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Micro - Overview of Enteric Gram -ve Bacilli (ii) (Klebsiella (pneumonia…
Micro - Overview of Enteric Gram -ve Bacilli (ii)
5 types of E Coli cause gastroenteritis
Enterotoxigenic
traveller's diarrhoea
esp in underdeveloped countries (poor sanitation - contaminated food/water)
in small bowel
non-invasive
2 toxins
heat labile toxin
cholera toxin
only 1 may be expressed
destroy epithelium
watery non-bloody diarrhoea (hypersecretion of food + electrolytes)
! dehydration risk
fever, nausea
can be mild or severe (cholera-like syndrome)
give IV fluids not antibiotics
monitoring essential if patient is elderly
Verocytotoxic (VTEC)
most common serotype = O157:H7
in colon
invasion of intestinal epithelial cells
Shigella-like toxin
acute inflamm response
tissue destruction
bloody diarrhoea
PCR finds antigen - then confirm in ref lab
source = cattle + other vuminents (survive for long periods in environment)
transmitted to humans through contaminated food, water, animal faeces (direct human-human transmission also occurs)
variable symptoms (e.g. possible vomiting)
more severe in extremes of age
complications
haemolytic uraemic syndrome
in 10% of infected children under 10 y/o
acute renal failure
thrombocytopenia
haemolytic anaemia
rehydration NB
no antibiotics - cause increased toxin production
incubation = 2-4 days
less than 100 bacteria ingested can cause infection
Enteropathogenic
esp in infants under 6 months in developing countries
high mortality - severe dehydration
Enteroinvasive
dysentry-like diarrhoea + pyrexia
rarely shigella-like toxin produced (bloody)
Enteroaggregative
persistent/chronic diarrhoea +/- nausea in young children
Klebsiella
e.g. k pneumoniae, k oxytoca
normal in GIT - NOT associated with gastroenteritis/diarrhoeal disease
may have ESBL - MDR
cause HCAIs
pneumonia
VAP
Friedlander's pneumonia
severe CAP
esp in immunocompromised
necrotising - red current jelly sputum
complication = abscesses on upper lobes
UTIs (esp with catheters)
intra-ab infections if bowel perforation occurs
BSIs
mucoid lactose fermentor
Tx
susceptibility testing NB
effective empiric agents: B-lactams, quinolones, aminoglycosides
Proteus
P mirabilis most common
normal gut flora, pathogenic outside this
cause infectctions esp in hospitalised patients
intra-ab
BSIs
UTIs
esp with catheters - multiple flagellae + fimbriae
produces urease
associated with renal calculi
splits urease into ammonia
increases pH
non-lactose fermenter, oxidase -ve, fishy smell
swarming appearance on blood agar (due to peritrichous flagellae)
empiric Tx: B-lactams. quinolones, aminoglycosides
Opportunistic pathogens
Enterobacter, Serratia, Citrobacter
HCAIs
pneumonia, sepsis, UTI, GIT infections, abscesses on wound/ulder
often MDR