L6 Gram negative bacteria Flashcards
what are the gram negative cocci
neisseria meningitidis
neisseria gonorrhoeae
moraxella catarrhalis
what is the gram negative cell wall
outer membrane (LPS) contains adhesins periplasmic space (thin PG) cytoplasmic membrane
what is the shape of neisseria meningitidis and neisseria gonorrhoeae
diplococci
how do neisseria meningitidis and neisseria gonorrhoeae grow and what is the best plate they grow on
fastidious
grow well on chocolate agar at 37°C in 5% CO2
what are the neisseria meningitidis and neisseria gonorrhoeae colonies like
transparent
non-hemolytic
1-5mm diameter
are neisseria meningitidis and neisseria gonorrhoeae oxidase +/-
positive as have cytochrome
what do neisseria meningitidis and neisseria gonorrhoeae metabolise
both metabolise glucose
meningococcus also utilises maltose
form acid
what pathogen is neisseria meningitidis
obligate human pathogen
where does neisseria meningitidis infect
back of throat
how many of the population are asymptomatic to neisseria meningitidis and where do they carry
10%
nasopharyngeal carriage
cant infect the blood stream
how are neisseria meningitidis segregated
Meningococci are segregated into 12 serogroups – serogroups A, B, C, W and Y cause most infections
what vaccine is there available for neisseria meningitidis
ACWY
B
what does neisseria meningitidis cause
bacterial meningitis in children and young adults septicaemia septic arthritis endophthalmitis conjunctivitis
what are the effects of meningococcal meningitis
marked neck
stiffness
photophobia
arching back
how is meningococcal meningitis diagnosed
lumbar puncture = CSF fluid meant to be clear like water, but if have bacterial meningitis = cloudy caused by the WBC
what are the effects of meningococcal septicaemia
purpuric non-blanching rash
how is neisseria gonorrhoeae transmitted
common bacterial infection transmitted by sexual contact or perinatally
how are neisseria gonorrhoeae inoculated
dont tolerate drying - need to be inoculated onto appropriate media immediately
what are the samples for neisseria gonorrhoeae diagnosis
cervial, pharyngeal, rectal
what does neisseria gonorrhoeae cause
urethritis (men)
cervicitis (mainly women)
women are asymptomatic
in neonates - opthalmia neonatorum - eye infection
why do neisseria gonorrhoeae not tolerate drying
no capsule
what is the gram stain of urethral discharge like
many polymorphonuclear cells
what does disseminated GC cause
skin lesions
septic arthritis
what is indistinguishable between moraxella catarrhalis and the neisseria
gram stains
where does moraxella catarrhalis colonise
upper respiratory tract
how many people carry moraxella catarrhalis (harmless)
5% adults (harmless)
what does moraxella catarrhalis cause
otitis media
sinusitis
pneumonia in the elderly and in patients with other lung diseases
where is E. coli a commensal
flora in GI tract
what is the ‘respiration’ of E. coli
facultatively anaerobic
what are is the indole test for e. coli
positive (most strains)
what can e. coli ferment
lactose (most strains)
is e. coli motile
yes
what is e. coli similar genetically to
shigella
what infections does e. coli cause
UTI neonatal adhesions wound infection intra-adbominal abscess diarrhoea haemolytic uraemic syndrome
what percentage of UTIs are caused by E. coli
70% as they have specific adhesion
what e. colis cause diarrhoea
enteropathogenic (EPEC) enteroaggregative (EAEC) enterotoxigenic (ETEC) enteroinvasive (EIEC) verocytotoxin-producing (VTEC; eg O157)
what is the air required for camplyobacter
micro-aerophilic (lower oxygen)
what shape bacteria is campylobacter
spiral
what temp does campylobacter grow
42
what is the oxidase for camyplobacter
positive
what sample is used for campylobacter
stool
what is campylobacter caused by
food poisoning
when does campylobacter peak
summer
esp children/young adults
what does campylobacter look like on selective agar
water droplets
what is the incubation period of campylobacter jejuni
3-4 days
sometimes 8-9
which is the most common campylobacter
c. jejuni
what are the symptoms of c. jejuni
prodromal fever headache diarrhoea, (+/- blood) vomiting abdominal pain
c. jejuni treatments
erythromycin or ciprofloxacin if required
how many pseudomonads species are there
> 200
what environments are pseudomonads associated with
moist
which pseudomonads is most associated with human disease
pseudomonads aeruginosa
is pseudomonads sporing
no
has pseudomonads got a capsule
no
are pseudomonads motile
usually
what is the ‘respiration’ for pseudomonads
