Lesson 10

Question 1

-population of bacteria grown in the laboratory

Answer 1

culture

Question 2

• contains only one single type of bacteria

Answer 2

pure culture

Question 3

-it is done to keep the bacterial population growing

Answer 3

Subculturing

Question 4

contains two or more different bacteria.

Answer 4

mixed culture 🧫

Question 5

if a bacterial culture is left in the same media for too long what will happen?

Answer 5

the cells will use up the available nutrients
excrete toxic metabolites
eventually the entire population will die

Question 6

is used to obtain a pure culture of an Infectious agent, and also for studies leading to the identification of the pathogen.

Answer 6

Subculturing

Question 7

• means using practices and procedures to prevent contamination from pathogens.

-

Answer 7

Aseptic technique

Question 8

The most effective way to isolate a single type of bacteria from a source that contains many by diluting the individual cells by spreading them over the surface of an agar plate using a platinum or inoculating loop of 2–4 mm diameter.

Answer 8

Streak plate method

Question 9

-The piles of bacterial cells observed after an incubation period

Answer 9

Colonies

Question 10

-Also called as carpet culture, prepared by flooding the surface of the plate with a liquid culture or suspension of the bacterium, pipetting off the excess inoculum and incubating the plate. Also provides a uniform growth of the
bacterium.

Answer 10

Lawn culture

Question 11

-provides a pure growth of bacteria for carrying
out slide agglutination and other diagnostic tests. It is carried out in tubes usually containing slanted nutrient agar slopes.

Answer 11

Stoke culture

Question 12

-This method is used for
(a) mainly for demonstration of gelatin liquefaction
(b) demonstration of oxygen requirement of the bacterium under study,
(c) for the maintenance of stock cultures,
(d) to study motility of bacteria in semisolid agar

Answer 12

Stab culture

Question 13

-is used to determine approximate number of viable organisms in liquids, such as water or urine.
It is used to quantitate bacteria in urine cultures and also to estimate the viable bacterial count in a suspension.

Answer 13

Pour plate culture

Question 14

-pour plate culture ml needed of molten

Answer 14

15 ml

Question 15

-the molten agar in tubes is left to cool in a water bath at what degree?

Answer 15

45 degree Celsius

Question 16

-a deep culture of agar or gelatin through which the inoculum is evenly distributed by shaking before the medium is solidified and which is used chiefly for the demonstration of anaerobic colonies.

Answer 16

Shake culture

Question 17

-This method is used for
(a) blood culture and for sterility,
(b) dilution in the medium, o
r (c) large yields culture. However, it does not provide a pure culture from mixed inocula—the major disadvantage, nor identify a bacteria.

Answer 17

Liquid culture

Question 18

-may be inoculated by touching with a charged loop or by adding the inoculum with pipettes or syringes.

Answer 18

Liquid culture

Question 19

-require extra CO2 in the air in which they are grown

Answer 19

Brucella abortus and capnophilic streptococco

Question 20

, grow better in air supplemented with 5 to 10percent CO2

Answer 20

pneumococcus and gonococcus

Question 21

-require incubation without oxygen and differ in their requirement and sensitivity to oxygen.

Answer 21

Anaerobic culture method

Question 22

• will not grow from small inocula unless oxygen is absent and the Eh of the medium is low

Answer 22

Obligate anaerobes

Question 23

-a method routinely employed in clinical bacteriology and enables the isolation of distinct colonies which may be picked out, if necessary for further purification and study.

Answer 23

Surface plating

Question 24

• are widely used for the isolation of pathogens from specimens such as feces, with varied flora

Answer 24

Enrichment, selective and indicator media

Question 25

-example is tellurite media for the diphtheria bacillus, have been devised so that, the majority of organisms likely to be associated with those for which the media are used will not grow, and the isolation of pure cultures is thus facilitated.

Answer 25

Selective media

Question 26

-selenite broth for Salmonella sp, favor the multiplication of particular species as a step towards their isolation in
pure culture.

Answer 26

Enrichment media

Question 27

-such as Willis and Hobbs medium for Clostridium sp, contain ingredients that change in appearance with particular organisms and so assist their isolation.

Answer 27

Indicator media

Question 28

-can be used to separate spores from vegetative bacilli but does not guarantee that spores will germinate under subsequent cultural conditions.

Answer 28

Heating at 65°C for 30 minutes or at higher temperatures for shorter periods:

Question 29

-This method is useful for the isolation of tetanus bacilli from dust and similar sources.

Answer 29

Heating at 65°C for 30 minutes or at higher temperatures for shorter periods

Question 30

-destroy the unwanted bacteria. This method is the standard practice for the isolation of tubercle bacilli from sputum and other clinical specimens, by treatment with alkali, acid or other substances to which most commensals are susceptible but tubercle bacilli are resistant.

Answer 30

Pretreatment of specimens with appropriate bactericidal substances

Question 31

-The temperature and atmosphere chosen for a culture automatically preclude the growth of many bacteria.

Answer 31

Separation of bacteria with different temperature optima

Question 32

-thermophilic bacteria grow at this temperature

Answer 32

60ºC

Question 33

will not grow in air

Answer 33

Strict anaerobes

Question 34

grow less vigorously under anaerobic than under aerobic conditions

Answer 34

facultative anaerobes

Question 35

• This consists of a tube of semisolid agar, with a narrow tube open at both ends placed in the center of the medium in such a way that it projects above the level of the agar

Answer 35

Cragies tube

Question 36

• also serves the same purpose, inoculation being performed in one limb and the subculture taken from the other. This method can also be used to obtain phase variants in Salmonella species

Answer 36

U-tube

Question 37

-may be isolated from mixtures by inoculation into appropriate animals due to the fact that laboratory animals are highly susceptible to certain organisms

Answer 37

Pathogenic bacteria

Question 38

can be distinguished from other aerobic
sporulating bacilli by inoculation into mice or guinea pigs.
produce a
fatal septicemia and may be cultured pure from the heart blood.

Answer 38

Anthrax bacilli

Question 39

-Bacteria of differing sizes may be separated by the use of this .

Answer 39

selective filters.

Question 40

-are widely used for separating viruses from bacteria.
-

Answer 40

filters

Question 41

can be isolated from
contaminating organisms by inoculation of an infected specimen into a guinea pig.
is found in a pure state in the resulting lesions.

Answer 41

Tubercle bacillus

Question 42

is inoculated subcutaneously into a mouse, the animal dies of
pneumococcal septicemia in 12 to 48 hours and the organism can be obtained in
pure culture from the heart blood.

Answer 42

Pneumococcus