micro-classification and identification fo bacteria of medical importance Flashcards
why do we need to learn medical microbiology
to study microbes that cause disease
help with diagnosis prevention and treatment
what is the germ theory of disease
Changed peoples perception of microbes and the aetiology agents of disease
discovered by louis pasteur
what are the three main types of organisms
eukaryotes
prokaryotes
viruses
give examples of eukaryotes
fungi and protozoa
give examples of prokaryotes
eubacteria
describe viruses
non cellular
50-100 mm in length
what are bacteria divided into
gram +ve and gram -ve
describe gram negative bacteria
have a thinner cell wall by a phospholipid membrane with LPS molecules attached
what shape are cocci bacteria
circular
what shape are rod/bacilli bacteria
long straight noodle shape
what shape are coccobacilli
stretched out oval
what shape a vibrio
curved C shape
what shape are spirilla
wiggle shaped
how do we identify bacteria in the lab
they need to be isolated and in pure culture
then cultivated on columbia blood agar
how many bacteria can we currently cultivate
around 700 app
why can we not cultivate all bacteria
due to the fact we cannot correctly simulate all the conditions needed to grow certain bacteria
what are the types of differential characteristics
colony morphology
cell morphology
what is colony morphology
a change in shape haemolysis and pigment
what is cell morphology
shape spores and gram staining
describe the different types of haemolysis
a - species produce enzymes that cause oxidation of the iron in the haemoglobin molecule and that leads to a yellow green shine around these species
b - enzymes that causes complete rupture of the haemoglobin cells
gamma - no haemolytic enzymes produced
what is the procedure of gram staining
fixation WASH crystal violet WASH iodine WASH decolorisation using alcohol WASH counter stain WASH
describe +ve bacteria
+ bacteria have a thick peptidoglycan outer wall and therefore the cell wall absorbs the violet and binds to the iodine
describe gram -ve bacteria
bacteria have a thin outer membrane wall and therefore cannot retain the crystal violet and iodine colour
what colour does gram +ve bacteria change to
purple
what colour does gram -ve bacteria change to
pink
what are some other differential characteristics
metabolic activity
antigens
cellular composition
DNA
example of another stain test
ziehl neelsen test
describe the ziehl neelsen test
adapted version of the gram stain
what are the steps to the ziehl neelsen test
carbol function
decolorisation
methylene blue
describe the catalase test
determines whether a sample of bacteria is capable of producing the catalase enzyme
using H202 and if the catalase is present then H202–> water and O2
describe the coagulase test
test the bacteria ia capable of producing a coagulase enzyme
soluble fibrinogen into insoluble fibrin
which bacteria is coagulase positive
s aureus
describe the oxidase test
testing for Cytochrome C oxidase
reagent turns dark blue when oxidised and colourless when negative
give examples for which bacteria we can use the oxidase test for
nicerella campylobacter and pasteurella sp
give examples of gram +ve bacilli
Mycobacterium tuberculosis
Mycobacterium leprae- Leprosy
Mycobacterium avium
give examples of spore producing gram +ve bacilli
bacillus anthracis bacillus cerus clostridium spp clostridium perferingens c tentani c botulinum
give examples of motile and non sporing bacilli
listeria spp
corynebacteria- c diphtheria
propionibacteria- p acnes
what does clostridium perfringens cause
gas gangrene
what does c tetani cause
tetanus
describe listeria spp
major human pathogen is listeria monocytogenes
causing listeriosis
not advised in pregnancy
babies who can this can suffer from meningitis or septicaemia
what is listeria monocytogenes found
in cheese and pates
describe diphtheria
mucosal disease of the throat and nose. prevented by vaccine. If untreated it can cause damage of kidneys and the heart
which bacterias are cala tase negative
streptococci
strep pneumoniae
which bacteria is catalase positive
staphylococci aureus
give examples of gram -ve cocci bacteria
veillonella spp
parvobacteria
acinobacters
neisseria spp
describe veillonella spp
obligately anaerobic meaning no oxygen for growth
important members of the human oral microbiota
isolated in dental plaque
describe parvobacteria and acinobacters
opportunistic bacteria causing infection in compromised pt
describe neisseria spp
neisseria meningitis causing meningoccal meningitis
n gonorrhoea causing gonorrhoea
give examples of gram -ve bacilli bacteria
haemophilus spp h influenza legionella app l pneumophilia bordetella spp
describe h influenza
associated with respiratory infections
may cause epiglossitis
describe legionella spp
L penumophilia caking legionaries disease
describe bordetella spp
bordetella pertussis causing whooping cough
which species are part of of the enterobacteriacaeae oxidase negative
E coli Y pestis S dysenteriae salmonella spp providencia spp
describe e coli
member of the commensal gut bacteria
describe y pestis
caused the plague
describe s dysenteriae
causes bacterial dysentery
describe salmonella
salmonella enterica causes gastroenteritis
salmonella typhi causes typhoid fever
describe providencia spp
causes UTI in people with catheters
give examples of gram -ve bacilli which are oxidase positive
campylobacter spp vibrio spp brucella spp flavobacterium spp pseudomonas spp