Yellow and white capsule
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Yellow and White Capsule: Insights from Recent Research
Identification of Erwinia amylovora Using Yellow and White Colony Morphology
Yellow Colony Formation on Copper-Containing Agar
Erwinia amylovora, the pathogen responsible for fire blight, can be identified by its distinctive yellow colony formation on minimal agar medium MM2 containing asparagine and copper sulfate (MM2Cu). This yellow coloration is a hallmark of the pathogen, distinguishing it from other plant-associated bacteria, which typically do not produce the same colony morphology on this medium. The yellow color is particularly useful for identifying strains from various host plants, including raspberry and other unusual hosts.
White Colony Formation in Absence of Copper
In contrast, E. amylovora forms white colonies on minimal agar without copper salt. This difference in colony color based on the presence of copper sulfate is a critical factor in the novel plating technique developed for the identification of E. amylovora. The method is especially effective for detecting natural levan-deficient strains, which do not grow well on semi-selective media with sucrose.
Capsule Staining for Confirmation
To confirm the identification of E. amylovora, capsule staining with FITC-labeled lectin from Abrus precatorious is used. This lectin has a high affinity for galactose residues, the main sugar in the capsular exopolysaccharide amylovoran of E. amylovora. This staining method is effective even for weakly mucoid strains but not for strains with mutations affecting amylovoran synthesis.
Allergic Reactions to Yellow Capsules Containing Tartrazine
Tartrazine as a Coloring Agent
Tartrazine, a synthetic dye used to provide a yellow appearance to capsules, has been associated with various allergic reactions. These reactions include generalized pruritus, urticaria, edema of the lips and tongue, vascular purpura, and severe asthmatic attacks . The presence of tartrazine in yellow capsules can trigger these adverse effects in sensitive individuals.
Alternative White Capsules
It is speculated that patients who react to tartrazine in yellow capsules might not experience the same reactions if they were to use an alternative uncolored white tablet distributed by the same manufacturer . This suggests that the colorant itself, rather than the active ingredient, may be responsible for the allergic responses observed.
Determination of Food Dyes in Yellow Capsules
RP-HPLC Analysis of Synthetic Dyes
Reversed-phase high-performance liquid chromatography (RP-HPLC) has been employed to determine the presence of synthetic food dyes, including Tartrazine (E102), in yellow-colored capsules. The analysis revealed that the concentration of Tartrazine in these capsules can be as high as 524 ± 0.01 µg/capsule. This information is crucial for consumers, especially those who may be sensitive to synthetic dyes.
Conclusion
The identification of Erwinia amylovora through yellow and white colony morphology on copper-containing agar and the use of capsule staining provides a reliable method for detecting this pathogen. Additionally, the presence of tartrazine in yellow capsules can lead to allergic reactions, highlighting the importance of considering alternative formulations for sensitive individuals. The determination of synthetic dyes in capsules using RP-HPLC further underscores the need for transparency in the content of pharmaceutical products.
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