ENTEROBACTERIACEAE Flashcards
A K/A reaction on a TSI slant indicates that the organism is a:
E. coli
Shigella
Klebsiella
EIEC
Shigella
A K/A reaction on a TSI slant indicates that the organism is a:
Yellow/yellow
Red/red
Yellow/red
Red/yellow
Red/yellow
Organisms that typically produce clear colonies (green without black centers) on Hektoen agar are:
Shigella
Salmonella
E. coli
Klebsiella
Shigella
he gram stain characteristic of Enterobacteriaceae should be:
Gram negative rod without spores
Gram negative rods with spores
Gram negative cocci with spores
Gram negative rods without spores
Gram negative rods without spores
Which organism species does not exhibit Phenylalanine deaminase (PD) production:
Morganella
Proteus
Providencia
Klebsiella
Klebsiella
Which species of Enterobacteriaceae has this unique characteristic- VP negative:
Shigella
Proteus
Salmonella
E. coli
E. coli
Resistant to heat and alcohol and detected by bacterial antigen:
H Ag
O Ag
K Ag
Vi Ag
O Ag
An organism gives the following reactions: TSI A/A, no H2S, gas produced. The most likely identification is:
Klebsiella pneumoniae
Salmonella typhi
Shigella dysenteria
Salmonella enteritidis
Klebsiella pneumoniae
The following are characteristics of Citrobacter, EXCEPT:
Citrate (-)
Slow lactose fermenter
Do not decarboxylate lysine compared to salmonella
None of the above
Citrate (-)
What is the treatment for cystitis caused by E. coli?
Ceftriaxone
Piperacillin
Amoxicillin
Nitrofurantoin
Nitrofurantoin
Which species of Enterobacteriaceae has this unique characteristic mucoid colonies?
Shigella
Klebsiella
Proteus
E. coli
Klebsiella
LT of ETEC is antigenic and cross-reacts with the enterotoxin of:
Vibrio cholera
Shigella
Salmonella
Proteus
Vibrio cholera
The enteric media XLD uses which pH indicator?
Methyl red
Phenol red
Both
Neither
Phenol red
A TSI tube is inoculated and incubated for 18-24 hours. After incubation, the TSI is completely yellow. The technologist should report the TSI reaction as:
K/A H2S (+)
A/A (-) H2S
A/K (-) H2S
A/A (+) H2S
A/A (-) H2S
Which species of Enterobacteriaceae has this unique characteristic- Green metallic sheen on EMB?
E. coli
Citrobacter
Morganella
Proteus
E. coli
- The common mode of transmission for Enterobacteriaceae.
a) blood-borne
b) fecal-oral
c) droplet
d) all are correct
b) fecal-oral
These species are normal human microbiota of the GI tract.
a) E. coli
b) Yersinia pestis
c) Klebsiella
d) options 1 and 3
d) options 1 and 3
E.coli
Klebsiella
This organism must be handled in BSL-3 because it produces a
highly fatal bacteremia.
a) Yersinia pestis
b) Yersinia enterolitica
c) Yersinia pseudotuberculosis
d) none are correct
a) Yersinia pestis
Transport media used in the specimen collection of
Enterobacteriaceae are the following, except:
a) Cary-Blair
b) Aimes
c) buffered glycerol saline
d) Stuart
c) buffered glycerol saline
Components of the CIN agar.
a) Ceftazidime
b) Irgasan
c) Nitrofurantoin
d) Cefsulodin
e) Indomethacin
f) Nalidixic acid
g) Cefoxitin
h) Iodine
i) Novobiocin
d) Cefsulodin
b) Irgasan
i) Novobiocin
An indole-negative, slow lactose-fermenting bacteria that is
known to cause infections from infected medical devices.
a) Citrobacter
b) Serratia marcescens
c) Klebsiella pneumoniae
d) E. coli
a) Citrobacter
These are facultative anaerobic, motile,gram-negative rods commonly isolated from the intestines of humans and animals.
