microbiology Flashcards
ectoparasites
head lice, scabies, ticks, fleas; parasite that lives on the exterior of its host
head lice (pediculus humanus capitis)
wingless insects, transferred by hair-hair contact, treated by combing or lotions (hedrin)
scabies (sarcoptes scabei)
small mites that burrow into skin, contagious and cause allergic reaction like symptoms; itchy pimple-like rash
treatment: permethrin, ivermectin
ticks
live on skin and feed off blood
transmit lyme disease, typhus
removed with tweezers
fleas
wingless insects that can jump, eggs may stay in carpets for a week
transmit typhus (rickettsia bacteria)
mosquitoes transmit
malaria, dengue, yellow fever, chikungunya, elphantiasis
sandfly transmits
leishmania which is a protozoal infection
tsetse fly
transmits trypanosoma which resides in blood and enters CNS causing neuronal damage and causing sleeping sickness
reduvid bug
chagas disease (trypanosoma)
simulum fly
onchocerciasis (river blindness)
endoparasites
parasites which live inside a host and inhabit the gut, lungs, heart and blood vessels
roundworms (nematodes)
intestinal nematodes:
cause diarrhoea, itch and anaemia
required orally or transmitted through faeces
extraintestinal nematodes:
trinchinella - present in infected meat and cysts in muscle
tapeworms
cestodes: flat segmented worms with both female and male organs
echonococcus granulosus
worms found in the gut of dogs
eggs release larvae in gut causing cysts in liver that can burst
pork tapeworm (taenia solium)
pigs are infected from ingesting human faeces - humans ingest uncooked pork
eggs are released in duodenum
larvae are carried in blood to CNS and become encysted (cysticercosis) causing pain and neurological problems - epilepsy
flukes (multicellular treatodes)
reside in blood (veins), guts, lungs
eggs become encysted in the liver, bladder, lungs, CNS
causing schistosomiasis
liver fluke (fasciola hepatica)
penetrates through colon wall and goes to liver via hepatic portal vein
causes cirrhosis/liver damage which induces jaundice
protozoal infections
single celled (eukaryotic) parasites which asexually reproduce inside human host
can be extracellular or intracellular
can be ingested or transmitted by blood transfusion, open wounds in aqueous environments, injected by ectoparasites in a blood meal
waterborne protozoal infections
giardia lamblia: causes GI upset and diarrhoea
Entamoeba histolytica: causes severe bloody diarrhoea and abscesses in brain
trichomonas: sexually transmitted disease, infects urinogenital tract causing vaginitis
insect-borne protozoal infections
Trypanosoma: transmitted by tsetse fly, extracellular and resides in blood
leishmania: transmitted by sandfly resides in macrophages causing skin sores and lysis of WBC
toxoplasmosis: from cat faeces, may cause foetal damage and schizophrenia
malaria
mosquito borne protozoal infection
plasmodium infection, untreated it results in cyclic fever/chills and destruction of RBC
life cycle of malaria
sporozoite is injected into human by mosquito and moves to liver forming a cyst which bursts open from hepatocytes releasing merozoites which infect RBC
they hoover up nutrients then burst cell - causing anaemia
releasing secretory granules/process haemoglobin - causing fever
viruses
parasites, non-living, hijack cellular process and produce virally encoded proteins and replicate genetic material
cannot reproduce asexually require host
viruses and their route of transmission
- polio/hepatitis A: faecal/oral route
- rabies: bite of infected animal
- herpes/HPV/HepB/HIV: sexually transmitted
- ebola: all body fluids/tissues
- ifluenza/colds/MMR: respiratory
- yellow fever/dengue fever/chikungunya: insect vectors
prion disease
prion protein disease - rare, fatal neurodegenerative disease
protein misfolding disease
clinically characterised by dementia and ataxia(staggering gait)
pathology characterised by neuronal loss, gliosis and spongiform change in brain
PrPc (cellular prion protein)
- normal cellular isoform
- monomeric and soluble
- protease sensitive
neuroprotective against oxidative stress
PrPsc (disease-specific protein)
- disease associated isoform
- aggregated and insoluble
- partially protease resistant
- infectious and toxic:
act as template to fold normal proteins into abnormal shape making them toxic
eukaryotes
- large cells
- organelle present
- multiple linear chromosomes
- some have cell walls (fungi)
prokaryotes
- small cells
- organelles absent
- 1 circular chromosome + plasmid
- cells walls (bacteria)
types growth media
- peptone (proteins)
- lactose (carbohydrates)
- bile salts + crystal violet (inhibit gram + bacteria)
- neutral red (pH indicator)
bacteria that use lactose
E. coli, Klebsiella
turn lactose into lactic acid
lowering pH
red colonies formed with surrounding precipitated bile salts causing haziness
bacteria that do not use lactose
Salmonella, Pseudomonas aeruginosa
use peptone which forms ammonia
causes higher pH
yellow medium agar and colourless colonies
gram + bacteria structure
- peptidoglycan layers
- cytoplasmic membrane
gram - bacteria structure
- lipopolysaccharides
- cytoplasmic membrane (outer)
- peptidoglycan layers
- cytoplasmic membrane (inner)
porins
found in gram negative bacteria outer membrane and let small hydrophilic molecules go through
gram - cocci
- staphylococcus aureus
- streptococcus pyogenes
- enterococcus faecalis
gram - cocci
- Neisseria gonorrhoeae
- Neisseria meningitidis
gram + rods
- clostridium difficile
- clostridium botulinum
- clostridium perfringens
- clostridium tetani
gram - rods
- Escherichia coli
- pseudomonas aeruginosa
- Klebsiella pneumoniae
mycobacteria
mycobacterium tuberculosis - TB
mycobacterium avium complex - TB like pulmonary infection in immunocompromised patients
mycobacterium Leprae - leprosy
symptoms of TB
- appetite loss
- fatigue
- chest pain
- coughing up blood
- productive prolonged cough
- night sweats
- pallor
pathogens with capsules
gram - bacteria:
- E.coli
- Klebsiella pneumonia
- haemophilus influenzae (rod)
- neisseria meningitidis
gram + bacteria:
- streptococcus pyogenes
- streptococcus pneumoniae
fungi:
Cryptococcus neoformans
bacteria with endospores
- all clostridium species
- bacillus anthracis (anthrax)
- bacillus cereus (food poisoning)
Clostridium difficile
gram + rod
pseudomembranous colitis -
diarrhoea, abdominal pain
usually following antibiotic treatment and changes in normal gut flora
fungi
yeasts (unicellular)
moulds (multicellular)
structure: proteins, beta-glucans, chitin, cytoplasmic membrane (ergosterol)
yeasts
candida albicans - oral/genital infections
Cryptococcus neoformans - meningitis
moulds
aspergillus - aspergillosis
aflatoxin - liver cancer
