Question

Laboratory & Exercises 1. You will not be physically performing these activities. However, you will be responsible for knowing how to perform and interpret them. View the following video clips: • SE Broth & Bile Esculin • CAMP Test 2. Review how to interpret the following tests by completing the chart: Positive Result Negative Result Gram Stain for cocci and bacilli purple Schaeffer-Fulton Stain for Endospores Negative Stain for Capsules Catalase (Reagent: Hydrogen peroxide) Coagulase (Reagent: Rabbit Plasma) Oxidase (Reagent: Redox Indicator) pink CAMP Test Bile Esculin Hydrolysis (BE slant) SF Broth Optochin Sensitivity Test 3. View the clip on how to develop a Dichotomous Key. Review the dichotomous keys provided that aids in the identification of the following organisms: • Streptococcus agalactiae (Group B Strep) • Streptococcus pyogenes (Group A Strep) • Viridans Streptococcus Streptococcus pneumoniae Enterococcus faecalis Staph aureus Staph species; coagulase negative (e.. Staph epidermidis & Staph saprophyicus) Bacillus species • Corynebacterium species (AKA diphtheroids) • Listeria species • Clostridium species 4. Using the dichotomous keys provided, identify the gram-positive bacteria causing the infection presented in the case studies. After you finish the case studies, you are ready to input your answers into Lab 8 quiz. Five will be randomly selected. They are worth 5 points each. 8.5

Answer 1

	Positive result	Negative result
Gram stain for cocci and bacilli	purple	pink
Schaffer Fulton stain	green	red
Negative stain for capsules
Catalase test	Formation of bubbles	No bubble formation
Coagulase test	plasma will coagulate	plasma remains liquid
Oxidase	colour change violet to purple, within 10–30 seconds.	result in a light-pink or absence of colouration.
CAMP test	clear zone (arc or circle) of enhanced hemolysis.	No enhancement of hemolysis.
bile esculin test	blackening of the broth	No dark brown complex is formed.
SF broth test	turbidity and a yellow-brown colour due to the fermentation of dextrose and the resultant colour change of the bromcresol purple indicator.	indicated by no change in the purple colour of the medium.
optochin sensitivity test	Zone of inhibition is 14 mm or greater in diameter with 6 mm disk.	no zone of inhibition

A differential staining technique (the Schaeffer-Fulton method) is used to distinguish between the vegetative cells and the endospores. A primary stain (malachite green) is used to stain the endospores.

The capsule stain employs an acidic stain and a basic stain to detect capsule production.

Coagulase test is used to differentiate Staphylococcus aureus (positive) from Coagulase Negative Staphylococcus (CONS).

The oxidase test is used to identify bacteria that produce cytochrome c oxidase, an enzyme of the bacterial electron transport chain.