Identification is primarily based on the ability of the organism to use citrate as the sole carbon source and lysine as a nitrogen source in combination with hydrogen sulfide (H2S) production *
a) Salmonella
b) Proteus
c) Providencia
d) Serratia
a) Salmonella
Groups of organisms that are seen in mononuclear endothelial
cells of infected penile lesions are caused by which organism?
a) Klebsiella granulomatis
b) Neisseria gonorrhea
c) Klebsiella pneumoniae
d) Treponema pallidum
a) Klebsiella granulomatis
This medium contains glucose, sucrose, and lactose and differentiates glucose fermenters from non–glucose fermenters.
a) MacConkey
b) Triple sugar iron
c) Selenite broth
d) Salmonella-Shigella agar
b) Triple sugar iron
This bacterium is a lactose fermenter, forms blue black with a
metallic green sheen colonies and is the most common cause of
gram-negative health care–associated infections.
a) E. coli
b) Salmonella typhi
c) Citrobacter
d) Yersinia enterolitica
a) E. coli
Enterobacteriaceae is the most common group of [?] cultured in clinical laboratories both as normal flora and as agents of disease.
gram-negative rods
The taxonomy of the Enterobacteriaceae is complex and rapidly changing since the introduction of techniques that measure evolutionary distance, such as [?] and [?]
nucleic acid hybridization and nucleic acid sequencing.
GENERAL CHARACTERISTICS OF ENTEROBACTERIACEAE
Gram reaction and shape
spore
motility
capsule
oxygen requirement
oxidase
carbohydrate fermentation
nitrate reduction enzyme, which to what
Gram-negative bacilli
Non-spore forming
Motile (peritrichous)
capsule
oxygen requirement
oxidase
carbohydrate fermentation
nitrate reduction enzyme, which to what
Non-motile Enterobacters
[SKY]
Shigella
Klebsiella
Yersinia
Yersinia are nonmotile at [?]
35-37 degree Celsius
Yersinia are motile at [?]
room temperature
(somatic antigen or cell wall antigen)
O antigens
(capsular antigen or fimbrial antigen)
K antigen
(flagellar antigen)
H antigen
most external part of the cell wall lipopolysaccharide
O antigens
consisting of repeating units of polysaccharide
O antigens
usually are detected by bacterial agglutination
O antigens
HA-S
O antigens
H-L
K antigen
HA-L
H antigen
external to the O antigens on some but not all Enterobacteriaceae
K antigen
found on the surface of flagella.
H antigen
within a single serotype, flagellar antigens may be present in either or both of two forms, called phase 1 (designated by lower-case letters) and phase 2 (designated by Arabic numerals).
H antigen
organism tends to change from one phase to the
other; this is called phase variation
H antigen
aerobic and facultative anaerobic
non-sporeforming
gram-negative rods
cytochrome-oxidase negative
capable of growth in the presence of bile salts
COLIFORMS
ferment lactose at either 35 or 37 oC
include the normal enteric flora
COLIFORMS
COLIFORMS spp
[EKEC]
o Escherichia
o Klebsiella
o Enterobacter
o Citrobacter
differ from coliforms by their inability to ferment lactose; NLF
NONCOLIFORMS
Fecal coliforms
o most common facultative bacterium in feces of man and warm-blooded animals
o indicator organism of choice for fecal contamination
Escherichia coli
ferments lactose at 44.5 oC
FECAL COLIFORMS
Non fecal coliforms
[KEC]
Klebsiella
Enterobacter
Citrobacter
Opportunistic, normal gut flora spp
[SHE PPM]
Serratia
Hafnia
Edwardsiella
Proteus
Providencia
Morganella
Pathogenic enterics (true enteropathogens) spp
Salmonella
Shigella
Yersinia enterocolitica
Y. pseudotuberculosis
Pathogenic, non-enteric spp
Yersinia pestis
Escherichia coli was first described by [?] in 1885
Theodor Escherich
Escherichia coli common name
“colon bacillus”
accounts for approximately 90% of first urinary tract infections in young women
Uropathogenic E. coli
Strains of E. coli that cause UTIs usually originate in the large intestine as resident biota.
