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Figure 1: Staphylococcus aureus (Enlarged view). FIG. 1. Mannitol salt agar inoculated with Staphylococcus aureus showing mannitol fermentation (yellow medium). (Laura Cathcart and Patricia Shields, University of Maryland, College Park, MD)

Figure 2: Staphylococcus aureus (Enlarged view). FIG. 2. Closer view of mannitol salt agar inoculated with Staphylococcus aureus showing mannitol fermentation (yellow medium). (Laura Cathcart and Patricia Shields, University of Maryland, College Park, MD)

Figure 3: Staphylococcus epidermidis (Enlarged view). FIG. 3. Mannitol salt agar inoculated with Staphylococcus epidermidis showing growth but no fermentation of mannitol (pink medium). (Laura Cathcart and Patricia Shields, University of Maryland, College Park, MD)

Figure 4: Staphylococcus epidermidis (Enlarged view). FIG. 4. Closer view of mannitol salt agar inoculated with Staphylococcus epidermidis showing growth but no fermentation of mannitol (pink medium). (Laura Cathcart and Patricia Shields, University of Maryland, College Park, MD)

Figure 5: Staphylococcus saprophyticus (Enlarged view). FIG. 5. Mannitol salt agar inoculated with Staphylococcus saprophyticus showing mannitol fermentation (yellow medium). Fermentation varies by strain. (Anne Tsang, University of Maryland, College Park, MD)

Figure 6: Planococcus halophilus (Enlarged view). FIG. 6. Mannitol salt agar inoculated with Planococcus halophilus showing growth but no fermentation (pink medium). (Anne Y. Tsang, University of Maryland, College Park, MD)

Figure 7: Micrococcus luteus (Enlarged view). FIG. 7. Mannitol salt agar inoculated with Micrococcus luteus showing no fermentation of mannitol (pink medium). The colonies show a yellow pigment which is characteristic of M. luteus. (Anne Y. Tsang, University of Maryland, College Park, MD)

Figure 8: Enterobacter aerogenes (Enlarged view). FIG. 8. Mannitol salt agar inoculated with Enterobacter aerogenes showing fermentation of mannitol (yellow medium). (Anne Y. Tsang, University of Maryland, College Park, MD)

Figure 9: Staphylococcus aureus (Enlarged view). FIG. 9. Mannitol salt agar inoculated with S. aureus showing fermentation of mannitol (yellow medium) on one side and inoculated with Streptococcus durans showing no growth on the other side. (Anne Y. Tsang and Patricia Shields, University of Maryland, College Park, MD)

Figure 10: Staphylococcus aureus (Enlarged view). FIG. 10. Mannitol salt agar inoculated with Staphylococcus aureus showing fermentation of mannitol (yellow medium). (Anne Hanson and Matthew Pietraszewski, University of Maine, Orono, ME)

Figure 11: Staphylococcus citreus (Enlarged view). FIG. 11. Mannitol salt agar inoculated with Staphylococcus citreus showing fermentation of mannitol (yellow medium). (D. Sue Katz, Rogers State University, Claremore, OK)

Figure 12: (Mixed Staphyloccocus species (Enlarged view). FIG. 12. Mannitol salt agar inoculated with (clockwise from top) Staphylococcus citreus showing fermentation of mannitol (yellow medium), Staphylococcus epidermidis showing growth but no fermentation of mannitol (pink medium), Staphylococcus aureus showing fermentation of mannitol (yellow medium), and Staphylococcus saprophyticus showing growth but no fermentation of mannitol (pink medium). (D. Sue Katz, Rogers State University, Claremore, OK)

Figure 13: Multiple colony types (Enlarged view). FIG. 13. Tryptic soy agar inoculated with (A) Staphylococcus aureus, (B) Staphylococcus epidermidis, (C) and Escherichia coli. (Patricia Shields, University of Maryland, College Park, MD)

Figure 14: Multiple colony types (Enlarged view). FIG. 14. Mannitol salt agar inoculated with (clockwise from upper left) Staphylococcus aureus showing fermentation of mannitol (yellow medium), Staphylococcus epidermidis showing growth but no fermentation of mannitol (pink medium), and Escherichia coli showing no growth. (Patricia Shields, University of Maryland, College Park, MD)

Figure 15: Atypical staphylococci on mannitol salt agar incubated for 24 hours. FIG. 15. Atypical staphylococci on mannitol salt agar incubated for 24 hours at 37oC.  The culture is growing on the sides and lid of the petri plate and is gelatinous in consistency. The yellow pH indicator shows that it is fermenting mannitol. (Clarissa L. Kaup and J. L. Henriksen, Bellevue University, Bellevue, NE)

Figure 16: Atypical staphylococci on mannitol salt agar incubated for 48 hours. FIG. 16. Atypical staphylococci on mannitol salt agar incubated for 48 hours at 37oC.  The culture is still growing on the sides and lid of the petri plate but is less gelatinous in consistency compared to the culture at 24 hours. It is more like a film, with a tougher exterior, making the culture more difficult to subculture. (Clarissa L. Kaup and J. L. Henriksen, Bellevue University, Bellevue, NE)

Figure 17: Bacteria grown on Mannitol Salt Agar. FIG. 17. Bacteria grown on Mannitol Salt Agar (MSA) at 37°C for 24 hours Results: (A). Staphylococcus aureus: large yellow halo around growth indicates  fermentation of mannitol. (B). Staphylococcus epidermidis: Growth but not color change to the media indicating no fermentation of mannitol. (C). Staphylococcus saprophyticus: small yellow halo around growth indicates fermentation of mannitol. (10% of S. saprophyticus ferment mannitol)  (D). E. coli: no growth. Inhibited by the 7.5% NaCl. (Tasha Sturm, Cabrillo College, Aptos, CA)

Figure 18: Methicillin-Resistant Staphylococcus aureus (MRSA) on Mannitol Salt Agar. FIG. 18. Methicillin-Resistant Staphylococcus aureus cultured on Mannitol Salt Agar (MSA) for species confirmation. The formation of medium yellow colonies and fermentation of mannitol is a positive indication of S. aureus. The inoculum was transferred from an antimicrobial susceptibility bacterial lawn collected from a hospital using a sterile inoculating loop, streaked directly onto MSA and cultured for 48 hours at 37˚ C. (by Wai-Yew Ho and Choy-Hoong Chew, Universiti Tunku Abdul Rahman, Kampar, Malaysia)