of brains of deceased relatives
what is a endogenous infection?
disease arrising from an infectious agent already present in the body but previously asymptomatic - when normal flora of the gut gets in the wrong place and causes a UTI- cystisis
give an example of a endogenous infection
cystisis
-infection of the lower urinary tract resulting in :
lower abdominal pain, urgency and increased frequency of urinaation, dysuria (painful or difficult urination)
what is an exogenous infection?
a disease caused by a pathogen entering the body from the environment
host factors preventing disease
stomach acid native bacteria immune system genetics - inherited immunodeficieny behaviour
environmental factors affecting infection
geography climate poverty public health infrastructure distribution
barriers to infection:
skin and mucous membrane
-cuts and abrasions are bad
principles of diagnosis
take their history:
- non-specific symptoms (fever, loss of apetite, weight gain/loss, muscle ache (myalgia), joint ache (arthralgia)
- specific symptoms - according to source
- past medical history that would make more susceptible to diseasse
- lifestyle activites
what are some basic tests used to identify infectious agents
C-reactive protein (CRP) is a marker for inflammation
U&E -urea and electrolyte levels (kidney function indicator)
LFT - liver function tests
antigen testing - for pneumonia and hepatitis B
antibody testing
culture
antibiotic sensitivity testing
PCR
microsocopy
what are desired characteristic of antimicrobial agents?
selective toxicity
bacteriocidal(kills instead of inhibiting growth - bracteriostaitc)
no resistance
good pharmacokinetics(reach high level int he body and stay there allowing a few doses per day)
no side effects
not affected by enzymes secreted by microbes or by the host.
what are some problems with antimicrobials?
variable spectrum of activity - borad spectrum = kill lots of different organisms, narrow =v kills few organisms
cannot be given orally
many cause side effects which can be serious e.g. anaphylaxis
bacterial resistance
how would you prevent spread of a airborne infection
isolate infected patient in negative pressure room (filters out going air)
how would you prevent spread of a food/water borne infection
sanitation, clean water supplies, food preparation hygiene
how would you prevent spread of a contact infection
handwashing
wearing gloves, gown, mask
how would you prevent spread of a vector borne infection
avoid mosquito bites, insect repellant, bed nets, long sleeves
which organism causes dysentery?
entamoeba histolytica
which insect transmits plasmodium falciparum to humans?
mosquitoes
what type of parasitic worms are unsegmented and flat, give an example
trematodes (flukes)
schistosoma haemtobium
what is the intermediate host for the tapeworm taenia solium
pig
what sort of organism causes atheltes foot?
fungus
what is the basic structure of a virus
protein coat surrounding protein core with nucelic acid
how does varicella zoster virus cause shingles many years after it causes chicken pox
virus lies dormant in sensory nerve roots for many years
name 3 human disease caused by prions
Kuru
Creuztfeld jakob disease
vCJD
What is cystisis and what is the commonest cause
lower urinary tract infection
caused by infection with gut bacteria such as eschericia coli
what symptoms are causued by the norovirus
vomiting and diarrhoea
what bacterium cuases tetanus (lock jaw)
clostridium tetani
what type of infection is malaria?
parasitic
the spread of rubeela from mother to child during pregnancy is what type of transmission?
vertical
what is the mechanism by which cholera toxin acts
activates adenyl cyclase increasing cAMP
reduces Na+absorption
increases Cl- secretion
water and other electrolytes are drawn into the bowel lumen = diarrhoea
why woulda patient with TB be isolated in a negative pressure room?
disease is spread by airborne trasnmission
name 4 impotant diseases for which there is currently no vaccine available
HIV
meningococcus gorup B
HCV
malaria
which vaccination protects against cervical cancer
HPV
what is taenia seginata?
tape worm
what is entamoeba histolytica?
anaerobic parasitic protozoan
which zone of lung are you most likely to have collapsed vessels?
zone 1
what is most of co2 transported as in the blood?
bicarbonate ions
where in the repsiratory centre is the pneumotaxic centre located?
pons
what is atelectasis?
airway collapse
