Dienes Phenomenon of Proteus: Introduction,Test Procedure, Result Interpretation and Uses
Introduction of Dienes Phenomenon
Dienes phenomenon from the name of Dienes (1946) who first observed and explained about this. It is also called Dienes typing. Although the phenomenon has never been satisfactorily explained. It is using successfully to determine the relationship between strains of Proteus species in studies of cross-infection.
Principle of Dienes Phenomenon
When two different strains of Proteus species inoculate at different places of the same non-inhibitory medium (blood agar), the swarming of the two strains remains separated by a narrow visible furrow. However, in the case of two identical strains of Proteus, swarming of two coalesce without signs of demarcation. Such a condition is called the Dienes phenomenon.
Different strains of Proteus
Control strains: Negative control- the same Proteus mirabilis strain ( isolate) spotted twice on the plate those show no inhibition whereas for positive control- two different Proteus strains spotted opposite each other those show inhibition line as shown above picture.
Test Procedure of Dienes Typing
Take blood agar plate.
Sterile inoculating wire using Bunsen burner and leave for cooling.
Inoculate test strains with the help of inoculating wire in different places of sample agar plate as shown above. Note: The spots should be about 6 cm apart.
Again sterile the inoculating wire and finally incubate the plate at 37° C overnight.
Observe the growth of organisms for swarming of two coalesce without or with signs of demarcation.
A line of inhibition at the conjunction of the swarming zones: Dienes phenomenon or Dienes typing positive
Lacking a line of inhibition at the conjunction of the swarming zones: Dienes phenomenon or Dienes typing negative
Result: Dienes phenomenon or Dienes typing is positive as shown above picture.
Dienes phenomenon uses to determine whether the same or different strains of Proteus and therefore use as strain typing in epidemiology.
Limitation of Dienes Typing
The strain that fails to swarm or swarm too slowly can not be typed by this technique.
The organism to be tested must be swarming. If the swarming has been lost, passage the bacteria once through motility medium ( SIM or MIU) to help them recover the ability to swarm.
Swarming growth of Proteus on blood agar after overnight incubation is shown below-
Swarm and vegetative cells of Proteus in Gram stain as shown below-
Impression: Swarm cell-Multinucleate, densely flagellate, non-septate, elongated cell 20-80 micrometer in length. It is different from the vegetative cell in that it secrets virulence factors such as urease, hemolysin, and protease. The cyclical swarming and consolidation, which may occur evenly for 4 hours or so, give rise to series of alternating concentric cycles of thick and thin growth over a plate as shown in the video. Today, most regard swarming as neither a response to starvation nor on obligatory development stage but rather a means of maximizing biomass production and substrate utilization.
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