Microbiology of Diarrhea Flashcards
Rotavirus (reoviridae)
Genetic material, # of capsids, envelope?
Pop
CM
Transmission
Pathophys
dsRNA, 2, naked
Day care
Fever, NV, watery diarrhea (4-8days)
F/O- low infectious dose
Infect enterocytes in middle/upper villi- destroy epithelial cells- dec absorptive surface in SI, dec transfer of fat/carb
Noravirus (calciviridae)
Genetic material, envelope?
Typical areas
Incubation sx
CM
Transmission
ssRNA, naked, heat resistant capsid
cruise ship/plane/nursing
V/D
watery diarrhea for 2-3 days
F/O via food/water or surfaces/fomites
Shigella
Salmonella
E coli
Gram - rods
Camp
oxidase -, Lactose nonfermenter
oxidase -, lactose nonfermenter
lactose fermenter
Vibrio cholerae
Shape
Phage encodes
Transmission
CM
Gram -, vibrio
cholera toxin
food/water w feces
watery diarrhea (rice water), voluminous, vomiting/fever
Vibrio parahaemolyticus
Commonly transmitted via
CM
Lasts
shellfish
watery diarrhea, NV
10 days
Cholera disease pathway
A1 catalyzes
leads to
Ingested- release endotoxisns- binds to GM1 ganglioside
Gs w loss of GTPase activity
AC activation, inc cAMP/kinases- diarrhea, loss of electrolytes
C diff
Pathophys
A and b toxins cause
Detect toxins becasue
spores introduced, germinate, inc undigested carbs- watery diarrhea
epithelial cells to detach, ulcers to form, psuedomemebrane
Toxin mediated dz
Giardia lamblia
Type
Exposure areas
Cyst stage
trophozoite
Pathophys
Dx
anaerobic, flagellated protozoa
water/day care/pets
infectious (4 nuclei)
reproductive/pathogenic
troph to BB, attaches disk, blunts MV, fat malabsorption= steatorrhea
Stool antigen test/trophozoites (stingray w 2 nuclei
Crypto
CM competent
IC
Pathophys
Dx
ab pain, nausea, wl
chronic, watery diarrhea
oocysts in SI- sporozoites attach to epithelial cells-replicate in IC vacuole
acid fast oocysts in stool
ETEC patho
leads to
stimulates (LT)
ST
Dx
labile heat toxin binds GM1
travelers/watery diarrhea
AC-cAMP-secretion
GC
serology for toxin
EHEC patho
transmission
CM
Dx
bactera attaches, MV damaged, delivers toxin to EC fluid
undercooked meat
bloody diarrhea, no fever
0157H7 in stool
Campylobacter
Type
CM
Pathophys
gram - curved rod, microaerophilic
fever, malaise, watery diarrhea- blood, tenesmus, leukocytes (if bloody)
invades epithelium-inflamm- RBC/WBC in stool
Salmonella
Type
Infectious dose
Incubation time
Pathophys
diarrhea resolves in, fever in
Gram neg rod
high
24-72 hrs
bacteria invade enterocytes in SI/colon- migrate to LP of iliocecal region- cytokines cause cap dilation/PMN relase- water leaks into lumen
3-7 days
7 days
Shigella
Type
Infectious dose
CM
Due to shiga toxin, stools area*****
Shiga toxin targets
Complications
gram neg rod
low
high fever, ab pain, bloody diarrhea
frequent
60s ribosome- stops protein synthesis
TM and HUS
Shigella Pathophys
invades epithelial cell
uses actin tails to invade
uptake by M cells- macros- apoptosis and inflamm
release PMN- use T3SS to release toxin/rearrange cytoplasm- cells die (bloody/mucus)
neighboring epithelial cells
Yersinia
Type
Grows in
Incubation
CM
Avg length of time
Pathophys
Mimics
Encodes
Gram neg, urease pos rod
Cold temp
4-6 days
HA/anorexia/fever/bloody and mucus diarreha
2 wks
invades ileal epi- enters LP/PP- drains to LN- intestinal inflamm sheds PMNs/RBC in lumen
appendicitis
iron uptake system for virulence/dissemination
Entamoeba histolytic
Incubation time
Transmission
CM
Dx
Complication
2-6 wks
cysts from fecal/oral
lower ab pain, bloody mucoid stool, wl
amebic cysts (4 nuclei) or trophs (RBC)
infects liver, RUQ pain- abscess
Life cycle of entamoeba histolytic
ingested then
cysts released in
forms trophs- penetrates intestinal wall- multiplies- invasion
feces
Nematodes
body style
transmission
ingested
invasion of skin
round, unsegmented
eggs- enterobius/ascaris/trichuris
larval form- necator/stronglyoids
Ascaris
pathophys
complications
MC
dx
ingest egg- larvae to lungs- aspirate- enter SI
eosinophilia/IO/BDO
helminth
knobby eggs in stool
Enteriudes vermicularis incubation time
4-6 wks
Necator
Larvae penetrate
Strongyloides
Larvae penetrate
SX
intact skin of bare feet
intact skin, do not mature
Duodenitis/PNA/colits/malabsorption
Trichuris trichuria
transmission
pathophys
F/O or through soil
larva enter SI to cecum- release eggs in stool
