Mucosal surfaces, Enterobacteriacea-diarrheal diseases Salmonella and Shigella- invasive bacterial pathogens MM (2/27/18) Flashcards
types of gram-negative pathogens
Enterobacteriaecaeae
Vibrinoaceae
what is mucosal surface
interacts with air and secretes mucus
defense of mucosal surface
innate immunity, adaptive immunity, nonspecific barriers
why study GI diseases
lots of people get it, 500,000 in hospital, 5000 deaths
$10 bill in treatment\
begin in the oral/fecal route
why E. Coli outbreak in germany in 2011
alfa sprouts
852 cases of hemolyric uremic syndrome and 32 people died
E. Coli in chipotle
53 cases, 20 hospitalization
0 death
shiga toxin
how gram negative mucosal pathogens leaves the feces to get to your mouth
feces food fluid fingers flies formites fornication
inoculum size
how many needed to cause disease (some low-shigella and EHEC, EIEC, others high-ETEC, EPEC,vibrio)
natural barrier defences in GI
acidity:1-2 in stomach then 9 in Small intensine
Motility: stuff moves through Small intestine fast so bacteria can’t atach
Mucous layer and underlying glycocalyx
Tight juntion
where in the GI do we get lots of bacteria
near the end
what blocks infection with gram negative pathogen
normal flora natural defenses of GI Lysozymes (doesn't work too well against gram negative though to unexposed cell wall) Lactoferrin Cathelicidin Defensins Secretory immunoglobulins
action of lysozyme
cleaves beta 1,4-glycosidic linkage between N-acetylnuramic acid and N-acetylglucosamine
action of lactoferrin
stops bacteria by sequestering iron
action of cathelicidin
disrupts bacterial membrane of Gm- and Gm+ and fungi
action of Defensins
creates pores on all microbes
who produced alpha-defensins
neutrophils and paneth cells (intestine
who produced beta defenisn
epithelial cells
how do bacteria overcome innate barrier defneces
acid resitance
Fimbriae/pili_adhere to tissue and avoid being spread
BActerial strucutre
what bacterial tend to be acid resitant
low infectious dose (Shigella and Enteroinvasive E Coli
What bacterial strucutres aid in overcoming pathogenic innate barrier densences
gram-/gram+ cell membrane sesnitive to bactericidal compounds
Cationic amino acids into cell membrane to reduce efects of cationic antimicrobial peptides
Siderophoers sequester iron
what immunity are macrophages part of
cell mediated immunity via TH1
use PAMPS
whta receptor is activated by gram negative bacteria
TLR4
activation of pattern recognition receptors on macrophages laed to
inflammatory response
morphology of enterobacteriaceae family
gram -
no spor
non acid fast
rods (coccobacilli to elongate filamentous rods)
growth of enterobacteriaceae family
faculataticve growth and visible after 12-18 hours
toxins on enterobacteriaceae
all endotoxin, some secrete exotoxin
cell wall components of enterobacteriaceae family
antignic:
o- outer antigen, LPS
k- polysaccharide capsule
H- flagella
source of serotypes of in bacterial species due to
cell surface antigens
where do enterobacteriaceae infections come from
external from environment and animal
not: salmonella ser typhi and shigella: strickly human
how does enterobacteriaceae cause a pathogen
opportunistic
most common infections by enterobacteriaeceae
UTI’s and acute diarrhea
what do E. Coli ferment
lactose
what do E. coli produce
indole
how to determine serotype of E. coli
O, K, and H antigens
E coli pili
type 1: most common, bind D mannose residues on epitheliail cells with an on/off
p pili: bind digalactoside found within urinary tract and erythrocytes
other: common to diarrheal binding to erythrocytes
E. coli toxins
alpha hemolysisn
Cytoxoic necrotizing factor
Shiga toxin
action of alpha-hemolysin
pore forming
