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Figure 1: Escherichia coli on EMB (Enlarged view). FIG. 1. 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, Kamloops, BC, Canada)

Figure 2: Enterobacter aerogenes on EMB (Enlarged view). FIG. 2. EMB agar plate inoculated with Enterobacter aerogenes (a gram-negative coliform bacterium) showing good growth of brown, dark-centered, mucoid colonies indicating lactose fermentation and acid production. (Naowarat Cheeptham, Thompson Rivers University, Kamloops, BC, Canada)

Figure 3: Klebsiella pneumoniae on EMB (Enlarged view). FIG. 3. EMB agar plate inoculated with Klebsiella pneumoniae (a gram-negative coliform bacterium) showing good growth of brown, dark-centered, mucoid colonies (smaller than Enterobacter) indicating lactose fermentation and acid production. (Naowarat Cheeptham, Thompson Rivers University, Kamloops, BC, Canada)

Figure 4: Pseudomonas aeruginosa on EMB (Enlarged view). FIG. 4. EMB agar plate inoculated with Pseudomonas aeruginosa (a gram-negative noncoliform bacterium) showing good growth but no fermentation of sugars or acid production. (Naowarat Cheeptham and Carolynne Fardy, Thompson Rivers University, Kamloops, BC, Canada)

Figure 5: Proteus vulgaris on EMB (Enlarged view). FIG. 5. EMB agar plate inoculated with Proteus vulgaris (a gram-negative coliform bacterium) showing growth of pink colonies indicating non-lactose fermentation and some acid production. (Naowarat Cheeptham, Thompson Rivers University, Kamloops, BC, Canada)

Figure 6: Escherichia coli and Pseudomonas aeruginosa on EMB (Enlarged view) FIG. 6. EMB agar plate inoculated with a mixed culture of Escherichia coli and Pseudomonas aeruginosa. Note the metallic green sheen of the strong lactose-fermenting Escherichia coli and the pinkish colonies of nonfermenter Pseudomonas aeruginosa. (Archana Lal, Independence Community College, Independence, KS)

Figure 7: Acinetobacter baumannii on EMB (Enlarged view). FIG. 7. EMB agar plate inoculated with Acinetobacter baumannii (a gram-negative non-glucose-fermenting bacillus) showing a colony with a classic blue-grey center. This should not be mistaken for evidence of lactose fermentation on EMB agar. (Bobbi Pritt, Mayo Clinic, Rochester, MN)

Figure 8: Stenotrophomonas maltophilia on EMB (Enlarged view). FIG. 8. EMB agar plate inoculated with Stenotrophomonas maltophilia (a gram-negative non-glucose-fermenting bacillus) showing good growth and non-lactose-fermenting morphology. (Bobbi Pritt, Mayo Clinic, Rochester, MN)

Figure 9: Escherichia coli and Salmonella enteritidis on EMB (Enlarged view). FIG. 9. EMB agar plate inoculated with mixed enteric flora. The lactose fermenter Escherichia coli grew with purple-centered colonies while the lactose nonfermenter Salmonella enteritidis grew as colorless colonies. Salmonella enteritidis mixed with Escherichia coli is able to utilize the acid products as energy source, resulting in an insufficient acid buildup to precipitate out the Eosin Methylene Blue and no green metallic sheen is produced by Escherichia coli. (Jerry Keplinger, East Tennessee State University, Johnson City, TN)

Figure 10: Clostridium perfringens on EMB (Enlarged view). FIG. 10. EMB agar plate inoculated with Clostridium perfringens (a gram-positive bacterium) maintained under anaerobic conditions and showing no growth. (Naowarat Cheeptham, Thompson Rivers University, Kamloops, BC, Canada)

Figure 11: Bacillus subtilis on EMB (Enlarged view). FIG. 11. EMB agar plate inoculated with Bacillus subtilis (a gram-positive bacterium) showing poor growth. (Naowarat Cheeptham,Thompson Rivers University, Kamloops, BC, Canada)

Figure 12: Micrococcus luteus on EMB (Enlarged view). FIG. 12. EMB agar plate inoculated with Micrococcus luteus (a gram-positive bacterium) showing no growth. (Naowarat Cheeptham, Thompson Rivers University, Kamloops, BC, Canada)

Figure 13: Staphylococcus aureus on EMB (Enlarged view). FIG. 13. EMB agar plate inoculated with Staphylococcus aureus (a gram-positive bacterium) showing no growth. (Archana Lal, Independence Community College, Independence, KS)

Figure 14: Streptococcus group B on EMB (Enlarged view). FIG. 14. EMB agar plate inoculated with Streptococcus group B (a gram-positive bacterium) showing no growth. (Archana Lal, Independence Community College, Independence, KS)

Figure 15: Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, and Staphylococcus aureus on EMB (Enlarged view). FIG. 15. EMB agar plate inoculated with (A) Escherichia coli, (B) Bacillus subtilis, (C) Pseudomonas aeruginosa, and (D) Staphylococcus aureus. The two gram-positive bacteria Bacillus subtilis and Staphylococcus aureus did not grow, while the two gram-negative bacteria Escherischia coli and Pseudomonas aeruginosa grew with typical lactose fermenter (colonies with green metallic sheen) and nonfermenter (pink colonies) morphology. (Archana Lal, Independence Community College, Independence, KS)

Figure 16: Salmonella enteritidis on EMB(Enlarged view). FIG. 16. EMB agar plate inoculated with Salmonella enteritidis (a gram-negative coliform bacterium) showing good growth of grey mucoid colonies with no fermentation of lactose or acid production. (Naowarat Cheeptham and Carolynne Fardy, Thompson Rivers University, Kamloops, BC, Canada)

Figure 17: Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Enterobacter aerogenes on EMB (Enlarged view). FIG. 17. EMB agar plate inoculated with (A) Escherichia coli, (B) Pseudomonas aeruginosa, (C) Klebsiella pneumoinae, and (D) Enterobacter aerogenes. All four gram negative bacteria grew exhibiting different morphology. Escherischia coli grew with typical lactose fermenter morphology with excessive acid production and precipitation of green metallic pigment (colonies with green metallic sheen). Pseudomonas aeruginosa grew exhibiting the nonfermenter morphology (pinkish colonies), both Klebsiella pneumoniae and Enterobacter aerogenes grew with lactose fermentation and acid production morphology (with purple dark centered mucoid colonies). (Naowarat Cheeptham and Carolynne Fardy, Thompson Rivers University, Kamloops, BC, Canada)

Figure 18: Lactose Fermentation FIG. 18. Eosin-methylene blue agar plate inoculated with Escherichia coli. This plate shows a metallic green sheen on the colonies, which indicates strong acid production from lactose and/or sucrose fermentation. (Jesus Antonio Romo, University of Texas at San Antonio, San Antonio, TX)