6. Enterobacteroides Flashcards
Lactose fermenters (6)
Citrobacter
Cronobacter sakazakii
Enterobacter
E. coli
Klebsiella
Pantoea
Serratia
The only ox = GNR
Plesiomonas shigelloides
LLFs
Citrobacter koseri
Pantoea agglomerans
Serratia marcescens
Cfre on HE
yellow
black centers
E. coli on HE
bright yellow
salmon orange
Proteus on HE
clear
blue-green
black centers
Salmonella on HE
blue-green
black centers
Shigella on HE
clear, blue-green
Yersinia on HE
yellow
salmon orange
Cfre on XLD
yellow
colorless
black centers
most LFs on XLD
yellow
Mmor on XLD
clear
Proteus on XLD
yellow
colorless
black centers
Providencia on XLD
clear
Salmonella on XLD
black
red rimmed
Serratia on XLD
yellow
Shigella on XLD
colorless/red
Yersinia on XLD
yellow
NLFs that give an A/A TSI reaction
Pvul
Yersinia
The only H2S + LF
Cfre
Triple = SIM LF
Kpne
Triple + SIM
Pvul
Triple = SIM NLFs
Shigella
Yersinia
Nonmotiles (35°)
Klebsiella
Yersinia
Shigella
The only = citrate LF
E. coli
Citrate, urease and PAD ===
E. coli
Shigella
Y. pestis
Arginine +
Citrobacter
Cronobacter
E. cloacae
The only A/L/O triple = LF
Pantoea agglomerans
ONPG + NLFs
Shigella sonnei
Yersinia
The only ases +
Smar
Koxy vs Kpne
Koxy indole +
Kpne indole =
Cfre vs Ckos
Cfre H2S +
Ckos H2s =
Pvul vs Pmir
Pvul indole +
Pmir indole =
Pret vs Pstu
Pret urea +
Pstu urea =
Y. pestis vs other Yersinia
Y. pestis urea =
other Yersinia urea +
Yent vs other Yersinia
Yent ornithine +
misleading nonpathogenic appearance on XLD and HE
Yersinia
Definition of Enterobacteriaceae (5)
GNR
Ox =
Glucose-fermenting
Grow on MAC
Nitrate +
3 enterics that are always pathogenic
Salmonella, Shigella and Yersinia
cytotoxin-producing E. coli
E. coli O157:H7
Infections caused by Enterobacteriaceae
UTI
Pyelonephritis
Diarrhea
Respiratory infection
Wound infections
Sepsis
BAP enteric colonies
Large wet, gray colonies
LPS causes…
shock, fever, hypotension, circulatory collapse, capillary hemorrhage, DIC
toxic part of LPS
lipid A
3 antigens used to differentiate Salmonella strains
K (capsule)
O (outer membrane)
H (flagellar)
—- is heat-labile and has to be boiled away to reach other antigens
K
K antigen present on Sent Typhi
Vi antigen
HE and XLD used to isolate —— in stool
Salmonella
Shigella
CHO in HE agar
lactose, sucrose and salicin
2 pH indicators in HE
Brom-thymol blue
Acid fuchsin
Potential pathogens on HE
Colorless and take on green color of medium due to the lack of CHO fermentation
Black due production of hydrogen sulfide
Sugar fermented by Yersinia that gives a misleading HE result
sucrose
indicator in XLD
phenol red
CHO in XLD agar
lactose, xylose and sucrose
added to XLD to help detect salmonella
lysine
potential pathogens on XLD
Colorless and take on the red color of the medium (Shigella)
Black due to hydrogen sulfide production (Salmonella)
Red rimmed if lysine is decarboxylated (Salmonella)
present in TSI for H2S production
Sodium thiosulfate
pH indicator in TSI
phenol red
——- react with hydrogen sulfide gas to form a black precipitate
Iron salts
—– environment required to make H2S
acid
Mustache
S. enterica typhi
Explain indole reaction
Metabolism of the amino acid, tryptophan, creates indole, pyruvic acid and ammonia
para-dimethylaminobenzaldehyde
Ehrlich’s or Kovac’s reagent
used to detect indole
Indole spot can be performed on which agars?
SBA, CHOC
not MAC (no tryptophan present)
What does citrate determine?
Determines if organism is capable of using sodium citrate as the sole source of carbon for metabolism and growth (versus fermentation of carbohydrates)
Citrate pH indicator
Bromothymol blue
heavy inoculum for citrate can give false —— results
positive
(bring over CHOs or dying organisms release C and N)
Urease indicator
phenol red
Explain urease reaction
Organisms that possess urease are able to hydrolyze urea to produce ammonia, creating alkaline pH
Explain PAD reaction
Determines the organism’s ability to deaminate phenylalanine to produce phenylpyruvic acid
VP + metabolic pathway
glycolysis -> pyruvate -> acetyl-methyl carbinol
MR + metabolic pathway
glycolysis -> pyruvate -> mixed acids at pH <4.4
——- can use both pathways, but the VP reaction can be delayed so it appears as MR+/VP= at 48 hours
Proteus
Why does VP give a false positive if read after 1 hour?