action of cytoxoic necrotizing factor (CNF)
A-B toxin that produces G proteins (disrupt intraceullar signalling)
action of shiga toxin(Stx)
A-B toxin that blocks pr synth by ribosomal modification
pathogenic E coli
UropathogenicE. coli (UPEC) EnterotoxigenicE. coli (ETEC) EnteropathogenicE. coli (EPEC) EnteroinvasiveE. coli (EIEC) EnterohemorrhagicE. coli (EHEC) EnteroaggregativeE. coli (EAEC)
Enteropathogenic E. Coli (EPEC) causes
common causative agenet of nursery outbreaks in developing coutnries
adult inoculum of Enteropathogenic E. Coli (EPEC)
10^8 to 10^10 CFU
how does Enteropathogenic E. Coli (EPEC) attach to distal small intestinal enterocytes
bundle-forming pili (Bfp)
how does Enteropathogenic E. Coli (EPEC) inject into host cell
Type III secretion system to inject over 30 E. Coli secretion proteins(not toxin though)
how does Enteropathogenic E. Coli (EPEC) formation of attaching and effacing (A/E) lesion
Intimin-Tir interaction
how do we think Enteropathogenic E. Coli (EPEC) cause diarrheal disease
effacement of the microvilli and disruption of tight junctions
where does Enterohemorrhhagic E. Coli (EHEC) occur
developed countries
source of Enterohemorrhhagic E. Coli (EHEC)
animal products, unpasteurized juice, fresh veggies
inoculum of Enterohemorrhhagic E. Coli (EHEC)
100 CFU
what genes does Enterohemorrhhagic E. Coli (EHEC)
similar to EPEC (eae genes)
what toxin does Enterohemorrhhagic E. Coli (EHEC) produce
toxin the leads to hemolytic uremic syndrome (bloody diarrhea)
most notorious Enterohemorrhhagic E. Coli (EHEC)
E. coli O157:H7
primary reservoid of Enterohemorrhhagic E. Coli (EHEC)
cattle
how does Enterohemorrhhagic E. Coli (EHEC) cause problems
causes attaching effacing lesion in colon via long polar fimbriae leading to A/E lesion similar to EPEC
Shiga toxin: hemorrhagic colitis, Hemolytic uremic syndrome
what does Enterohemorrhhagic E. Coli (EHEC) act on
shiga toxinthe blood vessels under the epithelial cells of the villus
what does Enteroinvase E coli (EIEC) cause
similar to shigella, mild version of shigellosis
who gets Enteroinvase E coli (EIEC)
children under 5 in developing countires
where is Enteroinvase E coli (EIEC) found
contaminated food and water
humans the only reservoid
what does Enteroaggregative E. coli (EAEC) cause?
watery diarrhea that last longer than 14 days
how does Enteroaggregative E. coli (EAEC) do to cause problems
tight adherence to epithelial cells in a stacked brick pattern
symptoms of intestinal E. Coli infections
usually a couple days after inoculation and self limiting Except:: EAEC: can last for weeks EPEC: can be chronic EHEC and EIEC: bloody diarhhea
diagnosis of E. Coli mediated disease
not best to use culture because we have it in our bottle as part of the flora
assays available to detect toxins/genes with virulences
Screening tests
why not do assays
healthy people can test positive
Expensive
how to do a screening test for O157:H7
grown on MacConkey agar supplemented with sorbital (not lactose). cannot ferment sorbital so colonies will have no color
how to treat diarrheal disease
supportive therapy, keep hydrated
treating hemorrhagic colitis/HUS
hemodialysis/hemapheresis
why not use antimotility agenst on diarrheal disease
because it keeps the bacteria from leaving
what is shigella
specialized E coli
antigens of shigella
O and K, but no H (O is main)
do shigella invade cells
yes, and multiple within epithelial cells
what toxin does shigella produce
shiga toxin
4 types of shigella
- Shigelladysenteriae(serogroup A) –Type 1 causes most severe disease
- Shigellaflexneri(serogroup B) –Most common
- Shigellaboydii(serogroup C)
- Shigellasonnei(serogroup D) –Most common
- Subgroups found within each of these.
