exam 2 Flashcards
what sugar is fermented by ALL of the family enterobacteriaceae?
glucose
what arrangement of flagella is characteristic of motile members of this family?
peritrichous
what letter is used to represent the cell wall (somatic) antigen?
O
The flagellar antigen?
H
The capsular antigen?
K or Vi
which of the above antigens may mask the cell wall antigen in the serological typing of salmonella?
K or Vi
how would an organism that ferments lactose and produces H2S appear on XLD?
yellow with black center
how would an organism that ferments lactose and produces H2S appear on HE?
orange colonies with black center
name several media in which a positive result can be growth in the medium even if there is no accompanying color change?
citrate
KCM
malenate
what is the end product in the test for the enzyme phenylalanine deaminase?
phenyl pyruivc acid phenylalanine deaminase (enzyme)
which test utilizes Kovac’s reagent to test for the enzyme tryptophanase?
indol
what are the color changes observed in a positive decarboxylase test, starting with the initial uninoculated color?
starts purple because all ferment glucose so they turn yellow but if glucose runs out they utilize amino acids it turns back to purple
positive test - purple - yellow - purple
negative test - purple to yellow
a pH indicator is generally used to detect what type of reaction by enteric organisms?
carbohydrate fermentation that produces acid
interpret the following reactions observed on TSI : A/A K/A AND K/K
A/A: lactose &or sucrose fermenters / glucose fermenter
K/A: nonlactose &or nonsucrose fermenter/ glucose fermenter
K/K : nonfermenter
*if it cannot ferment lactose or sucrose it will utilize peptones to change the top the different colors
what is the principle of the nitrate test?
the reduction of nitrates (NO3) to nitrites (NO2) and may progress to liberation of NO2
test 1 examines for nitrites
if none test 2 is performed looking for residual nitrates
then if still none you add zinc dust
stays clear +
what does the development of a pink color only after the addition of Zn dust indicate?
negative test result
what biochemical test is especially useful for the detection of a late lactose fermenting organism?
ONPG
what endpoint is produced in a positive urea test that produces the alkaline retain of the indicator?
ammonia
what sugar is fermented by the coliforms (normal intestinal flora like E. Coli or Enterobacter) that is NOT fermented by most enteric pathogens (like salmonella and shigella)
lactose
what organism is indole positive, citrate negative, dry pink on MacConkey, and produces a green, metallic sheen on EMB?
E. Coli
what organism is most common cause of a UTI
E. Coli
what is the principle of the VP test?
inoculate .2 ml MR-VP broth with no more than one colony incubate for 4-6 hours add 3 drops alpha-naphthol then 2 drops KOH then wait five minutes for color change
what is the best single test to use to differentiate enterobacter and klebsiella?
motility
how can certain strains of Hafnia alvei be differentiated from enterobacter aerogenes?
sugar fermentation
what single test is best use to differentiate klebsiella oxytoca from kelbsiella pneumonia
indol
what is the causative agent for bronchial pneumonia?
klebsiella pneumoniae
what is its typical colonial morphology?
large, mucoid, pink, stringy, on mac
encapsulated
what is another test that can differentiate klebsiella pneumoniae from enterobacter?
urea
which test is particularly useful in distinguishing citrobacter and proteus both of which are H2S positive coliforms, from salmonella, which is an H2S positive pathogen?
LDC citrobactor and proteus are =
salmonella is +
how can citrobactor freundii be differentiated from citrobacter diversus?
freundii produces gas I= / ODC =/
diversus no gas / I+/ ODC +
which species is:
- chromogenic
- resistant to antibiotics
- associated with UTI , hospital acquired infections,
- wound infections from outdoorsy people
serratia marcesens
which genus is characterized by “swimming” motility that is best observed on chocolate and sheep blood agar
proteus
how can proteus mirablis and proteus vulgarism be differentiated?
indol
how do members of the genera proteus and providence appear on lysine iron agar
red over yellow
which three genera among the enterobacteriaceae are phylalanine positive?
proteus, providencia, morganella
how can morganella morganii be differentiated from proteus sp.?
it doesn’t swarm or produce H2S
what are the distinguishing characteristics of Yersinae pestis?
“safety pin” gram stain
coccobacillary and encapsulated
what species of enterobacteriaceae is non-motile at 37 C but motile at 25C
yersinea enterocolitica
which genera give the following reactions on the TSI ; K/A and H2S positive
salmonella, edwarsiella, proteus
which genera out of salmonella, edwarsiella, and proteus is pathogenic?
salmonella
what is the kauffman-white schema?
name given to all serological types of salmonella that helps with ID
what are the typical biochemical reactions of salmonella typhi?
K/A weakly positive H2S
what are the reactions of shigella sp. on TSI
K/A no H2S or gas
which species of salmonella is most frequently recovered from the septicemic type of salmonella infection?
sallmonella cholera-suis
why should stool specimens be planted on laboratory media as soon as possible?
shigella
which serological group of shigella is most frequently isolated in the US?
shigella sonnei, GROUP D
which of the rapid identification methods for the enterobacteriaceae discussed in the lecture has at the advantage of being the easiest to setup and producing reliable results in 3-4 hours?
micro ID
what age group shows the most cases of gastroenteritis due to E. Coli?
young children, babies, toddlers
what food is frequent source of contamination with salmonella?
chicken
which body fluids should be tested in cases of carriers of salmonella typhi?
bile
why do severe cases of shigella dysenteriae produce mental confusion?
because of the neurotoxin produced
what its he vector for the transmission of plague?
rat fleas
what type of plague is most contagious?
pneumonic plague
what test is used int eh laboratory to differentiate E. Coli 0157:H7 from normal strains of E. Coli?
selective MAC containing 1% D-sorbitol rather than lactose 0157:H7 strains are sorbitol = and will be colorless
in the classification of the tenterobacteriaceae what is a tribe?
group of biochemically similar genera
what are the IMViC tests?
I - indol
M- methyl red
Vi- voges proskaure
C- citrate
what would the be the test results from IMViC tests for E. Coli?
indol +
MR +
VP =
C =
what is the nickname for the klebsiella pneumoniae
friedlanders bacillus
what non-pathogenic organism is so similar to shigella biochemically that it is included in the serological typing of shigella isolates?
alkalescense dispar
what is the difference between a true food poisoning and a food infection
staphylococcus- food poisoning but onset is after only a few hours because you have ingested performed toxins
salmonella - food infection you are ingesting the viable organisms which take 48 hours to feel effects
