Lab 3

Continuation of Stains

Gram Unknown

• Each student gets one unknown tube of bacteria

• Gram stain and record– Your name– Unknown number– Gram reaction (positive or negative)– Morphology– Arrangement

Capsule Stain

• Another negative stain

• Use K. pneumoniae• Pg 96

Endospore Stain• An endospore is a dormant

form of a bacteria.• If a bacteria is capable of

producing endospores, it does so when environmental conditions are poor

• Steam is used to help stain penetrate the cell wall

• Stain B. cereus using procedure on page 99.

Acid-fast Stain• Takes advantage of

mycolic acid in the cell wall of slow growing mycobacterium

• Use M. smegmatis and S. aureus on the same slide using Ziehl-Neelsen method (pg 93)

Klebsiella pneumoniae

• Gram Negative• Non-motile• Rod shaped – bacilli• Enterobacteria• Causes Klebsiella pneumonia and

urinary tract infections• Pneumonia often found in alcoholics

and UTI in older people

Bacillus Cereus

• Gram Positive• Rod shaped – bacilli• Can produce endospores• Can cause foodborne illnesses

– Diarrheal type syndrome– Emetic (vomiting) type syndrome

• Can cause skin infections that are difficult to eradicate

• Can cause keratitis (inflammation of cornea)

Mycobacterium Smegmatis

• Acid-fast bacteria• Mostly considered a non-pathogenic

organism• Named for a similar organisms found

in smegma (genital secretions)

Staphylococcus aureus

• Gram-positive• Spherical – cocci• “the golden cluster seed”• Most common form of staph infections• Frequently part of skin flora found in

the nose and on the skin• 20% of population are long-term

carriers

Staphylococcus aureus – cont.

– Pneumonia– Meningitis– Osteomyelitis– Endocarditis– Toxic shock

syndrome– Septicemia– Post-surgical wound

infections

• Causes:– Minor skin infections

such as pimples– Impetigo– Boils– Cellulitis folliculitis– Furuncles– Carbuncles– Scalded skin syndrome– Abcesses

Methicillin-resistant S. aureus

• MRSA• Endemic in hospitals• Spread by human – to – human

contact• Resistant to penicillin• Must be treated by specialized

antibiotics