who does shigellosis infect
strictly human (150 million cases) and 600k global deaths per year
how id shigellosis spread
food.water contamination by humans
incidence and prevalence of shigellosis is related to whay
personal and community sanitiation, so wars enable outbreak
inoculum of shigellosis
as little as 10 organisms
what does shigellosis resist
acid resistant
pathogensis of shigella
infect M cells via invasion plasmid antigenin colon and pyers patch
enter macrophage, and lyse phagosome, killing macrophage
enters in the lamina propria to infect the basal part of enterocyte using invastion plasmid antigens (IpaA and IpaD) using type 3 secretion
uses actin fillaments to move around into new cells
eveutally killls epitehlial cells
shigella infection cycle is like
Listeria monocytogenes
diseases of shigella
ulcer develops when invaded cells die and foll off
Diarrhead as response of inflammatory response
what do ulcers do for shigella
allow shigela to reach lamina propria
what kind of diarrhea is a reuslt of shigella
classic dysentery - small volume diarrhea, leukocytes, and RBC’s
Shigella dysenteriae type 1 mortality rate
high mortality even with adults, alwaus have shiga toxin
shigella dysenteriae type 1 results in
kills intestinal epithelial and endothelial cells
Disrupts Na absorption
Toxin can be systemic
immunologic protection of shigella
does produce immunological protection, but no cross protection
diagnosis of shigella
stool culture, O antigen aglutination tests to determine serotype
how to treat diseases by shigella
self limiting, but antibiotics like ciproflaxacin and azithromycin can shorten illness time
vaccine for shigella
no, but in the works
two types of salmonella
S. bongori
S. enterica
medicall important infections arise from what salmonella
S. enterica
subspecies of S. enterica
multiple: medicall importatn belong to the enterica subspecies
naming salmonella species
diff subspecies have different disease
go by species name, subspecies, then serotype
but sorten to jus first part of species name, then serotype
salmonella enterica gastroenteritis occures where and why
industrialized nation and improper food handling, food born, eggs and poltry
inoculum range of salmonella enterica gastroenteritis
200-10^6, due to acid amount
symptoms of salmonella enterica gastroenteritis
abdominal pain, nausea, vomiting, and diarrhea
how long does salmonella stay in yo
recover after 3-4 days, but cary for 20 weeks (5% OF PATIENTS)
how to get salmonella
fecal (human or animal)– oral transmission
acid sensitivey of salmonella vs shigellae
more acid sensitive than shigellae
low pH causes salmonella to do what
express 40 PR found on pathogenicity islands on large virulence plasmds
where does salmonella infections colonize
small intestine
how does sallmonella infect
- Organism makes contact with M cell (likely via Type 1 pili) and injects effector molecules into cell with Type III secretion system.
- These events induce surface “ruffles” and uptake of the organisms (microbe-directed phagocytosis).
- Multiplies and remains within cell vesicles for many hours (unlike Shigella).
- Organisms released to lamina propria, inflammatory response is activated, ingested by phagocytes, then kills phagocyte.
- Macs engulf most, but some escape to cause a transient bacteremia
- -the typhoid serovarswill survive and grow within the macrophages
why does Salmonella typhi cause
no animal reservoid, sticktly human
but also asymptomatic carriers
salmonella typhi carries have what colonized in them
gall bladders, and organisms can be cultured from their feces
typhi can surive how long in the macrophage
long time due to inhibiting oxidative burst
how does salmonella typhi enter the lymph
via macrophage via mesenteric lymph nodes, spleen, liver, bone marrow, then blood
whay of typhi causes fever
endotoxin
how long can typhi fever last
weeks if untreated
prolonged infected by typhi results in
perforated bowel
immunity of salmonella
Humoral (Th2 and cell-mediated (Th1)
what does salmonella do with host response to survive long
exploit host response
how to identity salmonella
culture from stool or blood, identify O serogroup
how to treat gastroenteritis from salmonella
fluid/electrolyte replacement
(antibioitcs for severe cases cuz it can increase the duration of infection and the incidence of the carrier state
how to treat typhoid fever
antibiotics such as ciproflaxacin in the first line
