Heaphy 8 Pathogenesis Flashcards
Pathology:
study of disease (pathos = suffering).
progress of disease,
deviation from, or interruption of normal structure/function of any body part.
SEVERITY:
Mild, severe, localised, systemic.
syphilis:
mild & localized progressing to severe systemic
Symptoms: lesion goes, months=> rash, yrs => dementia arthritis major organ failure => fatal.
HPV:
warts, cancer, oval cancer, cervical cancer => 80% of population risk increase with partners
80-90% cleared by immune system some chronically infected, some severe pathology (cancers) over period of yrs.
Medical microbiology:
“pathology of infectious diseases, caused by micro-organisms, capable of being transmitted e.g person-to-person, animal-to-animal”.
Dynamic interaction:
between disease-causing organisms and their victims - host-pathogen/parasite interaction. – genetics, resistance
Pathogens:
- micro-organisms that cause disease (viruses, bacteria, fungi including yeasts and amoebae)
• Most microorganisms are not harmful (even helpful)
Parasites:
larger pathogens e.g. Plasmodium. (malaria)
Pathogenicity:
mechanisms employed to bring about disease
Virulence:
ability to cause disease, relative,
- measles virus is more virulent than cold virus, because it is more deadly/dangerous.
Opportunistic Pathogens
do not normally cause disease - may live in host as commensals, may cause disease when body compromised
E. coli:
Opportunistic
harmlessly in GI tract, but may contaminate urinary tract (poor hygiene?
• Especially babies and females), infect urethra & bladder (cystitis) => (pyelonephritis) inflammation of kidneys. (can occlude kidneys)
Pseudomonas aeruginosa :
Opportunistic
burns patients lose defensive barrier of skin destroyed, can invade.
• environmental bacteria
Pneumocystis carinii (protozoan) :
Opportunistic
infects lungs of immunocompromised patients=> pneumonia,
• From animal faeces
• Killed most people with HIV/AIDS which is zooninoses:
Staphylococcus aureus :
Opportunistic
problem in immunosuppressed transplant patients
• and weak patients in hospital
in blood stream
associated w/ spots/boils, fatal to elderly with pneumonia => septicaemia
Name opportunistic pathogens
x4
E. coli
Pseudomonas aeruginosa
Pneumocystis carinii (protozoan)
Staphylococcus aureus
Obligate pathogens
evolved virulence factors that cause disease in otherwise healthy hosts as part of the normal life cycle.
Obligate pathogens
x 5
Vibrio cholerae POLIO Salmonella typhi, typhoid fever Mycobacterium tuberculosis HIV causes AIDS
Vibrio cholerae
Obligate
makes powerful toxin to induce massive fluid loss into intestine
- large investment in sanitation & water systems reduces/eradicates . prone in places without this
- makes protein that stops gut working properly => nutrients normally absorbed.
- Switch fluid pump from gut to body to body to gut => 10L of cholera particles into environment. => infection cycle.
- Use rehydration therapy or fatal.
POLIO
Obligate
water born virus, GI infection => dierhera
Salmonella typhi, typhoid fever:
Obligate
invades gut wall, enters blood and lymph systems, systemic spread
-water sanitation = prevention
Mycobacterium tuberculosis:
Obligate
causes TB, induces tubercles that result in necrosis of lung tissue and possible systemic spread via blood-stream. Can infect other organs
-irritaion of lugs => cough => spread
HIV causes AIDS:
Obligate infects class of immune cells (CD4+ lymphocytes), reduces immunological defence => fatal
virulence factors:
toxin production, the ability to invade, cytotoxicity (kills cells).
BIOFILMS:
mucilaginous surface communities. Complicated as a tissue.
BIOFILMS:
Examples
• Contaminate implants,
• Catheters, stoma, hickman line in chest, dialysis => infection hard to treat with antibiotics because biofilm protects
• Lung infection
• Tooth decay=> prone to cardiovascular & artieriole cell walls that move from dental infections to blood stream.
•
=> polymicrobial infections = many microorganisms
Common features of pathogenic organisms
- infect the host - i.e. breach physical defences (immune system)
- reproduce in host - increase to critical population size
- transmit to another host.
- R value of 1 = infects 1 more host likely to die out
- R Value greater spreads more.
HORIZONTAL TRANSMISSION
• Pathogen transmitted from infected to non-infected host by:
- Aerosols
- Faecal-oral route
-vector-borne - bodily contact, person-to-person.
• sexually transmitted diseases
• zoonoses,
Aerosols:
HORIZONTAL TRANSMISSION coughing or sneezing, water droplets and fragments of mucus expelled- e.g. cold, influenza, measles virus,
- Bordetella pertussis (whooping cough), Streptococcus species (sore throat), common cold etc.
Faecal-oral route
HORIZONTAL TRANSMISSION
ingestion of water or food contaminated with faeces- gastrointestinal pathogens e.g. Norwalk virus, Vibrio cholerae, Shigella species
-food processing
Vector-borne:
HORIZONTAL TRANSMISSION
by insects, either externally or internally, malaria (mosquitoes), Lyme disease (ticks), encephalitis (mosquitoes), plague (fleas)
bodily contact:
HORIZONTAL TRANSMISSION
Breast-feeding => animal milk=> TB
• Warts
• EBV.
sexually transmitted diseases:
HORIZONTAL TRANSMISSION
gonorrhoea, genital herpes and AIDS
zoonoses:
HORIZONTAL TRANSMISSION
Animals=> rabies.
VERTICAL transmission
• From parent, usually mother, to offspring e.g.
Rubella (german measles):
VERTICAL transmission
1st trimester of pregnancy => natural abortion, brain/heart/organ damage, cataracts, spacing
syphilis:
VERTICAL transmission
, cytomegalovirus (herpes virus can be associated w/ brain tumors can transmit in utero & cause brain damage in children)
transmitted to babies as infected mother gives birth
VERTICAL transmission
gonorrhoea, HIV, HPV
oral throat & mouth requires surgery => scaring of trachea => respiratory problems
Retroviral germ line:
VERTICAL transmission
i.e. sperm and eggs, possibility of infection of early embryo.
DISEASE COURSE:
• dynamic series of events reflecting competition between pathogen & host
• variation even between individuals.
·operation of host defences to overcome & clear pathogen
·activity of virulence factors that allow pathogen to persist and proliferate in host
• Huge variation, but common stages in progress of infectious diseases.
DISEASE COURSE
1 Contact 2 Incubation period 3 Prodromal period 4 Acute phase 5 Crisis 6 Decline period 7 Convalescence
• incubation period
2 no symptoms, pathogen reaches site of infection, reproduces to critical population size;
- measles 10 days, but hours in some gastrointestinal infections, years in leprosy)
• prodromal period
3 general symptoms of distress, e.g. nausea, fever, headache, malaise, indicates pathogen ‘winning’ competition;
in measles days 10-13 after infection
• acute phase
4 - specific symptoms appear, rash on face and body,
- 13-16 days after infection, high fever, pallor as blood vessels in skin constrict
• crisis
5 body temp reaches dangerous level, death possible
• convalescence
7 restoration of normal health, in measles ~21 days post infection, life-long immunity to further infection
Different infectious disease show different progression; HIV kills, malaria never fully cleared and may recur, some do not leave lasting immunity.
Contact.
1 Exposed to measles virus thru aerosol expelled from infected person, coughs or sneezes;
decline period
6 balance swings in favour of immune system, prevents virus replication, profuse sweating releases excessive heat, normal skin colour restored; in measles days 16-18 after infection
