MacConkey
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FIG. 18. Same plate as FIG.17 at 48 hours, Burkholderia cepacia displays small non-lactose fermenting colonies. Some strains appear somewhat purple due to strong lactose oxidation. (Rebecca Buxton, University of Utah)
FIG. 19. Stenotrophomonas maltophilia grows as tiny pinpoints on MacConkey agar in 24 hours at 37C. (Rebecca Buxton, University of Utah)
FIG. 20. Same plate as FIG. 19 at 48hours, Stenotrophomonas has distinct non-lactose fermenting colonies. The indicator has turned an alkaline tan color. (Rebecca Buxton, University of Utah)
FIG. 21. Typical spreading non-lactose fermenting colonies of Pseudomonas aeruginosa. The heavy growth in the primary innoculum has begun to display a blue-green pigment. (Rebecca Buxton, University of Utah)
FIG. 22. Although Acinetobacter baumanii is incapable of fermentation, its very strong lactose oxidation leads to weakly acid/purple colonies on MacConkey agar. (Rebecca Buxton, University of Utah)
FIG. 23. An encapsulated strain of Pseudomonas aeruginosa recovered from a cystic fibrosis patient at 24 hours. (Rebecca Buxton, University of Utah)
FIG. 24. Same plate as FIG. 23 at 48 hours, this strain of Pseudomonas aeruginosa make abundant, muciod capsular material. (Rebecca Buxton, University of Utah)
FIG. 25. Normal fecal flora mixed with Salmonella. This unusual Salmonella strain ferments lactose. (The colonies were distinguished by producing abundant H2S on Hektoen Agar). (Rebecca Buxton, University of Utah)
FIG. 26. Normal Fecal Flora (lactose fermenters) mixed with Shigella sonnei (non-lactose fermenter). (Rebecca Buxton, University of Utah)
FIG. 27. This appears to be a pure culture of E.coli. (The patient was suffering from significant diarrhea due to Campylobacter jejuni, which doesn't grow on MacConkey agar.) (Rebecca Buxton, University of Utah)
FIG. 28. On very close observation, the tiny pinpoints of a Vibrio species are visible among the large, normal fecal lactose fermenters. On TCBS agar, this sample grew yellow, sucrose-fermenting colonies of V. alginolyticus. (Rebecca Buxton, University of Utah)
FIG. 31. Red-pigmented Serratia marcescens. Students often mistake the red pigment for lactose fermentation. (Rebecca Buxton, University of Utah)
FIG. 32. Klebsiella pneumoniae: Mucoid, lactose-fermenting colonies are typical of Klebsiella and Enterobacter species. (Rebecca Buxton, University of Utah)
FIG. 33. Proteus vulgaris: Non-lactose fermenters with slight swarming. (Rebecca Buxton, University of Utah)
PROTOCOL
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