Approach to identification

The colonies of these genera resemble those of the family Enterobaderiaceae but notably differ by their positive oxidase test (except V. metschnikovii, which is oxidase-negative). The oxidase test must be performed from 5% sheep blood or another medium without a fermentable sugar (e.g., lactose in MacConkey agar or sucrose in TCBS). The reason for this is that fomentation of a carbohydrate results in acidification of the medium and a false-negative oxidase test may result if the surrounding pH is below 5.1. Likewise, if the violet pigment of a suspected C. violaceum isolate interferes with performance of the oxidase test, the organism should be grown under anaerobic conditions (where it cannot produce pigment) and retested.

The reliability of commercial identification systems has not been widely validated for identification of these organisms, although most are listed in the databases of several systems. The API 20E system (bioMérieux, Inc., St. Louis, Mo) is one of the best for vibrios. Because the

Figure 28-3 Colonies of Vibrio chokrae (A) and V. parahemolyticus (B) on TCBS agar.
Table 28-5 Key Biochemical and Physiologic Characteristics of Aeromonas spp., P. shigelloides, and C. violaceum

Species

Oxidase

Gas from Glucose

Esculin Hydrolysis

Fermentation of Sucrose

Lysine

Decarboxylase

Arginine Dihydrolase

Ornithine Decarboxylase

Growth in 0% NaCI"

Growth in 6% NaCI3

TCBS» Growth

Aeromonas caviae

+

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Bacterial Vaginosis Facts

Bacterial Vaginosis Facts

This fact sheet is designed to provide you with information on Bacterial Vaginosis. Bacterial vaginosis is an abnormal vaginal condition that is characterized by vaginal discharge and results from an overgrowth of atypical bacteria in the vagina.

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