Infection is more common in women because of their relatively short urethras that promote ascending infection to the bladder (cystitis) and occasionally, the kidneys.
Uropathogenic E. coli
Uropathogenic strains possess ____ that have specifically elaborated virulence factors that facilitate colonization and subsequent clinical infections
O antigen types
most common cause of UTIs;
E. coli
primary virulence factor associated with the ability of E. coli to cause UTIs
Pili (P fimbrae)
allow the bacteria to attach to the urinary epithelial mucosa and not be washed out with urine flow
Pili (P fimbrae)
cytolysins which can kill immune effector cells and inhibit
chemotaxis and phagocytosis of certain white blood cells
Hemolysins
allows the bacterial cell to chelate iron; free iron is generally unavailable within the host for use by bacteria
Aerobactin
Enterovirulent E. coli
Diarrheagenic E. coli
E. coli may cause several different GI syndromes
Diarrheagenic E. coli
based on virulence factors, clinical manifestation, epidemiology, and different O and H serotypes, there are five major categories of diarrheagenic E. coli:
Enteropathogenic E. Coli (EPEC)
Enterotoxigenic E. coli (ETEC)
Enterohemorrhagic E. coli (EHEC)
Enteroinvasive E. coli (EIEC)
associated with diarrheal outbreaks occurring in hospital nurseries and daycare centers, but cases in adults are rarely seen
Enteropathogenic E. Coli
EPEC
Infection is characterized by low-grade fever, malaise, vomiting, and profuse, watery diarrhea. Stool typically contains large amounts of mucus, but apparent blood is not present. Fecal leukocytes are seen only
occasionally.
EPEC
Diarrhea is usually self-limited but can be prolonged or chronic.
EPEC
EPEC adhere to intestinal epithelial cells in localized microcolonies producing characteristic histopathologic lesions known as
“attaching and effacing lesions”
Facilitated by bundle-forming pilus encoded by a plasmid EPEC adherence factor (EAF) and the chromosomal locus of enterocyte effacement (LEE) pathogenicity island that promote the tight adherence, characteristic of EPEC
ATTACHMENT
occurs after attachment where there is loss of microvilli
EFFACEMENT
formation of filamentous actin pedestals or cup-like structures
EFFACEMENT
occasionally, entry of the EPEC into the mucosal cells.
EFFACEMENT
Associated with two clinical syndromes: “weanling diarrhea” among children in tropical and subtropical climates, especially in developing countries and “Traveler’s diarrhea” (also referred to as “Montezuma’s revenge”; “Delhi belly”).
ETEC
Infection is spread commonly via consumption of
contaminated food or water; poor hygiene, reduced
availability of sources of potable water, and inadequate
sanitation.
ETEC
Produces a typically mild, self-limiting disease which has an abrupt onset with short incubation period.
ETEC
Symptoms include profuse watery diarrhea (similar with V. cholerae), usually without blood, mucus, or pus; accompanied by mild abdominal cramps; usually without vomiting or fever.
ETEC
facilitates colonization of ETEC on the proximal small intestine by binding to specific receptors on the intestinal microvilli
Fimbrae
is similar in action and amino acid sequence to cholera toxin from Vibrio cholerae.
