Shigella spp

Gram Stain

• Gram negative bacilli - fermenter

Clinical Significance

These organisms cause bloody and non-bloody diarrhea.  Diarrhea may be watery at first and can progress to classic dysentery (mucousy/bloody).            

Transmission is by fecal oral route. Person to person spread is common due to low infective dose (10-100 organisms). Transmission has also been documented by contaminated water, food flies, and swimming pools.

Infections may be complicated by hemolytic uremic syndrome (HUS), -  especially with S. dysenteriae or chronic arthritis (Reiter’s syndrome) – especially with S. flexneri.

Bacteremia, keratitis, and urinary tract infections have rarely been reported.

Usual Susceptibility Pattern

There is increasing resistance to ampicillin, TMP/SMX, and quinolones.

Cefixime may be useful in children but has variable efficacy in adults and overall less efficacious than non-beta-lactam agents.

First/second generation cephalosporins are not recommended due to poor intraluminal concentrations.

Ceftriaxone is preferred over cefotaxime due to higher intraluminal concentrations.