Bacterial Morphology Flashcards
Most clinically significant bacteria range in size from 0.25 to 1 um by 1 to 3 um (measuring using a microscope).
Bacterial Morphology
Classifications of bacteria:
According to morphology
Cocci=
Coccobacilli=
Bacillis=
Fusiform=
Curved
Spiralis =
Pleiomorphic =
Classifications of bacteria:
According to morphology
Cocci= circular
Coccobacilli= ovoid
Bacillis= rod shaped
Fusiform= pointed-end or tapered end
Curved
Spiralis = spiral
Pleiomorphic = no definite shape
Is a fundamental staining technique used in bacterial identification schemes
Gram Staining
Developed by Hans Christian Gram in 1884
Most commonly used stain in clinical microbiology.
Gram Staining
Gram Stain Components:
Fixation=
Primary stain=
Mordant =
Decolorizer =
Counterstain=
Gram Stain Components:
Fixation= Heat
Primary stain= Crystal Violet
Mordant = Lugol’s lodine
Decolorizer = Alcohol or Alcohol-acetone
Counterstain= Safranin
Less commonly, ________________ (allows better staining of anaerobic bacteria)
Carbol Fuchsin
-Bacteria with thick peptidoglycan layer
• Retains the primary stain (Crystal Violet)
-Final stain is deep blue or purple.
-Seen in Streptococcus spp.Staphylococcus spp.
Gram-positive bacteria
-Bacteria with thin peptidoglycan layer *Primary stain is washed away due to the thin peptidoglycan layer and allows the counterstain (Safranin) to enter.
Gram-negative bacteria
___________________ is the most abundant substance on its cell surface.
Final color is ____ to ___.
Seen in Pseudomonas spp. and Enterobacteriaceae family..
Gram-negative bacteria
Lipopolysaccharide (LPS) is the most abundant substance on its cell surface.
Final color is pink to red.
Seen in Pseudomonas spp. and Enterobacteriaceae family..
AKA: Gram-Interdeterminate bacteria, Atypical bacteria, Gram-ghost bacteria, Gram-neutral bacteria
Gram-variable bacteria
Organisms that cannot be grouped as either negative or positive.
Final staining is a mix of ______ and ____ cells. (Unpredictable gram staining)
Seen In Bacillus spp., and Clostridium spp..
Also seen in Mycobacterium spp. (Necessitates the use of another stain= ________________)
Gram-variable bacteria
Organisms that cannot be grouped as either negative or positive.
Final staining is a mix of purple and pink cells. (Unpredictable gram staining)
Seen In Bacillus spp., and Clostridium spp..
Also seen in Mycobacterium spp. (Necessitates the use of another stain= Acid Fast staining)
Use of controls:
Gram positive control organism=
Gram negative control organism=
Use of controls:
Gram positive control organism= Staphylococcus aureus
Gram negative control organism= Escherichia coli
•According to Acid Fast Staining
The cell wall of Mycobacterium spp. contains ___________ (lipid) which makes it impervious to water-based stains (ex: Gram stain)
• ____________ discovered a tubercle bacillus (Mycobacterium tuberculosis / “MTB”) and developed a staining method to detect it.
_______, ______, ________ and __________ Acid fast staining aimed to improve Koch’s method
•According to Acid Fast Staining
The cell wall of Mycobacterium spp. contains Mycolic acid (lipid) which makes it impervious to water-based stains (ex: Gram stain)
• Robert Koch discovered a tubercle bacillus (Mycobacterium tuberculosis / “MTB”) and developed a staining method to detect it.
Ehrlich, Ziehl, Neelsen and Rindfleisch’s Acid fast staining aimed to improve Koch’s method
•______ Method
AKA: ___________ Method
Franz ________ introduced the use of _____________ as a mordant
Friedrich __________ then introduced the use of ____________ as a secondary
Components:
Primary stain= _____________
Decolorizer= ____________ (_______ in 95% ethanol)
Counterstain = _____________
•Hot Method
AKA: Ziehl-Neelsen Method
Franz Ziehl introduced the use of Carbolic Acid (Phenol) as a mordant
Friedrich Neelsen then introduced the use of Basic Fuchsin as a secondary
Components:
Primary stain= Carbolfuchsin stain
Decolorizer= Acid Alcohol (HCI in 95% ethanol)
Counterstain = Methylene Blue
•____ Method
AKA: _______ Method
_______ used a method without heat and Increased the concentration of _______________ as the primary stain.
Components:
Primary stain= __________________ stain
Decolorizer= ____________ (___ in 95% ethanol)
Counterstain= _____________
•Cold Method
AKA: Kinyoun Method
Kinyoun used a method without heat and Increased the concentration of
Carbolfuchsin as the primary stain.
Components:
Primary stain= Kinyoun Carbolfuchsin stain
Decolorizer= Acid-Alcohol (HCI in 95% ethanol)
Counterstain= Methylene blue