Heat-labile toxin (LT)
Consists of two fragments (A and B), which follow the A/B model of bacterial toxins
Heat-labile toxin (LT)
enzymatically active portion
A MOEITY
activates cellular adenylate cyclase, causing an increase in the conversion of adenosine triphosphatetocyclic adenosine monophosphate (cAMP)
A MOEITY
accumulation of cAMP results to hypersecretion of both electrolytes and fluids into the intestinal lumen, resulting in watery diarrhea similar to cholera
A MOEITY
also known as binding portion
B MOEITY
confers specificity to the LT
B MOEITY
associated with hemorrhagic diarrhea, colitis, and hemolytic uremic syndrome (HUS)
EHEC
characterized by low platelet count, hemolytic anemia, and kidney failure
hemolytic uremic syndrome (HUS)
produces a watery diarrhea that progresses to bloody
diarrhea with abdominal cramps and low-grade fever or an absence of fever but the stool does not contain
leukocytes which distinguishes it from dysentery caused by Shigella spp. or EIEC infections
EHEC
food and food products such as processed meats, unpasteurized dairy products and apple cider, bean sprouts, and spinach have been implicated in the spread of infection
EHEC
EHEC produces 2 cytotoxins
verotoxin I and verotoxin II
verotoxin I and verotoxin II are identical to the
Shiga toxin (Stx) produced by Shigella dysenteriae type I
African green monkey kidney cells; “verotoxin”; damaged by verotoxin I and verotoxin
Vero cells
phage-encoded cytotoxin
Verotoxin I
is biologically similar to, but immunologically different from, both Stx and verotoxin I.
Verotoxin II
Of the E. coli serotypes that produce Shiga toxin, [?] is the most common and is the one that can be identified most readily in clinical specimens
O157:H7
produce a diarrheal illness which is very similar to that produced by Shigella spp — dysentery with direct penetration, invasion, and destruction of the epithelial cells that make up the large intestinal mucosa
EIEC
Infections seem to occur in children in developing
countries and in travelers to these countries.
EIEC
Direct transmission of EIEC from person to person via the [?] has been reported.
fecal-oral route
Clinical infection is characterized by fever, colitis, severe abdominal cramps (tenesmus), malaise, and watery diarrhea with blood, mucus and leukocytes in stool.
EIEC
Causes acute and chronic diarrhea (>14 days in duration) in persons in developing countries; it also is the cause of food-borne illnesses in industrialized countries and have been associated with traveler’s diarrhea and persistent diarrhea in patients with HIV.
EIEC
Adhere to epithelial cells in a pattern resembling a pile of stacked bricks.
EIEC
Illness is characterized by watery, mucoid diarrhea with low grade fever and little or no vomiting, white blood cells and red blood cells are typically absent from the stool.
EAEC
Pathology has been associated with production of ST-like toxin, an LT toxin, and fibril colonization factors called “AAFs” (aggregative adherence fimbriae).
EAEC
fibril colonization factors
“AAFs” (aggregative adherence fimbriae)
E. coli remains one of the most common causes of septicemia and meningitis among neonates.
Extraintestinal Infections
A newborn usually acquires the infection in the birth canal just before or during delivery, when the mother’s vagina is heavily colonized or may also result if the amniotic fluid occurs becomes contaminated
Extraintestinal Infections
Sepsis may occur when normal host defenses are inadequate (e.g., newborns may be highly susceptible to E. coli sepsis because they lack IgM antibodies); or secondary to urinary tract infection.
Extraintestinal Infections
Approximately 75% of E. coli from meningitis cases have the K1 antigen which is said to cross-react with the group B capsular polysaccharide of N. meningitidis.
Extraintestinal Infections
Klebsiella species common name
“Friedlander’s bacillus”
have been associated with various opportunistic and hospitalacquired infections, particularly pneumonia, wound infections, and UTIs.
Klebsiella
the most commonly isolated Klebsiella species
Klebsiella pneumoniae
In addition to inhabiting the intestines of humans and animals
Klebsiella pneumoniae
It causes a small proportion (~1%) of bacterial pneumonias characterized as extensive hemorrhagic necrotizing consolidation of the lung resulting in the production of sputum that may be thick, mucoid, and brick red, or thin and “currant jelly-like” in appearance.
Klebsiella pneumoniae
found in the respiratory tract and feces of about 5% of normal individuals
Klebsiella pneumoniae
Also produces urinary tract infection, wound infections, meningitis, bacteremia with focal lesions (e.g., abscesses) in debilitated patients.
Klebsiella pneumoniae
Pathology has been associated with a large polysaccharide capsule that confers protection against phagocytosis and antimicrobial absorption.
