S6- infection Flashcards
2 types of infections
- endogenous infection= normal microbial flora on (mucocutaneous surfaces) skin/ gut/ airway/ genital tract gets in wrong place (they vary according to site)
- exogenous/ communicable infection= person to person/ aminals/ enviromnent ie soil
example of endogeneous infections
cystitis (inflammation of bladder)
due to infection of lower urinary tract
caused by bacteria from gut flora (enter urethra and move to bladder)
Symptoms:
lower abdominal pain
urgency
dysuria
frequency
3 routes of transmission of endogeneous infecions
- migration (ie: bowel flora to urethra cause local infection and spread to bladder= UTI)- easier in females
- perforation (lead to disease of bowel colon (cancer) and hole in bowel wall leads to contamination of abdominal cavity with faecal flora= life threatening infection called peritonitis)
- Blood= endocarditis (dental work might cause mouth flora to enter blood stream (streptocicci bacteria) and circulation of blood will allow it to reach the heart and cause invasion to heart valve (especially if abnormal valve tissue due to congenital defect))
7 routes of transmission of exogeneous infections
- contact (direct and indirect)
- injuries (trauma, bites)
- airborne
- Oral (food/ water)
- blood-borne
- Sex
- Mother to baby (vertical)
some infection transmitted more than one way: ie: HIV
- blood borne (injecting drug use)
- vertical (antenatal, perinatal, breast feeding)
- Sexual
some infections require more than one step
Ie: staphylococcus (soft tissue infection)
- colonisation of skin (joins skin flora)
- penetration of skin (spreads and damages)
factors that make an infectiin serious: pathogen
pathogen factors:
1. infectious dose= minimum number of organisms required to produce disease
2. virulence factors (molecules that assists bacterium to colonise)= allow invasion of host
3. toxins= cholera bacterium produce toxin that binds to gut cells= watery diarrhoea causes dehydration and kidney failure and death
4. resistance to antimicrobials/ antibacterial= mutations (advantageous mutation the more antobacterials used= failure of antomicrobial treatment)
factors the make an infection serious:
Host
- environment (geo/ climate/ financial/ public health infrastructure ie sanitation/ distribution of other infection hosts) ie dengue fever= viral infection transmitted by mosquitoes (fever, rash, muscle pain, bleeding, shock and multi organ failure)
- barriers to infection (skin, mucous membranes/ stomach acid/ native bacteria/ immune system/ behaviour)
- genetics
barriers to infection examples
- cuts and wound infections/ corneal abrasions (entry for pathogens/ conjunctivitis)
- stomach acid pH 2= very few organims can survive/ drugs for stomach ulcer increase pH and patients are more susceptible to food poisoning
- normal gut bacteria prevents colonisation by pathogenic bacteria (antibiotic treatments destroys good bacteria too= allow pathogens to cause infection)
- immune system= primary and secondary/ aquired immunodeficiencies
- behaviour= job/ travel/ pets/ sex/ drugs
primary immunodeficiencies are…
genetic variation can…
secondary immunodeficiencies include:…
Rare
protect against infection
treatments that suppress the immune system (chemotherapy for cancer/ suppressors for autoimmune diseases)
HIV= destroys immune cells AIDS
7 types of organisms that cause infection in order of size from biggest to smallest
helminths (ie tapeworms)
insects (fleas)
protozoe (malaria)
fungi (candida)
Bacteria (staphylococci)
viruses (influenza)
Prions (kuru)
all…are parasites (depends on another for survival) but 3 organisms are considered MEDICAL parasites
infections
helminths
insects
protozoe
endoparasites live…
Ectoparasites live…
inside the body (major cause of illness ie: helminths and protozoa)
outside the body (minor symptoms but transmit other infections)
protozoa are..
