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Levines EMB
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-Gram negative Bacilli
-Ferments lactose -Capable of fermenting glucose -Would not be chosen as a possible enteric pathogen |
-Gram negative bacilli
-Does not ferment lactose (from this info we can’t tell if its capable of fermenting glucose or note -Uses peptones for growth -Chosen as a possible enteric pathogen |
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MacConkey Agar
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-Gram negative Bacilli
-Ferments lactose -Capable of fermenting glucose -Would not be chosen as a possible enteric pathogen |
-Gram negative bacilli
-Does not ferment lactose (from this info we can’t tell if its capable of fermenting glucose or note -Uses peptones for growth -Chosen as a possible enteric pathogen |
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SS Agar
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-Gram negative Bacilli
-Ferments lactose -Capable of fermenting glucose -Would not be chosen as a possible enteric pathogen |
-Gram negative bacilli
-Does not ferment lactose (from this info we can’t tell if its capable of fermenting glucose or note -Uses peptones for growth -Chosen as a possible enteric pathogen |
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XLD
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-Gram negative bacilli
-Ferments lactose and or sucrose and or xylose -Since it ferments at least one of these carbs it is capable of fermenting glucose -Would not be chosen as a possible enteric pathogen -H2S is negative |
-Gram negative bacilli
-Does not ferment lactose, sucrose or xylose (from this info we can’t tell if its capable of fermenting glucose or note -Uses peptones for growth -Chosen as a possible enteric pathogen |
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HE Agar
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-Gram negative bacilli
-Ferments lactose and/or sucrose and/or salicin -Since it ferments at least one of these carbs it is capable of fermenting glucose -Would not be chosen as a possible enteric pathogen -H2S is negative |
-Gram negative bacilli
-Does not ferment lactose, sucrose or salicin(from this info we can’t tell if its capable of fermenting glucose or note -Uses peptones for growth -Chosen as a possible enteric pathogen - H2S producing (some colonies are black) |
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Purpose
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allow differentiation of bacteria based upon some characteristic
- usually based upon s biochemical reaction |
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pH indicators
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register the difference
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Growth factors (micronutrients)
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blood, carbohydrates, amino acids, vitamins, NaCl
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Fastidious bacteria
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Need additional nutrients in media or environment
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Auxotroph
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Bacterium which has mutatued (from the parent prototroph) and developed a specific growth requirement
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Halophile
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Bacterium needing NaCl in media
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Contrast with Enrichment media
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- Suppresses normal flora while enhancing growth of pathogens
- Usually for stool specimens |
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Purpose
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Selects for the growth of some bacteria while inhibiting others
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Enteric Media
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- Designed to isolate pathogens from the intestine
- All are selective for gram negative bacilli (inhibit gram positives and gram negative cocci) - Different classifications -> Differ in their ability to inhibit intestinal normal flora |
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Low Selectivity
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Moderate Selectivity
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Highly Selective
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Allow ALL gram negative bacilli to grow, whether intestinal pathogen or normal flora
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Allow intestinal pathogenic gram negative bacilli to grow while inhibiting some intestinal normal flora gnb
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Allow intestinal pathogenic gram negative bacilli to grow while inhibiting virually all intestinal normal flora gnb
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