BACTERIAL MORPHOLOGY (BACT211)

• Bacterial morphology:

  • Width: 0.25 to 1 μm, Length: 1 to 3 μm
  • Staining procedure separates medically relevant bacteria into Gram Positive and Gram Negative
  • Common bacterial cellular morphologies: cocci (circular), coccobacilli (ovoid), bacillus (rod-shaped), fusiform (pointed end), curved, spiral shapes
• Microscopic Shapes:

  • Thiomargarita namibiensis found in ocean sediment, diameter of 0.1 to 0.3 mm
  • Cocci are round or spherical shaped bacteria, arrangement depends on the plane of division
  • Bacillus are rod-shaped, cylindrical, or elongated bacteria
  • Spirals are helical or twisted bacteria, Spirillum spp. is rigid, Spirochetes are more flexible
• Staining:

  • Imparts artificial coloration to bacteria and other materials on clinical specimen smears
  • Four categories of staining: Direct/Simple Stain, Differential Stain, Selective/Special Stain, Indirect/Negative/Relief Stain
• Direct/Simple Stain:

  • Contains one specific active chromogen to enhance bacterial size, shape, and arrangement
  • Commonly used simple stains: Crystal Violet, Gentian Violet, Methylene Blue, Malachite Green
• Differential Stain:

  • Contains two or more chromogens to differentiate specific components within bacterial cells
  • Includes Gram Stain, Acid Fast Stain, Fluorochrome Stain
• Selective/Special Stains:

  • Highlight or emphasize certain bacterial cell structures or components for presumptive identification
• Selective/Special Stains for Metachromatic Granules/Babes Ernst Bodies/Volutin:

  • Loeffler’s Alkaline Methylene Blue (LAMB) stains granules
• Selective/Special Stains for Bacterial Spores/Endospores:

  • Fulton-Schaeffer stain for spores
• Selective/Special Stains for Flagella:

  • Leifson, Gray, Silver, Fisher-Conn
• Selective/Special Stains for Rickettsia:

  • Castaneda, Machiavelo, Giemsa
• Selective/Special Stains for Chlamydia:

  • Gimenez, Machiavelo, Giemsa
• Selective/Special Stains for Spirochetes:

  • Fontana-Tribondeau, Levaditi Silver Impregnation, India Ink Negative Stain
• Selective/Special Stains for Mycoplasma:

  • Dienes
• Stain for Bipolar Bodies (Yersinia pestis):

  • Wayson stains bipolar bodies
• Methods of Studying Bacteria:

  • After standard incubation, examine colonial or cultural characteristics of bacterial colonies in each culture media, known as plate reading
• Indirect/Negative/Relief Staining:

  • Provides coloration to the background of the smear while leaving bacteria and covering structures unstained
  • Useful for identifying capsulated bacteria
• O Antigen

  H Antigen

  K Antigen

  Vi Antigen


  Associated cell wall

  Associated flagella

  Associated capsule

  Specific capsular antigen Salmonella typhi
• Light wont shine

  Light will shine

  Light shines


  Colony Density (optical property to pass light throguh the bacterial colony):

  Opaque

  Transluscent

  Transparent
• Unwashed stockings

  Rancid potato

  Com totilla/fruity

  Ammonia like

  Freshly plowed field

  Mousy/ mouse nest

  Bacteria producing the odor (certain bacteria produce characteristic odor in culture media):

  Staphylococcus spp.

  Serratia odorifera

  Pseudomonas aeruginosa

  Acinetobacter spp.

  Nocardia spp.

  Harmophilus spp.
• Micrococcus luteus

  Staphylococcus aureus

  Pseudomonas aeruginosa

  Serratia marscesens

  Staphylococcus albus

  Chromobacterium violaceum


  Bacteria Pigment (ability to produce unique coloration to their colony):

  Lime yellow

  Golden yellow

  Blue green

  Red

  Porcelain white

  Violet
• Beta

  Alpha

  Gamma

  Alpha prime


  Description of Hemolysis Type(ability to lyse RBC in the culture media):

  Clear zone

  Greenish or brownish zone

  No hemolysis

  Inner alpha hemolysis, outer beta hemolysis
• Crumbling (Nocardia spp.)

  Butterlike (Staphylococcus spp.)

  Sticky (Diphteroids)

  Cauliflower (Mycobacterium spp.)

  Wet & sticky (Streptococcus pneumonia)


  Description of: Texture or Consistency

  Brittle or splinters

  Creamy or butyrous

  Dry & waxy

  Rough & warty

  Mucoid
• No visible elevation

  Slight elevation

  Dome shaped

  Depressed

  Raised


  Description of: Elevation/ height of the colony

  Flat

  Raised

  Convex

  Umbilicate Innie

  Umbilicate outie
• Smooth or entire

  Undulate

  Rough or rhizoid

  Lobate

  Fringed or filamentous

  Fingerlike

  Irregular


  Edge Colony of: Margin/ appearance of edge of the colony

  Circular

  Wavy edge

  Crenated edge

  Lobulated edge

  Branchlike edge

  Uneven rounded projections

  Uneven length projection with no definite shape
• Colonies less than 1mm

  Same size of pinhead

  Slightly larger than pinhead

  6-8mm diameter

  Description of: Size of the colony

  Pinpoint

  Small

  Medium

  Large
• Plate reading


  Cultural characteristics of bacterial colonies that grew each culture media for each specimen are examined reffered as?
• 18-24 hours


  Standard incubation
• India ink or Nigrosin - Background BLACK

  Congo red - Background RED

  Anthony - Background PURPLE


  3 Background of indirect
• Colored/stained


  Background of indirect
• Unstained


  Bacterial capsule of indirect
• Cryptococcus spp.


  Capsulated strains in indirect stain especially in CSF sample cases of meningitis
• Indirect stain


  Provides coloration to the background

  Capsule unstained
• Wayson - Bipolar bodies stainRed


  Stain for bipolar bodies (Yersinia pestis)
• Dienes - BLUE


  Stains for mycoplasma
• Fontana-Tribondeau - spirochetes DARK BROWN

  Levaditi Silver Impregnation - spirochetes BLACK

  India ink negative stain - spirochetes unstained, background BLACK


  3 stains for Spirochetes
• Gimenez - Elementary bodies RED

  Machiavelo - RED

  Giemsa - PURPLE


  3 stains for Chlamydia
• Castaneda - BLUE

  Machiavelo - RED

  Giemsa - BLUE


  3 stains for Rickettsia
• Leifson

  Gray

  Silver

  Fisher-Conn


  4 Tannic Acid
• Tannic Acid


  Stains for flagella
• Fulton-Schaeffer - spores GREEN

  Dorner - spores RED

  Wirtz-Conklin - spores GREEN


  3 stains for bacterial spores