Enterobacteriaceae Flashcards
Enterobacteria general characteristics (3)
- Facultative anaerobes
- Motile by peritrichous flagella (or nonmotile)
- Type 3 secretion system
Enterobacteriaceae are typed by…
Antigens: O, H, K/Vi
- all have capsules but large only in Klebsiella
Biochemical tests
- IMViC
- CHO fermentation: especialy lactose (MacConkey’s Agar)
- Lac+ are coliforms
What is IMViC?
- Indole - tryptophanase
- Methyl red - acid fermentation
- Voges-Proskauer - neutral fermentation
- Citrate - growth
Gut bacteria can respond to…
neuroendocrone hormone levels
(e.g. E. coli and norepinephrine)
Enterobacteria can inhibit the _______ in order to avoid immune detection
inflammasome
(Including NEMO,NFkB, IkBa, and MAPK)
In many cell types, bacterial manipulation of vesicular trafficking promotes bacterial survival. This occurs largely by the manipulation of…
GTPase signaling
E. coli metabolism and detection on growth medium
- Lac +
- Copius acid production
- Detected by green metallic sheen on EMB agar
6 pathotypes of E. coli
- EPEC
- EHEC
- ETEC
- EAEC
- EIEC
- DAEC
___ are the most common extra-intestinal E. coli infection
They are primarily caused by _____
UTI’s
UPEC (uropathogenic E.coli)
___ is becoming an increasingly common pathotype for meningitis and sepsis
MNEC
(meningitis-associated E. coli)
Three main presentations of E. coli infections
- Enteric (diarrheal)
- UTI
- Sepsis/meningitis
E. coli causes ___% of UTI’s
These can spread to what organ?
This is associated with ____ (blood cell binding)
90% of UTI’s
spread to kidneys (vesicoureteral reflux) to cause pyelonephritis
Associated with P pilus
5 E. coli pathotypes that cause diarrhea
P, T, H, I, A
EPEC diarrhea
(attachment protein, bundle forming pili)
efface small intestine microvilli –> inhibit water uptake
- Watery, self limiting diarrhea
- common in young children
ETEC, a.k.a…
Traveler’s diarrhea
Watery, increased motility & cramping
Pathotype of E. coli that is associated with CFA adhesion protein for brush border membrane
ETEC
ETEC toxins
-
2 LT toxins
- LT1 is an AB toxin (like Cholera…increases camp to cause secretory diarrhea)
-
2 ST toxins
- activate cGMP production (water secretion)
EHEC causes ____ diarrhea, without…
Bloody diarrhea without fever
EHEC toxin name and 3 characteristics
verotoxin (Shiga-like toxin)
- AB toxin
- Protein synthesis inhibitor
- acquired by phage conversion
EHEC has a tropism for what tissue?
Kidney
E. coli strain (EHEC) responsible for community epidemics from contaminated meat, water, or vegetable produce?
0157:H7
Disease caused by EHEC
What is its pathology? How is this handled?
Hemolytic Uremic Syndrome
- Damage to glomerular enothelium (by systemic toxin) causes uremia and organ failure
- You DO NOT GIVE ANTIBIOTICS for this disease – they upregulate the Stx gene (toxin)
EIEC diarrhea
“Invades” the colon, causing bloody diarrhea
EIEC is indistinguishable from…
Shigella dysenteriae (type 1)
EIEC colonization factor
Ipas
Produced from Shigella plasmid
This E. coli pathotype is known to form a biofilm on the intestine
EAEC
–causes malapsorptive-type diarrhea
When I say “noninflammatory pediatric diarrhea in developing countries, that is also the #2 cause of travelers’ diarrhea in most countries” you tell me that this is…
EAEC
EAEC form ______ via ______ in intestine
infective foci via “aggregative pili”
(hence, EAEC)
___, ___, and __ hit the small intestine
___ and ___ hit the large intestine
Small = EPEC, ETEC, EAEC
Large = EHEC, EIEC
The E. coli pathotypes that cause bloody diarrhea tend to hit where?
Large intestine
Major E. coli cause of neonatal meningitis?
What is it’s major pathogenic characteristic?