Klebsiella pneumoniae
Produces infections similar to those caused by K. pneumoniae.
Klebsiella oxytoca
Isolates have also been linked to antibiotic/antimicrobial-associated hemorrhagic colitis (AAHC)
Klebsiella oxytoca
a distinct form of antibiotic-associated diarrhea, in which C. difficile is absent and where patients experience a sudden onset of bloody diarrhea often in combination with severe abdominal cramps.
antibiotic/antimicrobial-associated hemorrhagic colitis (AAHC)
Has been isolated from cerebral abscesses and nasal mucosa in ozena
cerebral abscesses and nasal mucosa in ozena,
Klebsiella pneumoniae subspecies ozaenae
a fetid, progressive atrophy of mucous membranes (atrophic rhinitis and tissuedestructive disease restricted to the nose).
OZENA
rhinoscleroma
Klebsiella pneumoniae subspecies rhinoscleromatis
a destructive granuloma of the nose and pharynx that manifests as an intense swelling and malformation of the entire face and neck.
rhinoscleroma
Klebsiella granulomatis formerly called
Calymmatobacterium granulomatis
causes, granuloma inguinale, a chronic genital ulcerative disease and an uncommon sexually transmitted disease.
Klebsiella granulomatis
Resembles Klebsiella in terms of growth and most biochemical characteristics except that they motile.
Pathology is associated with capsule production for some strains.
Enterobacter species
are the two most common isolates of Enterobacter species
Enterobacter cloacae and Enterobacter (now Klebsiella) aerogenes
cause a broad range of hospital-acquired infections such as pneumonia, urinary tract infections, and wound and device infections, on occasion, septicemia, and meningitis
Enterobacter cloacae and Enterobacter (now Klebsiella) aerogenes
- A 17 year old boy experiences a bloody diarrhea.
CBC showed thrombocytopenia. What would you
ask his past food or fluid intake?
A. Poultry
B. Bread contaminated with cow’s manure
C. Fruit juice not properly prepared
D. Beef bought in a nearby market
Answer: [D.] BEEF BOUGHT IN A NEARBY MARKET.
Shiga Toxin-producing E. Coli has been associated with
hemorrhagic colitis, a severe form of diarrhea, with
hemolytic uremic syndrome(HUS), a disease resulting in
Acute renal failure, microangiopathic hemolytic anemia, and
thrombocytopenia. This E. coli strain is commonly found in
meat (burgers).
Ingested E.coli O157:H7 produces high levels of
toxins in the large intestine. These toxins are
closely related to those produced by which of the
following organisms?
A. Enteroinvasive E.coli
B. Shigella dysenteriae
C. Vibrio cholerae
D. Serratia marcescens
Answer: [B.] SHIGELLA DYSENTERIAE. O157-H7 is
one of the e.coli serotypes that produce shiga toxin.
Shiga-like toxin 1 is identical to the Shiga toxin of Shigella
dysenteriae type 1, and Shiga-like toxin 2 also has many
properties that are similar to the Shiga toxin.
- Ms. Lila, 56 year old, had history of travel to
Palawan for a business meeting. After 2 days, she
developed watery diarrhea? What organism will
you entertain?
A. ETEC
B. EPEC
C. EIEC
D. EAEC
Answer: [A.] ETEC. Enterotoxigenic E. coli is the
common cause of “traveler’s diarrhea”, a diarrhea that
develops during, or shortly after, travel abroad.
- Gram-negative rods that do not ferment lactose
A. Bacillus
B. Bacillus subtilis
C. Salmonella
D. Klebsiella
[C.] SALMONELLA. The inability to ferment lactose
distinguishes shigellae on differential media. Klebsiella is
a lactose fermenter. Bacillus is gram positive and Bacillus
subtilis is a gram positive non lactose fermenter.
Mrs. Simon, a retired teacher, developed diarrhea
4 days after eating chicken. On physical
examination, temperature is 38.5°C, heart rate is
45/min. Physical examination of the chest showed
a rose spot. This is suggestive of what organism?
