Bacteria of Medical Importance Flashcards
What is the first step in the diagnosis of infections?
History of the patient taken
What laboratory investigations may be used for the diagnosis of infections?
Haematological, biochemical, microbiology/virology
What other tests may be used in the diagnosis of infections?
x-rays and other scans as required
Why is taking the history of a patient important?
The laboratory will only look for things that are likely to be there
The symptoms and duration can either be
acute or chronic
Why is travel important in the history
risk of tropical or imported disease
Contact with animals should be noted down due to
the risk of zoonotic infections
contact with infected people should be noted down because of
tuberculosis/ meningitis contact
drugs should be noted down in the history
as antibiotic treatments can cause opportunistic infections
what is the gold standard in the classification and identification of bacteria?
the culture of the organism
the initial identification relies on a few simple tests including
microscopy and growth characteristics
further identification after the initial identification includes
biochemical tests, antigen demonstration, toxin demonstration
some organisms cannot be grown and indirect detection methods are used such as
immunofluorescnece, PCR and serologcial diagnosis 4 fold rise in specific IgM
What staining technique is most widely used
Gram stain
Gram positive stains
purple
gram negative stains
red/pink
Gram stain allows the morphology of the organisms to be seen such as
rods/cocci/pairs/clusters/chains
Ziehl-Nielsen stain is used for
mycobacteria
cotton blue stain is used for
fungi
darkfield microscopy is used for
spirochaetes
gram positive cell walls include a thick layer of
peptidoglycan
gram negative cell walls include
thin layer of peptidoglycan, LPS,
Give an example of gram positive cocci - clustering type
staphylococci
give three examples of staphylococci bacteria
s.aureus, s.epidermidis, s.saprophyticus
s.aureus is responsible for severe
soft tissue infections, bacteraemia and endocarditis, necroitising pneumonia,
s.aureus can cause outbreaks in hospitals this is called
nosocomial outbreaks
bacteraemis is
the presence of bacteria in the blood
s.epidermidis is part of the normal
skin commensal
s.epidermidis is an
opportunistic pathogen
an opportunistic pathogen causes infection in the
immunocompromised
s.epidermidis can cause infection through
prosthetic devices
virulence factors are produced by s.aureus in the form of
enzymes, toxins, other e.g. slime prod, capsule , cell wall
what are some of the enzymes produced by s.aureus
coagulase, catalase, lipase, nuclease, penicillinase,
what are some toxins produced by s.aureus
cytotoxins, enterotoxin,
what three laboratory tests allow for the detection of s.aureus
positive catalase production, coagulase production, dnaase production
what is an example of gram positive cocci in chains
streptococci
what are the two types of streptococci
haemolytic versus non-haemolytic
the haemolytic streptococci group can be divided into
alpha haemolytic and beta haemolytic
alpha haemolytic bacteria include the normal
oral commensal
give three examples of bacteria making up the normal oral commensals
s.oralis, s.salivaris, s.mitis
what can alpha haemolytic streptococci cause
sub acute endocarditis
s.pneumoniae which is part of the streptococci alpha haemolytic group can cause
severe pneumonia, bacteraemia and meningitis
the beta haemolytic group is split up into the groups
a, b , c , d and g
group a in beta haemolytic streptococci is known as
streptococci pyogenes
streptococci pyogenes causes
severe ssti (skin and soft tissue infections)
what is group b in beta haemolytic streptococci called
s.agalactaiae
what does s. agalactaiae cause
neonatal sepsis
what is group d streptococci
s.bovis / enterococci
what does s.bovis / enterococci cause
uti / biliary sepsis
give four examples of gram positive bacilli
clostridium. bacillus, corynebacterium, listeria
gram positive bacilli are primarily
toxin mediated diseases
give four examples of clostridium which falls under the gram positive bacilli group
c.tetanni, c.perfingens, c.botulinum, c.difficile
name two bacteria that fall under bacillus which falls under the gram positive bacilli group
b.antracus, b.cereus
give a example of a corynebacterium
c.diptheriae
give an example of listeria bacteria
l.monocytogenes
clostridial diseases involve bacteria which are anaerobic
spore forming organisms
c.perfringenes causes which three problems
gas gangrene, clostridial myonecrosis and food poisioning
c.tetani causes
tetanus
c.botulinum causes
would/systemic botulism
c.difficile causes
antibiotic associated diarrhoeae
what are the gram negative cocci
moraxellacae
list three respiratory pathogens that fall under gram negative cocci - moraxellacae
haemophilus influenzae, moraxella catarhallis and neisseria meningitidis
give an example of genitourinary pathogens that fall under the gram negative cocci
neisseria gonorrhoeae
give an example of an opportunistic pathogen that falls under gram negative cocci
acinetobacter baumannii
most gram negative cocci have more
fastidious growth requirements
gram negative cocci have more fastidious growth requirements, this includes
lysed blood added to the media, requirement for haemin (factor x) and NAD (factor V)
instead of culturing neisseria meningitidis , a gram negative cocci what has been developed
rapid tests for meningococcal disease
gram negative rods include
enterobacteriaciae
give two examples of enterobacteriaciae
e.coli, klebsiella, enterobacter, serratia, citrobacter, morganella
the severity of enterbacteriaciae is on a continuum, what is the weakest and worst types of infections it can cause
least severe - asymptomatic colonisation, worst - neurosurgical meningitis
there has been in an increase in ___ of enterobacteriaceae over the past 64 years
taxa
