Shigella –biochemical behavior

Shigella –biochemical behavior

Lactose (1)                         -	LSS=- -  -
Sucrose (2)                         -
Salicin                                  -
Glucose                              A	GMM=      +   +  -
Maltose                                    A
Mannitol                            V
Indole                                 V
MR                                       +
VP                                         -	IMVic=      ±      ±  -    -
Citrate utilization               -

Key :

1    = All are non-lactose fermented except shigella sonnei

2         = Usually negative but may be late positive.

A   =  Acid

V   = Variable

±    =  Variable

Laboratory diagnosis of shigellosis:

Step:

1. Specimen collection:

ð  Fresh stool

ð  Rectal swab.

2. Microscopic examination:

Findings:

ð  Plenty of pus cells.

ð  Macrophage.

ð  Some RBC.

3.  Isolation and identification from culture:

ð  The specimens are streaked on Mac-Conkey’s agar , S-S agar and DCA media and incubate at 37°C for over night.

ð  Pale colonies (colorless) are picled up.

ð  Biochemical behavior of shigella is noted.

ð  Serotype is identified by slide agglutination using a diagnostic set antis era.

ð  Perform antibiogram sensitivity test

4. Routine stool examination:

Physical –odorless, mucus & blood in stool , chemical –alkaline stool.

5. Serological tests:

ð  Co-agglutination test to detect the end toxin.

ð  Agglutinin levels in patient’s sera are determined by tube agglutination methods. A rising is helpful.