Picture 35
This picture shows Pseudomonas aeruginosa (on the right) and Shigella dysenteriae (on the left) in nutrient agar.
Pseudomonas aeruginosa
Morphology: Gram negative rods, do not ferment glucose and lactose, are oxidase positive, produce pyocyanin and pyoverdin
Route of transmission: Fomites and food
Investigations: Gram stain, culture in MacConkey's agar or Triple Sugar Iron medium
Diseases:
Pneumonia
Urinary tract infection
Wound infection
Septicemia
Meningitis
Otitis externa
Endophthalmitis
Osteomyelitis
Treatment:
Due to varied antibiotic resistance, choices for empirical treatment include the aminoglycosides (eg. gentamicin and tobramycin), some third generation cephalosporins (eg. ceftazidime and cefoperazone), extended spectrum penicillins (eg. piperacillin, azlocillin and carbenicillin), carbapenems (eg. imipenem and meropenem), and fluoroquinolones (eg. ciprofloxacin and ofloxacin) until results of sensitivity tests are known.
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