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Flashcards in Food & Water Bacteriology Deck (38)
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Perishable foods which can support the growth of harmful bacteria

high risk foods


Which is not part of the high risk food group?
(1) All cooked meat and poultry.
(2) gravy, stock, and roll/sandwich fillings
(3) eggs and egg products
(4) vegetable salad [no dressing]



Which is not part of the high risk food group?
(A)Milk, cream, artificial cream, custards and dairy
(B)Canola oil
(C)shell fish and other sea food
(D)cooked rice



Minimum weight range for food sample analysis

25-30 g


Why must delay be kept to a minimum (in food sample analysis)?

target organism may decline in number & spoilage organisms may increase in number


What are the four factors to consider in food sample collection?

(1) Time
(2) Temperature
(3) Container
(4) Manner of collection:


How much time is the limit between collection and reception into the laboratory?

2 hours


Identify the process used for analysis:
* gives evaluation of total population of aerobic microbes present (# of colonies that develop after incubation)
* Swabs of product are applied in sterile covered plates to culture media that non-selectively support growth.

Aerobic Plate Count


Which is not a disadvantage of the Aerobic Plate Count method?
a. only counts plates with 25-250 colonies
b. may not be done on fermented foods
c. Small colonies may be difficult to see
d. Sometimes hard to distinguish food particles from bacteria



Aerobic Plate Count is used for everything except:
a. Check the microbiological quality of final products only
b. Determine whether a food has been subjected to
temperature abuse during production, transport and
c. Estimate the potential storage life of product
d. Check level of contamination in processing envt


raw materials also


Identify the food analysis method:
* Involves the use of agar poured at 45˚C, which may kill
some pychrotrophs or psychrophiles, or damage cells and reduce count
* the technique gives both surface and subsurface colonies

Pour Plate Method


Identify the method: Only count plates with 25-250 colonies

Counting Plates


In Membrane Filtration Method, which does not happen?
A. Involves passing a known volume of liquid through a
cadmium acetate with a pore size of 0.45 um
B. Bacteria, yeasts and molds are removed from the liquid and precipitated on the membrane surface
C. When the membrane is transferred to a pad soaked in
nutrient medium or an agar plate and incubated, nutrients diffuse through the membrane so that organisms can grow on the membrane surface giving visible colonies that can be counted
D. none of the above


cellulose acetate dapat


MBF as a technique for assessing microbial numbers is
limited to __

clear liquids that do not contain debris or other
materials that will block the filter


False about Membrane Filtration Method
A. Has an advantage of detecting high numbers of organisms in small volumes of liquids
B. Particularly useful for testing treated water supplies for the presence of coliforms
C. both are false


Has an advantage of detecting low numbers of organisms
in large volumes of liquids


Most Probable Number is also known as __

multiple tube technique


In multiple tube technique, the number of __ in food samples is estimated if the criterion for a particular organism requires detection of low numbers



Which does not happen in Most Probable Number method?
A. Typical MPN technique for food analysis involves replicate tubes in groups of 3 containing liquid (selective/differential media)inoculated with 1 ml of samples from a dilution series
B.The decision as to whether a viable organism has been transferred to a tube is based on growth to give visible turbidity only
C. Both do not happen
D. Both happen


The said step is done in conjunction with another distinguishing property of the bacteria


Identify the method

statistical method based on the
probability of transferring a CFU from an original dilution
using multiple samples and is employed in conjunction
with a statistical table

Most Probable Number technique


False about Direct Microscopic Count
a. A small sample of food (0.01ml liquid food or food
homogenate in diluent) is spread as evenly as possible in
a 1 cm2 area etched on a microscope slide
b. the slide is dried, stained with suitable stain and examined with oil immersion lens on
the microscope
c. The numbers of organisms in 25 random microscopic
fields can be counted and a calculation based on the field
diameter, made to give the number of organisms/g or ml
original sample
d. The technique is tedious, and obtaining results takes a few days



Which is not a disadvantage of Direct Microscopic Count?
A. The technique cannot distinguish between living and
dead cells
B. The technique is tedious to carry out, particularly when dealing with large number of samples
C. procedure may not be applied to fermented foods
D. The sensitivity range is very limited
E. Limited to liquid and semisolid foods with no debris


this disadvantage --> Aerobic Plate Count


Dye reduction test for milk uses what dye?

methylene blue / resazurin


False about indicator organisms
(1) Be present in human feces in small numbers
(2) Be present in feces when the pathogen is present
(3) Survive for a similar period in the environment as pathogen
(4) Be quick and easy to isolate and identify in the laboratory

large numbers dapat


Trypticase soy-yeast extract (TSYE) broth is used for
a. Salmonella
b. Shigella
c. both of the above
d. none of those mentioned



Eosin Methylene Blue medium is used for
a. Salmonella
b. Shigella
c. E. coli
d. none of those mentioned



Preston broth is used for
a. Camyplobacter
b. Shigella
c. E.coli
d. none of those mentioned



Which is not a characteristic of enterobacteriaceae?
1. All are gram negative rods
2. All ferment glucose
3. All are oxidase positive
4. All are facultative anaerobes
5. Motile species have peritrichous flagella


negative dapat


What does CT-SMAC medium mean, in E.coli lab diagnosis?

Cefixime Tellurite Sorbitol MacConkey


Which is false?
A. Ecoli 157 forms sorbitol negative colonies
B. Yersinia enterocolitica is urease positive
C. Listeria monocytogenes uses cold enrichment
D. Campylobacter jejuni is oxidase negative



Which is not used for culturing L. monocytogenes?
A. McBride
B. Oxford agar
C. Buffered Charcoal Yeast Extract Agar