Worksheetslab 3 test practice pt.5
Total questions: 21
Worksheet time: 11mins
Which Lancefield group contains alpha-hemolytic Streptococci?
Group A
Group B
Group D
None; alpha-hemolytic species do not fall under Lancefield groups
S. pyogenes vs. S. agalactiae can be differentiated by using:
Optochin disk only
Blood agar with CAMP test and Bacitracin disc
Coagulase and Catalase
TSI slants
If bacteria grow on MacConkey (MAC) agar, what can be concluded?
They are Gram-positive
They are oxidase positive
They are Gram-negative
They are alpha-hemolytic
What indicates gas production in a sugar fermentation test?
Yellow color only
Black precipitate
Cracks or bubbles in the agar
No change in pH
Why do resident enteric bacteria make it hard for pathogens to colonize the gut?
They destroy toxins
They lower the temperature
They outcompete pathogens for nutrients
They are motile
Facultative anaerobes are bacteria that:
Require oxygen to grow
Cannot grow outside the large intestine
Can survive in and outside the large intestine
Only grow at high pH
The microbial population of the large intestine is:
Very low
Enormous, making isolation of individual pathogens difficult
Sterile in healthy individuals
Mostly fungal
What does selective media do?
Grows all bacteria equally
Selects for Gram-positive cocci only
Allows only one type of bacteria to grow
Allows only lactose fermenters to grow
Which of the following is a false statement about the Enterobacteriaceae family?
All members are Gram-negative
All are oxidase positive
All ferment glucose
All are rod-shaped
The term enteric refers to:
Blood
Lung tissue
Intestine
Skin
What does it mean when a microbe ferments a substrate?
It oxidizes sugars aerobically
It extracts energy through anaerobic degradation into simpler metabolites
It uses light to produce ATP
It performs photosynthesis to generate glucose
What is lactose?
A disaccharide found in meat
A six-carbon protein found in milk
A carbohydrate with a specific six-carbon configuration, commonly found in milk
A simple sugar in starch
What does selective media do?
Allows all bacteria to grow equally
Grows only fungi
Allows only some microbes to grow
Identifies sugar fermentation
What does differential media do?
Only grows Gram-positive cocci
Grows only anaerobes
Allows all microbes to grow but helps differentiate them based on appearance or color change
Prevents bacteria from fermenting
Which two organisms are differentiated using H₂S production, and which media can be used?
E. coli vs. Klebsiella / MAC
Proteus vs. Citrobacter / Urease
Salmonella vs. Shigella / TSI or SIM
Shigella vs. E. coli / Indole
Enterobacter vs. Escherichia can be differentiated using:
H₂S and SIM
Urease and MAC
Indole and SIM
Motility and TSI
Klebsiella vs. Enterobacter is differentiated using:
Lactose fermentation and TSI
H₂S production and SIM
Motility and SIM
Urease and blood agar
Klebsiella vs. Shigella is differentiated using:
Indole and SIM
Glucose fermentation and MAC
Lactose fermentation and TSI or MAC
H₂S and EMB
Proteus vs. Citrobacter is differentiated using:
H₂S production and glucose fermentation
Lactose fermentation and urease test using TSI or urease broth
Citrate and indole
Methyl red and catalase
If an organism is H₂S positive, what is automatically true?
It is lactose positive
It is glucose negative
It is motile
It is oxidase positive
If an organism is oxidase negative and H₂S positive, what else can be assumed?
It cannot ferment sugars
It is glucose positive
It is catalase negative
It is indole negative
