bacterial pathogens Flashcards
bacterial flora is
endogenous
endogenous bacteria
bacteria that naturally reside in a closed system
when does disease occur
when microbes including in normal bacterial flora enter a sterile area of the body such as the brain or muscle- endogenous infection
example of endogenous infection
when E.coli of GI tract enters urinary tract- uti
exogenous bacteria
microorganisms introduced to closed systems from the external world- can either be benign or pathogenic e.g. cholera
clostridium in being exogenous
can be introduced into a closed ecosystem as well, having mutualist benefits for both the microbe and the host
what can control the spread of infection
social and environmental factors; vector control, chemoprophylaxis, outbreak investigation, food safety, health education
examples of HCAI- hospital acquired infections
-intravenous canulae; surgery; skin infection; urinary catheter; Gastrointestinal infection
gram negative bacteria
thin peptidoglycan- stay red since cant retain dye
all proteobacteria are
gram negativw
Neisseria meningitidis- type of bacteria
beta proteobacteria
Neisseria meningitidis
carried in the nasopharynx in 10-15% of population- epidemics occur every 10-12 years. classified by serogroup
serogroup
these microorganisms, viruses or cells are classified together based on their cell surface antigens, allowing the epidemiological classification of organisms to the sub-species level
-reactivity to a bacterial polysaccharide capsule
how many serogroups of N-meningitidis
12, 6 of which (ABCWXY) can cause epidemics
serogroups are based on
cell surface antigens
vaccines available for Neisseria meningtidis
a meningococcal A conjugate vaccine, tetravalent A, C, Y and W conjugate vaccine and meningococcal polysaccharide vaccine
gram positive bacteria
these bacteria retain the crystal violet dye (one of the main chemicals used for gram staining
example of a gram positive bacteria
Corynebacterium diptheriae
Corynebacterium diphtheria causes
diptheria
diphtheria was first reported in
4th century
corynebacterium diphtheria
-immotile rod
where does corynebacterium diphtheria colonize
upper respiratory tract
- route of infection: droplets, person to person e.g. from coughing and sneezing
how does corynebacterium diphtheria cause damage
releasing exotoxins- killing host cells. these spread systematically and principally effects the lungs and the heart
main cause of mortality in diphtheria is
toxin spread
emerging infections
infections the are rapidly increasing in incidence or geographic range.
reasons for a pathogen to appear in a list of ‘new species’ (5)
(1) both pathogen and disease it causes didn’t occur before 1980
(2) disease was already recognised but the pathogen was not identified as the etiological agent before 1980
(3) the pathogen was already recognised but not associated with human disease before 1980
(4) neither the pathogen or disease it causes were recognised before 1980, but they dd occur
(5) what was considered to be a single pathogen before 1980 was subsequently recognise as comprising two or more species
the process of disease emergence can be divided into 2 steps
(1) introduction- where “andromeda- like” infections come from
(2) establishment and dissemination- which is much harder for most of these agents to achieve
basic lesson on the pathogens that cause epidemics
many may be called, but few are chosen.
main virulence factor of diptheria
AB toxin- controlled by immunisation (DTaB)
vaccines for diptheria
all babies are vaccine against it in a 5 in 1 vaccine given when they are two, three and four months old.
- vaccine known a DTaP/ IPV/ Hib vaccine
AB toxin and diptheria
AB toxin release by bacteria. Receptor in membrane of cell attaches to the toxin. a vesicle forms around the complex. As the now endosome goes further into the cell, it is acidified by a hydrogen pump. This causes the receptor to release the AB toxin and the complex leaves the endosome. The A part of the attaches to the EF-2 of the EF2/ADP molecule..
before/ after vaccine for diphtheria, tetanus, pertussis, polio, Hib disease
deaths before: 6430 deaths; deaths after: 3
zoonotic diseases
Zoonoses are infectious diseases of animals (usually vertebrates) that can naturally be transmitted to humans
how many species can be capable of infection animal hosts and humans
800
relatively few human pathogens are solely know was
human pathogens
why may zoonotic diseases becoming more occurrent
increased production of food to satisfy future and present demand, agriculture is ow in previously untouched areas of native environment
the impact of climate change has resulted in
disturbances in ecosystems and re-distribution of disease reservoirs and vectors.
what has increased the chance of transmission of zoonotic disease
increased globalisation and trail as increased the chance, extent and spread at which disease transmission occurs
how diseases present themselves in diff animals
many zoonotic agents cause little or no signs of disease in their natural hosts, such as wild birds and bats, but transmission hosts might present with disease symptoms ranging from moderate to sevre
there terminal or spill over cost can present with
severe symptoms and high mortality rate ( e.g. in the case of humans infected with H5N1 influenza)
example of humans transmitting pathogens to animals
MRSA
Streptococcus suis- zoonotic disease
S.suish is a pathogenic gram positive bacterial strain that represents a primary health problem in the swim industry,
key facts on S.suis
- spread over 30 countries, 1,300 human cases
- 35 serotypes based on capsular antigen. Most common in china (epidemics in 1998 and 2005).
- reason for few cases in N.America could be misdiagnosis
chinese serogrpup 2 strain 055zyH33 Streptococcus suis
Contains a system similar to a Type 4 secretion system which thought to stimulate the host immune reaction observed with streptococcal toxic shock like syndrome (STSLS)
AB toxins
The AB toxins are two-component protein complexes secreted by a number of pathogenic bacteria. They can be classified as Type III toxins because they interfere with internal cell function.
detailed AB TOXIN
1) B part of AB toxin attaches to the receptor on the outside of the cell
2) receptor mediated endocytosis
3) phagosome is acidified
4) causes AB toxin to separate
5) A part of the town binds to EF2 causing conformational change
6) prevents translation- causes cell death
AB toxin is a Type..
III
type III AB toxins
disrupt internal cell function
B part
attaches to receptor
A part
causes inactivation of EF2
EF2
elongation factor- needed for attachments of new a.a. sequences
