Picture 23
This picture shows Shigella dysenteriae (the yellowish bacterial growth on the left) and Klebsiella pneumoniae (the pinkish bacterial growth on the right) cultured in MacConkey's agar.
Shigella dysenteriae
Morphology: Gram negative cocci that do not ferment lactose, do not produce spores and is motile
Route of transmission: Food, fingers, flies, faeces
Investigations: Gram stain, organism cultured on MacConkey's agar and Triple Sugar Iron (TSI) medium
Diseases:
Usually mild watery diarrhea in developed countries and severe "bacillary dysentery" in developing countries
Treatment:
No antibiotics are given in mild cases
In severe cases, ciprofloxacin or trimethoprim-sulfamethoxazole is prescribed
Klebsiella pneumoniae
Morphology: Gram negative cocci that ferment lactose, has a very large capsule which gives it a mucoid appearance
Route of transmission: Fomites, aerosol
Investigations: Gram stain, organism cultured on MacConkey's agar
Diseases:
Lower respiratory tract infections (likely to progress to empyema and lung abscess)
Urinary tract infections
Surgical wound infections
Treatment:
Due to varied antibiotic resistance, gentamicin and cefotaxime are used empirically until results of sensitivity tests are known. Usually treatment consists of an aminoglycoside and a cephalosporin to produce synergistic effects.