Download V. cholerae M. tuberculosis

Pathogenic
A pathogenic organism causes disease or illness
to its host by disrupting normal physiology
BACTERIA
V. cholerae
M. tuberculosis
VIRUSES
smallpox
flu
TMV
PROTOCTISTA
P. falciparum
Infectious
TRANSMITTED BY
Infectious diseases are transmitted to other people
contagious
communicable
transmittable
transmissible
transferable
conveyable
spreadable
spreading
breathing
touching
eating & drinking
animal & insect bites
kissing
sexual contact
vaccines
hand washing
medicines
Disease reservoir
Long term host of a pathogen, with few or no symptoms,
which remains a potential source of disease outbreak.
EXAMPLES
Cholera in shellfish
Rabies in bats
Ebola in some primates
Tapeworms in pigs
Bird flu in ducks
Carriers are infectious
even though they do not
have the symptoms of
disease
e.g. Typhoid Mary
Vectors transmit disease
e.g. malaria transmitted
in a mosquito bite
Carrier
A carrier is an infected person, or other organism,
who shows no symptoms but can infect others.
Typhoid Mary
Herpes simplex virus
can be transmitted
before cold sores
develop
C. difficile can be
transmitted
e.g. in care homes
by people with no
symptoms
HIV may have a long
period of bring
infectious, before
symptoms appear
Endemic
GENETIC
Disease occurring frequently, at a predictable
rate, in a specific location or population.
Chicken pox has a
high, predictable
rate in school
children
Tay-Sachs disease
occurs with higher
frequency among
Jews and French
Canadians than other
groups
Liver fluke disease
especially in east &
southeast Asia, and
central & south
America
Epidemic
The rapid spread of infectious disease to a large number of
people within a short period of time, usually two weeks.
Altered ecology allows new
pathogen to make contact
with population
e.g. HIV in 1950s
Genetic change in pathogen
allows it to increase its
infectivity
e.g. Spanish flu in 1918
Pandemic
An epidemic over a very wide area, crossing international
boundaries, usually affecting a large number of people.
Characteristics:
• infects humans
• causes disease in humans
• spreads between humans
quite easily
Mild:
swine flu (2009)
Serious:
Polio (1950s)
Malaria 500M deaths annually
Vaccine
An antigenic substance prepared from a disease-causing organism,
or a synthetic substitute, used to provide immunity against disease.
Often made from:
• weakened or killed microbe
• its toxins
• one of its surface proteins.
Stimulates the body's immune
system to:
• recognize the agent as a threat
• destroy it
• keep a record of it
Provides active
acquired
immunity to a
particular disease
Antibiotics
Substance produced by a microorganism that
selectively kills or inhibits the growth of bacteria
Antibiotics kill sensitive
bacteria but mutant,
resistant bacteria grow and
multiply.
Methicillin-resistant
Staphylococcus aureus
(MRSA) causes infections that
are resistant to several
common antibiotics.
• Don't use antibiotics
for virus infection
• Finish the course:
some bacteria may
survive and cause
re-infection
Antigen
Any substance that causes your immune
system to produce antibodies against it
The body distinguishes “self” from
“non-self”.
“Non-self” molecules are antigens.
e.g. a foreign substance
from the environment
including chemicals,
bacteria, viruses, pollen
e.g. molecule formed
inside the body
including bacterial
toxins, tissue cells.
Antibody
A protein produced by the body's immune system in response to antigens.
An antibody is an
immunoglobulin (Ig), a
large, Y-shape protein.
The forks of the Y are the
‘variable regions’
An antibody recognises
an antigen at the
variable region.
In an autoimmune
disease, antibodies are
made against the
body’s own cells.
Resistance
Microbes that are not killed by antimicrobial
agents such as antibiotics show resistance.
Antimicrobial resistance
is often acquired as a
new mutation or
transfer of genes
Resistance causes
millions of deaths
every year.
All classes of
microbes can
develop resistance
AA
Microbes which are resistant
to several antimicrobials are
‘multidrug resistant’ (MDR).
Vector
A person, animal or microbe that carries and transmits
an infectious pathogen into another living organism
• Vector feeds on infected vertebrates
• Microbe multiplies in vector
• Microbe transmitted to new host
when vector feeds again.
Vector-borne diseases are often
tropical & sub-tropical and where
access to safe drinking-water and
sanitation systems are problems.
Education and sanitation
are important preventative
measures.
Spread by
• climate change
• international trade
• International travel
Toxin
A toxin is a poisonous substance produced within living cells or organisms
Toxins include small
molecules, peptides and
proteins
Toxins affect biological
macromolecules such
as enzymes and cellular
receptors
Toxins cause disease
following contact with or
absorption by body tissues
Antigenic type
Different individuals of the same pathogenic species may have altered
surface proteins. These individuals are ‘antigenic types’ or ‘serotypes’.
Different antigenic
types may not
recognised by host’s
immune system.
Having many serotypes is useful for
pathogens that
• Have long-lived hosts
• Infect a single host repeatedly
• Are easily transmissible
No long-term vaccines for
pathogens with frequent
changes of surface protein
e.g. flu, rhinovirus
Pathogens with serotypes:
Protoctista e.g. Plasmodium
Bacteria e.g. Neisseria gonorrhoea
Viruses e.g. influenza, HIV