A. Shigella boydii
B. Salmonella typhi
C. Escherichia coli
D. Klebsiella
E. Serratia marcescens
Answer: [A.] SALMONELLA TYPHI. Typhoid fever
presents rose spots, usually on the skin of the abdomen
or chest. The most important causative agent for this is
Salmonella serotype Typhi.
- Mrs. Simon, a retired teacher, developed diarrhea
4 days after eating chicken. On physical
examination, temperature is 38.5°C, heart rate is
45/min. Physical examination of the chest showed
a rose spot. You did a biochemical test on Mrs.
Simon’s specimen. What would you expect?
A. Alkaline/Acid with gas formation
B. Acid/Acid with gas formation
C. Alkaline/Acid without H2S formation
D. Acid/Alkaline with H2S formation
E. Serratia marcescens
Answer: [A.] ALKALINE/ACID WITH GAS FORMATION.
Salmonella and Shigella presents alkaline slant and acid
butt. Salmonella ferments glucose, producing acid and gas.
- Mrs. Simon, a retired teacher, developed diarrhea 4
days after eating chicken. On physical examination,
temperature is 38.5°C, heart rate is 45/min. Physical
examination of the chest showed a rose spot. What
differential media would you use on Mrs. Simon’s
specimen?
A. MacConkey agar
B. Eosin Methylene Blue
C. Chocolate agar
D. Hektons Enteric Agar
Answer: [D.] HEKTOENS ENTERIC AGAR. Hektoen
enteric agar, a selective medium, is able and favors growth
of salmonellae and shigellae over other Enterobacteriaceae.
- Mrs. Simon, a retired teacher, developed diarrhea 4
days after eating chicken. On physical examination,
temperature is 38.5°C, heart rate is 45/min. Physical
examination of the chest showed a rose spot. What
antibiotic will you give to Mrs. Simon?
A. Vancomycin
B. Ceftriaxone
C. Amoxicillin
D. Meropenem
Answer: [C.] AMOXICILLIN. Antimicrobial therapy of
invasive Salmonella infections is with ampicillin,
trimethoprim–sulfa
- Mrs. Miranda, 33 years old, experienced urinary
frequency. She also complained of hypogastric
pain. Urinalysis showed pyuria and hematuria. Her
vital signs are stable. Your diagnosis is?
A. Cystitis
B. Acute pyelonephritis
C. Acute Glomerulonephritis
D. Acute nephritis
Answer: [A.] CYSTITIS. Cystitis presents increased urinary
frequency, pain above the pubic region, bacteria and WBCs
in the urine (pyuria), possible hematuria, and usually the
absence of fever in adults.
- Mrs. Miranda, 33 years old, experienced urinary
frequency. She also complained of hypogastric
pain. Urinalysis showed pyuria and hematuria. Her
vital signs are stable. You did a biochemical test
suggestive of Escherichia coli? What would you
expect on TSI?
A. Non-lactose fermenter with gas formation
B. Lactose fermenter without gas formation
C. Lactose fermenter with gas formation
D. Non-lactose fermenter without gas formation
Answer: [C.] LACTOSE FERMENTER WITH GAS
FORMATION. E. coli produces gas from glucose. It is a
Lactose, Sucrose, and Glucose fermenter.
- Mrs. Miranda, 33 years old, experienced urinary
frequency. She also complained of hypogastric
pain. Urinalysis showed pyuria and hematuria.
What antibiotic will you give to her?
A. Ceftriaxone
B. Amoxicillin
C. Piperacillin tazobactam
D. Nitrofurantoin
Answer: [D.] Mrs. Miranda is experiencing Cystitis which
is a bladder infection usually accompanied with increase
urinary frequency/urgency, dysuria (painful urination),
pain above the pubic region (hypogastric), WBCs &
bacteria in urine and possible hematuria which is also
more common in women. The drug of choice would be
Nitrofurantoin that has uncommon resistance and little
systemic effect. It is widely used either short term to treat
acute urinary tract infections or long term as chronic
prophylaxis against recurrent infections.
