Lecture notes
Lecture notes Year 1 MBChB: Introduction to Medical Sciences (IMS)
Concise lecture notes from the infection strand of the IMS module taught in the first year of the MBChB course at the University of Leeds!
[Show more]
Connected book
Book Title:
Author(s):
- Edition:
- ISBN:
- Edition:
Content preview
INFECTIONINTRODUCTION TO INFECTION
Causes of infection Size Parasites in Medicine
Helminths - Tapeworm Parasite: organisms that depends on another for its survival to the
Insects - Fleas detriment to the host
Protozoa – Malaria All infections are parasites
Fungi - Candida Medical parasite: helminths, insects and protozoa
Bacteria - Staphylococci Endoparasites: live inside body; major cause of illness
Viruses - Influenza Ectoparasites: live outside body; minor symptoms but can transmit other
Prions - Kuru infections e.g. fleas, lice, bed bugs, ticks
Human endoparasites
Protozoa Helminths
Unicellular organisms Complex organisms
Some have complex lifecycles involving more than Some have complex lifecycles involving more than one
one host host
Other species have their own Helminths which can
accidently cause human disease
Protozoa
Amoebae Example: Entamoeba histolytica
Invades large bowel lining Worms – Helminths
Causes dysentery Cestodes (tapeworms) –
o Abdominal cramps segmented, flat
o Bloody diarrhoea Trematodes (flukes) –
Excreted with faeces unsegmented, flat
Spread via contaminated food & water Nematodes (round worms) –
Risks: poor hygiene/sanitation cylindrical, have digestive tract with lips,
teeth and anus
Sporozoa Example: Plasmodium falciparum (malaria)
Lifecycle in both humans and mosquitoes
Ringworm – colloquial term
Infects red blood cells and liver
Symptoms: fever, headache, joint pains
Cestodes
Trematodes
– tapeworms
- flukes
Complications: kidney failure, coma, death
Example:
Example: taeniaSchistosoma
saginata (beef
haematobium
tapeworm)(bilharzia)
Risk: geographical
Intestinal
Human parasite
host: infection
of humanof(obligatory
veins around
host)
bladder
Largely
Causes asymptomatic
bladder inflammation, bleeding into urine
o(haematuria)
abdominal pain
oIntermediate host freshwater snail
malnutrition
Diagnosis: urine microscopy for eggs
Diagnosis
o patient
o stool microscopy for eggs
Cattle are intermediate hosts
Ectoparasite – bedbug
Example: Cimex lectularius
Wingless insect
Worldwide infestation of human dwellings
Hide in cracks in furniture & walls
Emerge at night to feed – 5-10 minutes for a blood meal
Itchy rash after bite
Can transmit other infections - protozoa in South America (trypanosomiasis)
Fungal infections
Yeasts – single cells which bud
Moulds – filaments strands
Some can switch between yeast & mould (dimorphic fungi)
, Severe invasive fungal infections
Superficial fungal infections Example: cryptococcus neoformans (yeast)
Tinea pedis – athletes foot Infects patients with low resistance due to failing immune
Tinea corporis – ringworm system e.g. HIV
Usually due to 3 common species of mould Causes meningitis (inflammation of membranes lining brain)
Headache, neck stiffness, confusion, coma, death
Medical importance of bacteria
Bacteria - prokaryotes Responsible for:
Unicellular organisms o Pneumonia
Cell membrane, cell wall o Urinary tract infection
No nucleus – non-linear DNA o Cellulitis - skin
Reproduce asexually o Meningitis
Move using flagellae and pili o Cholecystitis
o Diverticulitis
o Appendicitis
Gram stain
Some retain crystal violet stain, others do not
Gram-positive (purple)
Gram-negative (pink)
Allows you to predict which antibiotics will be effective quickly
Tells you what antibiotic to prescribe
Bacterial infection
Example: streptococcus pneumoniae aka pneumococcus
Gram-positive cocci in pairs (diplococci)
Colonise nose & throat (40-50% adults)
Invade other sites e.g. lungs causing pneumonia
Cough, dirty sputum, chest pain breathlessness, fever
Complications: blood stream infection, meningitis, death, sepsis
Viruses
Dependent on infection of host cell for metabolism & replication
Contain protein core surrounding genetic material (DNA or RNA), protein coat +/- outer
membrane
Very small: 1/100th size of bacteria
Can only be seen with powerful electron microscopes
Virus life cycle – HIV
Turns RNA into cDNA integrates it into our own cell, protease
packages it and send it out of the host cell
Viruses cause a wide spectrum of disease
Some cause trivial infections e.g. rhinovirus – common cold
Some cause severe chronic disease e.g. HIV
Some cause acute life threatening disease e.g. Ebola – viral
haemorrhagic fever
Viruses infect host cells for differing
lengths of time
Acute infection: norovirus infects hosts for days, causing diarrhoea and vomiting (gastroenteritis)
Chronic infection: hepatitis C virus causes liver inflammation for years
Latent infection: herpesviruses can be dormant for decades before reactivating to cause disease
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller azreenafzal. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £7.49. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
52510 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now