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
