EX 3: Differential Stains

1. Staphylococcus epidermidis

2. Escherichia coli

What bacteria did we perform Gram Stain on?

1. Mycobacterium tuberculosis

2. Bacillus subtilis

What bacteria did we perform Acid Fast on?

Hucker’s Method

What method of Gram stain was used?

Crystal Violet - 1 Min

Gram’s Iodine - 1 Min

Acetone Alcohol (until all violet color has been removed or until a faint color flows from the slide)

Safranin - 30 Secs

What are the reagents and duration of each in Gram staining?

1. Carbol Fuschsin - 3-5 Min

2. Acid Alcohol (until there is no more carbol fuchsin or until a faint color flows from the slide)

3. Methylene Blue - 30-45 Secs

What are the reagents and duration of each in Gram staining?

Ziehl-Neelsen Method

What is the type of acid fast stain that utilizes heat?

Cold Kinyoun

What is the type of acid fast stain that does not use heat?

FALSE; Smears with M tuberculosis are AIR DRIED

True or False: Smears with M tuberculosis can be blotted dry.

100

The sputum slides must be searched thoroughly for at least ___ fields before rejecting them as negative for M tuberculosis.

To preserve the morphology of the bacteria.

What is the reason for air drying the bacterial smear?

All cocci are gram (+) except for the Neisseria group, moraxella catarrhalis, and Veillonella

General rule for Gram (+) bacteria

All bacilli are gram (-) except acid fast organisms (mycobacteria, nocardia), sporeformers (bacillus, clostridium), and corynebacterium species.

General rule for Gram (-) bacteria

1. M. tuberculosis

2. M. leprae

What are two clinically important acid fast bacteria?