some have complex lifecyles involving…
unicellular organisms (too small to see by eye)
more than one host
2 examples of protozoa
life cycle of malaria involves…stages
3
helminths are…organisms and some have complex lifecyles with more than one host
other species have their own helminths which can…
complex
Accidentally cause human disease
3 types of helminths are…
- Cestodes (tapeworm)- segmented, flat
- trematodes (flukes)- unsegmented, flat
- nematodes (round worms)- cylindrical, have digestive tract, lips, teeth, anus
example of cestode (taenia saginata- beef tapeworm)
example of trematodes (flukes- bilharzia)
example of ectoparasite insect (cimex lectularius- bedbugs)
2 main forms of fungal infections are:
some can switch between the 2 forms, they are called…
- Yeasts- single cells which bud
- moulds- filamentous strands
diamorphic fungi (yeast at body temp and mould at room temp)
fungal infections can be…for example related to skin structures
2 examples:
usually due to…
Superficial
1. tinea pedis (athlet’s foot)- (tinea= fungal and pedis= foot)
2. Tine corporis (ringworm)- (corporis= body)
3 common species of mould
Severe…fungal infections (ie: yeast)- infect patients with…
they cause…
invasive
failing immune system/ low resistance (ie: due to HIV)
meningitis (inflammation of membranes lining brain and spinal cord), headaches, neck stiffness, confusion, coma, death
bactria are…and they reproduce..
they use…to move and…for cell-to-cell interactions
unicellular organisms/ prokaryotes
asexually
flagellae and pili
bacteria are responsible fo rth emost common severe infections
for example:
- pneumonia (infection of lung tissue)
- UTI (bladder)
- cellulitis (skin)
- meningitis (brain)
- cholecystitis (gallbladder)
- diverticulitis (bowel)
- appendicitis (appendix- end of inestine- where faeces are formed)
3 ways bacteria are classified:
this is important because it allows to predict which…will be effective
- appearance on shape
- grouping
- gram stain
antibiotics
shapes of bacteria can be split into 2 groups:
- round= coccus
- rod= bacillus
coccus bacteria can group together in 3 different ways:
- clusters
- chains
- pairs
bacteria cell walls…in composition and some…the crystal…stain while other don’t
…stain is used to classify bacteria into 2 groups:
vary
retain
violet
gram stain
Gram-positive (purple)- bacteria have one cell membrane
Gram-negative (pink)- have inner and outer cell membranes
example of bactria infection (streptococcus pneumoniae- aka: pneumococcus)
-classification:
-colinises…areas
-also invades…
-cause…
-complications
Gram-positive cocci in pairs (purple, round)
nose and throat (40-50% of adults)
invades other sites ie: lungs- causing pneumonia
Cough, chest pain, breathlessness, fever
Blood stream infection, meningitis, death
viruses depend on…for metabolism and replication
their structure contains:
can be seen using…
host cell
Protein core around genetic material- protein coat and outer membrane
powerful electeron microscopes
3 enzymes used in lifecycle of HIV
- reverse transcriptase
- integrase (integrate viral DNA with host DNA)
- protease
viruses can cause a wide spectrum of disease:
new viruses always re-emerge with with chainging human behaviour
- tivial infections= ie: rhinovirus- common cold
- severe chronic disease= HIV
- acute life threatening disease= ebola
viruses infect host cells for differing lengths of time
- acute infection= norovirus for days causing diarrhoea and vomiting (gastro-enteritis- infection of stomach and intestines)
- chronic infection= hepatitis C virus cause liver inflammation for years
- latent infection= herpesviruses can be dormant for decades before reactivating to cause disease
example of virus that causes latent infection: varicella zoster virus
-primary infection causes…
-then the virus becomes dormant in…
-reactivates years later as…
Chickenpox (rash and fever)
sensory nerve roots
shingles (same rash but confined to dermatome= area supplied by single sensory nerve)
some viral infections contribute to…
Cancers
prions are…
they are also called:
they lack…(not a living organism)
they are a type of protein that…
they are very difficult to destroy (standard sterilisation techniques/ disinfectants and heating do not work)
smallest infective agents known
protein-aceous infectious particles
nucleic acid
makes other proteins fold abnormally and accumulate mainly in neural tissues
3 examples of prion diseases:
