LABORATORY Flashcards
Is the preferred specimen, collected and transported in Cary-Blair medium.
Feces
is not acceptable, because glycerol is toxic to vibrios.
Buffered glycerol saline
Are also acceptable
Rectal swabs
Gram-negative curved or comma-shaped bacilli, 2–4 µm long.
V. cholerae
On prolonged cultivation, vibrios may become [?] that resemble the [?].
straight rods
Gram-negative enteric bacteria
[?]
The [?] incorporated in this medium promotes the growth of Vibrio species, while the [?] of this medium inhibits most of the commensal intestinal bacteria.
Alkaline Peptone Water (APW)
- 1% (w/v) sodium chloride
- alkalinity (pH 8.6)
APW is incubated at [?] prior to inoculation of plated media.
35°C for 12-18 hours
is done when few organisms are present, as in specimens from convalescent patients and asymptomatic carriers.
Enrichment in APW
When the patient is in very early stages of illness and is passing liquid stool, it may not be necessary to [?] stool specimens.
enrich
Colonies are typically medium to large, smooth, convex, creamy in consistency, gray-white, and have entire margins, smooth, opaque; may be β-hemolytic
5% Sheep BAM
Colonies appear transparent and usually have a characteristic cloudy or opaque zone (due to [?] activity) around colony, which becomes more definite after few minutes of [?].
Gelatin Agar (GA)
- gelatinase
- refrigeration
[?]
When these colonies are viewed in oblique light
they appear [?] to [?] colored and [?]
Gelatin Agar (GA)
- iridescent green
- bronze
- finely granular
Selective medium of choice for the isolation of V. cholerae and V. parahaemolyticus as well as other vibrios.
Thiosulfate Citrate Bile Sucrose (TCBS) Agar
TCBS Agar
stimulates growth of Vibrio species.
inhibit gram-positive bacteria
1% Sodium chloride Bile salts (oxgall)
TCBS Agar
serves as a sulfur source, in combination with [?], detects hydrogen sulfide production
Sodium thiosulfate
ferric citrate
is included as a fermentable carbohydrate for the metabolism of vibrios.
Saccharose (sucrose)
The [?] of the TCBS agar inhibits most of the commensal intestinal bacteria.
alkaline pH (8.6)
are included as indicators of pH changes in Thiosulfate Citrate Bile Sucrose (TCBS) Agar
Thymol blue and bromthymol blue
Suspicious colonies for further testing in Thiosulfate Citrate Bile Sucrose (TCBS) Agar should be subcultured to a
noninhibitory medium
examples of noninhibitory medium
gelatin agar, heart infusion agar (HIA), Kligler’s iron agar (KIA), or triple sugar iron agar (TSI).
inhibits the contaminating gram-positive bacteria in TTGA or Monsur’s agar
Sodium taurocholate
is a selective and differential agent in Taurocholate tellurite gelatin agar (TTGA or Monsur’s agar)
inhibits many gram-positive bacteria and due to the reduction reaction the colonies form a grey to black color
Potassium tellurite
helps in maintaining the elevated pH of the medium which is also inhibitory to most Enterobacteriaceae and gram-positive bacteria.
Sodium carbonate
acts as an additional carbon and energy source and is the substrate of bacterial gelatinase causing halo effect around the colony.
Gelatin
support the growth of some but not all strains of V. cholerae.
MacConkey (MAC) Agar
Overnight colonies of V. cholerae on MAC tend to be small to moderately sized (1 to 3 mm) and usually appear as lactose-negative (colorless) or [?], often resembling colonies of [?] lactose-fermenting organisms.
slightly pink
“late” or “slow”
A characteristic that separates Vbrios from the Enterobacteriaceae.
Oxidase (+)
Conduct the oxidase test with fresh growth from an [?] or any non-carbohydrate-containing medium. Do not use growth from TCBS agar.
HIA slant
TSI: A/A, no gas, no H2S;
KIA:K/A, no gas, no H2S
Gluc+, Lac-, Suc+
- Modified by the addition of 1% NaCl = [?]
- Lysine decarboxylation =
- LIA:
- Ornithine decarboxylation =
- Arginine dihydrolase =
Decarboxylase/Dihydrolase Test
- (+)
- K/K
- (+)
- (-)
[?] Principle
Vibrio species suspended in [?] will be lysed. The suspension will lose [?], and [?] will be released from the lysed cells causing the mixture to become viscous.
String Test
- 0.5% sodium desoxycholate
- turbidity
- DNA
[?] Procedure
[?]-hour colonies from HIA or other noninhibitory medium are mixed with a few drops of [?] on a glass slide. An [?] is immersed into the mixture and pulled away from the drop.
String Test
- 18- to 24
- 0.5% sodium desoxycholate
- inoculating loop
[?] Result’
Vibrio cholerae produces a [?] that becomes more [?] after [?] seconds or more (other vibrios may give an initial string reaction that diminishes or disappears [?] seconds later.
String Test
- long string
- tenacious
- 60
- 45 to 60
[?] Principle
Vibrios either require [?] or have their growth stimulated by its addition.
Growth in Salt Broths
- NaCl