E. coli K1
- most meningitis strains have K1 capsule
- It functions as a molecular mimic of host’s NCAM receptors
E. coli K1 capsule is similar to…
N. meningitidis B capsular antigen
Salmonella metabolism and growth characteristics
- Lac (-)
- H2S (+) - S-S agar
- Grows in selective media with Bile salts (deoxycholate)
All Salmonella belong to _____ species, with how many subspecies?
- S. enterica
- 6 subspecies (e.g. S. enterica ssp. arizonae)
It is only important (for us) to distinguish what two Salmonella subspecies?
Typhi + Paratyphi
Salmonella diseases (and subspecies that cause)
- Typhoid fever (S. typhi or S. paratyphi)
- Bacteremia/Septicemia (S. cholerasuis)
- Enterocolitis / GE (S. Enteriditis)
Typhoid fever is a ____ disease that disseminates via ______to liver, GB
Death is usually from _______
invasive disease, disseminates via macrophages
death from intestinal hemorrhage
Salmonella septicemia mainly hits whom?
immunocompromised patients
Salmonella enterocolitis/gastroenteritis clinical features (3)
- nausea, profuse diarrhea, FEVER
- self limiting within 2-5 days
- may colonize GB and shed for weeks
Salmonella Enteriditis is especially transmitted via…
egg and poultry products
Two distinct features of Typhoid fever
- High sustained fever
- Roseate rash
Salmonella spread via
fecal-oral
from contaminated water, endemic sources in eggs and poultry, crops fertilized with human excreta, and pets
Salmonella pathogenic steps (4)
- Binds brush border
- invades gut epithelial cells
- invades deep tissues and bloodstream through the basal membrane
- produces cytotoxic enterotoxin
Typhoid toxin characteristics and function
A2B5 toxin
can grow in bile using efflux pumps and DNA repair to survive
Uses phospholipids as a carbon source
- A1 = ADP ribosylates G protein
- A2 = Damages DNA and stops replication of cell
Salmonella cytotoxin may cause _____
bloody diarrhea
Salmonella survives within…
MQ’s
Shigella metabolism and characteristics
Lac-, H2S- (S-S Agar)
Looks like other enterobacteriaceae
Shigella types
dysenteriae
flexneri (3rd world)
boydii
sonnei (US)
Shigella does not result in
systemic infection / sepsis
(only a GI pathogen)
Shigella diarrhea timeline
- acute onset watery diarrhea (WITH FEVER)
- 2 days later the volume is less, but more mucus/blood in stool
- Resolves in ~one week
Shigella transmits via
fecal oral
Spread via 4 F’s!
- Food
- Fingers
- Feces
- Flies
Associated with crowded unsanitary conditions
Shigella pathogenic steps
- Phagocytosed and transmitted by M cells
- engulfed by MQ
- Lyse MQ phagolysosome and replicate in cytoplasm
- MQ undergoes apoptosis
How does shigella change the basal membrane/cell-cell interactions?
Releases IL-1 and other cytokines to permeabilize the cell junctions
Induces Basal membrane phagocytosis by lumenal cells
Can spread via actin tails
What are shigella IPAS?
Invasion factors
secreted by T3SS
How does shiga enterotoxin kill cells?
It disrupts protein synthesis
“Classic symptom” of shigella
fecal leukocytes
(gaps opened up in the basal membrane by shigella cause leakage of polymorpholeukocytes, which show up in stool sample)
Yersinia may or may not be…
GIT infection
Yersinia appearance
Looks like other enterobacteriaceae, but may be coccobacillus
Yersinia staining
Bipolar
(Wright-Giemsa stain, Wayson’s)
Yersinia - three general pathogenic factors
- YadA adhesin
- YOP (T3SS encoded by plasmid)
- V and W antigens (allow for intracellular growth)
Non-GI version of yersinia
Y. pestis
- Zoonosis
- Bubonic = most common form
- painful buboes in groin or other lymph node
It is essential that yersinia buboes are differentiated from which other conditions/pathogens?
tularemia & pasteurella
Less common form of Yersinia pestis?
What are the characteristics?
Symptoms?
