The shigelles , the Bacterium S of the Shigella , are strict Enterobacteriaceae pathogenic, met exclusively at the man.

The Shigella dysenteriae is responsible for the bacillar Dysenterie . The Shigella are bacteria very close to Escherichia coli .

Ecology

Habitat

The Shigella do not belong to any Flore commensale at the man, they all are pathogenic and specific digestive tract; eliminated by the saddles and dispersed in the grounds and water where they survive only little of time.

Pathogenic capacity

They are responsible for the Shigellose S (specifically human infections intestinal), which are bacillar Dysenteries transmitted by the water of drink and food soiled by the saddles of the chronic patients or carrying. They are primarily localized intestinal infections to the large intestine where the germs multiply by causing an ignition of the mucous membrane resulting in a glaireuse diarrhea and sanguinolente. There is no swarming in circulation but the local phenomena can be accompanied by toxicose and dehydration.

The species most blamed is Shigella dysenteriae or bacillus of Shiga . Shigella dysenteriae is responsible for serious forms in the tropical areas (Asia and Central America). It is the only shigelle one which secretes a exotoxin.

The other species of Shigella are also responsible for Diarrhée S acute. On the other hand, their infections are generally more benign and are accompanied by attenuated Symptôme S. In certain chronic forms, the periods of diarrheas alternate with periods asymptomatiques.
One primarily meets these infections in Europe, for which Shigella flexneri (cosmopolitan Group causing of the epidemics and the sporadic cases of variable gravity) and Shigella sonnei (most frequent in a country like France: more or less 70% of Shigellas isolated. It is generally the cause of entérites benign which touches the children particularly and sometimes of small epidemics of cribs or schools) are generally blamed.

Classification

The Kind comprises 4 species. They are then subdivided in sérotypes on biochemical and antigenic bases. The stocks are different on an antigenic level by the structure of the Antigène O , on the biochemical level by the characters ONPG , Mannitol, Indole and ODC . There is no antigen H , Shigelles being deprived of lashes.

Bacteriological characters

Microscopic morphology

aspect : They are bacilli negative Gram S, motionless; deprived of spores and capsules.

Grouping : Variable, they are presented insulated, in diplobacilles and sometimes even in chains.

Character of culture

Conditions of culture

to supplement

Culture media used

On ordinary Gélose of 24 hours with 37°C, Shigella produces colonies of intermediate size (2 to 3 mms in diameter), rounds, regular and brilliant of type Smooth .

  • nonselective Mediums:

    • ordinary Gélose
    • Gélose BCP
    • Gélose CLED

  • selective Mediums:

    • Gélose Mac Conkey
    • Gélose lactosée with the désoxycholate
    • Gélose Hynes
    • Gélose Salmonella Shigella or Gélose S
    • Gélose Hektoen

Biochemical character

It is determined on a gallery traditional or miniaturized for Enterobacteriaceae with which they are different by a unit from negative natures:
  • Absence of Urease, Désaminase and Lysin décarboxylase.
  • Absence of production of H2S and acétoïne.
  • No use of the Citrate like only source of Carbon on citrate medium of Simmons.
  • motionless
The character ONPG , mannitol, indol and ODC vary according to the biotypes (see the table above).

Disease prevention

Same prophylactic measurements as in Salmonelloses: control water, food hygiene, monitoring of the carriers of germs.

Diagnosis

Coproculture on selective medium

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