After 1 hour, KOH reacts with alpha-naphthol to produce a copper color
At 24 hours, all Enterics will give a —- MR
+
2 types of positives for nitrate test
either the presence of one of the detectable end products, or the absence of nitrate
drop in pH required to turn on enzymes for Decarb reactions is accomplished by….
adding a small amount of glucose to the medium for fermentation
Decarb pH indicator
bromocresol purple
Forgetting to oil Decarb tubes gives a false ——
positive
ONPG long
Ortho-nitrophenyl-beta-D-galactopyranoside
ONPG detects…
Beta-D-galactosidase
If you can’t determine if LLF or NLF on MAC and do not have the ONPG result….
use TSI tubes
IMViC
Indole/MR/VP/Citrate
E. coli IMViC
+/+/=/=
Klebsiella IMViC
=/=/+/+
PAD +
Proteus
M. morganii
Providencia
Rapid E. coli ID (5)
Nonswarming GNR
Dark, dry LF
Spot indole +
Oxidase =
Beta-hemolytic
E. coli PYR
=
best test for lazy E. coli
serotyping
Most common cause of infections of the urinary bladder, renal pelvis and kidneys
E. coli
5 types of E. coli gastroenteritis
Enterotoxigenic (ETEC)
Enteroinvasive (EIEC)
Enteropathogenic (EPEC)
Enteroaggregative (EAEC)
Enterohemorrhagic (EHEC)
Profuse, watery diarrhea that is not bloody
Similar to Cholera
enterotoxigenic E. coli
Causes dysentery
Invades intestine like Shigella but organism does not leave the intestine to travel systemic in the body
enteroinvasive E. coli
Bind to cell and cause changes in the cell surface to produce lesions
Watery diarrhea with no blood and possibly a few WBCs
enteropathogenic E. coli
Several organisms bind together like a stack of bricks
Watery diarrhea but no blood or WBCs
enteroaggregative E. coli
Toxin destroys intestinal microvilli and damages vascular endothelium to produce bloody diarrhea without WBC
enterohemorrhagic E. coli
E. coli strain causing EHEC
Shiga-toxin producing E. coli (STEC)
About 4% of EHEC cases progress to…
hemolytic uremic syndrome (HUS)
Tx for HUS
do NOT use Ab (more LPS released)
Best method to dx EHEC
Shiga-toxin detection in stool via molecular methods
Unique about O157:H7
does not ferment sorbitol
SMAC used to…
differentiate O157:H7, which does not ferment sorbitol
enzymes for Ab resistance in Klebsiella
Extended spectrum beta-lactamase (EXBL)
Klebsiella pneumoniae carbapenemase (KPC)
Klebsiella colonizes…
URT of hospitalized patients
Bloody jelly sputum
Necrotizing pneumonia
Klebsiella
unusual sites of infection, potential for metastatis
hypervirulent Klebsiella
Hypermucoviscous colonies
hypervirulent Klebsiella
Common nosocomial organism in ICU
enterobacter
AmpC
enzyme
organism
induced by…
cephalosporinases
Enterobacter
cefoxitin, imipenem and ampicillin
pigment of Cronobacter sakazakii
yellow
Can survive under very dry conditions, like powdered infant formula, and cause neonatal meningitis/sepsis
Cronobacter sakazakii
red pigment of Smar indicates (high/low) virulence
low
Smar colonizes…
hospital patients’ respiratory and urinary tracts
especially after respiratory instrumentation and catheters
LLF with high MDR
Smar
1970’s nationwide outbreak of septicemia due to IV fluid contaminated with…
Pagg endotoxin
Pagg pigment
light yellow
causes most Proteus infections
Pmir
Kidney stone formation
Proteus
Seen primarily in those with long-term indwelling urinary catheters
Pstu
Poultry and reptile pathogen
Prett
Citrobacter is serologically similar to….
Salmonella
2400 serotypes based on the Kaufmann-White scheme
Salmonella
S. enterica Typhi is serotype —
D
Salmonella
Differentiates Typhi serotype from other Salmonella
TSI mustache
5 F’s for spreading Salmonella
Friends, flies, fingers, food, feces
Typhoid fever has a (high/low) infectious dose
low
(other Salmonella infections are high)
High fever and constipation with positive Salmonella blood cultures but negative stool cultures
week 1-2 of typhoid fever
Invades peyer’s patches (lymph nodes) of ileum then invades liver, spleen, lymph nodes , bone marrow and gallbladder
week 2-3 of typhoid fever
Diarrhea phase (similar to pea soup) with negative blood cultures and positive stool cultures
week 3 of typhoid fever
carries of Sent Typhi have organisms hiding in the….
gallbladder
Nontyphoidal Salmonella tx
Often resolves in 5-7 days without treatment
Fluid and electrolyte replacement
Antibiotics do not shorten the course of the disease
Groups of Shigella O antigen serotypes
S. dysenteriae – group A
S. flexneri – group B
S. boydii – group C
S. sonnei – group D
(dead flies on boy scouts)
Shigella has a (high/low) infectious dose
low
disease of armies
Shigella
Bloody diarrhea with WBC (dysentery)
Shiga toxin
Shigella and E. coli
Most dysentery is due to ——-, but the most severe is due to ——
S. sonnei
S. flexneri
S. dysenteriae
Retains methylene blue or Wayson stain at ends of rods
Safety pin
Yersinia pestis
Yersinia pestis
how to select/differentiate for Yersinia
CIN (Cefsulodin, Irgasan, Novobiocin) agar at room temperature
Yersinia appearance on CIN
bull’s eye
3 forms of plague
bubonic
pneumonic
septicemic (black death)
Contaminates swine food products
Infects Peyer’s patches
Y. enterocolicita
Mimics appendicitis
Y. enterocolitica
High risk individuals for septicemia from Yent
Iron overload
Yersinia on CIN
uses a mixture of colored beads to serotype Salmonella and Shigella
Wellcolex Colour kit
mini biochemicals for enterics
API20E
test that follows a suspicious SMAC
latex agglutination for O157:H7
transmission of the 3 types of plague
bubonic—Organism from flea bite travels to the lymph nodes inside macrophages
pneumonic—Direct exposure to respiratory droplets
septicemic—Organism is inoculated directly into bloodstream via flea bite or spread from lymph nodes
