Beta-haemolytic API32A Fine and Fine rods - D Ostrich bacillus from ostrich stomach. Gram-positive Pleomorphic or fine + D CoryneAPI Pleomorphic and Fine white - D CAMP test sometimes branched haemolytic Large, usually white, Staphylococcus, Cocci or tetrads sometimes yellow and + D Micrococcus beta-haemolytic. Cocci or coccobacilli in Fine alpha- or beta-, or broth can occur as - - Streptococcus gamma-haemolytic chains) Large oval to round cells Large dull, sticky + D Yeasts with budding. colonies. Rarely slimy Branched large hyphae, Large, chalky, fluffy or sometimes with fruiting D D Fungus leathery. bodies Branched filamentous Nocardia, Usually into the bacteria, sometimes + D Streptomyces, agar. breaks up into cocci. Actinomyces Table 3: Recognition of the different bacterial genera by their Gram’s stain and colony morphology Blood agar MacConkey agar Gram’s stain Bacterium General comment Colony Growth LF/NLF Shape Pale colonies on MAC and agar. No smell (unlike shiny Salmonella spp. - + NLF - R most other members of 2-3 mm the Enterobacteriaceae Non-haemolytic but Greyish, round otherwise similar to the Non haemolytic E. and shiny - + LF - R strains. coli Characteristic 2-3 mm “coliform” smell. Greyish, round and shiny Yersinia spp. - + NLF - R 2-3 mm Red/orange Produces red pigment Serratia convex, and (prodigosin). Some marcenscens and - + NLF - R shiny. strains are white at 37°C S. rubidea (no pigment) 2-3mm Grey, mucoid Colonies tend to be colonies that Klebsiella spp. - + LF - R mucoid and light pink on coalesce. MAC agar. Non-motile. 2-4mm
Beta-haemolytic API32A Fine rods Fine and from ostrich stomach. - D Ostrich bacillus Pleomorphic or fine + D Gram-positive CoryneAPI Pleomorphic and sometimes branched Fine white - D CAMP test Cocci or tetrads Large, usually white, sometimes yellow and beta-haemolytic. + D Staphylococcus, Micrococcus Cocci or coccobacilli in broth can occur as chains) Fine alpha- or beta-, or gamma-haemolytic - - Streptococcus Large oval to round cells with budding. Large dull, sticky colonies. Rarely slimy + D Yeasts Branched large hyphae, sometimes with fruiting bodies Large, chalky, fluffy or leathery. D D Fungus Branched filamentous bacteria, sometimes breaks up into cocci. Usually into the agar. + D Nocardia, Streptomyces, Actinomyces Table 3: Recognition of the different bacterial genera by their Gram’s stain and colony morphology Bacterium Blood agar MacConkey agar Gram’s stain General comment Colony Growth LF/NLF Shape Salmonella spp. and shiny 2-3 mm - + NLF - R Pale colonies on MAC agar. No smell (unlike most other members of the Enterobacteriaceae Non haemolytic E. coli Greyish, round and shiny 2-3 mm - + LF - R Non-haemolytic but otherwise similar to the haemolytic strains. Characteristic “coliform” smell. Yersinia spp. Greyish, round and shiny 2-3 mm - + NLF - R Serratia marcenscens and S. rubidea Red/orange convex, and shiny. 2-3mm - + NLF - R Produces red pigment (prodigosin). Some strains are white at 37°C (no pigment) Klebsiella spp. Grey, mucoid colonies that coalesce. 2-4mm - + LF - R Colonies tend to be mucoid and light pink on MAC agar. Non-motile.
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