Septicemic
- may be primary/secondary to bubonic
- (if secondary, it develops within a few days of the appearance of buboe
Sx = purpura, DIC, necrosis
Third presentation of yersinia pestis?
What are the types/origin, symptoms?
What shows up on labs/imaging?
Pneumonic
- Primary from inhalation, Secondary from DIC
- X-rays show bilateral alveolar involvement
Y. pestis spread via ____
rat flea (xenopsylla cheopis)
- Bacteria toxin blocks fleas gut - clot forms
- When flea bites again, the clot is transferred into the animal host
Main reservoirs for Y. pestis in the US?
deer mice
ground squirrels (prairie dogs)
Yersinia pestis pathogenesis (in flea and mammal)
Flea:
- YMT phospholipase helps survival within flea (key to expanding host range)
Human:
- Capsular genes turned on at 37 degrees
- Yop T3SS injects toxins
- MAPK pathway is inhibited by Yop-J
- Phagocytosis is prevented by Yop-E
- Platelet aggregation is inhibited by Yop-M
Yersinia YopJ effects
Inhibits MAPK pathway
- prevents cytokine production
- prevents cell replication (apoptosis and necrosis)
Y. pestis control is based around
prevention: insecticide kills fleas before infection
Is there a Yersinia pestis vaccine?
Yes! Formalin-killed OR live attenuated
*must be boosted every year, so it’s only for people who are repetedly exposed
Y. pestis post-exposure treatments
Oral tetracycline for those exposed but asymptomatic
streptomycin (i.m.) for symptomatic pts.
**pneumonic plague treatment is rarely successful (virtually 100% fatal within 24 hours)
GiT version of yersinia
Y. enterocolitica
Y. pseudotuberculosis
2 major Y. enterocolitica symptoms
- enterocolitis with intestinal abscesses (SEVERE bloody diarrhea)
- Mesenteric adenitis (mimics appendicitis)
GIT yersinia reservoirs and spread
Cattle/hog reservoir
Spread in feces or via contaminated drinking water/milk
Control for Yersinia enterocolitica/pseudotuberculosis
Ampicillin
*note: does NOT control y. pestis
Can also use Third Gen Ceph’s or Bactrim
What are the “other” enterobacteriaceae?
- Klebsiella pneumoniae
- Klebsiella oxytoca
- Klebsiella granulatomatis
- Proteus mirabilis
- Proteus vulgaris
- Serratia marcascens
K. pneumoniae virulence, symptoms/prognosis
virulence = large capsule
hemorrhagic, necrotizing infection (currant jelly)
50-100% fatal
K granulomatis infection type
Possible presentation?
STD, not GIT
Donavonosis = “granuloma inguinale” = granulomatous infection that can mimic syphillis
K. granulomatis may mimic…
- syphillis (genital granulomas)
- genital cancers (because of progressive destruction of tissue)
What enterobacteriaceae exhibit “swarming motility” on agar?
What other pathogenic feature is present in this organism, and what happens as a result of it?
Proteus! (due to many flagella)
** this makes it ascent possible in the urinary tract – Associated with UTI
Proteus also makes UREASE (similar to mycoplasma)
- causes alkaline urine, precipitates formation of BLADDER STONES
Serratia marcescens:
- Infection route?
- What kinds of infections that tend to result?
- Opportunistic nosocomial pathogen
- PNA, bacteremia, endocarditis
** in immunocompromised patients
General control for “other enterobacteriaceae”
What antibiotics can we use (if any)?
General control: isolate source and decontaminate (esp. for fecal oral)
Antibiotics: Ampicillin, Third Gen Ceph’s, Quinolones, Sulfas, Streptomycin
**Antibiotic resistance greatly influences ability to treat. (R plasmids are very common in enterobacteriaceae)
Antibiotic guidelines for uncomplicated UTI (enterbacteriaceae)
BACTRIM is 1st choice, followed by Fosfomycin
DON’T use fluoroquinolones (resistance)
Most common prophylactic for traveler’s diarrhea
Rifamixin
What is MUC2? What are three things it does?
- hyperglycosylated mucin
- subdues inflammatory response from Dendritic cells
- stimulates production of Treg cells (by DC signaling)
- Normal flora use it as a carbon source –> non-inflammatory
