API 10S Short & long rods on XLD + - Enterobacteriaceae Salmonella API 20E API 10S Short & long rods (beaded) Large or fine, MacConkey positive. + D Pseudomonas API 20NE Microbact 12A & 12B Diplococci Large or fine + D Pseudomonas API 20NE Microbact 12A & 12B Diplococcobacilli Large or fine + D Pseudomonas API 20NE Microbact 12A & 12B Pleomorphic Fine D D Haemophilus, Pasteurella, Actinobacillus API 20NE Microbact 12A & 12B Pleomorphic from chickens or ostriches D D Fowl Pasteurella API20NE (identification is not listed, you must use own tables). Pleomorphic Large and sometimes beta-haemolytic D + Fish bacteria (with salt broth) Pleomorphic Large or fine, growth at 25°C. Found in fish, tortoises & snakes. D D Fish bacteria (with salt broth) Rods Flat & spreading at 25°C. Found in fish D D Myxobacteria Pleomorphic, bent or spiral-shaped Fine. Growth better with CO2 D D Campylobacter Table 2: Selection of biochemical tests for the Gram-positive bacteria, according to microscopic morphology, colony appearance, catalase and oxidase tests Shape Colony Morphology Colonies Cat. Oxi. Biochemical Short & long rods, sometimes with spores Usually large + D Bacillus Short & long rods Fine D D Gram-positive CoryneAPI Short & long rods, sometimes with spores AnO2, - D Clostridium
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.
Enterobacter spp. Grey, mucoid colonies that coalesce. 2-4mm - + LF - R Very similar to colonies of Klebsiella spp. Motile. Proteus spp. Grey, swarming growth over the agar. - + NLF - R Characteristic swarming on non-selective agar which can be in waves. Turns BTA brown. Very foul smell. Colonies pale and discreet on MAC, but edges may be irregular. Pseudomonas spp. other than P. aeruginosa Grey or yellowish-green, flat and spreading. 2.5-4mm - + NLF - R Some may produce the yellowish-green pigment, pyoverdin. Corynebacterium renale Grey-white, round and moist 0.5-1 mm - - + R Colonies older than 48 hours become drier. Urease Brucella spp. Translucent, convex and round 0.5 mm - - - R(C) Some brucellae require 10% CO2 for growth. Colonies not visible until days after incubation. MZN positive. Campylobacter fetus Small, round and opaque 0.5 mm - - - R curved Requires 2-3 days for growth reduced oxygen tension. Curved rods, if in pairs they have a "seagull" appearance Actinobacillus spp. Grey to translucent, round and shiny 0.5-1mm - V V - R Usually urease positive Pasteurella multocida Translucent, smooth, round and shiny 1-2 mm - - - R Colonies appear pinkish on BTA. Characteristic sweetish Indole positive. Bordetella bronchiseptica Small and round 0.5-2 mm - + NLF - R Colonies very small at 24 hours but become much larger later. Unreactive bacterium. Rhodococcus equi Salmon pink and mucoid. Colonies coalesce - - + R(C) The colour becomes more definite with time. Mucoid colonies tend to merge. Staphylococcus epidermidis (coagulase negative) White, shiny, round and convex 2-3 mm - + LF Most + C Colonies are similar to coagulase + staphylococci, but always white and non-haemolytic. Micrococcus spp. White, yellow, tan or pink. - - + C Colonies are usually pigmented. 3
Galactose Sucrose Lactose Maltose Adonitol Dulcitol Sorbitol Salicin Table 5: Identification of some Gram-negative bacteria Campylobacter Fish bacteria Myxobacteria AnO2 BTA BTA in Campylobacter gas BTA in candlejar @ 42°C BTA in candle jar at 25°C. TSI Sodium hippurate Nitrate Bruc. glucose & H2S Selenite Nutrient broth 25°C for motility Gershman’s 0% Sout broth 5% Salt broth 7% Salt broth 3 ml MRP broth Methylred Citrate Arginine Lysine Ornithine Urea Gelatine Glucose Arabinose Maltose Sucrose Mannitol Trehalose Glycerol Sorbitol Salicin 5% BTA 37°C BTA-ONPG 0129 BTA disc Starch Vibrio agar At 25°C: 0% Salt broth 2% Salt broth Gelatin Aesculin Glucose O & F without oil Casein agar DNAse agar Nitrate Bruc. gluc. & H2S Citrate Gershman’s Starch AnO2 @ 25°C AnO2 Cytophaga agar Eggyolk Phosphatase agar Table 6: Biochemical tests recommended for the isolation of Gram-positive bacteria Gram-positive Staphylococcus Streptococcus Bacillus Actinomyces/ Corynebacterium O & F (x2) Nitrate Glucose Urea Aesculin Horse serum Brucella glucose & H2S Sodium Hippurate Nitrate Glucose Maltose O & F DNAse For identification of coagulase negative staphs: Lactose Mannitol Raffinose Salicin Sorbitol Trehalose Inulin Aesculin Methylene blue Egg yolk Anaerobic BTA Citrate 3ml MRP Nitrate Glucose Horse serum Xylose Galactose Mannose Lactose Sucrose Trehalose Raffinose Salicin Phosphatase agar
P. aeruginosa; Cl. perfringens; Candida albicans; Cryptococcus neoformans, chlamydia; mycoplasmas; Moraxella spp., aeruginosa; Clostridium perfringens; Candida albicans; chlamydia; mycoplasmas; Moraxella spp., and Neisseria flavus. Strep. equisimilis; Staph. aureus. Joints Staphylococcus aureus; Pseudomonas aeruginosa; various streptococci; Candida albicans; Malassezia pachydermatis; Proteus spp.; Clostridium perfringens. A. equuli; Staph. aureus; pyogenic and faecal streptococci; E. coli; Rhodococcus equi; Klebsiella; Salmonella Urinary infections Proteus (usually mirabilis); P. aeruginosa; enterococci; E. coli; Enterobacter; S. aureus; pyogenic and fecal streptococci; Corynebacterium pilosum (rare), C. cystitidis. E. coli C. pilosum, C. cystitidis.