strictly aerobic
what do many pseudomonads strains make
pigments e.g. pyocyanin (green)
what is pseudomonads metabolism
oxidative
where does pseudomonads colonise
wounds
otits externa (ear infection)
maliganant otitis media (middle ear infection)
eyes
what can pseudomonads infections cause
septicaemia in immunocompromised/ burn patients
pneumonia in cystic fibrosis patients
what is seen on cystic fibrosis patients from pseudomonads infection
Lots of extra cellular polysaccharide production in CF patients
what are examples of non-fermenting heterogeneous bacteria
acinetobacter
flavobacterium
alcaligenes
what are non ferments like biochemically
biochemically inert
what is the effect of antibiotics on non-fermenters
no effect - resistant
what is the shape of vibrionaceae
short
comma shaped
bacilli
are vibrionaceae motile
actively motile
are vibrionaceae fermentative
yes
are vibrionaceae oxidase +/-
positive
are vibrionaceae halophilic
Halophilic (eg. V. vulnificus) or non-halophilic (eg. V. cholera)
what plates can vibrionaceae be grown on
thiosulphate, citrate, bile-salt, sucrose (TCBS) agar
in alkaline peptone-water
what enhances vibrionaceae growth
alkaline enviro
growth of vibrionaceae on TCBS
ferments sucrose and makes yellow colonies
what vibrionaceae cause epidemic cholera
v. cholerae O1 and O139
how do you get infected with v. parahaemolyticus
food poisoning - shellfish
what does v. vulnificus cause
fulminating septicaemia
cellulitis
acute diarrhoea
what is important for cholera patients
replace the water lost
what is the most common pathogen of haemophilus
h. influenzae
what is the shape of haemophilus
pleomorphic (different lengths/shapes)
coccobacilli
does haemophilus have a capsule
have capsular types a-f
but also non-capsulate strains are common
what is the most important capsular type
b - polysacchairde polymer of ribosyl ribitol phosphate
what agar does H. influenzae grow well on under what conditions
chocolate agar in CO2– requires haemin (X factor) and NADP (V fcactor)
why is H. influenzae the most invasive
due to serotype b
what does H. influenzae cause
major cause of severe sepsis in childhood
is there a vaccine for H. influenzae
Hib vaccine
can adults be infected with H. influenzae
occasional infections in adults with underlying disease
examples of the invasive infections caused by H. influenzae
meningitis epiglottitis bacteraemia pneumonia septic arthritis cellulitis
how is H. influenzae identified
grown on plate with XV factor, X factor onown and H. influenzae factor on own - only growth around the H. influenzae factor disk
what is the habitat of legionellae
water
what does legionellae cause
pneumonia
what is the most important legionellae species
L. pneumophila serogroup 1 causes most infections
how does legionellae infect
inhalation of aerosols from manmade water sources e.g. cooling towers
how are legionellae detected
urine antigen detection often useful – capsule from organism excreted in urine = rapid test
why cant legionellae be diagnosed via culturing and plating
Culture on Buffered charcoal yeast extract agar with alpha-ketoglutarate – grows slowly 5+ days needed
why are legionellae still cultured even though takes too long to diagnose from plate
useful to detect where the source is from
what does legionella look like on BCYE agar
ground glass colonies
what are the gram-negative anaerobe species
Bacteroides / Prevotella / Fusobacterium spp.
where are gram negative anaerobes a normal flora
GI tract
how are gram negative anaerobes identified
colonial appearance
metronidazole sensitivity
biochemical reactions
where is it best to isolate gram negative anaerobes from
pus or tissue specimens
NOT swab
what do gram negative anaerobes cause
intra-abdominal sepsis abscesses wound infection bacteraemia (rare) aspiration pneumonia Lemierre’s disease - rare
what is the shape of Pasteurella multocida
pleomorphic bi-polar bacilli
is Pasteurella multocida oxidase +/-
positive
is Pasteurella multocida penicillin sensitive
yes unlinke other coliforms
what agar cant Pasteurella multocida grow on
macconkey
what does Pasteurella multocida cause
septicaemia and respiratory tract infection, often fatal
what pathogen is Pasteurella multocida
animal
can humans be infected by Pasteurella multocida
yes via animal bite
what happens following Pasteurella multocida infected animal bite
cellulitis/local abscesses
occasionally septic arthritis or even meningitis
what is the Moraxella catarrhalis like
intracellular
gram negative
diplococcus