Lab 3
Continuation of Stains
Gram Unknown
• Each student gets one unknown tube
of bacteria
• Gram stain and record
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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
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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.
• Causes:
– Minor skin infections
such as pimples
– Impetigo
– Boils
– Cellulitis folliculitis
– Furuncles
– Carbuncles
– Scalded skin syndrome
– Abcesses
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Pneumonia
Meningitis
Osteomyelitis
Endocarditis
Toxic shock
syndrome
– Septicemia
– Post-surgical wound
infections
Methicillin-resistant S. aureus
• MRSA
• Endemic in hospitals
• Spread by human – to – human
contact
• Resistant to penicillin
• Must be treated by specialized
antibiotics