Department of Pathology UCD-School of Medicine



Self Assessment Exercises VI (02/19/06)

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The non-fermentative gram-negative bacilli are gram-negative rods that grow well within 24-hours on the surface of Kligler Iron agar (KIA) or Triple-sugar iron agar (TSI) slants, but neither grow in nor acidify (develop a yellow pigment) in the deep of these media. Characteristics by which a clinical gram-negative bacillus isolate might be suspected of being a non-fermenter include:


Lack of evidence of glucose fermentation (alk/alk KIA)

Positive cytochrome oxidase reaction

Failure to grow on MacConkey agar

Before setting up a definitive differential identification system, it is recommended to first assess the oxidative-fermentative (OF) characteristic of an unknown gram-negative bacillus isolate by inoculating a KIA or TSI slant.




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