Urine Culture Technique and the Importance of Selective and Differential Media for Gram-Negative Rods Day 2 Remember this plate?

Eosin-methylene blue (EMB) agar plate inoculated with Escherichia coli (a gram-negative coliform bacterium) showing good growth of dark blue-black colonies with metallic green sheen indicating vigorous fermentation of lactose and acid production which precipitates the green metallic pigment. (Naowarat Cheeptham, Thompson Rivers University)

Eosin Methylene Blue Agar (EMB) Results and Interpretation Presumptive ID Poor growth or no growth (P) Organism is inhibited by eosin and/or methylene blue Gram-positive Good growth (G) Organism is not inhibited by eosin and methylene blue Gram-negative Growth is “colorless” (no pink, purple, or metallic sheen) (C) Organism does not ferment lactose or sucrose. No reaction (NR) Noncoliform, such as P. aeruginosa Growth is pink and mucoid (Pi) Organism ferments lactose with little acid production (A) Coliform, such as Klebsiella pneumoniae “Dark” growth (purple to black, with or without green metallic sheen) (D) Organism ferments lactose and/or sucrose with much acid production (A) Coliform, such as E. coli

the end Day 2 Materials needed per table: Your “cystitis patient” plate and your control species plate, both after 24 h of incubation. Gram staining reagents the end