Reproducing Clinically Significant Multi-Organism Cultures to Improve Clinical Microbiology Education and Practice †
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Authors:
Rebecca Barr1,
Mary Feller Davis1,*
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Received 03 May 2017 Accepted 27 November 2017 Published 16 February 2018
- ©2018 Author(s). Published by the American Society for Microbiology
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[open-access] This is an Open Access article distributed under the terms of the Creative Commons Attribution-Noncommercial-NoDerivatives 4.0 International license (https://creativecommons.org/licenses/by-nc-nd/4.0/ and https://creativecommons.org/licenses/by-nc-nd/4.0/legalcode), which grants the public the nonexclusive right to copy, distribute, or display the published work.
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†Supplemental materials available at http://asmscience.org/jmbe
- *Corresponding author. Mailing address: 4007 LSB, 701 E University Parkway, Provo, UT 84602. Phone: 801-422-6207. E-mail: [email protected].
Abstract:
Medical microbiology courses focus on clinically relevant organisms, but designing laboratory experiments that mimic clinical specimens can be challenging. Many clinical specimens produce multi-organism cultures, which are difficult to reproducibly create in the academic laboratory. With experience with only single organism cultures, students may find it challenging to transition to the clinical laboratory where they must identify pathogens and normal flora from mixed cultures. Here, we present protocols for the creation of multi-organism cultures for mock wound, stool, urine, and throat cultures with medically relevant bacteria that allow these principles to be taught in an academic laboratory prior to clinical experiences.
References & Citations
Supplemental Material
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Appendix 1: Wound culture protocol, Appendix 2: Stool culture protocol, Appendix 3: Urine culture protocol, Appendix 4: Throat culture protocol, Appendix 5: Organism ATCC numbers
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Abstract:
Medical microbiology courses focus on clinically relevant organisms, but designing laboratory experiments that mimic clinical specimens can be challenging. Many clinical specimens produce multi-organism cultures, which are difficult to reproducibly create in the academic laboratory. With experience with only single organism cultures, students may find it challenging to transition to the clinical laboratory where they must identify pathogens and normal flora from mixed cultures. Here, we present protocols for the creation of multi-organism cultures for mock wound, stool, urine, and throat cultures with medically relevant bacteria that allow these principles to be taught in an academic laboratory prior to clinical experiences.

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Author and Article Information
-
Received 03 May 2017 Accepted 27 November 2017 Published 16 February 2018
- ©2018 Author(s). Published by the American Society for Microbiology
-
[open-access] This is an Open Access article distributed under the terms of the Creative Commons Attribution-Noncommercial-NoDerivatives 4.0 International license (https://creativecommons.org/licenses/by-nc-nd/4.0/ and https://creativecommons.org/licenses/by-nc-nd/4.0/legalcode), which grants the public the nonexclusive right to copy, distribute, or display the published work.
-
†Supplemental materials available at http://asmscience.org/jmbe
- *Corresponding author. Mailing address: 4007 LSB, 701 E University Parkway, Provo, UT 84602. Phone: 801-422-6207. E-mail: [email protected].
Figures
An overview of the general protocol.

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FIGURE 1
An overview of the general protocol.
Mixed pathogen wound culture with Escherichia coli ( 1 ) and Staphylococcus aureus ( 2 ). A) Sheep blood agar (SBA): both organisms grow on this enriched media. E. coli colonies tend to be slightly larger and grayer, and S. aureus colonies tend to be smaller and whiter. B) Bile esculin agar (BEA): neither organism grows on this selective agar. C) MacConkey agar (MAC): only E. coli grows on this Gram-negative selective media. Due to lactose fermentation by E. coli, pink colonies are observed. D) Mannitol salt agar (MSA): only S. aureus grows on this selective agar. Due to mannitol fermentation by S. aureus, yellow colonies are observed.

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FIGURE 2
Mixed pathogen wound culture with Escherichia coli ( 1 ) and Staphylococcus aureus ( 2 ). A) Sheep blood agar (SBA): both organisms grow on this enriched media. E. coli colonies tend to be slightly larger and grayer, and S. aureus colonies tend to be smaller and whiter. B) Bile esculin agar (BEA): neither organism grows on this selective agar. C) MacConkey agar (MAC): only E. coli grows on this Gram-negative selective media. Due to lactose fermentation by E. coli, pink colonies are observed. D) Mannitol salt agar (MSA): only S. aureus grows on this selective agar. Due to mannitol fermentation by S. aureus, yellow colonies are observed.
Mixed pathogen wound culture with Citrobacter freundii ( 1 ) and Enterococcus faecalis ( 2 ). A) Sheep blood agar (SBA): both organisms grow on this enriched media, with C. freundii as a larger colony and E. faecalis as a small colony. B) MacConkey agar (MAC): only C. freundii grows on this Gram-negative selective media. Due to lactose fermentation by C. freundii, pink colonies are observed. C) Mannitol salt agar (MSA): inhibited growth of E. faecalis can be seen in the first quadrant as small, yellow growth. D) Bile esculin agar: only E. faecalis grows on this selective agar. Due to hydrolysis of esculin by E. faecalis, black colonies are observed.

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FIGURE 3
Mixed pathogen wound culture with Citrobacter freundii ( 1 ) and Enterococcus faecalis ( 2 ). A) Sheep blood agar (SBA): both organisms grow on this enriched media, with C. freundii as a larger colony and E. faecalis as a small colony. B) MacConkey agar (MAC): only C. freundii grows on this Gram-negative selective media. Due to lactose fermentation by C. freundii, pink colonies are observed. C) Mannitol salt agar (MSA): inhibited growth of E. faecalis can be seen in the first quadrant as small, yellow growth. D) Bile esculin agar: only E. faecalis grows on this selective agar. Due to hydrolysis of esculin by E. faecalis, black colonies are observed.