Basics of Microbiology: Shapes & stains Flashcards
Most cocci are
gram positive (ex: Streptococcus, Staphylococcus)
Most rods (and coccobacillus) are:
gram negative
Other Shapes: Spirochetes (3)
Treponema (syphilis)
Borrelia (Lyme disease)
Leptospira (leptospirosis)
Other Shapes: Vibrio
• Vibrio cholerae
Pleomorphic Bacteria:
Take on many shapes : ex: Rickettsia & Chlamydia which are obligate intracellular pathogens
Gram Stain Limitations
1.
2.
3.
4.
1.) Treponema (syphilis)
Too thin to see
2.) Mycobacteria (tuberculosis)
Mycolic acids in cell wall
3.) Mycoplasma
No cell wall
4.) Intracellular bacteria
Rickettsia (obligate intracellular) • Chlamydia (obligate intracellular; no muramic acid cell wall) • Legionella (mostly intracellular)
Giemsa Stain: stains _ because _
used for 2 protozoa and 3 intracellular bugs
Enters cells and stains nucleic acids
used for:
Protozoa
Plasmodium • Trypanosomes •
Intracellular bugs
Chlamydia • Rickettsia • Borrelia (sometimes intracellular)
Ziehl-Neelsen
aka_
contains _
used to detect:
also useful for _
The “acid fast” stain
Contains carbolfuchsin
Used to detect mycobacterium (especially TB)
Also used for Nocardia
Acid fast bugs resists decolorization with acid solvents
Silver Stain
Special stain for 3 organisms:
Pneumocystis pneumonia (HIV/AIDS) • Fungal infection Diffuse interstitial pneumonia
Legionella • Pneumonia • Contaminates water (outbreaks in nursing homes)
H. Pylori • Gastric ulcers
India Ink
stains _ not _
Primarily used for_
Negative stain
Background stained, not bug, Unstained organisms stand out in contrast
Primarily used for cryptococcus neoformans
Some bacteria produce special colors
1.
2.
3.
4.
Staph Aureus • Golden, yellow color
Pseudomonas aeruginosa • Blue-green pigment (pyocyanin)
Serratia • Red pigment
Actinomyces • Filamentous bacteria that “cements” together • Colonies have yellow-orange appearance • Known as ”sulfur granules”
