MCQs:Culture Media: Answers

1) Louis Pasteur was the first person to use solid culture media? T/F

False, this is historically attributed to Robert Koch, who initially used potatoes, before progressing to agar.

2) On MacConkey Agar, non-lactose fermenting bacteria will use peptone as their energy source instead.? T/F

True, utilisation of peptone creates ammonia as a byproduct, turning the agar alakaline.

3) Streptococci grow well on Mannitol Salt Agar? T/F

False, the high levels of salt in the agar favours the growth of staphylococci, but not streptococci. The presence of mannitol differentiates between Staphylococcus aureus which can ferment mannitol, from Coagulase Negative Staphylococci.

4) Hektoen Agar picks up the production of Hydrogen Sulphide by Salmonella species? T/F

True, the agar contains thiosulphate, which produces a black precipitate in the presence of hydrogen sulphide (H2S).

5) Thayer-Martin Agar contains gentamicin, amongst other antibiotics? T/F

False, gentamicin can actually be used as a treatment for Neiserria gonorrhoeae, so will not be in an agar used to select it out.

6) Amies Transport media contains high levels of carbon and nitrogen? T/F

False. As it is a transport media, it contains no potential nutrient sources in order to prevent over-multiplication of bacteria.

7) The chocolate within chocolate agar provides the nutrients required for bacterial growth? T/F

False. Chocolate Agar contains no chocolate.(I have tasted it and this is correct). The chocolate refers to the blood which has been heated to lyse the cells releasing growth factors like NAD and haemin, perfect for fastidious organisms like Haemophilus influenzae.

8) Buffered Charcoal Yeast Extract media is a good media for the isolation of Corynebacterium diptheriae? T/F

False, BCYE agar is good for detection of Legionella pneumophilia. Corynebacterium diptheriae traditionally cultured on Hoyles medium.

9) Lactose Fermentors produce yellow colonies on CLED agar? T/F

True. Cysteine Electrolyte Deficient Agar used in some laboratories for the identification of urinary organisms.

10) Lowenstein-Jenson slopes contain penicillin? T/F

True, in order to suppress growth of bacteria thus selecting out mycobacteria.

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