You are on duty at the ER. An infant was brought
presenting with seizure and nuchal rigidity. Your
diagnosis is?
A. Febrile seizure
B. Encephalitis
C. Meningitis
D. Typhoid fever
Answer: [C.] Seizures and nuchal rigidity (stiff neck) is
the usual symptoms of meningitis that are accompanied
by headache, nausea, vomiting and sensitivity to light.
- You are on duty at the ER. An infant was brought
presenting with seizure and nuchal rigidity. The
organism causing this is:
A. Klebsiella pneumonia
B. Enterobacter aerogenes
C. Shigella dysenteriae
D. Escherichia coli
Answer: [D.] The leading cause of Meningitis in infants is
caused by a disease-causing strain known as E. coli
K1(Ag). Most cases of E. coli meningitis occur in newborn
babies or babies under 3 months of age. Other leading
cause is Group B streptococci which is not included in the
choices.
- Mr. Romantico was diagnosed with UTI. Urinalysis
showed a pH of 8 (alkaline urine). What typical
organism is causing Mr. Romantico’s UTI?
A. Salmonella typhi
B. Proteus vulgaris
C. Escherichia coli
D. Providencia sp.
Answer: [B.] Proteus species produce urease, resulting in
rapid hydrolysis of urea with liberation of ammonia. Thus, in
urinary tract infections with Proteus species, the urine
becomes alkaline, promoting stone formation and making
acidification virtually impossible. The rapid motility of
contribute to its invasion of the urinary tract.
- Mr. Romantico was diagnosed with UTI. Urinalysis
showed a pH of 8 (alkaline urine). You did a urease
test. The positive result showed:
A. Orange to pink
B. Magenta pink to orange
C. Red ring on top
D. Green turned into blue
Answer: [A.] Positive urease test would demonstrate a
change in color in from Orange to Pink. The test organism
is placed in a urea agar which contains urea and phenol red.
If the strain produces urease, this enzyme will convert urea
to CO2 and ammonia. NH3 then combines w/ H2O to form
ammonium hydroxide (NH4OH), a strong base which
increases pH of the medium. Accordingly, this pH shifts
causes phenol red to change color from light orange at pH
6.8 to a deep pink color at pH 8.1.
- Mr. Suave developed hospital acquired infection.
MacConkey agar showed (refer to image below).
cont. The microorganism involved is:
A. Klebsiella pneumoniae
B. Escherichia coli
C. Pseudomonas aeruginosa
D. Serratia marcescens
Answer: [A.] Klebsiella pneumonia demonstrates moist
pink colonies in EMB due to the presence of capsule and
it is a common nosocomial (hospital acquired)
infection, specifically pneumonia in the general
community
- Mr. Suave developed hospital acquired infection.
MacConkey agar showed (refer to image below)
You did a biochemical test to Mr. Suave’s specimen.
You will expect:
A. Lactose fermenter, motile
B. Lactose non-fermenter, motile
C. Lactose fermenter, nonmotile
D. Lactose non-fermenter, nonmotile
Answer: [C.] The image shows Klebsiella pneumonia on
EMB media which is a gram-negative, lactosefermenting, non-motile, aerobic rod-shaped bacterium.
- Which of the following exhibit the “swarming
effect”?
A. Proteus
B. Providencia
C. Morganella
D. E. coli
Answer: [A.] Proteus species move actively by its
peritrichous flagella (typical), resulting in “swarming
effect” on solid media.
- Prodigiosin is seen in
A. Klebsiella pneumoniae
B. Escherichia coli
C. Pseudomonas aeruginosa
D. Serratia marcescens
Answer: [D.] A class of tripyrrole antibiotic pigments with
red color produced by strains of Serratia marcescens is
known as the prodigiosin. Only about 10% of isolates form
the red pigment(prodigiosin) that has long characterized
S. marcescens.
