Exam (elaborations)
Microbiology Tests Questions and Answers 2024
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Exam of 5 pages for the course microbiology at microbiology (Microbiology Tests)
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Microbiology TestsWhat are the reagents used for gram staining? (4) - answer Crystal violet (stains all
cells purple)
Gram's iodine (binds with dye forming large crystals)
95% ethanol or acetone (removes unbound dye, gram negative will now be colorless)
Safranin (now gran negative appears pink)
Name 3 types of all purpose media – answer BAP (sheep blood agar)
NA (nutrient agar)
TSA (tryptic soy agar)
Provide the definition for "all-purpose media" - answer support the growth of a wide
variety of bacteria; contain all required nutrients need; do not contain inhibitors to
bacterial growth
Provide a definition for "enrichment media" - answer Contain substances that enhance
the growth of bacteria. Example: chocolate agar
Provide a definition for "selective media" - answer Media that has antimicrobial
substances added, thus inhibiting some bacteria while allowing others to grow.
Examples: Columbia CNA agar, Mac agar, mannitol salt agar
Provide a definition for "differential media" - answer Media used to distinguish between
bacterial types by identifying specific enzymes the bacteria possess. The media
characteristics or color will chance because of the enzyme. Examples: MAC, mannitol
salt agar, MRSA agar
List 3 types of selective media - answerColumbia CNA agar
MacConkey agar (MAC)
Mannitol salt agar
Name Columbia CNA agar's inhibitors (antimicrobial substances) & then what
organisms grow and which are inhibited - answerinhibitors: colistin, nalidixic acid
grows: gram positive
inhibited: gram negative
Name MAC agar's inhibitors (antimicrobial substances) & then what organisms grow
and which are inhibited - answerinhibitors: bile sats, crystal violet
grows: gram negative
inhibited: gram positive
, Name Mannitol Salt agar's inhibitors (antimicrobial substances) & then what organisms
grow and which are inhibited - answerinhibitors: sodium chloride
grows: staphlycoccus species
inhibited: most other bacteria
Name the 3 types of differential media & what they differentiate - answerMAC agar: pink
colonies are lactose fermenters, clear colonies are lactose nonfermenters
Mannitol Salt agar: staph aureus colonies are yellow, other colonies are not yellow
MRSA agar: methicillin0resistant staph colonies will grow, meticillin-sensitive colonies
will not grow
What grows on a BAP? - answeranything
What grows on Choc? - answeranything + haemophilus (needs growth factors)
What grows on MAC? - answergram negative rods
pink=lactose fermentation
What grows on CNA? - answergram positive cocci
Which media distinguishes between types of hemolysis reactions? - answerBAP
Discuss the 3 types of hemolysis - answerAlpha-partial destruction of RBC, green zone
Beta-total destruction of RBC, clear zone
Gamma-lack hemolysin that attacks RBC, no zone of hemolysis
Name the reagent for the catalase test - answer3% hydrogen peroxide added to slide
+ bubbles means there is oxygen and thus enzyme catalase broke down hydrogen
peroxide
- no bubbles means there is no oxygen and hydrogen peroxide was not broken down
(no enzyme catalase)
(differentiates between staph and strep)
Name the reagent for the coagulase test - answerrabbit plasma added to slide
immediate clumping= + for coagulase (protein for clotting, means it is staph aureus)
no clumping (15 sec) = - for coagulase (thus it is coagulase negative staph)
What is the optochin test for and what does it involve? - answerdifferentiates between
strep pneumoniae and other alpha strep
BAP--spread bacteria--put optochin disc on--incubate--next day look for growth/no
growth
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